Download - Feasibility of Generating Green Power through Anaerobic Digestion

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Final Report April 2005

Report to SMUD

Advanced Renewable and Distributed Generation Program

Prepared By

In Association with MacViro Consultants Inc.

Table of Contents Page Executive Summary i Glossary of Terms vi

1.0 Introduction 1-1

2.0 Quantity and Composition of Garden Refuse as Feedstock 2-1 2.1 Quantity of Garden Refuse Available 2-1 2.2 Composition of Garden Refuse 2-2 2.3 City of Sacramento 2-3

3.0 Anaerobic Digestion of Garden Refuse and Municipal Solid Waste 3-1 3.1 Anaerobic Digestion Process 3-1 3.2 Experience to Date with SSO, MSW and Garden Refuse 3-1 3.3 Anaerobic Digestion Design Options 3-4 3.4 Anaerobic Digestion Technology Designs Available 3-9 3.5 Feedstock and Gas Production 3-11 3.6 Energy Uses 3-13 3.7 Anaerobic Digestion of Garden Waste 3-15 3.8 References 3-15

4.0 Technical Information on AD Technologies - DRY 4-1 4.1 Methodology 4-1 4.2 Kompogas 4-3 4.3 Dranco/OWS 4-9 4.4 Linde-DRY 4-15 4.5 Biopercolat 4-19 4.6 ISKA 4-21 4.7 Valorga 4-26 4.8 Wright 4-31

5.0 Technical Information on AD Technologies - WET 5-1 5.1 Methodology 5-1 5.2 Onsite Power Systems 5-2 5.3 Arrow Ecology Ltd 5-7 5.4 BTA 5-11 5.5 Waasa, WABIO and Citec 5-17 5.6 Linde - WET 5-21 5.7 BioConverter 5-25 5.8 Entec 5-28

0 Screening and Analysis of Available AD Technologies 6-1

6.1 Overview 6-1

6.2 Technical Screening Criteria 6-2

6.3 Summary of Technical Data for AD Technologies 6-4

6.4 Technical Analysis of AD Technologies By Design Parameters 6-7 6.5 Gas Production and Net Energy Available From Different AD Technologies 6-9 6.6 Technical Screening of AD Technologies 6-11 6.7 Evaluation of Broader Concept Using SMUD Criteria 6-13 6.8 Evaluation Using Sacramento Waste Authority Criteria 6-14 7 Economic Analysis of Anaerobic Digestion of Garden Waste 7-1 7.1 Overview 7-1

7.2 Description of Facility Components 7-2

7.3 Plant Energy Balance 7-5

7.4 Costs and Financial Analysis for 100,000 ton/year Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site – Option 1

7-6

7.5 Costs and Financial Analysis for 200,000 ton/year Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site – Option 2

7-10

7.6 Costs and Financial Analysis for 100,000 ton/year Garden Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Options 3 & 4

7-10

7.7 Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food Waste AD Facility (Wet, Mesophilic) at a Greenfield Site – Option 5

7-12

7.8 Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food Waste AD Facility (Wet, Mesophilic) at a Co-located Site – Option 6

7-13

7.9 Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Option 7

7-13

7.10 Costs and Financial Analysis for 50,000 ton/year Garden Waste with Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Option 8

7-14

7.11 Discussion of Costs For Greenfield Site 7-14

7.12 Economic Conditions Which Make AD Viable 7-16

7.13 Next Steps in Research 7-17

8.0 Conclusions and Recommendations 8-1 8.1 Conclusions 8-1

8.2 Recommendations 8-2

Appendices Appendix A 100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site Appendix B 200,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site Appendix C 100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Co-located Site Appendix D 100,000 ton/yr Garden Waste and Food Waste AD Facility (Wet, Mesophilic) at a

Greenfield Site

Appendix E 100,000 ton/yr Garden Waste and Food Waste AD Facility (Wet, Mesophilic) at a Co-located Site

Appendix F 100,000 ton/yr Garden Waste and Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site

Appendix G 50,000 ton/yr Garden Waste and Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site

Tables Page Table 3.1

Key Firms Generating Biogas from MSW Feedstock in Europe in 2003 3-2

Table 3.2

Communities in the United States Investigating Anaerobic Digestion for MSW 3-3

Table 3.3

Biogas Yield from MSW Materials 3-11

Table 3.4

Biogas Yield 3-12

Table 3.5

Biogas Composition 3-12

Table 3.6

Biogas Production 3-12

Table 4.1

Anaerobic Digestion Technologies Profiled 4-2

Table 4.2

Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected Kompogas Facilities

4-4

Table 4.3

Full Scale Kompogas Plants 4-5

Table 4.4

Planned Full Scale Kompogas Plants or Facilities Under Construction 4-6

Table 4.5

Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected DRANCO Facilities

4-10

Table 4.6

DRANCO Demonstration Plants 4-11

Table 4.7

Full Scale DRANCO Plants 4-12

Table 4.8

Planned DRANCO Plants 4-12

Table 4.9

Feedstocks of Linde Dry Digestion Facilities 4-16

Table 4.10

Energy Production for Selected Linde Dry AD Facilities 4-17

Table 4.11

Existing and proposed Linde Dry AD Facilities 4-17

Table 4.12

Linde Mechanical-Biological Treatment Facilities featuring Aerobic Treatment 4-18

Table 4.13

Energy Characteristics of ISKA Facilities 4-23

Tables Page Table 4.14

Land Requirements of Selected ISKA AD Facilities 4-24

Table 4.15

ISKA Operational and Proposed AD Facilities 4-24

Table 4.16

Typical Average Gas Yields for Different Feedstock 4-28

Table 4.17

Land Requirements for Selected Valorga Facilities 4-28

Table 4.18

Valorga AD Facilities 4-29

Table 5.1

Operating and Planned BTA Facilities 5-15

Table 5.2

Energy Information for Selected Waasa Facilities 5-18

Table 5.3

Waasa Facilities 5-19

Table 5.4

Feedstock Used in Linde Wet Facilities 5-22

Table 5.5

Energy Outputs from Selected Linde Wet Facilities 5-22

Table 5.6

Existing and Proposed Linde Wet AD Facilities 5-23

Table 5.7

Energy Information for Entec Facilities 5-30

Table 5.8 Entec Operations 5-30 Table 6.1

Summary of Key Technical Data For Thirteen Anaerobic Digestion Technologies Processing Some Garden Waste

6-5

Table 6.2

Classification of AD Technologies As One Vs Two Stage Systems 6-7

Table 6.3

Classification of AD Technologies As Wet Vs Dry Systems 6-8

Table 6.4

Characteristics of Mesophilic Vs Thermophilic Designs 6-8

Table 6.5

Available Information on Reported Gas Production and Net Energy Available for Export For Dry Anaerobic Digestion Technologies

6-10

Table 6.6

Available Reported Information on Gas Production and Net Energy Available for Export For Wet Anaerobic Digestion Technologies

6-10

Table 6.7 Screening of Anaerobic Digestion Technologies 6-12

Table 7.1 Plant Capital Cost Estimate – 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

7-7

Table 7.2 Plant Operating and Maintenance Cost Estimate – 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

7-7

Table 7.3 Financial Analysis: Input Assumptions and Data –100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

7-8

Table 7.4 Tipping Fee and Power Price Calculation – 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

7-9

Tables Page Table 7.5 Summary of Costs for Options 1-4 7-12 Table 7.6 Summary of Costs for Greenfield Sites 7-16 Table 7.7 Summary of Costs for Co-located Sites 7-17 Table 7.8 Financial Analysis Summary 7-19

Figures Page Figure 2.1

Garden Refuse Collected In the City of Sacramento By Month, 2002 and 2003

2-1

Figure 3.1

Flow Diagram for Anaerobic Digestion 3-4

Figure 3.2

Possible AD System Processes

3-5

Figure 3.3

AD Technologies Supplied By Different Vendors

3-10

Figure 7-1

On-Site Cogeneration Schematic with Annual Energy Flows 100,000 Ton per Year Garden Waste Facility

7-6

Green Waste To Energy Economic Feasibility Study – Final Report

Executive Summary Anaerobic Digestion Anaerobic digestion is a naturally occurring biological process that uses microbes to break down organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of organic waste takes place in a special reactor, or enclosed chamber, where critical environmental conditions such as moisture content, temperature and pH levels can be controlled to maximize microbe generation, gas generation and waste decomposition rates. Anaerobic digestion has been in use for several decades to treat sewage sludge, animal wastes and industrial wastewater. Only in the past decade, has the technology become a recognized method for processing solid organic waste from residential and commercial sources. The benefit of an AD process is that it is a net generator of energy which can be sold off-site in the form of heat, steam or electricity. Background To Study The Advanced Renewable and Distributed Generation Technologies (AR&DGT) group of SMUD engaged the services of IEC, with RIS International Ltd as sub-contractor, to explore the feasibility of generating green power through the anaerobic digestion of garden refuse from the Sacramento, Citrus Heights and Sacramento County areas. About 260,000 tons of garden refuse are potentially available as a feedstock for a processing facility. Sacramento Waste Authority (SWA) is currently searching for a local site for aerobic composting of garden refuse, in order to reduce transportation outside the county. SMUD’s Renewable Portfolio Standard (RPS) requires 20% of SMUD’s energy needs to be met with non-large hydro renewable energy by 2011. The RPS requirement can be met by conventional renewables such as wind and geothermal, as well as emerging renewable energy sources such as solar and biomass. Biomass based sources of renewable energy are seen as desirable because they use a locally generated and sustainable feedstock material (such as agricultural and municipal waste streams), and create local economic and environmental benefits. The purpose of this study was to collect and evaluate data on anaerobic digestion technologies, and assess the viability and costs of digesting garden wastes generated in the Sacramento area, and how this technology could be used to generate green energy from garden wastes.

i April 2005


Anaerobic Digestion Technologies And Facilities Processing Solid Municipal Waste In total, 74 existing AD facilities are known to be operating at full scale and are processing some type of municipal solid waste. Most of these anaerobic digesters are located in Europe, with a few in Asia. There are two full scale digesters operating in Canada and no full scale operations in the US at this time. There are an additional 33 AD facilities planned or under construction which will process the organic fraction of the municipal solid waste stream.

28 in Germany 12 in Switzerland 7 in Spain 5 each in Austria and Italy 4 each in Japan and France 3 each in Belgium and Netherlands 2 in Canada 1 each in Finland, Sweden and Denmark (this

may be closed), Libya, Korea and Portugal

Distribution of 74 Existing AD Facilities Processing the Organic Fraction of MSW

8 Kompogas 6 Dranco 3 ISKA 3 APS (UC Davis, Industry, Vancouver

Washington) 1 Bioconverter (Los Angeles) 3 Valorga 2 BTA 6 Linde 1 Biopercolat

Distribution of 33 Planned AD Facilities Processing the Organic Fraction of MSW

Some of the key points from the research conducted on the AD technologies are:

Gas production for the same materials is similar for most of the AD technologies; Gas production for all technologies is lower for garden waste and higher for food waste,

paper waste and MSW; Dry AD technologies appear to use 20% to 30% of the energy produced on-site for

internal requirements, leaving 70% to 80% of the energy produced for export; Wet AD technologies appear to use more energy (up to 50% reported) for internal

operations, and about 50% is available for export although reported values were inconsistent from one wet technology to another; and

Dry technologies, therefore, are preferred where energy production is a key evaluation criterion.

Europe has experienced some success handling garden waste in AD systems. Several AD facilities located throughout Europe process a feedstock consisting primarily of garden waste. Screening of AD Technologies Anaerobic digestion systems are broadly defined as wet or dry technologies. Wet AD technologies are suitable for situations where significant removal of contaminants such as plastic bags is desirable at the front end of the process. Dry AD technologies are more suited to relatively clean feedstocks which do not require significant contaminant removal. Dry AD technologies were considered more suitable for the application under consideration. Thirteen (13) commercially viable AD technologies were identified during the course of this study. Six dry AD technologies were researched and evaluated:

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Kompogas (Kompogas, Switzerland) Dranco (Organic Waste Systems, Belgium) Linde (Linde-KCA-Dresden GmbH, Germany) Biopercolat (Wehrle-Werk, Germany) ISKA (U-plus Umweltservice AG, Germany) Valorga (Valorga, France)

Seven wet AD technologies were evaluated:

APS (Onsite Power Systems, United States) ArrowBio (Arrow Ecology Ltd, Israel) BTA (Biotechnische Abfallverwer-tund GmbH, Germany) Waasa (Citec Environmental, Finland) Linde (Linde-KCA-Dresden GmbH, Germany) BioConverter (Bioconverter, United States) Entec (Environment Technology GmbH, Austria)

The viability of using these technologies to treat garden waste, or a feedstock incorporating some garden waste was assessed using a preliminary, qualitative screening process. The technical screening criteria used to assess and compare the 13 wet and dry technologies included:

Proven Technology (has facilities in operation) Flexible Technology (can handle a range of feedstocks, including garden waste) Company Track Record (has a good operating record in established AD facilities) Energy Available for Export

Having a local presence in the US or North America was considered an advantage, but not essential. The Onsite Power Systems pilot project at UC Davis provides a valuable opportunity to carry out local research on AD technology. However, this technology will not be ready to construct a facility with a capacity of 50,000 to 100,000 tons/year in the short term, as the pilot plant will only start operation in late 2005, and will require a number of months of operation to generate the results needed to scale to a larger unit. On the basis of the preliminary screening, four dry technologies were considered viable options for a future AD facility: Kompogas, Dranco, Valorga and Linde. Cost Estimates For AD Facilities Costs were estimated for a number of different AD options:

Three facility sizes (50,000, 100,000 and 200,000 tons/year capacity); Two AD system designs (wet and dry), Two types of feedstocks (garden waste only and garden waste with food waste) and Two site situations (Greenfield site and co-located with other waste management

facilities)

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Costs for 8 different options are shown in Table ES.1

Table ES-1 Cost Estimates for Different AD Facility Options

Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8

Feedstock Garden Waste Garden Waste Garden Waste Garden WasteGarden and Food Waste

Garden and Food Waste



AD Technology Dry Dry Dry Dry Wet Wet Dry DrySize (TPY) 100,000 200,000 100,000 100,000 100,000 100,000 100,000 50,000Location Greenfields Greenfields Co-Located Co-Located Greenfields Co-Located Co-Located Co-LocatedCapital Grants ($) 0 0 0 16,760,000 0 0 0 0Capital Cost ($) 30,960,000 54,970,000 27,670,000 10,910,000 34,400,000 31,090,000 27,670,000 17,440,000Annual Capital Cost ($) 3,271,562 5,808,713 2,923,906 1,152,866 3,635,069 3,285,299 2,923,906 1,314,542Annual Operating and Maintenance (O&M) (Excluding Digestate Composting and Residue Disposal Cost) ($) 2,460,000 3,957,000 1,905,000 1,905,000 2,836,000 2,281,000 1,905,000 1,341,000Annual Digestate Composting and Residue Disposal Cost ($) 1,650,000 3,300,000 0 0 1,775,000 0 0 0

Amortized Capital Per Ton ($/Ton) 32.72 29.04 29.24 11.53 36.35 32.85 29.24 26.29Annual O&M Per Ton ($/Ton) 24.60 19.79 19.05 19.05 28.36 22.81 19.05 26.82Annual Digestate Composting and Residue Disposal Cost Per Ton ($/Ton) 16.50 16.50 0.00 0.00 17.75 0.00 0.00 0.00Total Annual Cost Per Ton ($/Ton) 73.82 65.33 48.29 30.58 82.46 55.66 48.29 53.11Annual Electricity Revenue Per Ton (If Electricity Rate is $0.065/kWh) ($/Ton) (5.58) (5.58) (5.58) (5.58) (7.38) (7.38) (7.59) (7.59)Net Cost Per Ton ($/Ton) 68.23 59.75 42.71 25.00 75.08 48.29 40.70 45.52Cost per kWh Input (If Input Tipping Fee is set at $25/ton) 0.568 0.470 0.271 0.065 0.506 0.270 0.199 0.241 The analysis showed that capital costs are highest for a greenfield site, and that co-located AD facilities result in considerable capital and operating cost savings. On this basis, a greenfield AD site was eliminated from further consideration, and the analysis focused on co-located site options. Phase 2 should explore co-located AD site options in further detail. The analysis shows that the addition of some food waste to the AD facility feedstock improves the financial performance of the facility by increasing energy revenues. Energy revenues could increase considerably from those shown in the table if the AD facility could be located close to a heat or steam customer, so that all of the energy and heat generated by the AD biogas can be sold. The cost analysis did not evaluate this option, as a specific location was not evaluated. The cost analysis shows that the highest cost component per ton of input is the amortization of capital costs, therefore efforts should be made to identify potential capital grants for construction of the AD facility. The California Energy Commission (CEC) and the California Integrated Waste Management Board (CIWMB) are both interested in supporting biomass based conversion technologies such as anaerobic digestion. Greenfield Site vs. Co-Location It was concluded that establishing an AD facility on a greenfield site (constructing an AD facility on a new, undeveloped site) was not viable economically, because of the high costs of constructing various components such as a scale house, admin building, engine generator set, wastewater treatment, tipping floor and conveyors which would already be established at other waste management facilities. Co-locating the AD facility at an existing waste management

iv April 2005


facility was considered preferable from a cost point of view, and also because of the reduced social impacts of using an existing rather than a new site. Co-locating at an existing facility will also require less time for new permits. In addition, staff costs can be shared. Co-locating at a landfill, MRF, transfer station or composting facility is viable, and each type of site has different advantages. If the AD facility can be located at a landfill, with landfill gas recovery, the scale-house, gas engines, admin building and wastewater treatment system can be shared. If the AD facility is co-located at a composting site, the digestate (the solid material produced from the digester) can be cured on-site and stronger, more oxygen demanding wastes can be processed by the composting facility, using the digester to handle the early days of biological breakdown. The scale house and admin building can be shared, as well as wastewater treatment facilities. If the AD facility is co-located at a MRF or transfer station, the tipping floor, scale house and admin building can be shared. The net traffic impacts due to slight increases in truck traffic are likely minor. Additional benefits can be gained by locating the AD facility near any existing steam or heat customer which can use the biogas in gas boilers. Conclusions and Next Steps It is concluded that anaerobic digestion of garden waste is technically feasible. It produces a low energy yield compared to anaerobic digestion of other materials such as food, paper and animal manures. The energy yield can be improved by adding these materials to the digester. Anaerobic digestion of garden waste is also expensive compared to open windrow composting, which is the traditional technology used. However, new air quality regulations for open windrow composting sites (not finalized) will increase costs of composting, making AD more cost competitive. Co-locating an AD facility at an existing waste management facility (transfer station, MRF, composting or landfill) is considered the most viable approach in the short to medium term, as this reduces both capital and operating costs of the AD facility, and social impacts. This analysis shows the considerable benefits of co-located site options. Considerable time can also be saved if an existing site, already permitted to receive waste, is used, as modifications to the existing permit require less time than obtaining permits for a new site. Phase 2 should explore co-location options, and options to locate the AD facility close to potential heat and steam customers in more detail to identify firmer cost estimates for the AD facility. Firm costs should be obtained through a formal Request for Proposal process. Capital grants should be pursued to assist with financing of the AD facility.

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Glossary of Terms

Biosolids – Also known as sewage sludge. Biosolids are produced from primary, secondary or tertiary wastewater treatment systems. Biowaste – The organic fraction of the municipal waste stream, which includes food waste and green waste. Digestate – The solid organic residual produced at the end of the anaerobic digestion process. This material can be turned into compost or can be directly land applied depending on the local regulations. Garden Refuse – The leaf and yard waste fraction of the municipal waste stream. Also known as green waste. Green Waste - The leaf and yard waste fraction of the municipal waste stream. Also known as garden refuse. Grey Waste – The residual municipal solid waste remaining after the organic fraction and recyclables have been source separated. Grey waste contains large amounts of paper as well as other materials. MSW – Municipal solid waste – includes non-hazardous solid portions of residential waste (e.g. from single family and multi family households) and industrial, commercial and institutional (IC&I) waste (e.g. small, local businesses). SSO of MSW – Source separated organics of the municipal waste stream – includes sold organic materials collected from the residential waste stream (e.g. single family and multi-family) and the industrial, commercial and institutional (IC&I) waste stream. Typically includes food and garden waste.

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1.0 INTRODUCTION The Advanced Renewable and Distributed Generation Technologies (AR&DGT) group of SMUD engaged the services of IEC, with RIS International Ltd as sub-contractor, to explore the feasibility of generating green power through the anaerobic digestion of garden refuse from the Sacramento, Citrus Heights and Sacramento County areas. About 260,000 tons of garden refuse are potentially available as a feedstock for a processing facility. Sacramento Waste Authority (SWA) is currently searching for a local site for aerobic composting of garden refuse, in order to reduce transportation outside the county. SMUDs Renewable Portfolio Standard (RPS) requires 20% of SMUD’s energy needs to be met with non-large hydro renewable energy by 2011. The RPS requirement can be met by conventional renewables such as wind and geothermal, as well as emerging renewable energy sources such as solar and biomass. Biomass based sources of renewable energy are seen as desirable because they use a locally generated and sustainable feedstock material (such as agricultural and municipal waste streams), and create local economic and environmental benefits. The criteria established by SMUD to assess the options for biomass energy projects are:

Potential for low cost kW-hrs; Local benefits of improved air and water quality and economic benefits; High quality fuel (BTU content, organic fraction, etc.); Sustainable supply of fuel; Proximity to SMUD distribution.

The Sacramento Waste Authority is open to exploring alternatives to aerobic composting of garden refuse, if they meet the following criteria for an acceptable technology:

Cost effective: Can be financed by public-private partnership to deliver costs which are in line with current costs;

Durable equipment: the equipment supplier has a good track record, and the equipment or technology employed provides good warranties and serviceability;

Nuisance free: There are little or no odors, litter, vectors, traffic impacts or negative effects on property values;

Final Product: The technology produces a saleable residue for marketing by the private sector party involved.

The purpose of this study was to collect and evaluate data on anaerobic digestion technologies, and assess the viability and costs of digesting garden wastes generated in the Sacramento area, and how this technology could be used to generate green energy from garden wastes. Data was collected on thirteen (13) anaerobic digestion technologies which are operating at various scales throughout Europe and Asia to treat solid, non-hazardous waste from residential and commercial sources, with a particular focus on facilities that processed garden wastes as part of their feedstock.

1-1 April 2005


The viability of using these technologies to treat garden waste, or a feedstock incorporating some garden waste was assessed, and a preliminary, qualitative screening process narrowed down the list of 13 technologies to 4 which show promise. Costs were estimated for a greenfield AD facility to process 100,000 tons/year of garden refuse. The economies of scale of constructing a 200,000 ton/year facility were also identified, as well as the cost savings associated with co-locating the AD facility as an existing waste management facility such as a transfer station, MRF, composting or landfill site. The costs of 50,000 ton co-located were identified. While this size of facility has higher capital cost per ton per year installed capacity, the capital investment required is less. Various options to decrease net operating costs were explored and identified. The study draws a number of conclusions and recommends next steps for SMUD.

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2.0 Quantity and Composition of Garden Refuse Available as Feedstock This section discusses the amount and composition of the garden refuse that may be processed at a future anaerobic digestion facility. 2.1 Quantity of Garden Refuse Available The research carried out for this study is based on an available feedstock of about 260,000 tons/year of garden refuse from:

the City of Sacramento (83,000 tons), Sacramento County (104,000 tons), commercial and self haul (70,000 tons), and miscellaneous sources (3,000 tons).

Figure 2.1 shows the tonnages of garden refuse collected and diverted through composting for the City of Sacramento for each month in 2002 and 2003. The table and figure serve to illustrate the significant variation on the amount of garden waste which is produced each month.

Figure 2.1 Garden Refuse Collected

In the City of Sacramento By Month, 2002 and 2003

02,0004,0006,0008,000

10,00012,00014,00016,00018,000

Jan

Feb Mar AprMay

June Ju

lyAug

Sept

Oct Nov Dec

month

tons 2002

2003

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Total Diverted

2002 (tons) 6,526 5,029 5,965 7,212 6,699 6,464 5,366 5,641 5,538 6,153 6,145 16,591 83,3292003 (tons) 5,216 4,307 5,633 8,341 6,059 5,651 5,613 4,964 5,078 6,249 10,831 10,885 78,827

2-1 April 2005


This presents challenges for biological processes such as anaerobic digestion, where a steady rate of loading to the reactors is ideal. However, the loading rate can be equalized through stockpiling of some peak-season materials, and slowly blending these into the feedstock to the units. 2.2 Composition of Garden Refuse Typically, the garden refuse stream consists of a wide range of putrescible material including leaves, grass-clippings, perennial and annual plant material, tree and shrub branches and other woody waste, etc. The City of Sacramento and surrounding areas experience a full complement of seasons which have a great impact on the quantity and composition of their garden refuse stream. Open windrow composting sites which traditionally process garden waste are adaptable to changing waste composition, whereas anaerobic digestion processes require closer operational control to adapt to changing feedstock composition. Seasonality of garden refuse amounts and also the composition of the garden refuse present a challenge in the design of an anaerobic digestion system which must adjust to different feedstock mixtures resulting from the impact of the seasons. In order to better understand the composition of Sacramento’s green refuse, a review of other relevant waste composition studies was undertaken. We did not identify residential waste composition studies from jurisdictions in California and west coast states that provided garden refuse composition and generation information. Either garden refuse specific studies had not been undertaken1 or in the case of the California Integrated Waste Management Board (CIWMB) and the City of Portland, the waste audits targeted residential waste collected in refuse trucks and destined for disposal and focused only on the garbage picked up after recycling or composting programs. Therefore, the results were of limited value to this study. In general, the composition of the garden refuse stream varies by the following seasons:

Spring – high grass clippings; Summer – high garden waste and grass clippings; Fall – high leaf waste; Winter – high woody waste (i.e. tree branches and trimmings).

In the Sacramento area, the spring and summer season is characterized by the generation of mostly tree trimmings and grass-clippings; whereas leaves are generated in the fall, especially late fall (November and December). Few waste composition studies have addressed either the composition of the garden refuse waste stream which is picked up separately from garbage for separate processing and diversion, or its seasonality. Any composition studies identified during the course of this research have to date focused on the garden waste remaining in the garbage stream and do not address the composition of the garden refuse stream itself. 1 Contact with the City of Seattle, the City of San Francisco and Alameda County failed to identify relevant garden refuse composition studies that would be useful for this study.

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The composition and generation information identified cannot be used as a reliable substitute for the City’s garden refuse composition data. Efforts should be made to establish a detailed seasonal breakdown of the garden refuse stream, through garden refuse composition studies carried out on a monthly basis for a 12-month period, to capture seasonal variations. 2.3 City of Sacramento Garden Refuse The City of Sacramento has some unique features that will impact the type and mix of garden refuse received at an anaerobic digestion facility. The City has the second highest number of trees per capita than anywhere else in the world (Paris, France takes top spot). There are an estimated 1 million trees within the City resulting in a large portion (35%) of the residential waste stream comprising of garden refuse. The City has a well established garden refuse diversion program offering separate garden refuse collection since 1953. Most of the leaf and yard waste is collected using vehicle with a “claw”. Residents sweep their yard waste into a bundle at the curb and a vehicle with an articulating claw picks up the green refuse pile and places the material in the back of a waiting city truck. The City is testing a lawn and garden cart service. The City actively promotes backyard composting, grasscycling2 and mulching of yard waste. This practice reduces the amount of grass entering the garden refuse stream, although the extent to which is unknown at this time.

2 The City does not prohibit grass clippings from being collected at the curb at this time.

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3.0 Anaerobic Digestion of Garden Refuse and Municipal Solid Waste This section describes the different anaerobic digestion system design options available, and the key variables involved in choosing an anaerobic digestion system. 3.1 Anaerobic Digestion Process Anaerobic digestion is a naturally occurring biological process that uses microbes to break down organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of organic waste takes place in a special reactor, or enclosed chamber, where critical environmental conditions such as moisture content, temperature and pH levels can be controlled to maximize gas generation and waste decomposition rates. Landfills generating noxious odors are often demonstrations of the impact of organic waste digestion in an enclosed environment with little or no oxygen. However, in the case of anaerobic digestion technology, the gases are captured, so odors are greatly reduced. Commercial anaerobic digestion systems can replicate this natural process in an engineered reactor that produces methane gas much faster (2-3 weeks compared to 30-100 years) then anaerobic conditions in a landfill. One of the by-products generated during the digestion process is biogas, which consists of mostly methane (ranging from 55% to 70%) and CO2 . The benefit of an AD process is that it is a net generator of energy. The excess energy produced by the AD facility, which is not required for in-plant operations, can be sold off-site in the form of heat, steam or electricity. The level of biogas produced depends on several key factors including the process design, the volatile solids in the feedstock (composition of the feedstock) and the carbon/nitrogen (C:N) ratio3. Each of these factors is discussed in more detail below. 3.2 Experience to Date with SSO, MSW and Garden Refuse There are over 100,000 wastewater treatment plants around the world using anaerobic digestion to process biosolids from wastewater treatment operations. More recently, anaerobic digestion systems have been used to treat other biosolids, such as animal manures. At the lower end of the technological scale, anaerobic digestion is used at a household and community level in many developing countries, such as China and India, to generate heating and cooking fuel. Europe is generally considered to be the international leader in commercial AD technology, although their experience with digestion of solid non-hazardous municipal solid waste (MSW) is fairly recent, with most activity taking place over the past decade. Virtually all examples of anaerobic digestion facilities treating municipal waste (source separated organics or mixed waste) are located in Europe, with commercially available technologies implemented primarily in Denmark, Belgium, France, Germany and Switzerland. High capacity systems to treat mixed municipal solid waste have been introduced recently in Spain, Portugal and Italy. Japan also has some facilities. It was estimated that in 1999 European anaerobic digestion plants

3 Hackett, Colin and Williams, Robert. September 2004. Evaluation of Conversion Technology Processes and Products. Prepared for the California Integrated Waste Management Board

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processed about one million tons/year of mixed municipal solid waste (MSW) or source separated organics (SSO) in 53 plants. Figures for 2004 suggest that 107 AD plants are being constructed or processing the organic fraction of municipal solid waste operate worldwide. Most (95%) of these are located in Europe4. Table 3.1 shows key AD companies processing MSW feedstock in Europe in 2003.

Table 3.1 Key Firms Generating Biogas from MSW Feedstock in Europe in 2003

Company Technology Number of Plants Total Capacity (Tpy)

Linde-KCA, Switzerland BRV 205 992,500 Valgora International, France Valgora 11 884,400 OWS, Belgium Dranco6 7 165,000 Kompogas, Switzerland Kompogas 19 274,000 Citec Environmental, Finland Wassa 117 288,500 Source: EurObserv’ER, August 2004 Over the past decade, a number of low tech anaerobic digestion systems have been installed in the North American market to treat animal manures. In 2002, there were an estimated 40 farm-scale projects in operation on swine, dairy, and poultry farms across the United States. These systems use a low-tech approach to anaerobic digestion to process and treat livestock manure and produce gas, which meets some on-farm energy needs. AgStar (a partnership of the U.S. Departments of Agriculture and Energy and the Environmental Protection Agency (EPA) to promote bio-gas projects) estimates that anaerobic digestion could be cost-effective on about 3,000 U.S. farms8 The use of anaerobic digestion technology to treat municipal solid waste has been slow to penetrate the North American market, mostly because of high costs compared to other options. The North American market currently has only two operating anaerobic digestion plants that process municipal waste. Both are located within a one-hour drive of Toronto, Canada. The Canada Compost Inc. (CCI) facility in Newmarket, Ontario (less than one hour north of Toronto) uses BTA technology and has the capacity to process up to 150,000 tons/year of source separated organics and also some mixed waste loads. A second facility located within the City of Toronto also uses BTA technology. It has a throughput capacity of 15,000 tons/year of mixed MSW, or 25,000 tons/year of SSO. A third, two-stage digestion facility was constructed in Guelph, Ontario in the late 1990’s, but closed within the last two years because of financial problems. Currently, there are no pilot or commercial anaerobic digestion facilities operating in the United States that process municipal solid waste or source separated organic waste. In the United States, processing MSW using AD technology experienced a flurry of activity in the early 1980s. Several pilot projects were conducted in Pompano Beach, Florida; Walt Disney World, Florida;

4 Cragg, Robert. Anaerobic Digestion: Can It Be Successfully Applied to MSW Management? Recycling Association of Minnesota and Solid Waste Association of North America 9th Annual Fall Conference, Fall 2004. 5 The Linde figure includes AD facilities processing animal liquid manure; therefore, the number of plants cited do not match those provided in this report which deal only with those facilities processing biowaste. 6 Dranco did not provide figures in the Eurobserv’ER. Numbers have been added from this report. 7 Three of the facilities are demonstration plants or in the conceptual stages, which were not included in this report. 8 Balsam, John. October 2002. Anaerobic Digestion of Animal Wastes: Factors to Consider. Appropriate Technology Transfer for Rural Areas.

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and University of Berkley, California9 In all three cases the organic feedstock was augmented with sewage sludge (biosolids), so that the pilots were actually testing co-digestion rather than pure digestion of MSW. More recently, the City of Greensboro, North Carolina conducted a pilot in 2000 to process 30,000 tons per year of yard waste using anaerobic digestion technology. The yard waste comprised of leaves, grass clippings, plant material and branches. The AD system was designed by Duke Engineering & Services, which invested two-thirds of the required capital, with the City investing the remaining one-third. The team intended to turn the pilot into a full scale system and to show that AD was viable for garden waste. The pilot was not successful and the plant was eventually dismantled10. The system encountered many problems including difficulty maintaining the necessary heat in the reactor to optimize biogas generation; the lignocellulosic material failed to break down and removal of plastic bag pieces in the feedstock created problems. Over the past year, numerous large communities within the United States have entered into agreements to process source separated organic waste using anaerobic digestion technology, are in negotiations with AD suppliers or have undertaken feasibility studies examining anaerobic technology among a range of other “Conversion” technologies to treat municipal waste. Details are presented in Table 3.2 for details.

Table 3.2 Communities in the United States Investigating Anaerobic Digestion for MSW

Community Status Documents City of Los Angeles, California Have entered into agreement with

BioConverter, United States to construct an AD plant to process 3,000 tpd (780,000 t/y) of green waste

Los Angeles Department of Water and Power Board Letter for Approval (available from LADWP)

City of Lancaster, California In negotiations with BioConverter to construct an AD plant to process 200 tpd (52,000t/y) of green waste. The project is waiting Council approval.

None available

City of Seattle, Washington Evaluated 26 food waste anaerobic digestion technologies to determine the feasibility of implementing a facility capable of processing up to 50,000 tpy of food waste

Summary report and supporting documents available from staff “Anaerobic Digestion of Source Separated Food Study: Final Technical Memorandum” Sept 2002

Santa Barbara County, California AD one of a number of conversion technologies evaluated to process municipal solid waste

Study report available “Alternatives to Disposal Final Report” Sept 2003

Linn County, Iowa A study was conducted to analyze the feasibility of anaerobic digestion (AD) of organic solid wastes

Study report available “Anaerobic Digestion Feasibility Study” June 2004

9 SRI International. October 1992. Data Summary of Municipal Solid Waste Management Alternatives; Volume 1: Report Text. Prepared for National Renewable Energy Laboratory, Colorado. 10 Conversation with Ms Covington, Director of Environment, City of Greensboro, North Carolina on December 4th, 2004.

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3.3 Anaerobic Digestion Design Options Most AD technologies use a similar approach to processing organic waste. At the front end of the process, the organic feedstock is blended to reduce the size of the material and is mixed with other materials to optimize digestion in the reactor. The blending process may involve the use of a sieve, trommel screen, chopper, magnet and/or other device to remove contaminants such as stones, metal, glass and plastic from the feedstock prior to the mixing stage. In the mixing stage, the feedstock is mixed with heated water and a starter innoculum to initiate microbial activity. The water is heated using biogas from the digestion process. Mixing with the warm water raises the temperature of the waste to increase the rate and extent of degradation within the reactor. The innoculum is supplied from either the waste stream from the reactor or from the wastewater produced during de-watering. The mixed waste is then fed into the reactor, in which digestion occurs, producing a relatively solid residue and biogas. Enough biogas will be generated to produce a self sustaining energy supply for the facility. Excess energy can be sold in the form of electricity, steam or heat. The solid waste that is produced by the digester is de-watered using a range of dewatering technologies (centrifuges and belt filter presses are the most common). The liquid from the dewatering process is directed to the wastewater treatment system, with some re-introduced back into the earlier digestion steps. The solid produced by dewatering is referred to as digestate. The digestate is at about 50% solids, is most frequently sent to composting for additional stabilization prior to sale as a compost product. In some European situations, the digestate is land applied without further stabilization. The process is illustrated in Figure 3.1.

Figure 3.1 Flow Diagram for Anaerobic Digestion

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Anaerobic Digestion Process

MSW

kitchen and garden wastefeedstock

Source separatedorganic waste and

garden waste

mechanicalseparation

Mixing or Pulping orHydrolysis

Digestion

Digestate

Dewatering

Biogas

Energy- electricity

- steam- heat

AnaerobicDigestion Process

excess energy forsale

Sale

Disposal

Recyclables

Residual

WastewaterTreatment

Composting


The key features of anaerobic design technology are: A. Digestion Stages, characterized as:

- Single Stage - Two Stage

B. Feed Total Solids (TS) Content, characterized as:

- Wet Process (<15% TS) - Dry Process (>20%% TS)

C. Operating Temperature, characterized as

- Mesophilic Process (approx. 93 to 98 °F or 34 to 37 °C) - Thermophilic Process (approx. 131 to 140 °F or 55 to 60 °C)

These features can be arranged in a multitude of AD systems (see Section 3.3 for details) as illustrated in Figure 3.2.

Figure 3.2 Possible AD System Processes

One StageProduction

Wet Process

Mesophilic Process

Thermophilic Process

Dry ProcessMesophilic Process


Two StageProduction

Wet Process

Mesophilic Process


Dry ProcessMesophilic Process


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A. Digestion Stages The production of biogas from organic waste in an environmentally controlled anaerobic digestion system involves a series separate biological processes; acidification and methanogenisis as the prominent processes. In one stage AD systems, both of these biological reactions take place at the same time in a single enclosed reactor. Two stage systems provide a separate reactor for the acidification step and one for methane production. Single Stage Process - European plants that process household organic waste are mostly one-stage systems. A number of two-stage AD systems have been constructed within the past four years. The predominance of one-stage systems is in part due to this technology’s relatively simple design compared to two stage or multi-stage systems, less frequent technical failures and lower capital costs11. In addition, the overall performance of the one stage system measured in terms of the production rate of biogas is comparable to approaches that utilize more than reactor to control biological processes.

r a

Two Stage process – The two stage system is based on the concept that the optimal reactor environment for microbes that produce biogas is one that is separate from environmental conditions for the other microbes that produce the acids and acetates needed for initial breakdown of the organic material. Two stage systems have been used for processing biosolids in wastewater treatment plants for over 50 years, to optimize the environment for “acid forming” and “methane forming” bacteria”. A number of new two stage processes have been introduced, piloted and are now being offered for commercial sale to handle mprocesses feature a front-end percolation process ubreak down the cellulose in the organic material ove

Single Stage AD Process

3-6

11 Vandevivere. P. et. Al. 1999. Types of Anaerobic Digesters for Solid Wa

shorter retention time.

unicipal solid waste. Some multi-stage nder semi aerobic conditions to begin to

Hydrolysis(breakdown of complex organic matter into

sugars and amino acids)

Acidogenesis(material reduced to simple acids)

Acetogenesis(further breakdown of material into acetate,

CO2 and H2)

Methanogenesis(formation of methane and CO2)

HYDROLYSIS and DIGESTER STAGE

Adapted from Ostrem, 2004 and Erickson, 2004

April 2005

stes.


The key advantage of a two stage AD process is that the different processes can occur under different preferred pH conditions. The processes that occur in the first stage, the hydrolysis stage, occur most effectively under acidic conditions (below 5 pH)12. Under these conditions, the methanogenic bacteria (methane formers) would die since they need to live in pH conditions above 6.0, with optimum pH conditions between 7.0 to 7.2 pH13 . These conditions can be achieved in the second stage, the digester stage, in a two stage process. The theory behind

two-stage processes is that optimizing each process will lead to higher gas yield and breakdown of organic matter. However, experience to date with MSW systems is that the additional costs of the extra tankage cannot be justified in terms of the higher gas yield, therefore some companies who experimented with two stage systems in the past have reverted to one stage, or prefer one stage systems.

Two Stage AD Process

First StageHYDROLYSIS STAGE

Hydrolysis(breakdown of complex organic matter into

sugars and amino acids)

Acidogenesis(material reduced to simple acids)

Acetogenesis(further breakdown of material into acetate,

CO2 and H2)

Adapted from Ostrem, 2004 and Erickson, 2004

Second StageDIGESTER STAGE

Methanogenesis(formation of methane and CO2)

B. Total Solid Content The total solid content within an anaerobic digester depends on the type of system employed (wet or dry). Wet System - A “wet” system is designed to process a dilute organic slurry with 10-15% total solids, which has the consistency of soup. This wet slurry is created by adding approximately 30cu ft of water per ton (one cubic metre of water per tonne) to the incoming waste. BTA and Wassa are two examples of wet or low solids digestion technologies.

12 Ostrem, Karena. May 2004. Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University. 13 Vermer, Shefali. May 2002. Anaerobic Digestion of Biodegradable Organics in Municipal Solid Wastes. Columbia University.

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Wet AD systems used to treat municipal solid waste have been adapted from well established systems used to treat wastewater treatment plant biosolids. Despite its established use in the treatment of wastewater biosolids (sludge), the wet system approach has had to overcome a number of challenges to treat municipal solid waste. The production of a wet slurry from mixed residential waste can result in the loss of volatile organics, the part of the organic waste which is required to produce biogas. A wet slurry inside the digestion reactor will tend to separate into layers of material, with a floating layer of scum at the top of the reactor. This can prevent proper mixing, while the heaviest particles will settle to the bottom where they can cause damage to the reactor’s pumps14. “Short circuiting” is another potential drawback associated with wet one-stage systems. This problem occurs when particles of organic waste are removed from the digestion reactor before they have been fully digested. This results in a less than optimal rate of biogas production as segments of organic waste are not processed inside the reactor for the most efficient length of time. Some systems, particularly two stage systems, have reduced the potential for short circuiting through various design modifications. One of the challenges associated with single stage wet AD systems is that the slurry inside the reactor requires frequent mixing in order to reduce the chance of over-acidification, causing a drop in pH and the potential death of the methanogenic bacteria. A number of advances have been made to address this issue. A study by Iowa Department of Natural Resources concluded that “In general, the wet single-step systems are not very well suited for digesting the OFMSW (organic fraction of municipal solid waste) alone. Besides the accumulation of sand and stone sediments in the reactor and a formation of plastic films, a fibrous material has a tendency to form strings that wind around the CSTR’s (continuously stirred tank reactor) stirrer”15 Dry Systems - “Dry” systems mix approximately 10 cu ft of water per ton (0.3 cu m per tonne) of incoming waste to produce an organic slurry of 20-40% total solids. Examples of commercially available high solids content dry digestion systems (one stage) include Dranco, Kompogas and Valorga. Dry systems use considerably less water as part of the process than wet systems. This in turn leads to lower energy requirements for in-plant needs, because less energy is needed for heating process water, and for dewatering AD reactor contents. This in turn leads to more energy available for export. Many dry systems use plug flow reactor designs. This approach helps to maintain a balanced organic load inside the reactor by adding partially fermented slurry into the reactor while fully digested residue is extracted. One of the advantages of the single stage dry system is that it can more readily handle contaminants (i.e. stones, glass, plastic, metals) in the process compared to wet systems.

14 Vandevivere. P. et. Al. 1999. Types of Anaerobic Digesters for Solid Wastes. 15 R.W. Beck. June 2004. Anaerobic Digestion Feasibility Study: Final Report. Prepared for the Bluestem Solid Waste Agency and Iowa Department of Natural Resources.

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C. Operating Temperature Commercial AD reactors are generally operated within either mesophilic or thermophilic temperature ranges. Mesophilic Process – An mesophilic AD process operates within a temperature range of 86oF to 95oF (30oC to 35oC), and at an optimal temperature of about 35oC (95oF). The advantage of the mesophilic process is that the bacteria are more robust and more adaptable to changing environmental conditions16. Thermophilic Process – A thermophilic AD reactor operates at an optimal temperature of about 55oC (130oF) and must be maintained at a temperature ranging from 122oF to 14oF (50oC to 65oC) for most effective performance17. The main advantage associated with a thermophilic reactor is that higher temperatures can yield a superior rate of biogas production in a shorter period of time. 3.4 Anaerobic Digestion Technology Designs Available Many AD technologies are available that claim to process municipal organic waste, either as separately collected residential organic waste (including food waste and garden waste) or as part of the municipal waste stream (MSW). Depending on the feedstock and operating restrictions (e.g. energy and water requirements), some technologies may be better suited to processing municipally sourced organic waste than others. Figure 3.3 shows the vendors which supply AD technologies in the different categories discussed above (wet, dry, single stage and two stage).

16 Ostrem, Karena. May 2004. Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University. 17 Ibid

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Figure 3.3 AD Technologies Supplied By Different Vendors

TechnologiesAnaerobic Digestion Process

OWtswbmsf Bho(ri WWwwT

Single Stage Production

Two StageProduction

Wet Process

Wet Process

Dry Process

Dry Process

WaasaLinde BRTBTABioConverterEntec

ValorgaKompogasDranco

Linde BRTAPS (Onsite Pow er Systems)Arrow Bio

BioPercolatISKALinde BRT

ne Stage vs. Two Stage hen processing municipal solid waste, the advantages of separating biological processes into

wo or more reactors do not appear to yield many significant advantages. According to some ources, both single and two-stage systems perform equally well when processing municipal aste in terms of the amount of waste that can be processed on an annual basis and the rate of iogas production. Approximately 90% of all European anaerobic digestion plants that process unicipal organic waste utilize one-stage technologies. The predominance of one-stage

ystems is in part due to this technology’s relatively simple design compared to two-stage, less requent technical failures and lower capital costs.

ioPercolate and ISKA have both recently developed 2-stage systems. These systems both ave a front end separation process to remove non organic materials from the organic fraction f the MSW. The organics are processed through two separate stages, a percolation hydrolysis) stage and a digester stage. The advantage of the two stage approach is the educed retention time (less than 8 days total retention time) due to the introduction of the ntense biological activity in the percolation stage.

et vs. Dry et systems used to process municipal organic waste have tended to be used in combination ith more dilute feedstocks such as animal manures or sewage sludge. Where municipal solid aste is processed along with another feedstock, the process is referred to as co-digestion. his approach is popular in some municipalities in Europe, as it addresses two processing

3-10 April 2005


needs at the same time with the same technology. Approximately 50 of the 90 wet systems in Europe co-digest the MSW with manure18 3.5 Feedstocks and Gas Production Comparatively little information is available on the amount of biogas produced by different feedstocks in an anaerobic digester. The only pure research available at this time is from bench-scale studies carried out by Barlaz for the USEPA19, where the relative contributions of different materials to landfill gas generation (through anaerobic digestion) were measured. Results of this work, which have been used extensively, are presented in Table 3.3.

Table 3.3 Biogas Yield from MSW Materials

Material Moisture (% wt)

Biogas Yield m3/kg of material feed*

Biogas Yield ft3/lb of material

feed Paper Newspaper 0.061 0.98 Cardboard/Boxboard 0.125 1.89 Telephone Directories 0.061 0.98 Office paper 0.178 2.85 Mixed paper

10

0.112 1.80 Kitchen Waste Food 70 0.113 1.82 Yard waste Grass 0.034 0.55 Leaves

60 0.023 0.37

Brush 40 0.067 1.08 Other organic 0.101 1.62 Sources: ICF, 2001 and Hackett & Williams, 2004 The table shows that each material has a different natural moisture content, and yields a different amount of biogas through the digestion process. The amount of biogas produced by each material depends on the percentage of volatile solids available in each material. The volatile solids fraction of each material refers to the biodegradable portion of the solid content of each material, and varies from one material to another. The gas production values shown in Table 3.1 assume a methane yield of 3.52 f3/lb (0.22 m3/kg) VSS (Volatile Suspended Solids). Table 3.1 is most useful for showing the comparative gas yield from different materials under the same degradation conditions. It shows that the comparative gas yield (from most to least) is: 18 R.W. Beck. June 2004. Anaerobic Digestion Feasibility Study: Final Report. Prepared for the Bluestem Solid Waste Agency and Iowa Department of Natural Resources. 19 ICF Consulting. 2001. Determination of the Input of Waste Management Activities on Greenhouse Gas Emissions. Report submitted to Environment Canada.

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Office paper, mixed paper, cardboard and boxboard, Food, Telephone directories and newspaper, Brush, Grass, and Leaves.

Grass and leaves will make up most of the material which would be received at an AD facility processing only garden waste in the Sacramento area. They are the materials which yield the least biogas; therefore most digesters need a certain amount of paper and food waste to increase the gas yield to a reasonable and economic level (see Table 3.4).

Table 3.4 Biogas Yield

Input Digestion Nm3CH4/raw ton Biogas (m3/t) Biogas (ft3/t)

Biowaste + garden waste 50-60 80-90 2,800-3,200

Biowaste + low level of cardboard 65-75 104-112 3,700-4,000 Biowaste + cardboard + garden waste 65-75 104-112 2,700-4,000 Biowaste + cardboard 75-85 112-136 4,000-4,800 MSW 75-90 112-144 4,000-5,100

Typical biogas composition from the anaerobic digestion of source separated food waste is provided by in Table 3.5 and is based on the experience of BTA in Europe and their Toronto facility20.

Table 3.5 Biogas Composition

Biogas Composition Average Minimum Maximum Methane Vol. % 65 52 70 Carbon dioxide Vol. % 35 30 48 Hydrogen sulphide ppm 50 1,800 Total chlorine mg/m3 0.6 0.02 1.2 Total fluorine mg/m3 < 0.1 <0.03 0.2

Table 3.6 provides typical European experience with the production of biogas per weight of food waste processed.

Table 3.6 Biogas Production

Biogas Production m3 /tonne f3/ton

Single Stage Digestion 85 2,720 Two Stage Digestion 95 3,040

20 Source: Seattle reports – Final TECHNICAL MEMORANDUM NO. 4: Biogas Markets, February 2003

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3.6 Energy Uses Biogas produced during anaerobic digestion is primarily composed of methane (CH4) and carbon dioxide (CO2) and some parts/million (ppm) of hydrogen sulfide. The biogas contains approximately 55%-70% methane, is water saturated (100% humidity), and may contain dust particles and siloxanes. Production of biogas from an anaerobic digestion process will vary depending on:

The anaerobic digestion process design chosen, the extent to which volatile solids are converted to biogas (which depends on retention times and reaction temperature, etc. ) and

The volatile solids content of the feedstock, which depends on the composition of the waste sent to the digester; this impacts on the amount of gas which can be produced through microbiological decomposition.

Biogas Utilization Biogas from an anaerobic digester can be used as a substitute for natural gas, either in boilers producing hot water and steam for industrial processes, in combined heat and power (CHP) applications to generate electricity, as well as heat, as a pure natural gas substitute (high-graded for insertion into the natural gas supply), or for more exotic uses such as fueling a fleet of vehicles or as a fuel for fuel cells. Where biogas is used in a boiler, minimal treatment and compression is required, as the boiler is much less sensitive to sulfide and moisture levels in the fuel, and also can operate at a much lower input gas pressure. Where biogas is used for onsite co-generation, a generator of the type used in landfill gas and wastewater treatment plant applications is appropriate, as these generators are designed for digester and landfill gas, and are less sensitive to moisture and sulfides. Compression equipment would be required to boost the gas pressure to the level required by the generator. Biogas can be used as a fuel for vehicles, but significant upgrading is required to produce:

A higher calorific value A consistent gas quality No enhancement of corrosion due to high levels of hydrogen sulfide, ammonia and water A gas without any mechanically damaging particles.

This option is not likely of interest to SMUD, as it simply displaces traditional fossil fuels, rather than producing power from renewable sources. There are many examples in the US where landfill gas (which is similar to the biogas from an AD facility) is used for fuel in a vehicle fleet. An example of using biogas from an AD facility in a vehicle fleet is described in the Kompogas section of Section 4 of this document.

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The methane contained in biogas can also be used as a fuel for fuel cells. This combination produces a pure “green energy” source, as one of the criticisms of fuel cells is that they use traditional fossil fuels as their energy source and are not therefore truly “green”. This option can be considered by SMUD at a future time when fuel cell technology is further advanced and the AD facility is fully functional. Biogas Upgrading If biogas from the AD facility is used in the gas turbine, moisture and hydrogen sulfide must be removed, to minimize corrosion and other impacts on the equipment, which is designed for natural gas use. A boiler is much more tolerant of contaminants such as moisture and H2S than a gas turbine. Biogas comes out of the digester at about 1psi. If used in a gas turbine, it must enter the compression equipment at the same pressure as natural gas, which typically is supplied at 200-250 psi. If used in a boiler, a pressure of 30psi is sufficient. Sulfur Removal An H2S scrubber uses iron to oxidize the sulfide to elemental sulfur, which precipitates out of the gas stream, and thus removes H2S from the biogas. The scrubber reduces the sulfide concentration by over 90%, and a removal rate of up to 99% is claimed by some manufacturers. Sulfur removal is not required if the biogas is used in a boiler. An onsite co-generation system may also be able to handle the untreated biogas if the unit is specifically designed for biogas applications (more typically landfill gas or digester gas applications). Carbon Dioxide Removal Removal of carbon dioxide enhances the energy of the biogas either to reach vehicle fuel standard or natural gas quality. At the present time, there are four methods used commercially:

water scrubbing polyethylene glycol scrubbing carbon molecular sieves membrane separation.

At this time, it is contemplated that SMUD will not embark on biogas applications which would need CO2 removal, because as less technically complex options are available to meet their renewable energy production needs. Moisture Removal Moisture removal is required for transmitting biogas offsite and for use in some gas turbines. A knockout pot can be used to remove liquid water in the biogas by gravity, due to its larger diameter. A desiccant dryer or a dryer that chilled the gas would be necessary for removal of water vapor from the biogas, for transmission of the biogas by pipeline. Neither of these applications is contemplated for any SMUD AD proposals at this time. Utilization of the biogas in a boiler may not require moisture removal. Pressurization To boost the biogas pressure to the 200 psi pressure required at a co-generation unit, a large two-stage compression system is required. If the biogas is used in a boiler, compression of the gas to 30 psi is generally sufficient and necessary for transport of the biogas through a pipeline.

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Compression to 30 psi is also necessary for the gas mixing used by the wet mesophilic digestion technology. 3.7 Anaerobic Digestion of Garden Waste No AD facilities were identified which process only garden waste (100%) as the feedstock. Several Dranco and Kompogas AD facilities have garden waste as the primary feedstock (up to 75%). Suppliers contacted and interviewed for this project responded positively to supplying a system that could handle garden waste only (i.e. Linde, Kompogas, and Dranco). Some of the problems encountered trying to digest garden waste as a dedicated feedstock include:

Establishing optimal nutrient, trace element and nitrogen conditions; Maintaining the heat in the reactor; Attaining optimal biogas yield; Dealing with poor biodegradation conditions of the lignocellulosic materials (woody

wastes). One of the most critical factors for most anaerobic digestion processes is to maintain an optimal carbon to nitrogen (C:N) ratio. The ratio represents the amount of carbon present in the digester contents in relation to the amount of nitrogen present. The optimum C:N ratio in an anaerobic digester is between 20 and 3021. In situations where the carbon to nitrogen ratio is high, methanogens swiftly consume the nitrogen resulting in lower biogas production. When the carbon to nitrogen ratio is low, it means that there is an accumulation of ammonia in the AD reactor, and higher pH values (>8.5) are reached22. These pH levels are toxic to the methanogens. (methanogenic bacteria), and can result in failure of the reactor.23 In the case of garden waste, maintaining the carbon to nitrogen balance is highly dependent on the composition of the garden waste. When there is an excess of leaves in the feedstream, the digester gets too much carbon and not enough nitrogen. Nitrogen needs to be added to the digester to increase the nitrogen concentration in the reactor and restore the correct C:N ratio. This is generally done by adding chemicals (e.g. urea) or another feedstock with a high nitrogen content to the digester. Conversely, when there is a high grass content in the feed stream, the digester gets too much nitrogen and not enough carbon. In this case, additional carbon needs to be added to the digester to restore the correct balance. Discussions with AD technology suppliers indicate that a mesophilic process would best suit garden waste since the nitrogen content becomes less of an issue at mesophilic operating conditions. However, the trade off using the mesophilic process is a reduction in the amount of biogas generated. 3.8 References Balsam, John. October 2002. Anaerobic Digestion of Animal Wastes: Factors to Consider. Appropriate Technology Transfer for Rural Areas. 21 Monnet, November 2003 22 Ibid 23 Ibid

3-15 April 2005


Cragg, Robert. Anaerobic Digestion: Can It Be Successfully Applied to MSW Management? Recycling Association of Minnesota and Solid Waste Association of North America 9th Annual Fall Conference, Fall 2004. Erickson, Larry et. Al. August 2004. Anaerobic Digestion – Chapter 7 from Carcass Disposal: A Comprehensive Review. National Agricultural Biosecurity Centre Consortium. EurObserv’ER. August 2004. Biogas Energy Barometer. Hackett, Colin and Williams, Robert. September 2004. Evaluation of Conversion Technology Processes and Products. Prepared for the California Integrated Waste Management Board. Haight, Murray. March 9, 2004. Technical Report: Integrated Solid Waste Management Model. School of Planning, University of Waterloo. ICF Consulting. 2001. Determination of the Input of Waste Management Activities on Greenhouse Gas Emissions. Report submitted to Environment Canada. Lynn, Matt. November 1999. “Live and Times of an Organics Recycling Company”. In Biocycle, vol. 40, pg. 34-39. Ostrem, Karena. May 2004. Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University. R.W. Beck. June 2004. Anaerobic Digestion Feasibility Study: Final Report. Prepared for the Bluestem Solid Waste Agency and Iowa Department of Natural Resources. Remade Scotland. November 2003. An Introduction to Anaerobic Digestion of Organic Wastes. SRI International. October 1992. Data Summary of Municipal Solid Waste Management Alternatives; Volume 1: Report Text. Prepared for National Renewable Energy Laboratory, Colorado. US Environmental Protection Agency (EPA). 1998 Greenhouse Gas Emissions from Management of Selected Materials in Municipal Solid Waste: Final Report. Prepared by ICF. EPA 530-R-98-013. Vandevivere. P. et. Al. 1999. Types of Anaerobic Digesters for Solid Wastes. Wise, Donald L. 1983. Fuel Gas Developments. CRC Series in Bioenergy Systems. CRC Press Inc., Boca Raton, Florida. Valorga International. 2004. Presentation made to the 10th World Congress on Anaerobic Digestion 2004. In Montreal, Canada, August 29th to September 2, 2004. Vermer, Shefali. May 2002. Anaerobic Digestion of Biodegradable Organics in Municipal Solid Wastes. Columbia University.

3-16 April 2005


4.0 Technical Information on AD Technologies - DRY 4.1 Methodology The approach to collecting information for the technical description component of the study was as follows:

The list of 15 AD vendors in the Request for Proposal was used as the starting base for the study research;

RIS in-house files from other AD projects were reviewed; A literature search was carried out at the outset of this study. Reports and articles were ordered and reviewed; A list of 36 AD suppliers in Biocycle magazine was used as a secondary data source. All 36 suppliers on this list were contacted to identify which technologies they represented; More detailed information was requested directly from AD suppliers.

The available written information was summarized and follow-up contact was made with vendors of AD technologies to clarify the written information and to ask the following questions:

- Type of technology (wet, dry, thermophilic, mesophilic one stage, two stage, etc.); - Number of facilities in operation; - Ability of the technology to process pure garden refuse; - Identification of facilities which process garden refuse and % of feedstock which garden

refuse represents; - Requirement for additional feedstock in order to process garden refuse; - Extent to which additional feedstock enhances performance; - Identify all existing plants in operation, which process municipal solid waste (MSW),

source separated municipal waste (SSO) or municipal waste in combination with other feedstocks (location, annual capacity, feedstocks, energy production);

- Expected energy output per ton of waste (scfm biogas and MWhrs of electricity) - Amount and availability of heat or electricity required for operation (parasitic loads) - Infrastructure requirements (power, wastewater treatment); - Land requirements (footprint plus buffer); - Company track record (years in operation); - Warranties; - Parts and service support; and - Lead time required to fabricate equipment.

For all technology descriptions, the information is presented in imperial units used in the United States as well as metric units used in Canada, Europe and Asia, which will enable comparison to other studies and literature, if required. The following two sections are divided into dry AD process technologies, described in Section 4.0, and wet AD process technologies, described in Section 5.0. The AD technologies profiled are summarized in Table 4.1 along with their key features.

4-1 April 2005


Table 4.1 Anaerobic Digestion Technologies Profiled

Technology Facilities Processing Residential Waste Total*

# Capacity

(# of facilities in full operation only) <20,000

(tpy) 20,000 to

50,000 (tpy)

50,000 to 100,000

(tpy)

>100,000 (tpy)

DRY AD FACILITIES Kompogas (Kompogas, Switzerland)

19 full 8 part 15 4 0 0

Dranco (Organic Waste Systems, Belgium)

7 full 6 part 3 3 1 0

Linde (Linde-KCA-Dresden GmbH, Germany)

4 full 1 part 1 3 0 0

Biopercolat (Wehrle-Werk, Germany)

1 full 1 part 1 0 0 0

ISKA (U-plus Umweltservice AG, Germany)

1 full 3 part 0 1 0 0

Valorga (Valorga, France)

10 full 3part 1 2 4 3

WET AD FACILITIES APS (Onsite Power Systems, United States)

0 full 3 neg. 0 0 0 0

ArrowBio (Arrow Ecology Ltd, Israel) 1 full 0 0 1 0

BTA (Biotechnische Abfallverwer-tund GmbH, Germany)

13 full 2 part 4 6 2 1

Waasa (Citec Environmental, Finland)

8 full 5 1 1 1


6 full 5 part 1 2 2 1

BioConverter (Bioconverter, United States)

0 full 2 neg. 0 0 0 0

Entec (Environment Technology GmbH, Austria)

4 full 2 1 0 1

Total 74 full 28 part 5 neg.

33 23 11 7

* full = full operation; part = under construction; neg. = under negotiations

4-2 April 2005


4.2 Kompogas 4.2.1 Description of the Technology Kompogas is a thermophilic process which takes place at 131-140oF (55-60oC). The Kompogas technology uses a plug flow digester with a 15-20 day retention time. The incoming waste is shredded, then sorted to remove contaminants such as plastic and glass. A magnetic separator is used to recover any ferrous metal material ahead of the digester.

Waste goes to a second shredder or a sieve, then to an intermediate bunker, which is used as a storage unit for mixing and regulating the flow to the digester. The shredded waste stays in this tank for 2 days, where it warms up to some extent prior to entering the digester. Water from the dewatering unit is added to the waste in the storage unit, to adjust the feedstock moisture content to 28% dry solids content, 72% moisture content. A piston pump delivers the shredded waste to the digester, which is typically a concrete or steel tank. For a plant which processes 12,000 tons per year, a digester with a capacity of 1 ton is required. A heat exchanger heats the waste from 77-131oF (25-55oC). The waste mass also heats while in the storage unit. The digested waste is dewatered by a screw press to 50% solids content. Management of digestate varies by location.

In the Otelfingen facility in Switzerland, after 2 days, the solid digestate is sent to farmers’ fields for land application without curing. No revenue is received for the digestate. In some regions Kompogas pays for the transportation. The farmers like the structure of the digestate, and spread the digestate with a compost spreader. The Kompogas digestate quality is usually at half the current limits for heavy metals.

Management of press-water also varies by location. For some plants, some of the water from the dewatering process goes back to plant. IN Otelfingen, farmers use the remainder as fertilizer (the N and P content is of value), and some is directed to on-site aquaculture greenhouses.

The Kompogas System

Kompogas have determined that for small plants, the most efficient construction approach is to pre-fabricate steel digesters elsewhere and move them to the site in one piece. The Volketswil digester is 82 feet (25 m) long and 13 feet (4m) diameter. It was welded together in the fabrication shop, and was assembled and moved to the site in one piece (on trucks, by road, at night). For big plants, digesters are made from concrete on site. Kompogas also feels that shop assembly allows better quality control for electro-mechanical equipment. Kompogas have moved to a modular approach for assembly and construction of pre-fabricated units (e.g. containers for control, heating).

4-3 April 2005


4.2.2 Typical Feedstocks Kompogas operates facilities using source separated biowaste (food waste and garden waste combined) as a feedstock. Some plants report biowaste and separate yard waste as feedstock (it is assumed that the two feedstocks are source separated). They also accept commercial food waste from companies such as McDonalds, or companies working in the food preparation business. 4.2.3 Energy Specifications Kompogas uses a rough rule of thumb that biogas production is 3,500 f3 (100 m3) per ton of biowaste input, and up to 5,300 ft3 (150 m3) per ton if there is a high food waste content. The process designs are based on adequate analysis of the expected input material. Table 4.2 identifies the reported energy production, internal use and export energy for selected Kompogas facilities.

Table 4.2 Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected Kompogas

Facilities

Plant Capacity Gas Production

Electric Energy Production

Electric Energy Use For Plant

Energy available for Export

Passau Hellersberg,

39,000 tpy 4,000 ft3/t (115m3/t)

9.1million kWhr 1.6 million kWhr/year

7.5 million kWhr/year

Sample facility 10,000 tpy 3,700 ft3/t (105 m3/t)

2.1 million kWh/yr

0.3 million kWh/yr

1.8 million kWh/yr

Energy usage varies by site. At the Otelfingen site, Kompogas clean the biogas on-site and use it as a fuel in their fleet of cars and trucks. The gas cleaning process is proprietary, and the company have invested heavily in perfecting it. 4.2.4 Infrastructure Requirements Power Usage of biogas for electric energy production needs appropriate equipment to feed the produced power into the local grid. Wastewater from Dewatering Filter Press Kompogas have adopted an approach of directing wastewater from dewatering units to beneficial use. It is stored in a tank for use by farmers and some is also directed to aquaculture greenhouses. This approach was considered preferable to constructing pre-treatment facilities before discharging filter press wastewater to local sewers. This may or may not be viable in the Sacramento area, depending on the location of the AD facility. Other vendors (e.g. Dranco, discussed later) pre-treat the wastewater on-site through either on-site systems (e.g. a small rotating biological contactor - RBC) or add the wastewater to an existing wastewater treatment lagoon processing landfill leachate, which is also a high-strength wastewater.

4-4 April 2005


Land Requirements The footprint for a typical 50,000t/y digester facility is about 3 Acres24, excluding any composting requirements. The Otelfilgen plant in Switzerland processes 12,500 tons per year and requires about 3 Acres (5,000 m2) for its total footprint. It is located in an industrial area with an office building as a neighbor, and reportedly does not experience odor complaints.

Lead Time to Fabricate Equipment Kompogas does not have a local agent in the US and currently handles all North and South American requests from Switzerland. If they were to become involved in a project in Sacramento, they would need to develop a local partnership, preferably with a construction company who is also involved in the waste management business. The equipment would likely be fabricated locally with engineering input from Kompogas designers. 4.2.5 Operations Elsewhere Kompogas have 19 facilities in operation, mostly in Switzerland (8), Germany (8) and Austria (3) and one pilot facility in Kyoto, Japan, with a capacity of 1,000 tons/year, which has lead to the construction of a full scale facility with a capacity of 20,000 tons/year in 2004. Another 8 facilities are scheduled to come on-line in 2004-2005. Three of these are in Switzerland, with the others in Spain, Martinique, Japan and Germany. Table 4.3 lists the full scale Kompogas AD facilities in operation at the end of 2004.

Table 4.3 Full Scale Kompogas Plants

Location Feedstock (Substrate)

Plant capacity Start-up Energy Use

Weissenfels, Germany

biowaste 12,500 2003 Electrical and thermal energy

Bachenbulach, Switzerland

biowaste, yard 4,000 2003 Biogas fed to the national gas network

Oetwil am See, Switzerland


Roppen, Austria biowaste 10,000 2001 Electrical and thermal energy Volketswil, Switzerland

biowaste, yard 5,000 2000 Electrical and thermal energy

Frankfurt, Germany


Alzey-Worms, Germany


Niederuzwil, Switzerland


Braunschweig, Germany

biowaste 20,000 1997

Hunsruck, Germany biowaste 10,000 1997 Electrical and thermal energy Lustenau, Austria biowaste 10,000 1997 Electrical and thermal energy Leesternau, Austria biowaste 8,000 1997

24 Seattle Tech Memo, 2003

4-5 April 2005



Plant capacity Start-up Energy Use

Munchen-Erding, Germany


Otelfingen, Switzerland

biowaste 12,500 1996 Electrical and thermal energy, biogas upgrading, fuel station

Kempten, Germany biowaste 10,000 1996 Electrical and thermal energy Simmern, Germany biowaste 10,000 1997 Electrical and thermal energy Bachenbulach, Switzerland

biowaste 4,000 2003 Electrical and thermal energy, fuel, long distance heating

Rumlang, Switzerland

Biowaste, yard

8,500 1992 Electrical and thermal energy

Samstagern, Switzerland

Biowaste, yard

10,000 1995 Electrical and thermal energy, biogas upgrading, fed to the national gas network, fuel

Planned Kompogas plants, and plants under construction are listed in Table 4.4

Table 4.4 Planned Full Scale Kompogas Plants or Facilities Under Construction


Plant capacity Planned Opening Date

Energy Use

Weiningen, Switzerland

biowaste 12,500 2005 Biogas upgrading, fuel

Jona, Switzerland biowaste 5,000 2005 Biogas upgrading, fuel Lenzburg, Switzerland


Passau, Germany biowaste 39,000 2004 Electrical and thermal energy Martinique, Caribbean

n.a. 20,000 2005 Electrical and thermal energy

Rioja, Spain n.a. 75,000 2005 Electrical and thermal energy Kyoto, Japan n.a. 20,000 2004 Electrical and thermal energy Dietikon, Germany biowaste 10,000 2005 Electrical and thermal energy

4.2.6 Company Standing Kompogas is a Swiss company which is an off-shoot of a construction company. The AD division has developed an anaerobic digestion technology which is about 10 years old. Kompogas have 19 AD plants in Europe; 10 in Switzerland, 8 in Germany and 3 elsewhere, and one pilot plant in Japan. The list includes 5 plants which they own and operate themselves around Zurich airport. These 5 plants allow easy access to show prospective clients. To date the company has invested US $25.3 million (30 million Swiss Francs) in the business, and have learned how to do things more efficiently as time has passed. They traditionally spent US $ 8.4 million (10 million Swiss Francs) to construct their early plants, which can now be constructed for about half of that amount. The cost savings have been achieved through a more modular and pre-fabricated approach, and building as much of their digesters outdoors, to avoid the need for construction of explosion proof buildings and fixtures.

4-6 April 2005


Kompogas has agents and licensing arrangements with companies in Austria, Germany, France and Japan. Current Licensees are identified on the Kompogas web site. The North and South American markets are currently serviced through their head office in Switzerland. The Austrian office is the agent for Russia as well as Eastern Europe, and the French agent serves Spain, Portugal and the UK.

Kompogas prefer to make arrangements for local licensees rather than try to enter new markets themselves.

4.2.7 Descriptions of Some Kompogas Facilities Kompogas Otelfingen Facility The Otelfingen Kompogas facility was constructed in 1997. Located near Zurich airport in Otelfingen, the plant processes about 13,000 tons per year of source separated organic waste. The waste comes from both households and commercial operations (e.g. food waste from McDonalds).

Three people work at the plant 5 days/week, 8 hours/day. At the weekends, one person looks after the 5 Kompogas plants in the area. There is an alarm system which alerts the operator to any problems at a specific location. The waste processed at the plant consists of 70% source separated organic waste (garden and food waste) from a population of 100,000 in small cities and villages near the plant. About 70%-80% of the household waste is garden waste and 20% is food waste. Thirty percent of the incoming waste is commercial waste (e.g. from companies who make salads for McDonalds). McDonalds also delivers boxes of french fries and other expired foods to the facility.

Two engines (180kW and 110kW) generate power on-site. Twenty five percent of the energy is required for in-plant needs; 75% is surplus energy which is sold or used for other purposes (e.g. fuel for fleets). Kompogas receive no revenues for the digestate, they receive all of their revenues from tipping fees and energy sales. They receive electricity revenues of US $0.13 (0.16 Swiss Francs) per kWhr (required by Swiss law for renewable energy), and this energy is sold into the local grid. Some of the biogas is cleaned up and used in the Kompogas car and truck fleet. Filter press effluent is directed to an aquaculture greenhouse. This facility was funded 50% by Kompogas, and 50% by the Swiss government. Schools got involved in doing research at the AD facility, figured out aeration rates for water hyacinths, etc. Volketswil Kompogas Facility, Switzerland The Volketswil AD facility is located at a composting site, and was constructed to solve an odor problem at an existing open windrow composting site. The government instructed the owner to install an AD facility to process critical components of the waste stream (mostly wet food wastes).

4-7 April 2005


The tipping fee at the open windrow facility is US $108 (128 Swiss Francs) per ton; this tipping fee was raised to US $125 (148 Swiss Francs) per ton to cover the costs of adding the AD facility. The AD facility cost US $2.1 million (2.5 million Swiss Francs) for equipment and buildings; it has a 5,000 t/year capacity. The digestate is directed to on-site curing in the open windrow composting area adjacent to the digester. The total site (composting plus AD) has a capacity of 15,000 t/year. The digester is made of plain steel with a thin aluminum coating covering the thermal insulation. The steel does not need to be stainless, as no corrosion occurs because there is no oxygen inside the AD tank. Mixing and storage are core parts of the fermentation process; these operations take place inside a building, but the digestion takes place outdoors. Where digesters are located within a building, all fixtures and the building itself have to be explosion proof; locating the digesters outdoors saves money. There is enough heat available within the digester contents to keep the digester at the right temperature, even in the cold winters in the area. This installation has proven that outside installation is viable in cold climates. Kompogas tried to sell the heat from the Volketswil facility, but this received much lower revenues compared to electricity. Local farmers help themselves to the wastewater produced from dewatering digester contents. This wastewater is stored in a tank on-site – no data are available on the impact that this liquid has on crops but farmers like the effluent because it contains nutrients in liquid form at no cost.

4-8 April 2005


4.3 DRANCO 4.3.1 Description of Technology DRANCO is a dry, thermophilic, single stage anaerobic fermentation process, followed by a short aerobic curing phase. During the AD phase, the organic material is converted into biogas in an enclosed vertical digester capable of treating a wide range of incoming material with a solids or dry matter content from 15% to 40%. Steam is injected into the incoming waste stream to raise its temperature to 122oF (50oC) before introduction to the digester. The steam adds moisture to the incoming feedstream, and Dranco have found that steam provides very efficient heat transfer. The process operates with minimal addition of water and is quite flexible in its feedstock requirements.

The Dranco System

Digestion takes place in the thermophilic range of 122-131oF (50-55oC). Incoming feed material is fed to the top of the digester once per day. Mixing of digester contents occurs via re-circulation of the materials extracted at the bottom of the digester, mixing with fresh wastes (usually one part fresh wastes for six parts digested wastes), and pumping the material to the top of the digester. Apart from feeding and removal of the digestate, there is no further mixing or agitation needed in the digester, which works at very low pressure (less than 50 mbar). There is no internal mixing equipment within the DRANCO digestion tank; this simple process design ensures that there is little wear and tear on the digester and has proven effective for treatment of wastes ranging from 20% to 50% TS (total solids) range. The reactor retention time is between 20 to 30 days, and the biogas yield ranges between 2,800-4,200 ft3 /t (80-120 m3/t) of waste feedstock. The collected biogas is sometimes stored temporarily for further purification before it is sent to gas engines or combined heat and power (CHP) facilities.

The digested material is extracted from the bottom of the digester. It is then dewatered to a total solids (TS) content of about 50%, and is stabilized aerobically for a period of about two weeks. The Humotex solid composted product is used as a soil conditioner, and can be purchased by soil blenders, landscapers or consumers. Some composting operations bag and mix their own products for sale to market; others have long standing arrangements to sell their compost to well established soil blenders. The finished compost contains some plant nutrients (nitrogen, phosphorus and potassium) but its main advantage is as a soil conditioner rather than as a fertilizer. DRANCO has also developed the SORDISEP-process which can be used prior to and after DRANCO digestion to recover metals and other materials from mixed waste (garbage). In the dry sorting step, the high-calorific fraction of the incoming waste stream (generally mixed municipal waste or grey waste) is separated for production of a Refuse Derived Fuel (RDF), and ferrous and non-ferrous metals are recovered. A wet separation step after digestion recovers sand, fibers, and inert material.

4-9 April 2005


4.3.2 Feedstock Specifications DRANCO digesters can digest a feedstock which is 100% garden waste, but operators prefer to have some food and paper in the waste stream also, in order to increase gas yield. The gas yield from pure garden waste is about 2,500-2,800 ft3/t (70 to 80m3/t), and is about 3,500-4,200 ft3/t (100 to 120 m3/t) for biowaste (a mixture of garden and food waste). The Brecht 2 Dranco plant in Belgium operates on a feedstream of 75% garden waste with the remaining 25% made up of food, diapers and paper. Woody materials do not contribute to gas production; therefore, they are removed from the feedstock ahead of time, or kept separate (if collected as brush) rather than using up digester capacity. The most critical factor for the Dranco process, as with other digestion processes, is to maintain the carbon to nitrogen (C:N) ratio in the optimal range. When there is an excess of leaves in the feedstream, the digester gets too much carbon, and nitrogen needs to be added to the digester (usually as urea); when there is a high grass content in the feedstream at certain periods of the year, there is too much nitrogen in the system and carbon needs to be added as wood chips to ensure optimal digestion conditions. 4.3.3 Energy Specifications Biogas consists of methane and CO2. The methane content of the biogas is about 55%, therefore biogas production needs to be converted to energy content. The DRANCO process uses a small amount of the energy from the gas (or imported energy) for in-plant needs, therefore the net energy available for export is what is of greatest interest in this analysis. Available information on net energy exports from existing DRANCO plants is summarized in Table 4.5.

Table 4.5 Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected DRANCO

Facilities

Plant Capacity Gas Production

Energy Production

Energy Use For Plant

Energy available for Export

Kaiserslautern 20,000t/y grey waste

5,600 ft3/t (158m3/t)

5.2 million kWhr

0.7 million kWhr

4.5 million kWhr

Aarberg, Switzerland

13,500 tpy garden waste

520MWhrs electricity

Steam: 1120 MWhr generated; 719 MWhr used internally; 401 MWhrs sold to next door customer Electricity: 2400MWhrs sold

The Aarberg plant produces anywhere from 2,800-5,300 ft3/t (80-150 m3/t) of biogas, with an average typical value of 4,200-4,700 ft3/t (120-130 m3/t). The Aarberg plant produces 1,120 MWhr of steam at 110 degrees C, most of this is used in the plant (719MWhr). Some is exported to a neighboring business.

4-10 April 2005


4.3.4 Infrastructure Requirements The Aarberg facility operates with 2 staff plus one manager. Wastewater produced on-site is pre-treated in a RBC (rotating biological contactor) to reduce the pollutant load to a value suitable for discharge to the local sewer. Other DRANCO facilities are located adjacent to landfills, and treat wastewaters from their facilities in the landfill lagoons. 4.3.5 Operations Elsewhere Dranco has run seven (7) demonstration facilities in Europe and Japan, and one small facility in Florida in 1989. These are listed in Table 4.6.

Table 4.6 DRANCO Demonstration Plants

Location Feedstock (Substrate) Volume of digester

Year Constructed

Gent, Belgium Mixed garbage and biowaste 2,100 ft3 (60 m3)

1984

Bogor, Indonesia Market waste 1,100 ft3 (30 m3)

1986

Florida, USA Mixed garbage 35 ft3 (1 m3)

1989

Graz, Austria Mixed garbage 180 ft3 (5 m3)

1990

Kagoshima, Japan Garbage and manure 1,100 ft3 (30 m3)

1998

Yaku Island, Japan Biowaste and manure 1,100 ft3 (30 m3)

2001

Graincourt Les Havrincourt, France

Grey waste and miscellaneous 530 ft3 (15 m3)

2004

There are six full scale Dranco facilities in operation at this time:

2 in Belgium (Brecht 1 is no longer operating), 1 in Austria, 2 in Germany, and 2 in Switzerland.

Most of the existing facilities are in the 10,000 to 20,000 tons/year size range. The Brecht 2 facility is the largest of the existing plants at 50,000 tons/year. Each plant incorporates design features which improve on previous efforts, hence the Salzburg plant incorporated a number of features identified through the operation of the Brecht 1 plant, etc. Full scale DRANCO plants are listed in Table 4.7.

4-11 April 2005


Table 4.7 Full Scale DRANCO Plants


Plant Capacity

tpy

Year Constructed and First Year of Operation

Brecht 1 Brecht, Belgium near Antwerp

Biowaste and paper waste

20,000 July 1992 Ceased operation by Nov 04; Brecht 2

has replaced

Brecht 2 Biowaste and waste paper

50,000 January 2000

Salzburg, Austria

Biowaste 20,000 Dec 1993

Bassum, Germany

Grey Waste 13,500 June 1997

Aarberg, Switzerland

Biowaste 11,000 January 1998

Kaiserslautern, Germany

Grey waste 20,000 January 1999

Villeneuve, Switzerland

Biowaste 10,000 February 1999

Rome, Italy Originally designed for mixed waste, converting to

biowaste

40,000 July 2003

Planned DRANCO plants, and plants under construction are listed in Table 4.8. There are 8 plants in process (3 in Germany; 3 in Spain; 1 in Italy and 1 in South Korea). The trend is moving towards 40,000 t/year plants in Europe. Dranco provide this capacity through modular designs. Pusan, South Korea plan to construct a 75,000 tpy plant.

Table 4.8 Planned DRANCO Plants


Plant Capacity tpy

Planned Year of Operation

Leonberg, Germany

Biowaste 30,000 Planned for 2004

Hille (MBA Pohlsche, Heide)

Grey waste and dewatered sludge

38,000 Planned for 2005

Terrassa, Spain (near Barcelona)

Biowaste 25,000 Planned for 2005

Munster, Germany

Grey waste and industrial waste


Pusan, South Korea

Food waste and paper sludge


Vitoria, Spain Mixed waste 20,000 Planned for 2006 Alicante, Spain unknown unknown Not constructed; being

retendered

4-12 April 2005


4.3.6 Company Standing Organic Waste Systems (O.W.S) developed the DRANCO process (Dry Anaerobic Composting). The company was established in 1988 and is publicly owned and traded under Belgian law. The first Dranco Facility (Brecht 1) opened in 1992 with a capacity to process 20,000 t/yr of source separated organic waste and paper waste. O.W.S. has also developed the SORDISEP-process (Sorting, Digestion and Separation) for municipal and industrial waste, to recover recyclables and energy. OWS also has a laboratory and material testing business in the US, based in Dayton, Ohio. For this reason, staff from the Belgian operation travel to the US a number of times per year. 4.3.7 Short Descriptions of Full Scale DRANCO Facilities in Operation Aarberg, Switzerland At Aarberg, Switzerland there was an existing open windrow composting site for garden and food waste which experienced odor complaints. The owner needed to solve the odor problem associated with the wet fraction of waste being delivered to the site. The local municipalities of Biel, Grenchen and others produced 20,000 tpy of “wet fraction” waste (a combination of food and garden waste). They decided to build a 11,000 tpy digester to handle the wet fraction of incoming biowaste and send the remainder of the incoming bio-waste directly to the open windrow composting facility. This approach provided additional processing capacity and has solved the odor problems at the site. The site receives 50-60 t/d, 5 days per week. Incoming waste is crushed to 1.6 inches (40mm) maximum size, followed by magnetic separator to remove any metals. The waste is then sent to a dosing unit (intermediate hopper), and from there to a loading pump, which is a heavy duty piston type, also used in the concrete industry. The carbon content of the incoming waste is 30% to 35%; it has a low organic content (65%), and an average moisture content of 37.5%. The incoming waste is heated to 131oF (55oC), using steam exhaust from the motor – steam injection provides very efficient heat transfer and provides good temperature control, and is one of the unique elements of the DRANCO system. A small amount of the steam condenses during the heat exchange process and adds to the moisture content of the material going to the digester. DRANCO have found that heat transfer is more efficient with steam rather than using hot water. At Aalberg, 7 parts of recirculated material are mixed with 2 parts of fresh material and one part of steam to provide heat and increase the temperature of the feedstock to the digester. The incoming material is loaded into the digester at three points at the top of the digester to maintain plug flow. The retention time is 18-20 days, maximum 25 days. The digester contents are at 18% to 35% solids; the ideal is to keep digester contents as “dry” as possible, but no drier than 40% solids. Gas is burned directly in a gas motor to generate electricity at the site. There is gas storage capacity of 13,400 ft3 (380 m3) at the site, and a flare to burn the biogas if the motor is down. Steam from the gas motors is used to heat incoming material.

4-13 April 2005


Digested material is sent to a filter press at 18% to 20% solids for dewatering to 48% to 50% solids. The same trucks which deliver the waste take the digestate back to the aerobic open windrow facility where it is stabilized and further cured through 2-3 weeks retention at the aerobic facility. The aerobic compost is given to farmers at no cost, because other revenue sources are sufficient for the facility. Filtrate from the filter press is treated in a rotating biological contactor (RBC) before discharge to the local sewer which take it to the Lyss WPCP (water pollution control plant) for further treatment in a conventional activated sludge system.

4-14 April 2005


4.4 Linde - DRY Linde-KCA-Dresden GmbH based in Germany and Linde BRV Biowaste Technologies AG based in Switzerland are fully owned subsidiaries of Linde AG, Germany. The companies supply both anaerobic and aerobic organic waste treatment systems. Linde-KCA-Dresden GmbH has been supplying biological wastewater and sludge treatment systems since 1973 and opened its first manure processing AD facility in 1985. Linde BRV Biowaste Technologies AG was founded in 1981 (formally known as BRV) and introduced the first manure AD system in Europe. In 1999, BRV became a subsidiary of Linde. 4.4.1 Description of Technology Linde offers a range of different systems, including anaerobic digestion, aerobic systems and comprehensive mechanical-biological treatment systems (MBT) for MSW (municipal solid waste). There is an increasing interest in MBT systems in the last two to three years in the UK and Europe, as it avoids the need for households to source separate organic and recyclable materials from the waste stream. The biological treatment of wastewater and sewage sludge has been part of Linde’s range of services since as early as 1971. Linde started pursing anaerobic digestion for solid waste in 1980. Linde offer a complete range of AD systems, including both wet and dry digestion systems. Linde AD systems operate as single or two stage (wet) systems or as single stage (dry) processes and use both thermophilic and mesophilic digestion processes. The design of the system depends on the feedstock conditions and other factors. The dry system is described in this section and the wet system is described in Section 5.0 of this report. Dry AD System The dry AD system can treat material with a dry matter total solid (TS) content between 15-45%. The horizontal plug flow reactor uses agitators to prevent formation of floating scum and settlement of material. The organic material is fed into the digester/reactor by a compact feeding unit, which can be used to adjust the total solid content, if needed. The digested solid material is dewatered in a centrifuge and aerobically composted using a variety of approaches ranging from tunnel composting to an intensive composting module. The dry AD system is well suited to treat MSW.

4-15 April 2005


Linde Dry System

4.4.2 Feedstock Specifications

Linde state that their dry AD technology is well suited to handle organic waste, green refuse, and waste high in total solids content. Examples of existing facilities that process organic waste (including garden waste) alone or in combination with other feedstock using a dry AD system design are provided in Table 4.9.

Table 4.9 Feedstocks of Linde Dry Digestion Facilities

Location Feedstock Tons/year

Start-up Operations

Baar, Switzerland SSO – 6,000 tpy Garden – 12,000 tpy

1994 - batch process - 1 digester

Heppenheim, Germany SSO – 26,000 tpy garden waste – 5,000 tpy industrial waste – 2,000 tpy

1999 - thermophilic

Lemgo, Germany SSO – 34,000 tpy garden waste – 6,000 tpy

2000 - batch process - 3 digester - thermophilic

SSO – source separated organic (biowaste or food and garden waste with non-recyclable papers) 4.4.3 Energy Specifications

One source estimates that the Linde technology used to treat MSW yields biogas of 3,500 ft3/t (100 m3/t) feedstock25. Table 4.10 shows the energy production and energy outputs for selected Linde dry facilities. 25 Ostrem, Karena. May 2004. Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University.

4-16 April 2005


Table 4.10 Energy Production for Selected Linde Dry AD Facilities

Location Capacity tpy

Energy output

Dry System Baar, Switzerland 18,000 Biogas = 3,000 ft3/t (85 m3/t)

Gross electricity production – 640,000 kWh Lemgo, Germany (thermophilic)

40,000 Biogas = 3,600 ft3/t (102 m3/t) Gross electricity production – 6,000,000 kWh

4.4.4 Infrastructure Requirements Because the company offers a variety of AD technologies and waste treatment solutions, the infrastructure requirements vary by facility and plant location. 4.4.5 Operations Elsewhere Linde report that they have about 100 AD operational facilities in Europe that handle organic waste as well as sewage sludge and animal manures. Over the past two years, Linde has constructed 20 new biogas facilities in Europe. The company has been actively involved in mechanical-biological waste treatment facilities to process municipal solid waste, recently announcing several mechanical-biological treatment (MBT) ventures. Existing and proposed facilities that deal with organic wastes (including green waste) separated or as part of the municipal solid waste stream are identified in Table 4.11.

Table 4.11 Existing and Proposed Linde Dry AD Facilities


Feedstock Start-up Additional Information

Baar, Switzerland 18,000 biowaste, garden 1994 - Dry - 2.5 acres (10,000 m2 )

surface - cost US $17.6 million (SFr 21

million ) operation cost SFr 90/tonne

Heppenheim, Germany

33,000 SSO – 31,000, garden – 5,000 industrial – 2,000

1999 - Dry, thermophilic - Retention time 21 days - Gross electricity – 5.7 GWh/yr - Net electricity – 4.0 GWh/yr - Heat 8.8 GWh/yr

Lemgo, Germany 40,000 biowaste 2000 - Dry - 2.5 acres (50,000 m2)surface - cost US $21.3 million (DM 32

million) - operation cost US $117/t (Euro 90/t)

Hoppstadten-Weirsbach, Germany

23,000 Biowaste 2002 - Dry

Lille, France 110,000 SSO – 46,000, garden – 57,000 market waste – 7,000

Under construction

- Dry - Biogas productivity is

expected to be 265 million ft3 (7.5 million m3 )

4-17 April 2005


Lemgo, Germany - The Lemgo facility uses a thermophilic dry horizontal flow design. Some of the reactor heating is done outside the digester using a short heat exchanger, but most heating occurs within the digester walls using a heat exchanger. The feedstock is reduced in size by a screw mill and undergoes a 2 to 4 day period of anaerobic hydrolysis to facilitate inoculation. Before the material from the hydrolysis tank is fed to the digester, it is processed by a calibrator and chopped into smaller pieces. The digester has a retention time of 21 days. The digestate is cured at an aerobic composting site for 30 days As stated earlier, MBT facilities are gaining in popularity for the treatment of municipal waste, as they reportedly can handle an un-source separated waste stream. This simplifies collection for the municipality as all waste can be collected in one truck. Most of these facilities use aerobic composting technology, to break down the organic fraction of the waste stream. Some Linde aerobic facilities under construction or in the planning stages are listed in Table 4.12.

Table 4.12

Linde Mechanical-Biological Treatment Facilities featuring Aerobic Treatment


Feedstock Start-up Additional Information

Leipzig-Crobern, Germany

300,000 MSW Under Construction

- will become Germany’s largest mechanical-biological treatment facility for MSW

- US $89 million (68.5 million Euros) total with US $49 million (38 million Euros) for Linde's technology

Fridaff, Luxemburg MSW Ordered

Linde has not constructed any AD facilities in North America to handle solid wastes materials and do not appear to have any in the planning stages. 4.4.6 Company Standing Linde is a substantial German company with well established anaerobic digestion technologies and processes to treat source separated organic waste as well as municipal solid waste. The Linde Group supplies chemical and gas processing technology, design and installation services through a number of affiliates in the United States.

4-18 April 2005


4.5 Biopercolat The Biopercolat technology, patented by Wehrle-Werk in Germany, is part of a system designed to handle the entire municipal solid waste stream and not just the source separated organic fraction. 4.5.1 Description of Technology The Biopercolat process has been developed to treat municipal solid waste and is referred to as a mechanical-biological treatment (MBT) process. The process is similar to that of the ISKA process, relying on mechanical separation to remove non-organic materials at the front end, and using a percolation method, under slightly aerobic conditions, to treat the organic matter before being processed anaerobically in a digester. Mechanical separation of the non-organic components of the municipal solid waste stream from the organic components occurs first. The organic matter is fed through a two stage, wet, mesophilic biological process. This process involves two stages, the hydrolysis or percolation stage and the anaerobic digestion stage. The hydrolysis or percolation stage is carried out under partial aerobic conditions. Process water is continually percolated through the mechanically agitated (horizontal stirring) device under slightly aerated conditions in a horizontal tunnel. Conducting the percolation process under slighbreakdown of the organic material percolation unit is 2 – 3 days. Atthrough a screw press which separa(which are composted or further pro The liquid from the hydrolysis procmaterial operating as an upflow anof 4-5 days. The total process has is either recirculated within the digewater for the percolation process 4.5.2 Feedstock Specifications

The Biopercolat process is being umunicipal solid waste (MSW), whic

tly aerated conditions has the advantage of increasing the thus reducing the retention time. The retention time in the the end of the percolation process the material is passed tes the liquid (which is fed into the digester) from the solids

cessed).

ess is fed to an anaerobic plug flow filter filled with support aerobic blanket sludge (UASB) reactor with a retention time a retention time of only seven days. Liquid from the digester ster or fed back into the percolator and reused as process

sed in one location, Kahlenberg, Germany to treat unsorted h includes organic waste (food and garden waste). To date,

4-19 April 2005


the technology has been used to process municipal solid waste only. Garden waste is a component of the MSW but not identified as a main component. 4.5.3 Energy Specifications

At the Kahlenberg demonstration facility, which processes 20,000 tpy of MSW, the anaerobic process yielded about 2,500-2,800 ft3 (70-80 m3) of biogas per ton feedstock. The plant operation is self-sufficient in energy with more than one third of electricity available for sale. The digestion process uses about 50 kWh/ton leaving heat for sale up to 200 kWh/ton. The process reportedly generates a biogas containing about 70% methane. 4.5.4 Infrastructure Requirements

As with the ISKA process, the Biopercolat process provides a complete mechanical-biological treatment process to handle municipal solid waste. Screening, shredding and separation processes are used at the front end to separate non-organic from organic waste fractions. At the back end of the process, the “Percotrate” material (digestate material) is stabilized before landfilling or it undergoes an aerobic drying process, patented by Wehrle-Werk called the Percotry process, which enables the dried material to be used as refuse derived fuel. The footprint of the Kahlenberg facility is unavailable. 4.5.5 Operations Elsewhere The first facility to open was a pilot plant located at the landfill site of Kahlenberg, Germany . From 2000 to 2002, the plant became a full scale demonstration facility processing 11,000 tpy of MSW (with a design capacity of 20,000 tpy throughput) from the community of Kahlenberg. The plant was owned by the customer and operated by Biopercolat. In the last four months, Biopercolat has entered into an agreement with Kahlenberg to construct a full scale plant to handle all of the community’s MSW. As with the demonstration project, the full scale plant would be customer owned and operated by Biopercolat. 4.5.6 Company Standing Wehrle-Werk, Germany is a medium-sized company active in the field of waste water treatment, energy and environmental technologies and solutions. Wehrle-Werk has recently ventured into solid waste treatment with its first digestion facility at Kahlenberg, piloted in 1997 using the 'Biopercolat' process. The company has no supplier in North America and would want the customer to facilitate a suitable partnership or consortium with companies that could provide the mechanical installation and environmental qualification requirements.

4-20 April 2005


4.6 ISKA ISKA is a subsidiary of the German power and waste management conglomerate U-plus Umweltservice AG and is the exclusive license holder for the ISKA® Percolation patents. Developed by U-plus Umweltservice AG, the ISKA technology is a relatively new technology that uses a mechanical-biological percolation process to treat municipal solid waste (MSW). 4.6.1 Description of Technology As with the Biopercolat technology, the ISKA technology is designed to manage the entire municipal solid waste stream and not just source separate organic (SSO) component. The first stage of the process involves mechanical separation of the non-compostable components of the municipal solid waste stream from the organic or biodegradable components. Once separation is achieved, the organic fraction is put through a two stage, wet biological process. This process involves two stages, the hydrolysis or percolation stage and the anaerobic digestion stage. In the first stage, separated organic material is fed into the Percolator (horizontal, continuously operating, cylindrical reactor (plug flow), in which heated wash water from the anaerobic digester is sprayed over the organic material. The break down of the organic material occurs under aerobic conditions. The Percolator operates in a semi continuous fashion, accepting fresh material at the front end and removing unwanted solid waste material at the back end on a regular basis. Temperatures are maintained within a range of 113-140oF (40 to 45oC). During this process contaminants such as stones, glass, grit and other non-organic debris are removed using a sand washing removal process. Other compostable solids are passed through a screw press to remove the solid component for composting and the liquid component for anaerobic digestion. The percolation process has a retention time of two (2) days. Liquids from the percolator (process water and liquid removed from the screw press) are fed into an anaerobic digester, featuring a solid and fluidized bed in which the liquid enters the fluidized bed through nozzles at the bottom and flow upward. Bacteria in the upper part of the digester are retained in a packed, solid bed. The solution is recirculated through the digester filter bed with fresh liquid feed from the Percolator. The digester appears to operate under

4-21 April 2005


mesophilic conditions (30 C), although the literature remains very vague about the operating temperature conditions. The biogas is reported to typically contain 70% methane and 30% CO .

o

2 The process wastewater is treated on-site to remove accumulated nitrogen, salts and fine suspended solids using a variety of techniques including ultrafiltration, injection of hot air and reverse osmosis. Once operational, the entire percolation process is water self-sufficient. The remaining solid fraction is composted and used as landfill cover in most countries. Buchen, Germany – The Buchen facility is the first demonstration facility showcasing the ISKA technology and mechanical-biological treatment process. The mechanical separation system features a drum sieve with a mesh size of 3.5 to 6.0 at the front end to separate out the organic fraction of the municipal solid waste stream from plastics, paper, textiles and other contaminants. The mechanical separation process also employs a magnetic belt to remove metals. The organic fraction is then fed to the percolator, a horizontal, continuous feed (plug flow) cylindrical system made of steel. It features a central mixer and a hydraulically powered scraper. Heated water is fed from the top of the percolator and removed through screens at the bottom. Sand and small contaminants are removed using a sand washing system. The retention time in the percolator is two (2) days. The liquid from the percolator is directly fed into the digester along with the liquid produced by the screw press dewatering operation. The screw press dewaters digestate to 60% solids content. The digestate is then composted using an open windrow aerobic process for three weeks. The company claims that the overall process has a retention time of five days (2 days for the percolation process and 3 days for the digester) and produces a comparable amount of biogas as a dry, single-stage digestion system with a 20 day retention time. 4.6.2 Feedstock Specifications

The system is designed to process unsorted municipal solid waste (MSW) but the company claims to have no feedstock restrictions and can process source separated food waste “Processing plants will be designed and fitted to meet specific waste composition qualities in a given location and country in order to achieve the highest degree of commercial and operational efficiency, environmental soundness, and flexibility to respond to changing waste streams or management/disposal decisions over the lifespan of the facility”. To date, however, the technology has been used to process municipal solid waste only. Garden waste is a component of the municipal solid waste but not identified as a main component of the feedstock. 4.6.3 Energy Specifications

According to one source, the technology produces biogas at a rate of approximately 1,400-1,800 ft3/t (40-50 m3/t) of waste, equal to 300 kWh of “primary energy”.26 In its literature, ISKA estimates that the facilities under construction will generate 1,800 ft3/t (50 m3/t) of biogas for MSW. Other sources claim 1,400-2,700 ft3/ton MSW. The lower biogas yield compared with other technologies is probably due to the shorter retention time.

26 MacViro, October 2003

4-22 April 2005


The Sydney facility in Australia is projected to generate 17,500 MWh of electricity annually with a feedstock of 175,000 tpy. The energy characteristics of other facilities is presented in Table 4.13.

Table 4.13 Energy Characteristics of ISKA Facilities

Facility Date of Operation Annual throughput tpy

Energy generation

Buchen, Germany - demonstration

2000 30,000 Biogas – 1,800 ft3/t (50 m3/t)

Buchen, Germany - expansion

2005 (projected)

165,000 Biogas – 291 million f3 per year (8.25 million m3 per year) Electricity gross – 7.6GWh Electricity net – 1.3 GWh

Hellbronn, Germany 2005 (projected)

80,000 141 million f3 per year (4million m3 per year) (information provided

Sydney, Australia 2005 (projected)

175,000 Projected electricity gross – 17,500 MWh/yr

The Buchen facility produces gross electricity of 7.6 GWh annually of which 1.3 GWh is available for sale. Energy is used internally to power the various processes including the percolation process, the digestion process and the incineration process. ISKA is a comprehensive integrated waste management system, and energy production is not its primary objective. Net energy production is low; therefore, the technology will not meet SMUD’s primary objective of energy production and is likely not suitable for SMUD. 4.6.4 Infrastructure Requirements The ISKA technology provides a complete mechanical-biological treatment process to handle municipal solid waste. The anaerobic digestion system is one component of a larger MSW processing system, complete with front end garbage separation system (scalping trommel, magnets), the percolation process (first stage), the digestion process (second stage) and the aerobic composting system. Consequently, the land requirements are much greater than with a simple anaerobic digestion (one stage) system. The ISKA system points to its many advantages including “high mass reduction, minimal space requirements, high level of automation, energy self-sufficiency and low emissions”. ISKA modules are 30,000-40,000 tpy in size with plant size ranging from 75,000 to 200,000 tpy(minimum plant size 75,000 tpy and maximum plant size 200,000 tpy). The supplier states that multiple plants are possible. Land requirements for selected ISKA facilities are provided in Table 4.14.

4-23 April 2005


Table 4.14 Land Requirements for Selected ISKA AD Facilities

Facility Annual Throughput tpy

Area

Buchen, Germany - demonstration

30,000 Area – 1 acre (4,000 m2) Building – 0.3 acres (1,200 m2)

Buchan, Germany - expansion

165,000 Area – 3.5 acres (14,000 m2) Building – 2.3 acres (9,500 m2)

Hellbronn, Germany 80,000 Area – 2 acres (8,400 m2) Building – 1.3 acres (5,400 m2)

Sydney, Australia 175,000 Area – 7.4 acres (30,000 m2) Building – not available

Once operational the percolation process is water self-sufficient. The process is fed by wastewater from the dewatering process and re-condensation of moisture in the exhaust air. 4.6.5 Operations Elsewhere The technology is relatively new with the first demonstration plant opened in 2000 in Buchen, Germany. The Buchen facility is owned and operated by ISKA. Since 2000, the facility has processed 30,000 tpy of municipal solid waste. Success of the process at the Buchen facility has resulted in its expansion to handle municipal solid waste from the City of Ludwigsburg. The expanded facility will be able to handle 165,000 tons of waste per year and is expected to be operational in early 2005. Two new facilities are under construction in Heilbronn, Germany and Sydney, Australia. Both facilities will process municipal solid waste with the Sydney facility likely the largest facility of its kind in the southern hemisphere, with an annual MSW throughput of 175,000 tpy (with the ability to increase capacity to 260,000 tpy). The Heilbronn facility will process 80,000 tons per year. Both facilities are expected to commence operations in 2005. In addition, negotiations are underway with ISKA suppliers and two communities in the United Kingdom, one of which is Lancashire, to construct two new facilities to process municipal solid waste. Operational and planned ISKA AD facilities are identified in Table 4.15.

Table 4.15 ISKA Operational and Proposed AD Facilities

Facility Feedstock Date of Operation

Annual throughput

tpy

Capital Costs

Buchan, Germany - demonstration

MSW 2000 30,000

Buchan, Germany - expansion

MSW 2005 (projected)

165,000 US $52 million ($40 million Euros)

Hellbronn, Germany MSW 2005 (projected)

80,000

Sydney, Australia MSW 2005 (projected)

175,000 US $55 million ($71 million Australia)

4-24 April 2005


ISKA has not constructed any AD facilities in North America that handle solid waste materials and does not appear to have any in the planning stages. 4.6.6 Company Standing ISKA GMbH is a subsidiary of U-plus Umweltservice AG which is one of the largest waste disposal companies in Germany. The patented ISKA technology has been commercially available since early 2000 and has been assigned commercial status in the UC Davis Conversion Technology database.

4-25 April 2005


4.7 Valorga The Valorga anaerobic digestion process is a patent of Valorga International SAS, which is one of the oldest companies involved in anaerobic digestion of residential organic waste. 4.7.1 Description of the Technology The Valorga process is a single stage, dry processing technology that was developed in France and has been used extensively throughout Europe over the past 25 years. The process is designed to treat organic solid waste but some plants (e.g. Amiens, France) handle mixed, unsorted residential waste (garbage). The Tilburg plant (Netherlands) handles separated at source food and garden waste and therefore will be used in this report to describe typical Valorga operating features.

A Schematic of the Valorga System

The Valorga process dilutes and pulps the organic fraction to about a 30% solids content. Transport and handling of the material is carried out with conveyor belts, screws and powerful pumps especially designed for highly viscous materials. This type of equipment is very robust, and consequently, the only pre-treatment necessary is removal of coarse impurities greater than about 1.73 inches (40 mm). A schematic of the Valorga system is provided below. The Valorga digestion process is a semi-continuous, high solid, one step, plug flow type process. The reactors are vertical cylinders and with no mechanical devices in the reactor. This allows the process to operate in high solid conditions without any hindrance to circulation or maintenance of mechanical devices. Mixing is accomplished via biogas injection at high pressure at the bottom of the reactor every 15 minutes. One drawback of this design is that the gas injection ports become clogged and maintenance is cumbersome. Retention time in the Tilburg plant is 20-24 days at a mesophilic temperature of 95-113oF (35-40oC). Average dry matter content in the Tilburg feedstock is approximately 25%-30%. The range of retention times for all Valorga plants is 18 to 25 days.

4-26 April 2005


The Valorga Process The treated material is removed and the digestate is dewatered by a screw press into a fiber and liquid fraction.
The liquid is further treated: sand is removed by a hydrocyclone and suspended solids are later removed by a belt filter press. The Tilburg plant produces about 18,000 tons of compost yearly and testing shows that the compost is high quality. Although contaminant levels are low and the product is of high quality, the operators use it for landfill restoration. RIS staff visited the Valorga Amiens plant in 1992 and noted that digestate from the plant was land spread on nearby vineyards. We do not know if this practice is still in place in 2004.
4.7.2 Feedstock Specifications The Tilburg Valorga digestion system is designed to handle 40,000 tons VGF (vegetable and garden fraction) and 6,000 t paper and cardboard, or 52,000 tpy VGF alone. The VGF consists of 38% kitchen waste and 62% garden waste. Quantities handled vary between 400 and 1,100 tons per week. This variation is due to the seasonal nature of the garden waste. To characterize the waste stream variation, the total solids (TS) and volatile solids (VS) vary between 37-55% and 32-65%, respectively. The high TS and low VS content correspond with the peak production of garden waste. 4.7.3 Energy Specifications Biogas production varies (especially with the ratio of cardboard to VGF material). Average values are about 2,900 ft3/t (82m3/t), though these can be as high as 3,700 ft3/t (106 m3/t) of waste. Expressed in terms of volatile solids feed to the digester, average biogas production is 14,000 ft3/t (400 m3/t) of VS but can be as high as 19,000 ft3/t (550 m3/t) of VS (volatile solids) in winter when there is less woody material. Methane production is in the order of 7,000-8,800 ft3/t (200-250 m3/t) of VS (56%); the remaining 45% is CO2. The biogas is converted or upgraded in the upgrading plant to “natural gas quality”. If the gas is used to produce electricity or steam, there is no need to remove CO2. If it is to be used as compressed natural gas, CO2 must be removed. Some of the gas is used for process heat at the plant itself and the rest is sold to a gas distributor and is transferred to the gas distribution network. Typical average gas yields for different waste input composition for Valorga facilities are provided in Table 4.16.

4-27 April 2005


Table 4.16 Typical Average Gas Yields for Different Feedstock

Input Digestion Nm3CH4/raw ton Biogas (m3/t) Biogas (ft3/t)

Biowaste + garden waste 50-60 80-90 2,800-3,200

Biowaste + low level of cardboard 65-75 104-112 3,700-4,000 Biowaste + cardboard + garden waste 65-75 104-112 3,700-4,000 Biowaste + cardboard 75-85 112-136 4,000-4,800 MSW 75-90 112-144 4,000-5,100

The operation section provides information about the biogas yield for individual facilities. 4.7.4 Infrastructure Requirements A reported 30% of produced electricity is used within the plant; the remaining 70% is available for export. The volume of wastewater discharged is several fold less for a dry plant than for a wet plant, but no specific numbers are provided. Valorga report a space requirement of 3,200-4,300 f2 (300-400 m2) of area for each 1,000 tpy capacity. On this basis, a 50,000t/y plant would need a site of 4-5 acres. Larger plants would need comparatively less space, as common areas such as receiving areas, etc. experience considerable economies of scale as a plant gets larger, and therefore proportionally less space is required for larger plants. However, using the Valorga rule of thumb, a site of 8-10 acres would be needed for a 100,000t/y plant. The land requirements for selected Valorga facilities is presented in Table 4.17.

Table 4.17 Land Requirements for Selected Valorga Facilities

Location Capacity (tpy)

Total Area

Tilburg, Netherlands

52,000 4 acres (16,000 m2)

Amiens, France 93,000 8.3 acres (33,600 m2)

Barcelona, Spain 240,000 17.3 acres (70,000 m2)

4.7.5 Operations The Valorga AD system was first piloted in 1982 in a small facility located in Montpellier, France using municipal solid waste processed in a 180 ft3 (5 m3) digester. The Valorga process reached an industrial scale in the mid 1980s with plants built in La Buisse and Amies, France. The first industrial scale Valorga operating plant was implemented in 1984 in La Buisse, processing 8,000 tons of food waste annually. The average capacity of all plants in place in

4-28 April 2005


2003 was 60,000 tpy, with a total capacity of 884,400 tpy now in place world-wide (an increase of 45% between 2002 and 2003). Valorga AD plants produced nearly 2,800 million ft3 (80 million m3) of biogas in 2003. At present, Valorga operates 11 facilities in Europe, with three under construction as shown in Table 4.18.

Table 4.18 Valorga AD Facilities

Location Feedstock Capacity (tpy)

Start-up Operations

Geneva, Switzerland

SSO (+ green waste)

13,200 2000 - mesophilic - retention time 24-30 days - biogas productivity is 3,900-4,200 ft3/t

(110-120 m3/t) - capital cost US $5,million - gross biogas 286,000 m3 - gross electricity 435,000 kWh - electricity sold 160,000 kWh

Bassano Del Grappa, Italy

MSW (44,000 tpy) & biowaste

(8,000 tpy), sludge (3,000 tpy)

55,000 2004 - retention time 33 days - biogas productivity is 4,500 ft3/t (129

m3/t)

Mons, Belgium MSW (58,000) and biowaste

(37,000)

95,000 2001 - retention time 25 days minimum - biogas productivity is 3,900-4,200 ft3/t

(110-120 m3/t) - output is electricity and heat

Amiens, France MSW 93,000 1988 - retention time 18-22 days - biogas productivity is 5,300 ft3/t - (150 m3/t) - 95% steam (5,500 kW) is sold to

nearby industry (5% used internally)

Varennes- Jarcy, France

MSW 110,000 2001 - output is electricity - retention time 25 days minimum - biogas productivity is 5,500 ft3/t - (154 m3/t) - capital cost US $38.9 million

(30million Euros) (including existing equipment)

Cadiz, Spain MSW 126,000 2001 - output is electricity and heat

- retention time 16-20 days minimum - biogas productivity is 4,600-5,300 ft3/t

(130-150 m3/t) La Coruna, Spain MSW 156,200 2001 - retention time 25 days minimum

- biogas productivity is 5,200 ft3/t (145 m3/t) - output is electricity and heat

Engelskirchen SSO/biowaste 35,000 1998 - retention time 25 days minimum - biogas productivity is 3,500-3,900 ft3/t

(100-110 m3/t) - output is electricity and heat (4,820

tons biogas annually) - capital cost US $7.9 million (6.1

million Euros)

4-29 April 2005


Location Feedstock Capacity (tpy)

Start-up Operations

Frieburg, Germany

SSO/biowaste 36,000 1999 - output is electricity and heat - retention time 25 days minimum - biogas productivity is 3,900-4,200 ft3/t

(110-120 m3/t)

Tilburg, Netherlands

SSO/biowaste (+ garden)

52,000 1994 - retention time 20-24 days - biogas 2,900 ft3/t (82 m3/t) - biogas 106 million ft3/yr (3 million

m3/yr) - 18 GWh energy of which 3.3 GWh used internally and 14.7 GWh sold to gas distributor

- capital cost US $15.6 million (12 million Euros)

Calais, France SSO/biowaste – 27,000 tpy

Fats/oils – 1,000 tpy

28,000 Expected on line end of

2004

- expect to sell 6,500 MWh per yr electricity and produce 4,900 MWh hot water and 3,000 MWh steam per year for use internally

- capital cost US $22.1 million (17million Euros)

Barcelona, Spain MSW 240,000-300,000

Under construction

- output will be electricity - capital cost 52million Euros - retention time 25 days

Hanover, Germany

MSW 100,000 Under construction

- output will be electricity and heat – 4,100 ft3/t (114 m3/t)

4.7.6 Company Standing The French company Valorga International SAS was formed in 2002 by Steinmuller Valorga Sarl. Valorga was initially founded in 1981 as a MSW (municipal solid waste, i.e. garbage) treatment company. The first Valorga process pilot plant was built in 1982 in the company’s home of Montpelier, France. In 1988, the company started the first facility in the world to treat household waste by continuous anaerobic digestion with a high solid content in Amiens, France. Valorga currently runs 13 plants to treat mixed MSW, SSO and grey waste. The company has US agents.

4-30 April 2005


4.8 Wright Environmental Management Inc

Wright Environmental Management Inc was listed as one of the AD technologies to evaluate in this project. Wright Environmental Management Inc. produces an aerobic composting technology, which does not produce the biogas of interest to the SMUD proposal, and therefore could not be considered a primary energy producing technology for this assessment. It could however be considered for the add-on composting stage.

4-31 April 2005


5.0 Technical Information on AD Technologies - WET 5.1 Methodology The approach to collecting information for the technical description component of the study was as follows:

The list of 15 AD vendors in the Request for Proposal was used as the starting base for the study research;

RIS in-house files from other AD projects were reviewed; A literature search was carried out at the outset of this study. Reports and articles were

ordered and reviewed; A list of 36 AD suppliers in Biocycle magazine was used as a secondary data source.

All 36 suppliers on this list were contacted to identify which technologies they represented;

More detailed information was requested directly from AD suppliers. The available written information was summarized and follow-up contact was made with vendors of AD technologies to clarify the written information and to ask the following questions:

- Type of technology (wet, dry, thermophilic, mesophilic one stage, two stage, etc.); - Number of facilities in operation; - Ability of the technology to process pure garden refuse; - Identification of facilities which process garden refuse and % of feedstock which garden

refuse represents; - Requirement for additional feedstock in order to process garden refuse; - Extent to which additional feedstock enhances performance; - Identify all existing plants in operation, which process municipal solid waste (MSW),

source separated municipal waste (SSO) or municipal waste in combination with other feedstocks (location, annual capacity, feedstocks, energy production);

- Expected energy output per ton of waste (scfm biogas and MWhrs of electricity); - Amount and availability of heat or electricity required for operation (parasitic loads); - Infrastructure requirements (power, wastewater treatment); - Land requirements (footprint plus buffer); - Company track record (years in operation); - Warranties; - Parts and service support; and - Lead time required to fabricate equipment.

For all technology descriptions, the information is presented in imperial units used in the United States as well as metric units used in Canada, Europe and Asia, which will enable comparison to other studies and literature, if required. Dry AD technologies were described in Section 4.0. Wet AD technologies are described in this section.

5-1 April 2005


5.2 Onsite Power Systems Inc. Onsite Power Systems, Inc., (OPS), a privately held corporation, acquired the exclusive licensing rights to an anaerobic digester process recently patented by the University of California. This is a two stage, wet, thermophilic process suitable for a wide range of infeed materials. The anaerobic phased solids (APS) technology was created to process high solids waste streams. Recent laboratory and engineering design improvements allow system flexibility for processing high liquids, high solids or a combination of both organic wastes. 5.2.1 Technology Description The APS digester system combines the features of both batch and continuous operations into one biological system. Solids to be digested are handled in batches, while the biogas production is continuous. This allows the solids to be loaded and unloaded without disrupting the anaerobic environment for the bacteria. The OPS design utilizes a hydraulic mixing system in the tanks with no moving or mechanical systems inside the digester tanks (reportedly resulting in a much lower maintenance cost and higher system dependability). A few of the other technologies described in this report (Dranco, Valorga, etc.) also use the same approach.

Tank Drainage System

Water Recirculation from Gasification Tank

Residue Material & Reclaimed Process Water

BiogasBuffer Tank

Water Gravity Fed to Buffer Tank

Hydrolysis 2

APS Phased Solids - Circulation Process Flow

Soil Amendment

BiogasificationReactor

Hydrolysis4

Hydrolysis3

Hydrolysis 1

Solids Separator

Nutrient Enriched Water

A typical APS system consists of a number of hydrolysis tanks (typically four) coupled in a closed-loop configuration with one biogasification reactor tank. The hydrolysis tank(s) processes the organic waste in batches or semi-batches. Each hydrolysis tank is designed to hold a designated quantity of the identified feedstock based on site-specific requirements and

5-2 April 2005


feedstock characteristics. When the specific tank is loaded, it is then filled with water and sealed. Once filled, the tank remains in a sealed condition for a selected number of days, operating at an optimum process design temperature. This procedure enables the first phase of digestion to begin with the hydrolytic bacteria decomposing the feedstock materials and the acetogenic bacteria beginning to generate organic acids that become suspended in the digester liquid. The hydrolysis reactors are operated on different batch schedules so that the biogasification reactor is fed at a constant organic loading rate and therefore is constantly producing biogas. The biogasification reactor is specifically designed to maintain a high density of bacteria in the reactor to achieve efficient bioconversion. Liquid that carries soluble compounds is collected through filters installed in the reactor at three locations. This liquid is circulated intermittently between the hydrolysis tank and the biogasification tank to “feed” organic acids to the methanogenic bacteria. The collected liquid is transferred and distributed over the top of the hydrolysis reactor every 4 hours. The solids being digested are housed in the hydrolysis reactors, while most of the bacteria, especially methanogens, are housed in the biogasification reactor. The bacteria produce a mixture of 55 to 65 percent CH4 (methane) and 35 to 45 percent CO2 (carbon dioxide) resulting in a medium grade methane biogas. Biogas is collected from all the reactors and piped into an engine-generator for co-generation of electricity and heat. The APS digester operates at a thermophilic temperature of 135°F to achieve a high-rate of solids conversion. The solids retention time in the hydrolysis reactor ranges from 3 to 14 days, depending on the degradation rate of the solids. Food waste normally degrades very quickly, requiring a 3 to 5 day retention time. Crop residues such as rice straw are relatively slow to degrade and require a longer retention time of up to 14 days. The digested solid residue from the hydrolysis reactor can be dewatered and further processed into high-quality soil amendment and other agricultural products. When feedstock in the hydrolysis tank has reached the designed retention time, the tank is emptied. The remaining incompletely digested material or “residue” is in a solid form (digestate) or is dissolved in the liquid effluent. The company states that both of these products have value as landscaping fertilizer and other local agricultural applications, however, to date, other companies have not been successful at marketing the liquid fraction. The solid fraction is typically composted and becomes part of the compost marketplace. The company states that the APS digester system overcomes the fundamental obstacle of existing single-phase anaerobic digesters in that it separates the two distinct acids and methane phases into separate tanks or “reactors”, allowing each group of bacteria to thrive in their optimum environment. Separating the two phases provides the best environment, in terms of temperature and pH for each group of bacteria. However, a number of technologies described in this section also optimize digestion through two stage systems (e.g. Linde). Recent experience has shown that the additional cost of separating the AD process into two separate stages is not justified through the additional gas yielded, therefore some systems are tending towards a one-stage design.

5-3 April 2005


5.2.2 Feedstock Specifications The Onsite Systems APS design reportedly enables the processing of various sources of feedstock. The system efficiently digests organic waste streams ranging from process wastewater to high solids materials including “green” waste, bedding materials and food residues. On-Site Systems state that the only limitation in converting the system from a feedstock of 100% garden waste to 100% food waste is the time taken for the bacteria to adjust to the change in their food supply (the incoming waste stream). However, as shown elsewhere in this document, food waste yields higher amounts of gas, because of the different volatile solids and moisture content when compared to green waste. Incoming green waste is typically screened through a trommel (2”-4”) to remove large items like branches, etc. 5.2.3 Energy Specifications During the digestion process, methane is generated primarily in the gasification tank, however, some methane is generated in each of the hydrolysis tanks. The APS system operates at a gas pressure level of less than 1 PSI, and this biogas requires compression prior to its delivery to the power plant. Once the biogas arrives at the gas processing system, it is sent through a gas booster-compressor system and is raised to the required delivery pressure of the power generating plant. 5.2.4 Infrastructure Requirements A 400 tpd (100,000 tpy) facility would require about 2.5 acres (including plant, administration facilities, site, but not any pretreatment screening for yard waste). No other operating data are available. 5.2.5 Operations OPS’s first project was the installation of a 400 kW, dual fuel cell power plant, at the Las Virgenes Municipal Wastewater Treatment Plant completed in November, 2000. This was the first large anaerobic digester fuel project undertaken by OPS, producing electricity from two fuel cells and providing steam heat to the digesters. UC Davis Onsite Power Pilot Digester - In July 2004, OPS received a contract from UC Davis to construct a small scale commercial demonstration digester system to be located on the UC Davis campus at the current pilot digester site. The digester is capable of processing 3 tpd (1,400 tpy) of green waste and food waste. The pre-screened feedstock is augured to the top of a tank with gravity forcing the solids down into a door at the bottom of the tank. The mix water is heated to 180oF first, and is circulated through the tanks using a pump/mixer. In this process, approximately 70% of the volatile solids are digested, and about 65% - 70% of green waste is converted to energy. There are 4 hydrolysis tanks and one biogasification tank. Waste has a 10-day retention time. The hydrolysis tanks are filled to the top and after the ten days a new batch is put through. Digester contents are dewatered using a screw press. The solid digestate is sent to a composting facility to blend with other compost. Only the liquid carrying soluble compounds (organic acids) is transferred into the biogasification tank, and the level of the liquid in this tank is maintained at 5 feet. The hydrolysis and the biogasification tanks are filled with biomedia,

5-4 April 2005


plastic pieces with a high surface area that keeps the inoculants intact and distributes the methanogenic organisms evenly. This avoids stratification of the organisms and results in better gas production. The biogasification water circulates hydraulically and since there are no moving parts in the tanks, there can be no mechanical apparatus failure. Electricity is generated and a heat exchanger is connected to water jackets around the hydrolysis tanks. Excess waste heat is available for other energy recovery and use. In addition to the foregoing facilities, Onsite Power has described a number of other business opportunities currently under development: Grand Central Recycling & Transfer Station, Inc. (GCR), City of Industry, CA GCR has issued a conditional letter of intent to construct and install a 25 to 50 tpd (6,500 to 13,000 tpy) digester system utilizing green and food waste materials, subject to the verification of the digester performance in the UC Davis project. The system will include a complete digester system, gas storage system (designed to store biogas produced during 14 hours per day of non-operation of the recycling facility) and a 350 kW generator system. Construction could begin in July 2005 and is scheduled for nine months. California Energy Commission (CEC) will provide a sole source contract to fund the US $4 million project. CEC will spend US $995,000 over 3 years to test, validate and demonstrate the system. Onsite Power will provide US $500,000 and City of Industry will provide US $2,500,000 towards the project. California State University at Channel Islands (CSU CI) OPS has proposed a green-waste digester system on the campus at the California State University at Channel Islands (CSUCI) in Camarillo California. The plant will process 250 tpd (65,000 tpy) of municipal green waste diverted from Ventura County landfills, and the company states that it will generate enough biogas energy to yield over 3MW. The company states that the project will produce sufficient biogas to provide an energy source to power the existing campus electrical requirements. The project has reportedly gained extensive support from CSU CI, California State University Regents, California Integrated Waste Management Board, and Ventura county agencies. All of the necessary presentations and required permitting issues have been addressed and permits are ready to be issued. A third party review of the financial risks and technical issues was carried out and the report is currently under review. Gill’s Onions, Oxnard, CA The first project for the food processing industry will most likely be established at an onion processing facility in Ventura County. Gill’s Onions has funded laboratory testing of their onion product at UC Davis over the past twelve months. Longer term testing (6-12 months) is required to look at digestion stability of a single source of digester feedstock. This system will use the basic “two-stage OPS digester technology. West Coast Rendering Co., Vernon CA West Coast Rendering (WCR) currently processes 80 tpd (20,000 tpy) of problematic animals (veterinary, zoo animals, slaughter, etc.). WCR’s goal is to make a major paradigm shift in current operations and to use this large material source as feedstock for renewable energy

5-5 April 2005


production. The proposed project will also allow WCR to process BSE or “Mad Cow” suspect materials. WCR has issued a Letter of Interest to pursue this project, are securing project financing and are in the first stages of permitting this project. City of Vancouver, Washington The Solid Waste Division of Clark County Washington and the City of Vancouver Washington has presented a letter to OPS offering the opportunity to own and operate a 30 to 50 tpd (8,000 to 13,000 tpy) digester system. Vancouver and Clark County Washington have provided a commitment to provide the feedstock materials. The Solid Waste Division of Clark County is ready to begin the permitting process. 5.2.6 Company Standing Incorporated as Energy 2000, Inc. in April of 1996, a certificate of name change to Onsite Power Systems, Inc. was issued in October of 1999. In 1998, OPS acquired the exclusive licensing rights to a new anaerobic digester process, patented by the University of California. OPS, along with various engineering and design companies provided engineering and design support for this improved digester process. The companies that participated in the design meetings realized the market potential of the APS technology and offered participation in the demonstration project by sponsoring engineering and design services, installation support, and 70 % of the system’s material. This effort resulted in the construction of an OPS-sponsored pilot demonstration digester system on the UC Davis campus.

5-6 April 2005


5.3 Arrow Ecology Ltd. Arrow Ecology Ltd. is a large scale Israeli environmental engineering company that developed and markets an anaerobic digestion process under the name of ArrowBio. ArrowBio is promoted by an international group of companies and agents. This technology is a mesophilic, two-stage anaerobic digestion technology with front-end wet separation (flotation and settling tank). 5.3.1 Technology Description Mixed waste can be processed directly as tipped from the collection vehicle into a large flotation tank that is filled with bio-process liquid. The waste is then processed in two distinct stages:

(1) hydro-mechanical methodology for separating the non-biodegradable and biodegradable fractions from unsorted or partially sorted municipal solid wastes; and

(2) biological processing of the biodegradable fraction through acetogenic and then methanogenic bioreactors for intensive conversion to methane-rich biogas, water, and organic soil amendment products.

Stage 1: Hydro –Mechanical Separation In this stage, mixed MSW containing biodegradable and non-biodegradable materials is separated through a unique, liquid-based technology, involving gravitational settling, screening, and hydro-mechanical shredding of the waste. Heavy components such as glass and metals settle to the bottom of the tank, are removed and conveyed to a trommel screen that opens any plastic bags. Plastics and other light materials float to the top, while organics remain in suspension. The small fractions are returned to the settling tank. The large fractions go through mechanical and manual separation steps for recyclables (magnet, eddy current separation, hand sorting). Residuals from this mechanical sorting line are then sent back to the settling tank. The light fractions are removed from the tank by a paddle wheel, shredded and run through an inclined trommel screen. The schematic diagram provides an overview of how the system works.

Arrow Bio Schematic

5-7 April 2005


The biodegradable material that remains in the floatation tank then enters the filtration systems to pulverize the material into a watery organic solution. This energy-rich solution contains biodegradable material, organic matter, paper and other substances that can now be treated in the bioreactors. Typically two hydro-separation systems are constructed in parallel for each ArrowBio facility.

The first reactor, with a retention time of several hours, is where complex molecules such as carbohydrates are broken down into simpler fatty acids and sugars. The second reactor is the methanogenic reactor, in which the organics are converted to methane and CO2. The reported effective solids retention time in the reactor is 2-3 months. The actual time that material physically remains in this process element is a fraction of this time. Lime may be added in the process to correct the pH.

Stage 2 – Biological Treatment In the biological reactors section, the organic fluid undergoes another two processes. The first is an acid-forming stage, where separated and prepared organic-rich water enters the acetogenic bioreactors for several hours of preliminary treatment. There, biological hydrolysis splits certain molecules into their component, readily metabolized, parts (e.g. simple sugars and organic acids).

This rich mixture of organic liquid is then transported to the methanogenic reactor (b), for gasification by means of natural fermentation and other biological reactions. This process uses an advanced variant of anaerobic digestion that, with respect to solid waste processing, is unique to the ArrowBio Process. Known as Upflow Anaerobic Sludge Blanket (UASB) digestion, it results in a much faster and thorough degradation of biological materials, producing finished soil amendment products and a methane-rich biogas. UASB digestion is a well-established wastewater treatment process, but its application to MSW digestion is new.

Outputs of the Arrowbio process include biogas, recyclables, digestate, wastewater, and non-recyclable residuals. Two distinct soil amendment products are created; excess culture growths and organic matter that is not easily metabolized. Experience to date suggests that about 20% of the dry biodegradable input weight exits the UASB bioreactor as organic soil amendment products. A 100,000 tpy plant of typical waste would, therefore, contain about 66,000 tpy of biodegradable material, 50% of which is estimated to be water. The plant is projected to produce 14,000 tpy of the two soil amendment products – representing a significant reduction from input weight.

The biogas is collected at the upper part of the methanogenic reactor by means of a specially designed compartment. The gas is re-circulated by a compressor and re-injected into the methanogenic reactor close to its bottom, thus assuring a permanent agitation without mechanical devices. During routine operation, the biogas is also routed out of the system directly to energy generating units such as steam boilers or electrical generators. The biogas can also be stored in separate gas storage tanks or in simple inflatable buffer tanks.

The biological solids material (or sludge) formed in the reactors is drawn off as needed to maintain a pre-set “blanket” height. Two distinct products are produced; excess culture growths and organic matter that is not easily metabolized. The former is formed from the decaying organisms of the biological activity whereas the latter consists largely of the lignocellulose portions of food (e.g. orange rinds), woody fragments and the bulk filler in disposable diapers.

5-8 April 2005


Both products can be dewatered and used as soil amendment. The long solid retention time in the reactors ensure a fully stabilized product, free of pathogenic germs, bacteria, weed seeds, etc. Furthermore, the company claims it is odorless and requires no further processing.

The bio-liquid used in the ArrowBio Process is constantly re-circulated in the system. However, incoming waste contains water so that there would typically be a net export of water from the process.

Wastewater from the UASB bioreactor, upflow is transferred to a settling tank. A portion of the supernatant is transferred as makeup water to Stage 1 of the plant. The remaining portion is transferred to an aerobic tank for polishing, to the degree required for the best off-site use. Water may be stored or used immediately for irrigation or released to the municipal wastewater system.

5.3.2 Feedstock Specifications The ArrowBio Process eliminates any need for prior separation or classification of mixed waste streams. Residential waste is well suited to the processing capabilities of this technology. Variations in material composition can be managed by the technology because at various points it has the capacity to regulate the flows between components. Waste can be received in a compacted or loose form. According to the supplier, the following types of wastes can be treated as received in addition to MSW:

Mixed waste from food courts and restaurants;

Leachate from landfill; Sludge and/or biosolids from sewage and water treatment plants; Industrial organic waste from the paper and food processing industries; Off-spec and expired food wastes; Manures and agricultural residues; Industrial settling tank sludge; Yard waste, grass and other garden trash; Wastewater.

The vendor states that brush and excessive wood would likely not break down quickly enough, but leaves, grass, and other organics would be acceptable. 5.3.3 Energy Specifications ArrowBio claims as demonstrated ability to produce about 15,500 ft3 (440 m3) of biogas from each dry ton of organic matter. The biogas is reportedly 75% methane for each kg of dry biodegradable matter. A typical 100,000 tpy plant would generate about 33,000 tpy of dry biodegradable matter, producing 530 million ft3 (15 million m3) of bio-gas, or about 388 million ft3 (11 million m3) of methane. It is estimated that about 20% of the energy produced by the process is required internally, resulting in an export of 80% of the energy produced. One cubic meter of methane is equivalent to 10 KWh in energy potential. Assuming an efficiency of conversion to electricity of 35%, the potential electrical yield would be about 38,500MWh. Dividing by 8,760 hours per year means the plant could provide about 4.5 MW of electrical power.

5-9 April 2005


Process Consumables The ArrowBio Process is substantially self-sufficient. Methane rich biogas can provide all the energy requirements for operating the plant. City water is not needed, as the process generates excess water derived from the moisture content of the waste. A 100,000tpy plant would produce 33,000tpy of water. Wastewater treatment would be necessary before discharging effluent to a sewer. The wastewater would be of high strength (COD 600 mg/L, BOD 200 mg/L). All input materials required by the process are typically found within the MSW that is tipped at the facility, with the possible exception of the rare requirement to correct an aberrant pH in UASB digestion by adding slaked lime or sodium hydroxide. 5.3.5 Operations Tel Aviv, Israel - ArrowBio has one full-scale operational facility in Tel Aviv, Israel on a 1.5 acre site. It has a capacity of 70,000 tpy of MSW and has been operating since January, 2003, although it does not appear to be operating at design capacity yet (accepts 200 tpd or 51,000 tpy of MSW). The capital expenditure has been cited at US $12-17 million. A demonstration facility of 10 tons per day operated without interruption from 1999 to 2002 in Hadera, Israel. It is no longer in operation. 5.3.6 Company Standing Arrow Ecology Ltd. (since 1991), originally Hydro Power Ltd. (1975) specializes in project management of environmental programs for:

Bio-technological and physio-chemical treatment of wastewater and sludge; Hydro-mechanical systems; and Environmental consulting/planning/laboratory services.

The Company has only one plant in operation although they are pursuing a number of potential business opportunities. The company website notes that the first industrial contract for treating solid waste was signed June, 2001. A 200 tpd plant was scheduled to start in 2002 to process the town of Kfar Saba’s solid waste. There is no further information available as to the current status of that facility.

5-10 April 2005


5.4 BTA 5.4.1 Technology Description BTA (Biotechnische Abfallverwertung GmbH & Co KG) is a multistage, wet anaerobic digestion process primarily designed for the treatment of the organic fraction of municipal solid waste. A single stage process is mainly used for comparatively small, decentralized waste management units. Multistage digestion is mainly used for plants with capacity of more than 50,000 tpy. The BTA process was initially developed in a pilot plant in Garching, Germany to gain experience testing a range of feedstocks and to fine-tune the technology. The process can be operated in mesophilic or thermophilic temperature ranges. The process consists of two major steps: mechanical wet pretreatment and biological conversion. Mechanical pretreatment of the incoming waste separates out contaminants that are not digestible (such as plastics, textiles, stones and metals) by means of a rake and a heavy fraction trap. Biodegradable matter is pulped into a homogeneous suspension with a TS

coth

BTA System

s

m Tbfascth

oncentration of about 10% using re-circulated process water. Blending is achieved by means f an impeller at the bottom of the pulper stirring the mixture. The suspension is withdrawn rough a screen at the bottom of the pulper. The screen retains the coarse, non-digestible aterials. These are eventually extracted by an automated, mechanized rake.

uspension can then be heated to 149-158oF (65-70oC) for at least one hour, killing both

he BTA technology has a unique ability to distinguish and separate digestible matter from non-iodegradables. It is this unique feature that convinced the City of Toronto to construct a BTA cility at the Dufferin Transfer Station in Toronto, Ontario, Canada (described later in this

ection). One of the reasons for choosing the BTA technology was that the pre-treatment step ould reportedly remove plastics from the in-coming waste stream. BTA estimates that 98% of e biodegradable matter is suspended and sent on for digestion in their process. The

5-11 April 2005


pathogens and weeds. Alternatively, pathogen and seed kill can be achieved by aerobically composting the digestate. The BTA process then employs separate, subsequent bioreactors for the digestion of organic matter. Liquid and solids in the pulp are separated in a dewatering device. The liquid (containing all of the readily soluble organics) is immediately pumped into a methane reactor where the dissolved contents are turned into biogas. After 2-4 days, the hydrolyzed suspension is dewatered and the hydrolysis-liquid is also fed into the AD reactor for approximately 3 days. Approximately 60-70% of the organic substances (VS) are turned into biogas within only a few days. The digestion residue is dewatered and, in general, sent to aerobic after-treatment. The water demand of all process types is met by recirculating the process water, which is contained in the waste. Depending upon the waste composition and local requirements, excess water is sent to the sewage system, or will receive additional treatment on-site before it can be discharged.

Energy can be recovered from the generated biogas for use in gas engines or coheat and power stations. Depending on the waste composition, the gas yield ranges between 2,800-4,200 ft3/t (80-120 m3/t) of waste feedstock. 5.4.2 Feedstock Specifications The BTA process is designed to treat organic waste from domestic sources (kitchen scraps, garden waste, paper, diapers, etc), commercial sources (restaurants, hotels, etc.) and agriculture (manure). The system is geared to process MSW organics. Typically, large volumes of green waste delivered to a BTA plant are isolated and used as a bulking agent to assist in composting the digestate. Brown leaves are discouraged since the process thrives on green waste. In addition, woody waste (branches, etc.) cause problems in the pulper since there is no mechanical chipping or material size reduction. 5.4.3 Energy Specifications The BTA process produces between 3,900-4,600 ft3/t (110-130 m3/t) of biogas from every ton of biowaste. This biogas contains 60-65% methane. A 20,000 tpy plant will yield 14-16 million kWh annually, while consuming 1.7 million kWh electricity and 1.1 million kWh heat annually. BTA state that the biogas produced from biowaste or commercial waste is so clean that it can be used to drive gas engines or cogeneration units without further “purification” (treatment or upgrading). In the case of the AD facility in Ypres, Belgium, the 55,000 tpy facility generates 2,400 – 3,900 ft3 of biogas per ton feedstock (67-105 m3/t). 5.4.5 Operations

The BTA process was initially developed by Biotechnische Abfallverwertung GmbH & Co KG in 1986 to treat OFMSW (organic fraction of municipal solid waste) from households, agriculture and commercial plants. The first plant on an industrial scale was built in Elsinore (Denmark) in 1990 with an annual capacity of 20,000 tons. The Elsinore plant eventually closed because of

5-12 April 2005


high operating costs. Thirteen plants are reported in operation using the BTA technology with 4 more under construction. An additional 10 plants use BTA pre-treatment technology but do not digest the waste. Three companies hold site licenses for the BTA process, including Canada Composting, Inc. in Toronto (for all of North America), Hitachi Zosen Co. in Tokyo, and BIOTEC Sistemi S.r. in Italy. BTA CCI Facility in Newmarket, Ontario, Canada The first North American BTA facility was designed for 150,000 tons of waste per year and commenced operations in Newmarket, Ontario in 2000. The facility is situated on 5.4 acres of land and was designed to convert 150,000 tons of incoming waste into 50,000 tons of high quality compost and approximately 5.5 megawatts (MW) of electricity and heat. After plant use of 2-2.5 MW of this energy, the remaining electricity was to be sold as “green energy” to the Ontario power grid. Actual energy production is significantly less than these figures. Initially, only the front end of a two stage BTA process was constructed. A washed, largely undigested pulp, was produced and sent off-site for aerobic composting. The liquid resulting from the pulp dewatering process was digested and did produce a limited amount of biogas. The original business plan called for the construction of a solids digester once the first phase of the facility was on a firm financial footing. In 2002, the facility went into receivership due to odor problems and inadequate tipping fees. The plant was sold in 2003 to Halton Recycling (2003) Inc. Numerous modifications have since taken place to the facility, including enlarging the tipping floor, improving the biofilter and adding a backend Vertical Composting Unit (VCU) aerobic system to treat the pulp. In the VCU system, composting takes place inside modular chambers, 25 cubic meters in capacity. Processing is continuous with washed organic pulp mixed with wood waste amendment being loaded into the top of the chamber and the stabilized product removed from the bottom every day. Aeration is provided by natural convection forces that are accelerated by a fan mounted on top of each chamber (Halton Recycling /International Paper Industries hold a joint marketing agreement with New Zealand-based VCU Technology Ltd to jointly market VCU’s products and services in the Canadian market). The City of Toronto recently signed a contract with HRL to receive a portion of their SSO starting in the fall 2004 and SSO and yard waste from York Region (where the facility is located) is also being processed at the facility. HRL have purchased a 10 acre site near the Newmarket facility and plan to construct enclosed composting to cure the material produced by the BTA facility. The BTA site experienced odor problems in November, 2004, but these were reportedly related to the large volumes of garden waste arriving at the site, rather than related to a process upset. Odor problems have continued in December 2004. BTA Digester at City of Toronto, Dufferin Street Transfer Station Site CCI commissioned a 25,000 tonne per year single stage AD plant in Toronto (at the Dufferin St Transfer Station site). The city issued an RFP in 1997 for facilities to process MSW (municipal solid waste – garbage) and SSO and following the selection of the BTA process and final contract negotiations, construction began in 2001. During construction, the general contractor, Stone & Webster, filed bankruptcy and due to subsequent delays to sort out contract issues and to secure a new contractor, the facility did not begin processing material until September, 2002.

5-13 April 2005


The facility was originally designed to process 15,000 tpy of MSW or 25,000 tpy of SSO, or some combination of each. As a result of the City’s 2010 Task Force Report, the decision was

made to grocery wfacility. Fdesign caComposti SSO is sctransferrealuminumtransferreThe purifidigested pis now p(processinFarms wincuring, antpy. Tippi A listing o

process only SSO generated from the City’s curbside collection activities (mostly aste from the City’s new curbside food waste collection program) at the Dufferin St ollowing a lengthy commissioning period to stabilize the biological process at full pacity, the City assumed control of the plant in May, 2004 although Canada

ng continues to operate the facility under contract to the City.

reened into three fractions by a trommel screen. The small size fraction is directly d to the wet pre-treatment section. From the mid size fraction ferrous metals and are extracted by magnet and eddy-current separation. The remaining part is d to the wet pre-treatment comprising the BTA waste pulper and grit removal system. ed pulp is digested in a mesophilic reactor where it is mixed with infused biogas. The ulp is dewatered and the solids transferred to an aerobic composting site. The facility rocessing between 100-110 tpd over a five day per week operating schedule g about 30% of the City’s current generation of SSO). The digestate is sent to Alltreat drow composting facility in Arthur, Ontario (about 50 miles from the City) for further

d is blended with other feedstocks at the Alltreat site, which has a capacity of 170,000 ng fees paid by the City to Alltreat are not publicly available.

f BTA plants currently operating and under construction is presented in Table 5.1.

5-14 April 2005


Table 5.1 Operating and Planned BTA Facilities

Location Capacity (tpy)

Opening Date

Infeed

Plants Operating With The BTA Process Newmarket, Ontario 150,000 2001 commercial organics Toronto Dufferin 25,000 2002 SSO and commercial organics County of Munich Brunnthal, Germany

24,800 1996 residential SSO

Karlsruhe, Germany 12,000 1996 residential SSO Dietrichsdorf, Germany 20,000 1995 commercial and residential SSO Villacidro (Italy/Sardinia) 45,000 2002 mixed waste incl sewage sludge Mertingen (Germany) 20,000 1998 biowaste/commercial waste Erkheim (Germany) 11,500 1997 biowaste Elsinore (Denmark) (unconfirmed report that facility closed due to high operating costs)

20,000 1991 Closed due

to high costs

biowaste

Ypres (Belgium) 55,000 2003 SSO (+ green waste) capital cost US $27 million (Euro

20 million) Kaufbeuren (Germany)

2,500 1992 biowaste

Leper (Belgium)

50,000 2003 biowaste

Mülheim a.d. Ruhr (Germany) 22,000 2003 biowaste Ko-Sung (Korea) 3,000 2003 biowaste/commercial waste

Plants Incorporating BTA Pre-Treatment Technology Parramatta/Sydney (Australia)

35,000 2003 commercial waste and organic sludges

Verona (Italy) 70,000 2002 mixed waste Pulawy (Poland) 22,000 2001 mixed waste Nara City (Japan) 1,500 2003 food waste Kushima City (Japan)

1,000 2001 commercial waste

Münster 20,000 1997 biowaste Wels (Austria) 15,000 1997 biowaste Schwabach

12,000 1996 biowaste

Baden-Baden

5,000 1993 biowaste

Kaufbeuren 2,500 1992 biowaste BTA Plants Under Construction Alghoba (Libya) 11,000 mixed waste Komoro (Japan) 7,000 food waste

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5.4.6 Company Standing The BTA parent company is located in Germany. A Canadian company, Canada Composting Inc. (CCI) secured the rights to the BTA Process throughout Canada and the United States.

5-16 April 2005


5.5 Waasa, WABIO and Citec Originating from Finland and Sweden, CITEC Environment has been developing the Waasa anaerobic digestion technology for the past couple of decades to treat sewage sludge and later MSW. WABIO is no longer marketed but is very similar to Waasa. 5.5.1 Description of Technology The Waasa technology is considered a single stage, wet system using a thermophilic or mesophilic process (although most Waasa facilities use the thermophilic process). As with other recently evolving technologies, the Waasa system has been designed to treat municipal solid waste in which one component of the overall treatment involves anaerobic digestion. The organic fraction of MSW undergoes pretreatment in a pulper which shreds, homogenizes, and dilutes the material to the desired concentration of total solids (10-15% TS). Recycled process water and some fresh make-up water is used in the dilution. The slurry is then digested in large ‘complete mix’ (completely stirred) reactors. One of the features of the technology is the design of a pre-chamber within the reactor to act as a preliminary stage similar to a two stage system. The pre-chamber enables the feedstock from the pulper to undergo inoculation in order to reduce short-circuiting of the feed (i.e., passage of a portion of the feed through the reactor with a shorter retention time than that for the average bulk material). The pre-chamber uses a plug flow approach, requiring the new feed to move along the pre-chamber over the course of a day or two before reaching the main reactor. Mixing is carried out by injection of biogas at the base of the reactor. A process flow schematic is presented in the figure below.27

Process Flow Schematic for the Waasa System

2

5-17 April 2005

7 Vandevivere. P. et. Al. 1999. Types of Anaerobic Digesters for Solid Wastes.


One of the disadvantages of the system occurs during the pretreatment process (designed to produce appropriate slurry quality while removing contaminants). This pretreatment process is complex and results in a 15-25 % loss of volatile solids, which never make it to digester in order to generate biogas28 . The Waasa process is often confused with the WABIO technology. The WABIO and the Waasa technology, while having fundamental technical differences during their early years of development, are so similar now that the WABIO technology has become obsolete. “After the Waasa-process was modified to thermophilic condition, making the upstream sanitation step on the DBA-WABIO-process somewhat obsolete”29. Both technologies were used on the first MSW treatment facility of its kind in Vaasa, Finland in 1994. 5.5.2 Feedstock Specifications

To date, the technology has been used to process primarily municipal solid waste. Garden waste is a component of the municipal solid waste but is not identified as a main component of the feedstock for any of the plants identified. 5.5.3 Energy Specifications

In general the reported biogas production from the Waasa technology is in the range 3,500-5,300 f3/t (100-150 m3/t) which has a heat value of 200-240 kWh/ft3 (6-7 kWh/m3) biogas. A typical facility processing MSW generates 1,500 ft3/t (42 m3/t) of waste. Table 5.2 provides energy information for selected Waasa facilities. The company reports 20-30% internal use of biogas with the remaining 70-80% available for external use.

Table 5.2 Energy Information for Selected Waasa Facilities

Facility Feedstock Annual throughput tpy

Estimated biogas generation

Vagron/Groningen, Netherlands

MSW 230,000 Biogas – 1,500 ft3/t (42 m3/t) Energy - 48,000 MWh/year (35% electricity, 55% heat)

Pinerolo, Italy MSW and biosolids 30,000 Energy - 30,000 MWh/year (35% electricity, 55% heat)

Vaasa, Finland MSW 15,000 Energy - 9,000 MWh/year (30% electricity, 60% heat)

Friesland, Netherlands MSW 90,000 Energy - 50,000 MWh/year (35% electricity, 55% heat)

Kil, Sweden MSW 3,000 Energy – 2,000 MWh/year (100% electricity)

28 Farneti et al. 1999 29 Seattle Public Utilities, September 2002

5-18 April 2005


5.5.4 Infrastructure Requirements

The suppliers of the Waasa technology claim to accommodate a wide capacity range from 500 to 200,000 tons per year (tpy). Land requirements are not available. Land requirements are specified at 27,000 ft2 per 10,000 tpy (2,500 m2 per 10,000 tpy) feedstock processed. 5.5.5 Operations Elsewhere In 2003, Citec has 8 facilities (see Table 5.3), primarily in Europe, using the Waasa technology to treat municipal solid waste as well as other waste. The facilities had a total processing capacity of 288,500 tons per year. Countries using the Waasa technology include: Scandinavia, Spain, France, Italy, Switzerland, Japan and the Benelux countries of Belgium, the Netherlands, and Luxembourg although not all facilities located in these countries treat MSW. The facilities in Japan treat combined biowaste and biosolids (sewage sludge).

Table 5.3 Waasa Facilities

Location Feedstock (Substrate) Annual Throughput

tpy

Year of operation Features

Vagron/Groningen, Netherlands

MSW 230,000 2000 - thermophilic

Pinerolo, Italy MSW and biosolids 30,000 2003 - thermophilic Vaasa, Finland MSW 15,000 1994 - thermophilic

- mesophilic Friesland, Netherlands

MSW 90,000 2002 - thermophilic

Kil, Sweden MSW 3,000 1998 - thermophilic Jouestsu, Japan Biowaste and biosolids 12,000 2001 - thermophilic Ikoma, Japan Biowaste and biosolids 3,000 2001, status

unknown - thermophilic

Shimoina, Japan Biowaste and biosolids 3,000 2001, status unknown

- thermophilic

Pinerolo, Italy - The Waasa facility in Pinerolo, Italy, has a treatment capacity of 30,000 tons of household waste and produces an estimated 30,000 MWh per year, including 35% in the form of electricity. Vagron/Groningen, Netherlands -The Waasa technology has been used in one of the largest MSW digestion plants in the world, which started operations in May 2000. Located in Vagron/Groningen, Netherlands the facility processes 230,000 tons of MSW in combination with commercial waste per year using four AD reactors, each with a capacity of about 97,000 ft3 (2,750 m3). The retention time for the process is 18 days. Vaasa, Finland - The MSW facility at Vaasa uses both thermophilic and mesophilic processes, running in parallel. The thermophilic process has a retention time of 10 days; the mesophilic design has a retention time of 20 days.

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5.5.6 Company Standing Citec was founded in 1984 and is a group of companies, originating from Finland and Sweden, providing services in information, engineering and environment to international clients. The financial state of Citec is good with annual growth of 20-40% during the last five years and average net profits were 9% during the same period.

5-20 April 2005


5.6 Linde Wet Linde-KCA-Dresden GmbH based in Germany and Linde BRV Biowaste Technologies AG based in Switzerland are fully owned subsidiaries of Linde AG, Germany. The companies supply both anaerobic and aerobic organic waste treatment systems. Linde-KCA-Dresden GmbH has been supplying biological wastewater and sludge treatment systems since 1973 and opened its first manure processing AD facility in 1985. Linde BRV Biowaste Technologies AG was founded in 1981 (formally known as BRV) and introduced the first manure AD system in Europe. In 1999, BRV became a subsidiary of Linde. 5.6.1 Description of Technology Linde offers a range of different systems, including anaerobic digestion, aerobic systems and comprehensive mechanical-biological treatment systems (MBT) for MSW (municipal solid waste). There is an increasing interest in MBT systems in the last two to three years in the UK and Europe, as it avoids the need for households to source separate organic and recyclable materials from the waste stream. Linde offer a complete range of AD systems, including both wet and dry digestion systems. Linde AD systems operate as single or two stage (wet) systems or as single stage (dry) processes and use both thermophilic and mesophilic digestion processes. The design of the system depends on the feedstock conditions and other factors. Wet System A front-end automated separation using a pulper and drum screen removes contaminants in the one stage system. In the two stage system, the pulped and separated waste is sent to a buffer and hydrolysis tank and is then sent to the reactor/digester tank. A gas recirculation unit uses gas injection to recirculate the materials into a centrally located draught tube within the digester.

Linde Wet System

5-21 April 2005


5.6.2 Feedstock Specifications

Linde state that their wet AD technology is particularly well suited to handle organic waste, sewage sludge and manure. Linde wet systems have been used primarily to handle source separated organic waste in combination with manure or sewage sludge. Linde operates several wet AD design facilities throughout Europe for processing source separated organic (SSO) materials in combination with other feedstock, including those listed in Table 5.4.

Table 5.4 Feedstock Used in Linde Wet Facilities

Location Feedstock

Start-up Operations

Wels, Austria biowaste - 15,000 tpy 1996 -Thermophilic Furstenwalde, Germany SSO, industrial waste, agricultural

residues – 85,000 tpy 1998

Sagard, Germany Commercial, SSO, manure – 48,000 tpy

1996

Radeberg, Germany SSO & industrial waste – 15,000 tpy sewage sludge – 41,000 tpy

1999 -Single stage -Mesophilic -Co-digestion

Dunkirchen, France SSO, industrial waste, sewage sludge – 24,000 tpy

2004

Barcelona, Spain MSW – 325,000 tpy 2001 -Mesophilic SSO – source separated organic 5.6.3 Energy Specifications

Table 5.5 provides energy outputs from different Linde AD systems that have processed municipal organic waste. One source estimates that the Linde technology used to treat MSW yields biogas of 3,500 ft3/t (100 m3/t) feedstock30.

Table 5.5 Energy Outputs from Selected Linde Wet Facilities


Energy output

Wet System Wels, Austria (2-stage, thermophilic)

15,000 Biogas = 3,100-4,400 ft3/t (87-125 m3/t). Methane content – 60-65%

Radeberg, Germany 56,000 Biogas = 88 million ft3/yr (2.5 million m3/yr) Electricity production = 760 kW

30 Ostrem, Karena. May 2004. Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University.

5-22 April 2005


5.6.4 Infrastructure Requirements Because the company offers a variety of AD technologies and waste treatment solutions, the infrastructure requirements vary by facility and plant location. 5.6.5 Operations Elsewhere Linde report that they have about 100 AD operational facilities in Europe that handle organic waste as well as sewage sludge and animal manures. Over the past two years, Linde has constructed 20 new biogas facilities in Europe. The company has been actively involved in mechanical-biological waste treatment facilities to process municipal solid waste, recently announcing several mechanical-biological treatment ventures. Existing and proposed facilities that deal with organic wastes (including green waste) separated or as part of the municipal solid waste stream are provided in Table 5.6.

Table 5.6 Existing and Proposed Linde Wet AD Facilities

Location Capacity

tpy Feedstock Start-up Additional Information

Wels, Austria 15,000 biowaste 1996 - Wet, mesophilic Furstenwalde, Germany

85,000 Biowaste – 15,000, commercial – 13,000, agricultural – 57,000

1998 - Wet

Sagard, Germany 48,000 Commercial, biowaste, manure

1996 - Wet, thermophilic

Radeberg, Germany 56,000 Biowaste and industrial -15,000, biosolid – 41,000

1999 - Wet, horizontal plug flow, mesophilic

- Biogas productivity 1,400 ft3/t (40 m3/t)

Dunkirk, France 24,000 biowaste, industrial, biosolid

1999 - Wet

Barcelona, Spain 150,000 MSW 2002 - Wet, 2 stage, mesophilic - Total solid – 10.5% - Retention time - ~22 days - Biogas productivity estimated at

460 Mft3/yr (13 Mm3/yr) - Gross electricity – 36,000

MWh/yr - Consumption – 18,000 MWh/yr - Net electricity – 18,000 MWh/yr

Pinto/Madrid, Spain 73,000 MSW Under construction

- Wet

Lisbon, Portugal 40,000 Biowaste, market waste, industry waste

Under construction

- Wet

Camposampiero, Italy 49,000 Biowaste, biosolids, manure

Under construction

- Wet

Salto del Negro, Spain 75,000 MSW Under construction

- Wet

Burgos, Spain 40,000 MSW Under construction

- Wet

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Wels, Austria – The Wels plant uses a two stage thermophilic wet process. A batch separation stage uses a pulper followed by a drum screen to remove contaminants and reduce the organic material in size. The pulped organic material is sent to the hydrolysis tank to break down the organic material prior to the digester phase. Hydrolysis, acidogenesis and acetagenesis reactions occur in the hydrolysis tank; methanogenesis occurs in the digester (second stage). The retention time in the digester is 16 days. Linde has not constructed any AD facilities in North America to handle solid wastes materials and do not appear to have any in the planning stages. 5.6.6 Company Standing Linde is a substantial German company with well established anaerobic digestion technologies and processes to treat source separated organic waste as well as municipal solid waste. The Linde Group supplies chemical and gas processing technology and design and installation services through a number of affiliates in the United States.

5-24 April 2005


5.7 BioConverter BioConverter is an anaerobic digestion technology patented in 2001 by James McElvaney of McElvaney Associates Corporation. 5.7.1 Description of Technology BioConverter is the only US designed AD technology available, and has recently been re-introduced into the US marketplace. Bioconverter uses a wet, one stage, mesophilic, batch digestion process. A hydropulper at the front end of the process mixes and pulps the feedstock with water to reach the right consistency and moisture content. The pulped material is processed through a contaminant removal device before being delivered to Bioconversion digester. The slurry contains 10 to 15% total solids. Digestion takes place in heated cylindrical, fiberglass vessel(s) (verimmobilization matrix, a heating mixing/gas transfer. The digester (37oC). The company claims thatanaerobic digestion facilities and gto 60% methane content for other t 5.7.2 Feedstock Specifications The BioConverter technology is deswaste, manure and other agricultur(biosolids) from municipal and inprocess fats, oils and grease and in In 1984, a US $10 million investmHawaii, which processed 185-200 tLater the feedstock was changed The project went through 4 diffeBiowaste Technologies until 1999Biocycle article (Lynn, November 1from new regulations. By the end oin costs.

tical or horizontal). The BioConverter unit features a growth coil for temperature maintenance, and sparging tubes for vessel is maintained at mesophilic temperatures of 98.6oF the technology is 30 to 50% more efficient than other enerates a biogas which is 65% methane (compared to 55% echnologies).

igned to process all types of organic wastes, including green al waste, as well as primary and secondary sewage sludge dustrial wastewater treatment systems. It also claims to dustrial waste (i.e. pulp and fiber).

ent was made in a pilot Unisyn AD system in Waimanalo, ons of cow and poultry manure as well as agricultural waste. to mainly food waste and FOG (fats, oil and grease) waste. rent ownerships but continued to be operated by Unisyn , when the operation closed down. The reason cited in a 999) was an inability to meet capital upgrade costs resulting f the 1999, the project had accumulated over US $20 million

5-25 April 2005


Location Feedstock

Start-up Operations

Waimanalo, Hawaii Food processing waste, food waste and fats, oil and grease – 35 - 40 tpd

1984 Operations closed in 1999

Kihei, Hawaii Food waste (50%), green waste (25%), paper waste (25%) – 2 tpd

1994 Operated from 1995 to 1997

BioConverter has recently entered into a contract with the City of Los Angeles and is in negotiations with City of Lancaster, California to construct AD BioConverter facilities (privately funded) at both locations to process green waste and sell the electricity generated back to the Cities. The BioConverter AD facility at Los Angeles proposes to process 2,600 tons of green waste per day. BioConverter has entered into negotiations with the City of Lancaster to construct a facility (privately owned and operated) that would process 200 tons (52,000 tpy) of green waste per day, generating natural gas and other useful products (i.e. fertilizer) that would be sold back to the City. The proposal has not received City Council approval to date.

5.7.3 Energy Specifications The BioConverter technology claims to yield a biogas with 65% to 75% methane content during the digestion process. The early 1980’s project in Waimanalo Hawaii yielded 320,000 ft3/d of biogas, which was converted to 550 kW of electricity. The technology generated about 3,000 ft3 of biogas per ton of wet food waste. The announcements for the proposed Los Angeles BioConverter facility claim that the facility will generate 40 megawatts (MW) of electricity annually that will be sold back to Los Angeles at US $48 per MW. The City has committed to paying US $16 million per year for energy from the proposed facility over a period of 20 years. The company anticipates that about 20% of the energy produced will be used by the facility with the remaining 80% available for sale. The company, however, is permitted to use up to 25% of the energy produced for its operational use. The price will increase annually on a basis of 25% of the Los Angeles Consumer Price Index. The calculated 20 year levelized cost is about US $50/MW hour. The project will help Los Angeles displace about US $12 million of natural gas annually according to the LADWP (Los Angeles Department of Water and Power) Board Letter for Approval submission (November 18, 2003). The duration of the agreement is 25 years. 5.7.4 Infrastructure Requirements With the Los Angeles agreement, BioConverter will assume responsibility for developing and constructing the anaerobic digestion facility, including obtaining all necessary permits and required environmental approvals, as well as reimbursing the Los Angeles Board of Water and Power Commission for constructing a substation and transmission lines to connect the plant to the city's power system. Bioconverter also will operate the facility. A location has not been identified for the Los Angeles Bioconverter project. A relatively large footprint is required for the facility. The required environmental assessment study has not been

5-26 April 2005


started to date. The facility is expected to be in operation approximately five years from now (2010). The preliminary engineering project capital cost has been estimated at US $174 million. The Lancaster facility is expected to cost US $44 million and is to be located on 18 acres of land. 5.7.5 Operations Elsewhere Both operations in Hawaii were shut down. The Waimanalo facility was closed due to an inability to meet capital upgrade costs resulting from new regulations. It is not known why the Kihei facility closed. 5.7.6 Company Standing McElvaney Associates Corporation (MAC) is a solid waste consulting and technology development company, based in the United States, claiming over 36 years combined experience in BioConverter Technology development, management and operations. Although the Bioconverter technology has been patented only since 2001, it is based on previous experience with the two commercial BioConversion systems in Hawaii. The Conversion Technology database, developed by the California Integrated Waste Management Board and the Dept. of Biological and Agricultural Engineering at the University of California, Davis, classifies the BioConverter technology as pre-commercial. According to the LADWP Board Letter of Approval, “Termination of the Agreement occurs upon any of the following events: (a) if BioConverter Los Angeles, LLC fails to deliver the required electricity from the Project within 60 months after the Agreement’s effective date, (b) if a Notice to Proceed (certifying completion of environmental assessment, selection of project location and design work) is not issued by LADWP within 30 months from the Agreement’s effective date, (c) if the Project is not operational within 30 months from LADWP’s issuance of a Notice to Proceed, (d) 300 months from the Agreement’s effective date, or (e) by mutual agreement of the Parties. Termination may also occur due to contract default by either party”.

5-27 April 2005


5.8 Entec Entec (Environment Technology GmbH) is an Austrian based company that established its first biogas (anaerobic digestion) plant in 1977. Since then, Entec has constructed over 100 facilities in over 16 countries throughout Europe and Asia. Entec offers six different digestion technologies to handle an assortment of feedstocks, ranging from biowastes, sewage sludge, animal waste, and industrial food wastes. 5.8.1 Description of Technology Entec specializes in handling municipal solid waste that has not been source separated. The municipal solid waste received at the facilities undergoes a series of pretreatment processes to remove the non-organic portion of the waste stream. Pretreatment employs bag shredders and waste shredders and includes removal of unwanted material during the hydro pulping process. The hydropulper is fully automatic and removes plastic, glass, metal and sand from the waste stream, leaving behind the organic fraction in the form of a slurry. The system achieves a 90-95% contaminant removal rate.

Entec designed the BIMA (Biogas Induced Mixing Arrangement) system to handle the slurry or sludge containing high solid concentration. This technology features a single stage, wet system approach using either a thermophilic or mesophilic digestion process. The design of the system depends on the feedstock conditions and other factors. The BIMA technology is more commonly used for MSW or biowastes.

5-28 April 2005


The BIMA technology, patented by Entec, is a vertical digester requiring no mechanical stirring. The digester was designed as a self-mixing system not requiring mechanical parts. The BIMA digester uses water level rise caused by the digesting gas pressure to stir the contents. The technology requires only an automatic valve for mixing the contents, which has a service time of more than 10 years. This company states that the design results in lower investment, operation and maintenance costs and higher safety during operations, since no blower and stirring machine are required, no moving part is provided in the tank. Therefore, energy conservation and freedom from maintenance can be achieved. The retention time in the BIMA digester is 16 days. After the 16 days, the digester is drained, without using a pumping device, into a buffer tank and the contents are dewatered using a decanter centrifuge. The remaining solids are composted. 5.8.2 Feedstock Specifications

Entec can handle a variety of different feedstocks ranging from biowastes, sewage sludge, animal waste, and industrial food wastes. To date, the technology has been used to process municipal solid waste only. It is unclear to what extent garden waste is a component of the MSW (in the India and Japan facilities) but would not constitute a main component of the organic stream. 5.8.3 Energy Specifications The net export of energy from AD plants (engine power generated minus own consumption) can vary depending on the feedstock and plant configuration (including the pre-treatment and post-treatment system employed). Factors affecting design include the type and composition of input material as well as the local requirements with regards to application of final products. In the case of the Nakasorachi AD facility in Japan, the incoming municipal solid waste contains a lot of plastic bagged waste, requiring an intensive pre-treatment line to open the bags and remove plastic and other contaminants in the pulper. The post treatment process involves

5-29 April 2005


dewatering, composting and the wastewater is treated at an on-site wastewater treatment plant. The Nakasorachi facility produces 400 kW of electrical power and consumes 200 kW. In the case of the Kogel AD facility (which actually processes commercial and industrial based food waste rather than residential food waste), the food waste collected is much "cleaner" than MSW and the pretreatment is simpler. In Kogel, all residues after digestion are used in liquid/slurry type form as agricultural fertilizer, thus eliminating several post treatment processes such as dewatering. The Kogel facility produces 1400 kW of electricity and consumes 150 kW. Table 5.7 provides information about the gross and net energy for several Entec facilities.

Table 5.7 Energy Information for Entec Facilities

Facility Date of Operation

Capacity tpy

Estimated gross energy generation

Estimated net energy available for export

Nakasorachi, Japan 2002 19,000 400 kW electricity 200 kW electricity Kogel, Germany 2003 40,000 1.4 MW electricity 1.25 MW electricity Lucknow, India 2003 200,000 5.0 MW electricity 115011 kWh/day

5.8.4 Infrastructure Requirements

No information is available on the footprint requirements of the Entec facilities. 5.8.5 Operations Elsewhere Entec has constructed over 100 facilities in over 16 countries throughout Europe and Asia. The majority of the facilities process organic wastes other than municipal organic wastes. Table 5.8 lists those facilities handling MSW or biowaste as part of the feedstock. The anaerobic facility in Nakasorachi, Japan is one of Japan’s largest MSW biogas facilities.

Table 5.8 Entec Operations


Feedstock Start-up Additional

Nakasorachi, Japan 19,000 Municipal solid waste (MSW)

2002

Kogel, Germany 40,000 kitchen, restaurant, catering, and industry

food organics

2003 Estimated cost US $6.5 million (5 million Euros)

Lucknow, India 200,000 Municipal solid waste (MSW)

2003 Estimated cost – US $17 million

Kainsdorf, Austria 14,000 Biowaste, manure and industry food waste

1995

5.8.6 Company Standing Entec (Environment Technology GmbH) is an Austrian based company that established its first biogas (anaerobic digestion) plant in 1977. The services provided by the firm Entec - Environmental Technology, Umwelttechnik GmbH include consulting, planning and equipment supply for anaerobic and aerobic treatment of organic sewage, sludges and solid waste.

5-30 April 2005


6.0 Screening and Analysis of Available AD Technologies 6.1 Overview Anaerobic digestion has been in use for several decades to treat sewage sludge, animal wastes and industrial wastewater. Only in the past decade, has the technology become a recognized method for dealing with biowastes (municipal source separated organic waste) and more recently as part of an integrated process to handle unsorted or residual municipal solid waste. Anaerobic digestion is a naturally occurring biological process that uses microbes to break down organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of organic waste takes place in a special reactor, or enclosed chamber, where critical environmental conditions such as moisture content, temperature and pH levels can be controlled to maximize microbe generation, gas generation and waste decomposition rates. The biogas generated during the digestion process consists of methane and CO2 . Typically, the methane content ranges from 55 to 70%, which is influenced by the process design chosen and the volatile solids in the feedstock. The gas yield from pure garden waste is typically about 2,500 to 2,800 ft3/t (70 to 80 m3/t) and about 3500 to 4200 ft3/t (100 to 120 m3/t) for biowaste. The benefit of an AD process is that it is a net generator of energy which can be sold off-site in the form of heat, steam or electricity. SMUD are interested in supporting projects which are sources of green or renewable energy, therefore anaerobic digestion is being carefully evaluated at this time. The Sacramento Waste Authority is also looking for options to process garden waste. They are open to considering anaerobic digestion as an alternative to open windrow composting to treat garden waste. Open windrow composting is the ideal technology to treat garden waste. Relative to other materials, garden waste yields relatively little biogas. From an energy production point of view, garden waste is not an ideal feedstock for a digestion facility; addition of paper and food waste to the digester improves the performance of a digester intended to process predominantly garden waste. This project collected data on all anaerobic digestion technologies which were known to be operating at full scale and were processing some type of municipal solid waste. Most of these anaerobic digesters are located in Europe, with a few in Asia. There are two full scale digesters operating in Canada and no full scale operations in the US at this time. Anaerobic digestion systems are broadly defined as wet or dry technologies. Wet AD technologies are suitable for situations where significant removal of contaminants such as plastic bags is desirable at the front end of the process; these systems are not as tolerant of contaminants within the digester as dry systems. Wet AD systems are typically used when municipal solid waste is combined with animal manures (co-digestion). Dry AD technologies are more suited to relatively clean feedstocks which do not require significant contaminant removal. In general, for this assessment, dry technologies were considered more suitable for the application under consideration.

6-1 April 2005


Six dry AD technologies were researched and evaluated in this study. These were:

Kompogas (Kompogas, Switzerland) Dranco (Organic Waste Systems, Belgium) Linde (Linde-KCA-Dresden GmbH, Germany) Biopercolat (Wehrle-Werk, Germany) ISKA (U-plus Umweltservice AG, Germany) Valorga (France)

Each of the dry technologies is described in Section 4 of this report, along with data on operating or planned facilities. Seven wet AD technologies were evaluated in this study. These were:

APS (Onsite Power Systems, United States) ArrowBio (Arrow Ecology Ltd, Israel) BTA (Biotechnische Abfallverwer-tund GmbH, Germany) Waasa (Citec Environmental, Finland) Linde (Linde-KCA-Dresden GmbH, Germany) BioConverter (Bioconverter, United States) Entec (Environment Technology GmbH, Austria)

Each of the wet technologies is described in Section 5 of this report, along with data on operating or planned facilities. This section of the report (Section 6) applies technical screening criteria to identify which of the 13 technologies appear the most promising and also flexible for production of green energy from green refuse. It uses information from Sections 4 and 5 to narrow down the most appropriate AD technologies to meet SMUD objectives. The final section also discusses how the overall concept of digesting green waste fits within broader SMUD objectives described in Section 1. 6.2 Technical Screening Criteria It should be stressed that it would be a formidable task to contemplate the digestion of 100,000 tons/year of garden waste at one facility, and one which has not been done anywhere else globally as far as we could identify through the research carried out during this study. Therefore, if the Sacramento area were to embark on this project, it would be the first of its kind. Some digesters of this size have been recently constructed or are in the planning stages in Europe and Asia, but they generally process feedstocks, which are a mixture of municipal solid waste (MSW), or garden waste and food waste combined. A long track record of successful operation has not been established for any of these facilities. Given that it is such a large-scale and expensive undertaking, the AD technology used for the digestion of garden waste must demonstrate proven success elsewhere. In fact, this criterion is considered the most important for screening technologies in this study. Should SMUD get involved in an anaerobic digestion project using garden waste, it should use a technology which has already been proven elsewhere, rather than embark on developing a new variation on AD technology, as this type of developmental effort is time consuming and carries inherent risk.

6-2 April 2005


In order to handle an exclusive or predominant garden waste feedstock, the AD technology needs to be robust, and also needs to be flexible, should it prove necessary to supplement the garden waste with other feedstocks such as food and paper. The AD process chosen must be able to handle the inherent limitations of the garden waste feedstock for AD technology and still maintain optimal biogas production. The following technical screening criteria were used to assess and compare the 13 wet and dry technologies described in this report. The screening process was used to narrow down the AD technologies to the most promising to meet SMUD needs: A. Proven Technology

Has a number of AD facilities in operation Has full scale facilities in operation which have handled municipal solid waste, source

separated municipal waste from residences Has successful track record

B. Flexible Technology

Had been proven effective at processing a number of different feedstreams

C. Ability to Meet SMUD needs: Experience handling at least 100,000 tpy biowaste feedstock Facilities under construction to handle at least 100,000 tpy biowaste feedstock Energy generation and energy available for export is within acceptable range for AD

facilities Low water requirements (suitable for water conservation conditions)

D. Ability to Handle Garden Waste:

Proven record handling garden waste as primary feedstock (70%+ of feedstock) Proven record handling garden waste as prominent part of the feedstock (between 40-

70% of feedstock) Proven record handling garden waste as part of the feedstock (at least 40% of

feedstock) E. Company Track Record (Technical, Service and Reliability):

Number of AD plants in operation internationally Known track record of technology

F. Energy Available for Export (net energy); Does not have high parasitic loads and has a reasonable amount of energy available for

export. Net energy is high, med, low compared with other AD technologies

G. Local Presence

Has agents in the US Other operations in North America Company branch or affiliation in North America Has AD plants in operation in North America that handle any organic material i.e.

treating manure, biosolids, etc.) Has AD plants in operation in North America that handle biowaste specifically

6-3 April 2005


H. Known Information on Costs Cost effective, compared to other AD technologies

I. Footprint Requirements

Ability to fit within a confined site, to reduce the need to identify large sites The above criteria are applied qualitatively in Section 6.4 to screen out some technologies or groups of technologies from further consideration at this early stage, and also to identify the most promising of the technologies to meet SMUD needs. Cost and footprint information was not actually used in the technical screening as there was not sufficient costing data available to realistically compare one technology to another on the basis of cost; however, costs are known to be quite competitive. A Request for Proposal process needs to be initiated to obtain the amount of detail required to carry out a realistic cost comparison. 6.3 Summary of Technical Data for AD Technologies Table 6.1 summarizes the key features of the wet and dry technologies assessed in this study. It summarizes the technologies for which data were identified, the number of years the company has been involved in AD facilities; the number of facilities in operation for each vendor; the size range of the facilities; the types of feedstock handled; the amount of leaf and yard waste in the feedstock, and the amount of biogas produced per ton of input material. A few key points are worth noting regarding the information presented in Table 6.1:

Gas production for the same materials is similar for most of the AD technologies; Gas production for all technologies is lower for garden waste and higher for food waste,

paper waste and MSW; Dry AD technologies appear to use 20% to 30% of the energy produced on-site for

internal requirements, leaving 70% to 80% of the energy produced for export; Wet AD technologies appear to use more energy (up to 50% reported) for internal

operations, and about 50% is available for export although reported values were inconsistent from one wet technology to another;

Dry technologies, therefore, are preferred where energy production is a key evaluation criterion;

Very few AD vendors have facilities in operation at a capacity as high as 100,000 tons/year;

A number of AD facilities larger than 100,000 tons/year are planned, but there is virtually no long term track record for an AD facility of this size;

Valorga is the only dry AD technology which has a plant in operation at a capacity of greater than 100,000 tons/year;

There is no AD facility in operation which processes strictly garden waste; all include biowaste (food and garden waste combined) or biowaste and paper in their feedstock.

6-4 April 2005


Table 6.1 Summary of Key Technical Data For Thirteen Anaerobic Digestion Technologies Processing Some

Garden Waste

Technology Operating Experience

Facilities Processing Residential Waste

Total* #

Capacity #

Feedstock (75% or more )

Reported Biogas Generated

50 to 100,000

(tpy)

>100,000 (tpy)

Bio-waste

garden refuse

MSW

DRY AD FACILITIES Kompogas (Kompogas, Switzerland)

- 10 yrs operating AD facilities

- biowaste plants operating since 1994

- no subsidiaries in North America

19 full 8 part

19 0 b b no biowaste 3,500 ft3/t (100 m3/t) food 5,300 ft3

(150 m3/t) 25% use:75% net



- biowaste/MSW plants operating since 1992

- representation in the US

7 full 6 part

7 0 b b no biowaste 3,900 ft3/t (110 m3/t) garden 2,800 ft3 /t (80 m3/t) 80% use:20% net



- biowaste/MSW plants operating since 1994

- subsidiaries in North America

4 full 1 part

4 0 b no b biowaste 3,500 ft3/t (100 m3/t) 30% use:70% net



- MSW plant operating since 2000

- No subsidiaries in North America

1 full 1 part

1 0 no no b MSW 2,500-2,800 ft3 /t (70-80 m3/t) 20% use:80% net





1 full 3 part

1 0 no no b MSW 1,800 ft3/t (50 m3/t) Use:net ratio not available



- biowaste/MSW plant operating since 1988


10 full 3part

7 3 b no b biowaste 2,900 – 3,700 ft3/t (82 to 106 m3/t) 25% use:75% net

* full = full operation; part = under construction; neg = under negotiations

6-5 April 2005


Technology Operating

Experience Facilities Processing Residential Waste

Total* #

Capacity #

Feedstock (75% or more )

Reported Biogas generated

50 to 100,000

(tpy)

>100,000 (tpy)

Bio-waste

garden refuse

MSW

WET AD FACILITIES APS (Onsite Power Systems, United States)


- no plants operating

- based in North America

0 full 4 neg

0 0 - - - -

ArrowBio (Arrow Ecology Ltd, Israel)



- Representation in North America

1 full 1 0 no no b MSW 1,600 ft3/t (44 m3/t) 20% use:80% net



- Biowaste/MSW plant operating since 1986

- offices in US

13 full 2 part

12 1 b no b Biowaste 2,800-4,200 ft3/t (80-120 m3/t) 50% use:50% net



- Biowaste/MSW plant operating since 1994


8 full

7 1 b no b MSW 1,500 ft3/t (41 m3/t) 30% use:70% net



- Biowaste/MSW plants operating since 1994

- subsidiaries in North America

6 full 5 part

5 1 b no b Biowaste 2,900-4,400 ft3/t (83-125 m3/t) 50% use:50% net



- No plants operating

- based in US

0 full 2 neg

0 0 - - - -



- Biowaste/MSW plant operating since1995

- US agents

4 full 3 1 b no b 50% use:50% net

* full = full operation; part = under construction; neg = under negotiations

6-6 April 2005


6.4 Technical Analysis of AD Technologies By Design Parameter This section summarizes how each of the technologies presented in Table 6.1 fit within the commonly used AD system design descriptions or classifications:

Single or two stage, Wet or dry, and Thermophilic or mesophilic.

Digestion Stages are characterized as:

Single Stage – all biological processes occur as a single stage in one the digester unit or tank;

Two Stage – the biological processes take place in two separate stages and units, the hydrolysis stage/unit and the digester stage/unit.

Table 6.2 classifies the AD technologies in Table 6.1 as either single stage or two stage systems.

Table 6.2 Classification of AD Technologies As One Vs Two Stage Systems

Stage Features Examples

Single Stage - longer proven record - simple design - lower capital costs and technical problems - similar biogas yield as two stage

- Wassa - Entec - Valorga - Kompogas - Dranco - BTA

Two Stage - robust (not as pH sensitive) - lower retention time - newer technology (not as proven) - reduces problem of “short circuiting” – early removal

of digestate, resulting in lower biogas yield - better at breaking down cellulose fibers

- ISKA - BioPercolate - Linde/BRT - Arrow Bio - APS

Feed Total Solids (TS) Content of an AD system are characterized as: Wet Process (<15% TS) – the feedstock is watered down into a slurry with 10-15% total solid content;

Dry Process (>20% TS) – the feedstock is not as diluted but relies on the water content within the feedstock to promote degradation with 20-40% total solid content.

Table 6.3 shows which AD technologies in Table 6.1 are classified as wet and which are dry. Linde provide both wet and dry designs.

6-7 April 2005


Table 6.3 Classification of AD Technologies As Wet Vs Dry Systems

Wet vs. Dry Features Examples

Wet Process - proven record in treating wastewater biosolids - not as well suited for biowaste due to loss of volatile

organics during hydropulping process - increased problems of “short circuiting” – early

removal of digestate, resulting in lower biogas yield - less tolerance for contaminants in digester - more suited where large amount of contaminants

(e.g. plastic bags) need to be removed at front end - Higher energy consumption in-plant

- Wassa - BTA - Linde/BRT - Entec - APS - Bioconverter - Arrow Bio

Dry Process - Use less water as part of the process and can rely on circulation of waste water from the digester

- Able to handle contaminants (i.e. stones, glass, plastics) more effectively in the digester

- Lower energy consumption in-plant

- ISKA - Valorga - Kompogas - Dranco - BioPercolate - Linde/BRT

Operating Temperature, characterized as

Mesophilic Process – the digestion process operates at an optimal temperature of approximately 93 to 98 °F (34 to 37 °C);

Thermophilic Process – the digestion process operates at an optimal temperature of 131 to 140 °F (55 to 60 °C).

Table 6.4 summarizes key aspects of mesophilic and thermophilic process designs. Most AD technologies can be adapted to either temperature regime.

Table 6.4 Characteristics of Mesophilic Vs Thermophilic Designs

Mesophilic vs. Thermophilic

Characteristics

Mesophilic Process - Bacteria are more robust and more adaptable to changing environmental conditions

- Greater retention time required (15 to 30 days) - Nitrogen balance less of an issue - Typically lower gas generation - Larger footprint requirement if longer retention time

needed

Most AD technologies can be adapted to either process

Thermophilic Process - higher operating temperature must be maintained for optimal performance

- higher biogas yields - lower retention time (12 to 14 days) - higher use of energy - higher technology maintenance and costs

Most AD technologies can be adapted to either process

Operating Challenges of Digesting Pure Garden Waste The design parameters of an anaerobic digestion facility are greatly influenced by the composition of the feedstock. The most critical factor for most anaerobic digestion processes is to maintain an optimal carbon to nitrogen (C:N) ratio. In the case of garden waste, maintaining the carbon to nitrogen balance is highly dependent on the nature of the garden waste composition. When there is an excess of leaves in the feedstream, the digester gets too much

6-8 April 2005


carbon and not enough nitrogen, which needs to be augmented. Conversely, when there is a high grass content in the feed stream, the digester gets too much nitrogen and not enough carbon, which needs to be added to ensure the balance is achieved. Discussions with AD technology suppliers indicate that a mesophilic AD process would best suit garden waste since the nitrogen content becomes less of an issue. The trade off to using the mesophilic process is higher retention time and a reduction in the amount of biogas generated. In addition, due to the higher lingo-cellulosic content in garden waste, microbes have more difficultly breaking the feedstock material down and, consequently, generate a lower biogas yield than other organic materials such as paper products and food waste. Two stage AD system vendors suggest that their process is better at breaking down (hydrolyzing) the cellulose material and has a reduced retention time but does not generate more biogas than the single stage system. Garden waste often contains contaminants, such as stones and soil, which can burden some AD systems. It is generally recognized that the dry systems are better suited to handle garden waste and the contaminants associated with it. In addition dry AD systems use less water, which may be an important consideration in the Sacramento area. To date, only a handful of anaerobic digestion facilities have experimented exclusively with garden waste feedstock. A pilot study undertaken by the City of Greensboro, North Carolina to anaerobically digest garden waste experienced the following problems:

Maintaining optimal reactor heat and biogas yield;

Establishing optimal nutrient balance, especially nitrogen conditions; Experiencing poor biodegradation of lignocellulosic materials (woody wastes).

The mounting problems eventually forced the City to discontinue the pilot project and dismantled the AD facility. Europe has experienced greater success handling garden waste in AD systems. Several AD facilities located throughout Europe process a feedstock consisting primarily of garden waste. Two facilities using Dranco technology, located in Aarberg, Switzerland and Brecht, Belgium, process feedstocks with high garden waste content. 6.5 Gas Production And Net Energy Available From Different AD Technologies Tables 6.4 and 6.5 summarize available information on gas production from different wet and dry AD technologies. In general, gas production for similar feedstocks (garden, food and MSW) are in the same range for both wet and dry technologies with a few exceptions. Dry technologies tend to use 20% to 25% of the energy for in-plant needs, and export 75% to 80% of the energy they produce. Wet technologies use more of the energy they produce for in-plant needs, although in a number of cases in Table 6.5, no specific information could be identified during this research project. For those technologies, which reported information, it appears that the wet technologies use about 50% of the energy they produce, and export the remaining 50%. Because the prime purpose of the proposed facility is to generate energy for export, wet technologies appear less desirable from an energy production point of view.

6-9 April 2005


For the ISKA technology, gas production is lower (1,800 cu ft/ton), probably related to the shorter retention time for this technology. ISKA is generally considered part of an integrated waste management system where processing of the complete waste stream is top priority, and production of energy is not optimized. It is not considered a suitable technology for the proposed AD project because of its low reported gas production performance.

Table 6.5 Available Information on Reported Gas Production and Net Energy Available for Export

For Dry Anaerobic Digestion Technologies Technology Biogas Generated Energy Used and Net Energy

Available for Export Kompogas (Kompogas, Switzerland)

biowaste 3,500 ft3/t (100 m3/t)

food 5,300 ft3 (150 m3/t) 25% use:75% net


biowaste 3,900 ft3//t (110 m3/t) garden 2,800 ft3 (80 m3/t)

20% use:80% net


biowaste 3,500 ft3 /t (100 m3/t) 30% use:70% net


MSW 2,500-2,800 ft3 /t (70-80 m3/t) 20% use:80% net


MSW 1,800 ft3/t (50 m3/t)

Use:net ratio not available. Likely not much available as relatively low gas generator


Biowaste 2,900 – 3,700 ft3/t (82 to 106 m3/t)

25% use:75% net

Table 6.6

Available Reported Information on Gas Production and Net Energy Available for Export For Wet Anaerobic Digestion Technologies

Technology Biogas Generated Energy Used and Net Energy Available for Export

APS (Onsite Power Systems, US)

Not available Not available


MSW 1,600 f3 (44 m3)/t

20% use:80% net


Biowaste 2,800-4,300 f3/t (80-120 m3/t)

50% use:50% net31


MSW 1,500 ft3/t (41 m3/t) 30% use:70% net


Biowaste 2,900-4,400 ft3/t (83-125 m3/t)

50% use:50% net


Not available Not available


Not available 50% use:50% net

31 Based on anticipated biogas generation and internal usage rates for the Newmarket AD facility

6-10 April 2005


6.6 Technical Screening of AD Technologies The key technical screening criteria used to assess the AD technologies described in Table 6.1 (from Sections 4 and 5) were:

Net energy available for export (per ton), and Technical track record

Screening Based on Energy Available For Export The prime purpose of the proposed AD facility or AD facility partnership is to generate energy for export. Wet AD technologies generally produce less energy for export per ton than dry AD technologies. The research carried out for this study established that both wet and dry technologies produce similar amounts of biogas per ton of similar feedstock. However, dry technologies only use 20% to 30% of this energy to run the AD plant, and export 70% to 80% of the energy they produce. Wet AD technologies in most cases appear to export about 50% of the energy they produce. Therefore, on the basis of producing less available energy per ton for export or sale to SMUD, wet technologies were screened out from further consideration for this analysis. This eliminates Arrowbio, BTA, Wassa, Linde (wet) and Bioconverter from further consideration at this point in the analysis. The Onsite Power systems technology is not eliminated at this stage, as the local pilot program at UC Davis may be able to provide valuable data on energy available for export using various feedstocks. The ISKA technology is also screened out at this stage because of its reported low energy production ability. Screening Based on Track Record and Other Plants in Operation Six dry AD technologies remain from the previous screening step. Using the “track record” screening criteria, Biopercolat was screened out because it only has one pilot plant in operation. A longer track record is needed for the proposed AD facility. Linde is marginal, as it has 4 plants in operation, but none of these process mostly garden waste. However, it is retained for the preliminary assessment. Table 6.7 summarizes the results of the technical screening process, and the conclusions to date.

6-11 April 2005


Table 6.7

Screening of Anaerobic Digestion Technologies AD Technology Screening

Kompogas (Kompogas, Switzerland)

Good solid operating record with 19 facilities in operation for a number of years, and 8 more under construction. Current limitation is lack of local presence in US

Retain for further consideration


Good solid operating record with 7 facilities in operation for a number of years and 6 under construction. Has other company in US and European staff visit frequently


Linde (Linde-KCA-Dresden GmbH, Germany) DRY

Good operating record with 10 facilities in operation and 6 under construction. Very well established company; operations in US focus on chemicals.



Screen for now. Limited track record of only one facility: need to review detailed data before considering further

Screen out


Screened out due to low reported energy production

Screen out


Good solid operating record with 10 facilities in operation for a number of years and 3 under construction.


APS (Onsite Power Systems, United States)

Retain as a possibility and review UC Davis pilot data carefully

Screen out, because technology at an early stage of development


Screened out due to only one facility operating in Israel

Screen out


Screened out based on high in-plant energy needs and only 50% of energy available for export

Screen out


Good record with 8 facilities but no experience with source separated biowaste. Current limitation is lack of presence in the US

Screen out

Linde (Linde-KCA-Dresden GmbH, Germany) WET

Screened out based on high in plant energy needs and only 50% of energy available for export

Screen out


Screened out based no facilities in operation and lack of available information

Screen out

6-12 April 2005


On the basis of the preliminary screening, four dry technologies were considered viable options for a future AD facility:

Kompogas Dranco Valorga and Linde.

The Onsite Power Systems pilot project at UC Davis provides a valuable opportunity to assess locally generated research on AD technology. However, this technology will not be ready to construct a facility with a capacity of 50,000 to 100,000 tons/year in the short term, as the results from the small pilot are not scalable to this degree, and construction of a pilot plant is not expected to be completed until the summer 2005. It will likely be fall/winter of 2005 before it is fully commissioned, seeded and operating. 6.7 Evaluation of Broader Concept Using SMUD Criteria The criteria established by SMUD to assess the options for biomass energy projects are:

Potential for low cost kW-hrs; Local benefits of improved air and water quality and economic benefits; High quality fuel (BTU content, organic fraction, etc.); Sustainable supply of fuel; Proximity to SMUD distribution; and Ability to contract for fuel or energy.

This section briefly discusses how the concept of digesting garden waste addresses each of these criteria. Potential for low cost kW-hrs Anaerobic digestion of garden waste does not provide low cost kW-hrs to SMUD for a few reasons:

The technology itself is expensive; Competing landfill and open windrow tipping fees per ton are very low; and The AD technology is not an intensive energy generator; it is generally used to solve a

waste management problem with energy generation considered a side issue rather than having energy generation as the prime focus.

Local benefits of improved air and water quality and economic benefits The project improves local air quality by eliminating the need to ship green waste 80 miles to a composting site. Furthermore, biogas (methane) is a cleaner burning fuel than other fossil fuels (e.g. coal) in generating electricity, thus reducing local air pollution and smog problems. Since anaerobic digestion operations occur in an enclosed environment, the air quality concerns involving the generation of volatile organic compounds (VOCs) and ammonia emissions (associated with open window composting) are significantly reduced. While methane is generated as part of the anaerobic digestion process (and is classified a VOC) it can be effectively captured and treated because it is combustible to CO2 as part of the energy generation process. However, VOCs produced as part of an open windrow composting process cannot be captured or treated and are released directly into the air. However, new regulations

6-13 April 2005


on air emissions from open windrow composting sites may increase costs of these facilities and make AD more cost competitive with composting. There are no local water quality benefits to the project. Local economic benefits would include a few extra jobs at the AD site. High quality fuel (BTU content, organic fraction, etc.) Anaerobic digestion of garden waste produces a fuel which is about 60% methane. It requires some upgrading for various uses as a substitute for natural gas. Sustainable supply of fuel Anaerobic digestion of garden waste provides a sustainable supply of fuel, as garden waste is generated in the Sacramento area 12 months per year, although the amounts fluctuate by season (see Section 2). Proximity to SMUD distribution The proximity to SMUD distribution will depend on the final location of the AD facility, but there is certainly the possibility that the AD facility can be located near the SMUD distribution system. Ability to contract for fuel or energy If an AD facility is constructed, SMUD can contract with the owner or operator to supply a fixed amount of energy per month or per year. As long as the plant is operating efficiently, this energy should be delivered. However, digestion is a biological process, and can experience upsets every so often. These can destroy the biological system, which generates the biogas, and take time to re-establish. Gas production will cease, or be reduced, during periods of plant upset. 6.8 Evaluation Using Sacramento Waste Authority Criteria The Sacramento Waste Authority is open to exploring alternatives to aerobic composting of garden refuse, if they meet the following criteria for an acceptable technology:

Cost effective: Can be financed by public-private partnership to deliver costs which are in line with current costs;

Durable equipment: The equipment supplier has a good track record, and the equipment or technology employed provides good warranties and serviceability;

Nuisance free: There are little or no odors, litter, vectors, traffic impacts or negative effects on property values;

Final Product: The technology produces a saleable residue for marketing by the private sector party involved.

Cost Effective Garden waste collected from the Sacramento area is currently composted in open windrow composting sites for a tipping fee of about $23/ton. The current contract expires in 2007. At a tipping fee of $23/ton, it is difficult to make the case that AD is cost effective. However, new air quality regulations for open windrow composting sites will require more stringent control of ammonia and VOC emissions from these sites. It is likely that some type of cover system will be required to meet these regulations; therefore, the cost of composting will increase possibly to as high as $35-$40/ton to cover this higher operating requirement. In this case, an AD proposal could be cost effective.

6-14 April 2005


Durable Equipment and Vendor Track Record The track record of available AD suppliers is discussed earlier in this section. It is considered the most important consideration (next to energy export) in evaluating AD technologies. A number of the dry technologies considered suitable for this application have a good track record in Europe, but none in the US or Canada. This is one of the inherent risks in this project and one that needs to be recognized by all involved. Nuisance Free It difficult for a waste management facility to have no odors, litter, vectors, traffic impacts or negative impacts on property values, but all of these impacts can be mitigated by a series of good designs and management processes. Odors are controlled by housing operations indoors and scrubbing all exhaust air through a biofilter. Litter and vectors are controlled by good site management practices. Traffic impacts can be minimized in a number of ways depending on the location of the AD facility. Negative impacts on property values depend on where the AD facility is located. If it is located in a Greenfield site, there will be impacts on surrounding property values. If it is co-located on an existing transfer, MRF, composting or landfill site, then the incremental impact on property values is likely minimal.

6-15 April 2005


7.0 Economic Analysis of Anaerobic Digestion of Garden Waste

7.1 Overview The following provides an outline of an anaerobic digestion (AD) plant, its associated costs and the financial viability for facilities processing 50,000, 100,000 or 200,000 tons per year (tpy) of garden waste. It is estimated that the garden waste feedstock will contain up to 10% residue. There are also cost estimates for 100,000 tpy facilities processing garden and food waste with up to 15% residue, the higher residue being attributed to primarily plastics and plastic film in the food waste components. For garden waste only, a dry, thermophilic, single-stage AD technology forms the basis of the description, cost estimates and financial analysis. Dry AD technology is considered better suited to the processing of garden waste, where low contamination levels are expected, and removal of significant amounts of plastic will not be required. A wet, mesophilic, single-stage AD technology is somewhat better suited to deal with a more highly contaminated (i.e. containing more unwanted material or residue) feedstock, particularly if a lot of plastic is collected and needs to be removed before digestion. However, if the feedstock is clean (low levels of plastic and other contaminants) then dry AD technology is appropriate. Costs for both wet and dry AD technologies are provided in this section. The economic analysis was completed by MacViro Consultants Inc of Markham, Ontario under sub-contract to RIS International Ltd. The cost estimates and financial analyses have been carried out using detailed cost information from one technology vendor for the digestion-specific components of the facility sizes used, supplemented by component-specific costs developed by the study team. The technology specific cost information is generally applicable to other dry technologies as the major technology providers are all price competitive. The cost estimates are based on the development of a new facility on a greenfield site. A site area of 8 acres would comfortably accommodate a 100,000-tpy facility and allow for expansion to a 200,000 tpy facility. If expansion is not contemplated, a minimum site area of 6 acres would be sufficient. These site areas assume that digestate curing by aerobic composting is conducted in a rural area off-site. Cost estimates are also provided for a facility co-located with an existing integrated waste management facility such as a transfer station, MRF, composting site or landfill. The assumption that the facility is co-located with an existing facility serves to reduce both the estimated capital and operating costs. In addition, in the “co-located” alternatives, a number of optimistic assumptions are made with respect to other cost variables, to identify the most optimistic cost estimate for the potential project. These assumptions can be found in Section 7.6. The cost analyses were carried out to see what combination of factors would make the economics of the AD facility viable. For these analyses, we looked at:

1. How much subsidy would be required to keep the tipping fee at $25/ton; 2. What energy revenue (in cents per kWhr) is required to in order to keep the tipping

fee at $25/ton; and 3. What tipping fee would be needed to make the economics of AD viable.

7-16 April 2005


7.2 Description of Facility Components The greenfield dry facility components would consist of the following:

Site Services; Material Receiving; Front-End Pre-Processing; Anaerobic Digestion Process; Digested Material Dewatering; Off-site Post-Digestion Curing of Digestate; Wastewater Treatment; Biogas Handling and Electrical Power Generation; and Environmental Controls

Most of these components would also be utilized in a “greenfield” wet facility. 7.2.1 Site Services The AD facility would require basic services common to any waste management facility, including water and sewer, natural gas connections and access roads for entry to and exit from the plant. Counter-clockwise truck traffic flow would be the best arrangement for large trucks and roadways would require road-turning radii suitable for full size transfer trailers. As electrical energy production is proposed, an electrical grid connection will be required. However, should the biogas be used for heat or steam generation (depending on location), this cost would be eliminated.

7.2.2 Material Receiving Similar to other waste management facilities, the AD plant would have an area for receiving feedstock. The material reception system would include the following components: Weigh Scales For a 100,000 ton/yr facility, it is recommended that two scales be provided (inbound and outbound) with a common scalehouse located in between the two scale decks. Trucks would be weighed before and after unloading material onto the tipping floor. The weigh scales should be sized and rated for the capacity expected from a full-length (53’) transfer trailer carrying in excess of 30 tons. Tipping Floor The tipping floor must be enclosed inside the building to minimize noise and odor emissions. On the tipping floor, an operator would visually inspect the material and remove large non-digestible items or any other unacceptable items such as household hazardous waste, before the material is fed into the AD process. The tipping floor should be sized for two days of material storage, allowing for plant downtime, 4-day weeks and daily variations in material delivery truck quantities and capacities. Additional tip floor space would be needed to facilitate truck drive through and tipping, front-end-loader movement, rejects bin and the main feed conveyor. 7.2.3 Front-End Pre-Processing An extensive front-end pre-processing system would not be required for a garden waste only facility, although a shredder would be recommended for separately handling brush if brush

7-17 April 2005


forms a significant fraction of the feedstock. The only manual removal of contaminants would be by the tipping floor loader operator as discussed above. Size reduction, through use of a comminuting drum(s) followed by a trommel screen, is the main waste-conditioning step for dry AD technologies. In the rotating comminuting drum, softer organic materials break down into smaller particles while inert materials do not break apart. Depending on the nature of the feedstock, an average retention time in the drum of 1.5 hours can be expected, after which the material is sent through a trommel screen. A trommel screen is a large rotating drum containing openings of various sizes, normally installed at a slight decline to move material through the unit as it rotates. For garden waste, a trommel with only one opening size would be used to separate the material into “fines” (likely less than 50 mm), and “overs” (all remaining material). The fines will contain a high percentage of organic material suitable for digestion (although grit and pieces of broken glass or brick may also be present). The “overs” fraction would be directed to landfill disposal.

7.2.4 Anaerobic Digestion Process: Dry, Thermophilic, Single-Stage The components of the dry, thermophilic digestion process assumed for costing purposes are described below. A description of the components of a wet, mesophilic digestion process is provided in Section 7.7. Mixing Unit In the mixing unit, incoming material from the pre-processing steps is mixed with some recirculated material from the digester, which acts as an inoculant and minimizes process disruptions due to nutrient spikes. Low-pressure steam is injected here to heat the material to a temperature of between 118OF to 131OF (48 and 55°C). Although it may be possible to generate the necessary steam as part of the electrical co-gen package, discussed later, for the financial analysis, a conventional boiler (biogas-fired) is assumed. Some AD vendors use steam injection for this purpose and therefore have more energy available for export. The assumption of use of a biogas fired boiler results in a more conservative estimate for preliminary planning (i.e. lower energy revenues). Feed Pump The mixing unit feeds to the feed pump, which is designed to pump high-solids slurries. The feed pump moves the material, typically at 20-40% solids, into the digester. Digester Most dry AD technologies use a plug-flow design with a vertical cylindrical steel, insulated digester. Mixing can occur by recirculation of the material in a continuous loop. The feed pump moves the material through a pipe up to the top of the tank, from which it makes its way down to the bottom to pass through an outlet back to the pump. This cycle happens a number of times over a retention time of approximately 25 days. Alternately, the material may pass through the digester only once, but the inside configuration of the walls and a central baffle prevent short-circuiting of the path from the inlet to the outlet, ensuring the retention time of 25 days. There are no moving parts inside a high-solids digester. For a 100,000 tpy plant, it is anticipated that two digesters, each of approximately 123,600 ft3 (3,500 m3) capacity would be required.

7-18 April 2005


7.2.5 Digested Material Dewatering Following digestion, the digested solids would require dewatering before being sent to the final curing location. This dewatering would occur by means of filter presses, screw presses and/or centrifuges. A polymer solution would be added prior to the presses to flocculate the solids and facilitate solids separation. The water removed at this stage would be wastewater, which may require some treatment for the reduction of nitrogen, phosphorus and suspended solids as discussed below.

7.2.6 Off-Site Post-Digestion Curing of Digestate The dewatered solid digestate requires final aerobic curing to ensure full stabilization and also pathogen reduction, which occurs when the material self-heats to over 131oF (55°C). Due to the extensive space requirements involved in windrow composting, coupled with the risk of odor generation during windrow turning, this curing step is generally done offsite at another facility located in a rural area and dedicated for this purpose. This step is required because most of the technology vendors do not claim to meet the EPA’s rule for pathogen reduction during the digestion process alone, and all depend on the post-digestion curing of the material, during which temperatures rise above 131oF (55°C) for an extended period of time, to guarantee pathogen kill. This step also serves to minimize vector attraction and phyto-toxicity of the product and is required for both mesophilic and thermophilic digestion technologies. The digestate exiting from the pressing stage could be discharged directly into a waiting container (trailer, lugger or roll-off) or would require an intermediate storage area, from which it would be loaded onto trucks for hauling to the final composting site. While AD vendors state that generally 14 days of windrow composting is sufficient for the digestate, the curing time required may be three to four weeks or possibly longer. Also, a bulking agent may be necessary to increase the pore space within the compost piles and absorb moisture. This could be chipped yard or wood waste, or another relatively inert organic material. It would be added to make up approximately 20% by mass of the composting material. Discussions with the Sacramento Regional Solid Waste Authority (SWA) have indicated that composting of digestate at future facilities which they may own or operate will likely be accomplished for a tipping fee of about $25/ton. This value has been used for preliminary financial analysis of the AD facility, although anticipated, more stringent air emission requirements from open windrow site may increase this cost in the future.

7.2.7 Wastewater Treatment

It is expected that the liquid effluent generated from the dewatering operation at the plant will need to be treated prior to discharge to a sanitary sewer system, although depending on the location, local sewer surcharges may suffice. The main parameters of concern would be suspended solids, nitrogen and phosphorus. A packaged wastewater treatment process consisting of a clarifier and aeration tank, or alternatively a packaged rotating biological contactor (RBC) could be installed. The final decision depends on the AD facility location and sewer discharge requirements, if a sewage system is available.

7-19 April 2005


7.2.8 Biogas Handling and Electrical Power Generation For an AD facility operating on garden waste only, biogas (approximately 55% methane content) will be generated at a rate of approximately 2,900 ft3/t of feedstock. The biogas is produced from the digester at approximately 100% humidity and to reduce corrosion in piping and gas utilization equipment, moisture removal would be necessary. This would consist of a knockout device for condensate removal. It may also be necessary to remove hydrogen sulfide (H2S) from the biogas. Sulfides would be removed by a chemical scrubber. The H2S content of the gas out of the digester could be in the range of 200-2500 ppm. A compressor(s) would be required to deliver the biogas fuel to the engine package at appropriate pressure. Based on the biogas generation rate noted above, the co-generation engine package or prime mover would be sized for a 100,000 tpy facility, at approximately 1.8 MW (likely 2 or 3 units). Surplus heat could be captured to address the on-site, or possibly an external, thermal load, again, depending on the AD facility location. An energy balance is presented elsewhere in this report. A stand-by flare would be required in the event that biogas cannot, temporarily, be burned in the co-gen system. 7.2.9 Environmental Control Systems The facility would include control measures for odor, noise and litter. Odor would be addressed using a biofilter. All of the process buildings would be maintained under negative air pressure, and this air would be exhausted through a biofilter. The biofilter would be sized at approximately 243 ft3/hr per square foot (75 m3/hr per m2) of biofilter surface area, which translates into about 3 air changes per hour in the process buildings. The biofilter would be equipped with a humidification system and utilize a control system to monitor important operating parameters. Noise control would primarily be achieved by ensuring that process building doors are normally closed (which also addresses odor control) and utilizing enclosures for noisy equipment items such as compressors if located outside (compressors for example). A drive-through tip floor, with fast closing doors should serve to minimize noise and odor escape. Berms and landscaping would also serve to mitigate noise to a certain extent. The main areas with a potential for release of litter would be the tipping floor and the digestate loading area. Both of these would be enclosed inside the building. Fencing the site and conducting daily litter removal patrols would be typical of a facility of this nature. 7.3 Plant Energy Balance This section provides details on the energy balance associated with the proposed facility. The energy input to the system is calculated using the waste input to the facility and the estimated gas production rate. The gas production rate varies according to the volatile solids content of the waste, which is related to the type of waste being digested. In the case of garden waste, a

7-20 April 2005


gas generation rate of approximately 2,900 ft3/t of waste is expected. The energy value of this gas is expected to be approximately 520 BTU/ft3. This energy density allows the total gas energy available from the digester to be calculated. The energy flow of a dry, thermophilic facility is shown in Figure 7-1. Note that an AD process operating on garden and food waste is projected to have a slightly higher gas yield of 3,500 ft3/t.

Figure 7-1 On-Site Cogeneration Schematic with Annual Energy Flows

100,000 Ton per Year Garden Waste Facility

AnaerobicDigestionProcess

CogenerationProcess

45% ThermalEfficiency

35% ElectricalEfficiency

Parasitic Electrical Load5,337 MWh

Engine Heat Production50,050 MMBTU

Gas Produced289 Million ft3

150,835 MMBTU

ExternalThermal

Load50,050

MMBTU

ExternalElectrical

Load8,586 MWh

ExternallyPurchased Gas(Start Up Only)

ExternallyPurchasedElectricity(Start Up

Only)

Gross Electric Output13,923 MWh

Waste Input100,000 tons/

yr

Plant Heating Load11,038 MMBTU

Engine Heat Recovered61,088 MMBTU

Once the gas input to the engine is known, the motor generator set can be sized, and the thermal and electrical outputs calculated. As shown on the schematic, the outputs are determined assuming 45% thermal conversion efficiency, 35% electrical conversion efficiency, and 90% engine availability, which are typical values for a cogeneration plant, with a reciprocating engine as its prime mover. The plant parasitic electrical load is determined using an average rate of electricity required per ton of waste for an anaerobic digester. This electricity will be used to power the entire plant. Once this has been removed from the cogeneration electrical output stream, the electricity available for sale (external electrical load) is determined.

7.4 Costs and Financial Analysis for 100,000 Ton per Year Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site – Option 1

Tables 7-1 and 7-2 provide summary capital cost and operating cost estimates for a 100,000 tpy AD facility, located on a “greenfield” site, i.e. a brand new site where no other waste management facilities are located and the site has to be developed from scratch. Appendix A provides detailed costs. While 100,000 tpy is a large facility, this size was chosen for the cost analysis to achieve some economies of scale with respect to capital cost per constructed capacity in tons per year. These tables list various items and assumptions included in each cost category along with the estimated cost for the category.

7-21 April 2005


Table 7.1

Summary AD Plant Capital Cost Estimates 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

Categories Costs

($ US) General Site Works 850,000 New Buildings 5,015,000 Major Tankage (including foundations) 3,700,000 Pre-Processing Equipment 1,700,000 Main and Post-Processing Equipment 6,650,000 Flaring and Odor Control 525,000 Electrical and Steam Generation 4,180,000 Miscellaneous 1,200,000

Total of Above 23,820,000 Unforeseen and Estimating Allowance (20%) 4,760,000 Engineering and Contract Administration (10%) 2,380,000

Total 30,960,000

Table 7.2

Summary AD Plant Operating and Maintenance Estimates 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

Categories Costs

($ US)

(consisting of 1 plant manager, 3 process control operators, 2 tip floor operators, 2 maintenance technicians, 2 scale house operators, 1 lab technician 1 marketing manager and 7 general laborers)

863,000

Utilities and Fuel 42,000 Maintenance (based on 4% of equipment capital costs, 0.05% buildings and site works capital costs and 1% of tankage and odor control capital costs)

725,000

Other (based on wastewater treatment, licensing fees, lab costs, administration, legal and accounting costs, service contracts, tip fees at curing site and residual disposal fees, etc.)

420,000

Total of Above 2,050,000 Unforeseen Allowance (10%) 250,000 Estimating Allowance (10%) 250,000

Total 2,460,000

Staff Requirements (based on 3 shift operation)

7-22 April 2005


Table 7-3 summarizes the financial analysis input assumptions and data. Appendix A lists the key input data and assumptions for the financial analysis including summaries of the material mass balance, assumed base case unit prices, the energy balance, facility costs and capital financing assumptions.

Table 7.3 Financial Analysis Summary: Input Assumptions and Data

100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site) Category Input Assumptions & Data Annual Mass Material Balance

Input Quantity Residue to disposal

Digestate to composting

100,000 tons 10,000 tons 56,000 tons

Unit Prices Tipping fee/digestate composting fee/ residue disposal fee

Electricity selling price

$25/ton

$ 0.065/kWh Annual Energy Balance

Gas generation rate (imperial) Total gas heat energy produced

Gross annual plant heat load Annual engine heat recovered

Gross electric output power Net power

Annual electricity available for sale

2,889 ft3/ton

150,835 MMBTU 11,038 MMBTU 61,088 MMBTU

1,766 kW 1,089 kW

8,587,663 kWh Capital Financing

Before tax cost of capital Amortization period

Annual capital charge Annual inflation rate

6.4%

15 years 3,271,562

2% The key base case unit pricing assumptions, reflective of current economic conditions, listed in this table are:

$25/ton tipping fee received by the facility for each ton of material received and processed (based on competing with current $25/ton cost of open windrow composting, without air quality regulations in effect).

$25/ton fee paid by the facility for each ton of digestate sent off-site for composting. $25/ton for each ton of residue sent off-site for landfill disposal. $0.065/kWh received by the facility for each kWh of net output power sold to the grid. No process heat, potentially recoverable from the engine, sold. No capital or operating grants funding provided. Capital financed at a public sector utility interest rate of 6.4%.

Table 7-4 illustrates that under these base case assumptions, if electricity is sold at $0.065/kWh, an input material tipping fee of $68 per ton is required for financial viability. Part b) of Table 7-4 illustrates that, with a base case input material tipping fee set at $25 per ton and without any additional grants or subsidies, an output electricity price of $0.57/kWh is required for financial viability. Details from with this summary table was created are provided in Appendix A.

7-23 April 2005


Table 7.4

Tipping Fee and Power Price Calculation 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

Category Cost

($US) a) Input Tip Fee Calculation if Electricity Price Fixed at $0.065 per kWh Annual Operating Costs - Operating and Maintenance Cost - Digestate Composting and Residual Disposal Cost Annual Capital Charge

Gross Annual Cost Electricity Sales Revenue

Net Annual Cost

Cost per Input ton

2,460,000 1,650,000 3,271,562 7,381,562 (558,198) 6,823,364

68.23

b) Electricity Price Calculation if Input Tipping Fee set at $25 per ton Annual Operating Costs Annual Capital Charge

Gross Annual Cost Tipping Fee Revenue

Net Annual Cost

Cost per Output kWh

4,110,000 3,271,562 7,381,562

(2,500,000) 4,881,562

0.568

This base case analysis illustrates that given current, very low composting tipping fees of $25/ton, low waste disposal costs of $25/ton and low electricity prices (6.5 cents/kWhr), the proposed facility is not economically viable without additional capital grants and operating subsidies. AD facilities are financially viable in Europe where waste and composting/digestion tipping fees are often over $100US/ton, and green power is sold for a mandatory 15 cents/kWh. Economic conditions in North America are very different to Europe, which is why many more AD facilities have been constructed in Europe than have been constructed in North America. However, potential new air quality regulations for open windrow composting sites will likely increase costs of these facilities, therefore, future composting prices will likely be higher if air quality requires more stringent covered composting. Typically costs may increase by $40/ton or more.

7-24 April 2005


7.5 Costs and Financial Analysis for 200,000 Ton per Year Garden Waste AD

Facility (Dry, Thermophilic) at a Greenfield Site – Option 2 In order to investigate the implications of economies of scale on financial viability, the costs and a financial analysis for a 200,000-ton per year facility were developed. At the scale being considered, the technology is somewhat modular and only minor economies of scale are gained in the capital cost estimate (e.g. 4 digesters required instead of 2). Some economies of scale are gained in direct facility operating costs, but external costs for digestate composting and residue disposal vary in direct proportion to the quantities managed. Capital and operating costs for this option are provided in Appendix B along with the associated financial analysis. In summary, with the larger facility the cost per input ton falls to $60. Also, with a base case input material tipping fee set at $25 per ton, the larger facility also causes the electricity-selling rate to fall to $0.47/kWh. 7.6 Costs and Financial Analysis for 100,000 Ton per Year Garden Waste AD

Facility (Dry, Thermophilic) at a Co-located Site – Options 3 and 4 In this option (Option 3), it is assumed that the facility is developed on an existing transfer station, MRF, landfill or integrated waste management facility site. As a result, estimated capital and operating costs are reduced. A transfer station would be the most suitable of these facilities as it already has a tipping floor and weigh scales, therefore our co-location cost estimates are based on this assumption. The detailed assumptions are as follows.

The existing transfer station will be used as the AD facility tip floor and has adequate capacity (floor space);

The existing site has sufficient area to accommodate the 100,000 tpy AD facility; The existing site configuration allows for the AD facility to be located adjacent to the

existing transfer station (tip floor) such that extensive conveyor system is not required; The existing transfer station has suitable weigh scales; With use of the existing transfer station, only approximately 50% of the typical site works

(geotechnical work, clearing, roadworks, lighting, signage, fencing, stormwater management and utility connections) necessary for a greenfield site are required;

The existing transfer station has adequate administration buildings and maintenance buildings to serve the AD facility;

Operating costs for maintenance associated with existing buildings are covered under another operating account;

The following staff that would otherwise be required at a greenfield site are existing and their salaries are covered under another operating account:

- Tip floor operators (2) - Maintenance technicians (1) - Scale house operators (2) - Receptionist (1)

The following operating cost items that would otherwise be required at a greenfield site are partially accounted for under another operating account:

7-25 April 2005


Rolling equipment leases and maintenance (75% accounted for); Tip floor rolling equipment fuel (100% accounted for); Administration, legal and accounting costs (50% accounted for); Service contracts (50% accounted for).

In addition to the reduced capital and operating costs, the following optimistic assumptions are made:

There is no cost associated with digestate composting, rather the revenue received from the ultimate sale of the resulting compost is assumed to cover this cost.

There is no cost associated with the disposal of the residue generated by the process (or alternatively, there is minimal unacceptable material in the garden waste).

The capital and operating costs for the 100,000 tpy garden waste (dry, thermophilic AD facility, co-located site) are present in Appendix C. Table 7.5 illustrates that if electricity is sold at $0.065/kWh, an input material tipping fee of approximately $43 per ton, rather than the estimated base case fee of $68 per ton (see Table 7-4) is required for financial viability. Also, with a base case input material tipping fee of $25 per ton, this facility allows the electricity-selling rate to fall to $0.27/kWh. This analysis shows considerable benefits of co-locating at the AD facility at another existing waste management facility such as a transfer station, composting, MRF or landfill sites. If co-located at composting site, the curing location is there. If co-located at a landfill, the compost can be used as landfill cover. If co-located at a MRF, the AD facility can possibly share staff and other facilities. The ideal site is a landfill with existing LFG engines which can burn biogas directly and has an existing wastewater treatment system. An alternative is to locate the facility near an industrial heat customer. We assessed options to reduce tip fee to $25/ton. Given that operating costs were reduced as much as possible and capital alone costs $30/ton of input, the remaining option is to reduce the capital costs through direct capital grants (from entities such as CEC, CIWMB, etc.) A capital grant of $16.8 million (shown as Option 4) would be required to achieve the $25 per ton set tip fee with electricity sold at $0.065/kWh.

7-26 April 2005


Table 7.5 Summary of Costs for Options 1-4

Option 1 Option 2 Option 3 Option 4

Feedstock Garden Waste Garden Waste Garden Waste Garden WasteAD Technology Dry Dry Dry DrySize (TPY) 100,000 200,000 100,000 100,000Location Greenfield Greenfield Co-Located Co-LocatedCapital Grants ($) 0 0 0 16,760,000Capital Cost ($) 30,960,000 54,970,000 27,670,000 10,910,000Annual Capital Cost ($) 3,271,562 5,808,713 2,923,906 1,152,866Annual Operating and Maintenance (O&M) (Excluding Digestate Composting and Residue Disposal Cost) ($) 2,460,000 3,957,000 1,905,000 1,905,000Annual Digestate Composting and Residue Disposal Cost ($) 1,650,000 3,300,000 0 0

Amortized Capital Per Ton ($/Ton) 32.72 29.04 29.24 11.53Annual O&M Per Ton ($/Ton) 24.60 19.79 19.05 19.05Annual Digestate Composting and Residue Disposal Cost Per Ton ($/Ton) 16.50 16.50 0.00 0.00Total Annual Cost Per Ton ($/Ton) 73.82 65.33 48.29 30.58Annual Electricity Revenue Per Ton (If Electricity Rate is $0.065/kWh) ($/Ton) (5.58) (5.58) (5.58) (5.58)Net Cost Per Ton ($/Ton) 68.23 59.75 42.71 25.00Cost per kWh Input (If Input Tipping Fee is set at $25/ton) 0.568 0.470 0.271 0.065 7.7 Costs and Financial Analysis for 100,000 Ton per Year Garden Waste with

Food Waste AD Facility (Wet, Mesophilic) at a Greenfield Site – Option 5 Wet AD technologies represent a viable alternative to the dry systems described earlier. Fundamental differences between the two technologies are described below. Wet AD technologies typically have more process elements for front-end waste conditioning and contaminant removal than dry technologies. In addition to the initial size screening common to both wet and dry digestion, wet digestion technologies typically include two-step wet separation devices to remove heavy and light non-digestibles, followed by a further grit removal cyclone, after which the waste is pumped to the digester. It is because of these inherent wet separation steps that wet technologies are somewhat better suited than dry technologies to deal with a more highly contaminated feedstock (for example, garden waste mixed with household food waste packaged in plastic bags). Generally, although not always, this advantage comes at a higher cost due to greater system complexity. Different vendors supply different proprietary devices for wet separation. In general it involves mixing the incoming waste with water to produce a pumpable pulp, from which heavy non-digestibles (such as glass and grit) are removed by settling and then flushing through a de-gritter. Light non-digestibles (such as plastics and plastic film) are removed by raking off floatables from the pulp. The pulping device serves two other important functions, namely to defiber the material thus increasing its surface area and better preparing it for digestion and

7-27 April 2005


secondly, initiating the digestion process by using process water that already contains micro-organisms. Wet digestion systems typically have more moving parts within the digester than a dry digestion system, as mechanical mixing or biogas recirculation for gas mixing is often employed. Although wet technologies use more water in their process, most of this is recycled process water so the net amount of wastewater produced is not necessarily significantly higher than for dry technologies. Nevertheless, wet systems require comparatively larger digesters, more and greater capacity water pumping and piping/valving, more extensive digestate dewatering and higher capacity wastewater treatment. The estimated capital and operating costs for a 100,000 ton per year garden and contaminated food waste AD facility (wet, mesophilic) located on a greenfield site are presented in Appendix D. Table D-4 (in Appendix D) illustrates that if electricity is sold at $0.065/kWh, an input material tipping fee of approximately $75 per ton is required for financial viability. Also, with a base case input material tipping fee set at $25 per ton and with no additional grants or subsidies, an electricity selling price of $0.51/kWh is required for financial viability. 7.8 Costs and Financial Analysis for 100,000 Ton per Year Garden Waste with

Food Waste AD Facility (Wet, Mesophilic) at a Co-located Site – Option 6 Similar to the option discussed in Section 7-6, in this option (Option 6) it is assumed that the wet AD facility is developed on an existing integrated waste management site such as a transfer station, MRF, composting or landfill site. A transfer station is probably the most suitable of these as it already has a tipping floor and weigh scales. However, a landfill site would have other advantages, as it already will have gas handling equipment and wastewater treatment. As a result of co-location with other waste management operations, estimated capital and operating costs are reduced. The same detailed costing assumptions apply to this option as to the dry co-located facility. These assumptions were presented in Section 7-6. The estimated capital and operating costs for a 100,000 ton per year garden and food waste AD facility (wet, mesophilic) at a co-located site are provided in Appendix E. Table E-4 (in Appendix E) illustrates that if electricity is sold at $0.065/kWh, an input material tipping fee of approximately $48 per ton is required for financial viability. Also, with a base case input material tipping fee set at $25 per ton and with no additional grants or subsidies, an electricity selling price of $0.27/kWh is required for financial viability. 7.9 Costs and Financial Analysis for 100,000 Ton per Year Garden Waste with

Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Option 7 In this option (Option 7), garden waste is combined with food waste in a dry, thermophilic AD facility that is co-located. The assumptions used to calculate the costs are the same as those described in Section 7-6. It is assumed that this facility is developed on an existing integrated waste management site such as a transfer station, MRF, composting or landfill site. As a result of co-location with other waste management operations, estimated capital and operating costs are reduced. The same detailed costing assumptions apply to this option as to the dry co-located facility (see Section 7-6).

7-28 April 2005


The estimated capital and operating costs for a 100,000 ton per year garden and food waste AD facility (dry, thermophilic) at a co-located site are provided in Appendix F. Table F-4 (in Appendix F) illustrates that if electricity is sold at $0.065/kWh, an input material tipping fee of approximately $40 per ton is required for financial viability. Also, with a base case input material tipping fee set at $25 per ton and with no additional grants or subsidies, an electricity selling price of $0.20/kWh is required for financial viability. 7.10 Costs and Financial Analysis for 50,000 Ton per Year Garden Waste with Food

Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Option 8 In an effort to reduce the capital costs, a 50,000 ton per year AD facility (dry, thermophilic) processing garden and food waste was evaluated. The costing assumptions apply to this option (Option 8) as with the dry co-located facility in Section 7.6. The estimated capital and operating costs for a 50,000 ton per year garden and food waste AD facility (dry, thermophilic) at a co-located site are provided in Appendix G. Table G-4 (in Appendix G) illustrates that if electricity is sold at $0.065/kWh, an input material tipping fee of approximately $45 per ton is required for financial viability. Also, with a base case input material tipping fee set at $25 per ton and with no additional grants or subsidies, an electricity selling price of $0.24/kWh is required for financial viability. While the capital and operating costs for the 50,000 tpy AD facility are lower than for a 100,000 tpy equivalent AD facility (taking green and food wastes), the overall net cost per ton is higher at $45 per ton for the 50,000 tpy AD facility compared with $40 per ton for the equivalent 100,000 tpy AD facility. The lower throughput of 50,000 tpy compared with 100,000 tpy throughput results in reduced economies of scale and higher capital investment per ton of throughput capacity. 7.11 Discussion of Costs for Greenfield Site

The preceding financial analysis shows that the economics of digesting garden waste (and garden plus food waste) to generate biogas and green power are not encouraging for a greenfield site in the Sacramento area, because of the very low composting tipping fees with which the digestion facility would compete, and the high capital costs of setting up a greenfield site. The cost analysis for a 100,000 ton/year greenfield location breaks down as follows:

Annualized, amortized cost of financing of capital with no subsidy is $29-$33/ton; Operating costs are $20-$24/ton, and are not very flexible; Composting of the digestate costs $14/ton of input; Disposal of residue is a small cost item at $2.50/ton of input; Electricity revenues are small, at $5.76/ton of input.

For the preliminary analysis, we assumed that biogas would be used in a boiler to generate steam for heating the digester contents. Various AD vendors use different approaches to digester heating, and some of these approaches would reduce the demand for biogas through heat exchange mechanisms, and use the energy to create more electricity of export or heating. Also, we have assumed that there is no customer for the 69,000 MMBTU of heat energy which would be available for sale. A customer may or may not be available for the excess heat

7-29 April 2005


energy. This will depend on the location of the AD facility. It was considered more conservative to exclude any potential heat sales for the preliminary financial analysis, but this exercise illustrates the advantage of locating the AD facility where a heat/steam customer is available. The cost analyses were carried out to see what combination of factors would make the economics of the AD facility viable. For these analyses, we looked at:

4. How much subsidy would be required to keep the tipping fee at $25/ton; 5. What energy revenue (in cents per kWhr) is required to in order to keep the tipping

fee at $25/ton; and 6. What tipping fee would be needed to make the economics of AD viable.

In order to make a 100,000 ton/year facility viable with a $25 per ton input material tipping fee and $0.065/kWh electricity selling price, a capital grant for the full estimated capital cost of the facility - $31 million - plus an annual operating grant or subsidy of over 40% of the estimated annual O&M costs (or $1 million per year) is required on this basis, a Greenfield AD facility is not considered economically viable and a co-located site is considered essential for economic viability. The economics of the proposed facility are particularly sensitive to the input tipping fee, which needs to be competitive with future composting tipping fees, as this revenue stream is much larger than the electricity sales revenue stream. A net present value analysis over a 15-year life cycle was carried out for the 100,000 ton/year AD facility. The 100,000 ton per year AD facility is viable assuming public sector utility debt financing and the following key assumptions:

$55/ton input material tipping fee; $0.065 kWh electricity selling price; a capital grant of approximately one third of the estimated capital cost or $10,000,000; no grants or subsidies for operating costs.

If the 100,000 ton/year dry AD facility (Option 1) were implemented by a private sector proponent with an assumed before tax, cost of capital of 15%, then even with the assumed $10 million capital grant a tipping fee in the order of $68 per ton would be required. A 100,000 ton/year wet AD facility (Option 5), under the same assumptions, requires a tip fee of $75/ton to be financially viable. Therefore, a greenfield site is not viable (see Table 7.6 for a summary of costs). A similar analysis was carried out for the 200,000 ton/year facility (Option 2). For this case, in the absence of grants, an input material tipping fee of $60 per ton (rather than $68) is required for viability. From the electricity sales perspective; with a $25 per ton input tipping fee and electricity selling price of $0.47 per kWh (rather than $0.57 per kWh) is required for viability. The conclusion of this analysis was that a greenfield site would not make sense, because of the high additional costs associated with setting up a new site. Co-location with other waste management facilities was the most promising option to reduce costs.

7-30 April 2005


Table 7.6 Summary of Costs for Greenfield Sites

Option 1 Option 2 Option 5

Feedstock Garden Waste Garden WasteGarden and Food Waste

AD Technology Dry Dry WetSize (TPY) 100,000 200,000 100,000Location Greenfield Greenfield GreenfieldCapital Grants ($) 0 0 0Capital Cost ($) 30,960,000 54,970,000 34,400,000Annual Capital Cost ($) 3,271,562 5,808,713 3,635,069Annual Operating and Maintenance (O&M) (Excluding Digestate Composting and Residue Disposal Cost) ($) 2,460,000 3,957,000 2,836,000Annual Digestate Composting and Residue Disposal Cost ($) 1,650,000 3,300,000 1,775,000

Amortized Capital Per Ton ($/Ton) 32.72 29.04 36.35Annual O&M Per Ton ($/Ton) 24.60 19.79 28.36Annual Digestate Composting and Residue Disposal Cost Per Ton ($/Ton) 16.50 16.50 17.75Total Annual Cost Per Ton ($/Ton) 73.82 65.33 82.46Annual Electricity Revenue Per Ton (If Electricity Rate is $0.065/kWh) ($/Ton) (5.58) (5.58) (7.38)Net Cost Per Ton ($/Ton) 68.23 59.75 75.08Cost per kWh Input (If Input Tipping Fee is set at $25/ton) 0.568 0.470 0.506

7.12 Economic Conditions Which Make AD Viable Earlier analysis concluded that a Greenfield site is not economically viable and a co-located site is essential. Co-located options are provided on Table 7.7. The table shows that to operate an AD facility (Option 4) at a tipping fee of $25/ton and sell electricity at 6.5 cents/kWhr, the AD facility would need to be co-located at an existing waste management facility, and a capital grant of $17 million would be needed to reduce the cost of servicing debt. This situation assumes status quo in which no air quality regulations for open windrow composting sites have been introduced. Operating cost assumptions are discussed in Section 7.6 and are considered very optimistic. Various partners would need to be involved in the project to make some of the operating cost assumptions viable (e.g. use of digestate at no cost; free disposal of residual). However, the analysis shows that if the right conditions and partnerships are in place, the project could be viable. The costs for an AD facility will become more competitive if the proposed air quality regulations for open windrow composting sites are introduced in the future. The proposed air quality regulations will likely increase the costs of these facilities making future aerobic composting costs higher and possibly becoming competitive with even the $40/ton option (Option 7), with no built in grants or subsidies.

7-31 April 2005


Table 7.7 Summary of Costs for Co-located Sites

Option 3 Option 4 Option 6 Option 7 Option 8

Feedstock Garden Waste Garden WasteGarden and Food Waste



AD Technology Dry Dry Wet Dry DrySize (TPY) 100,000 100,000 100,000 100,000 50,000Location Co-Located Co-Located Co-Located Co-Located Co-LocatedCapital Grants ($) 0 16,760,000 0 0 0Capital Cost ($) 27,670,000 10,910,000 31,090,000 27,670,000 17,440,000Annual Capital Cost ($) 2,923,906 1,152,866 3,285,299 2,923,906 1,314,542Annual Operating and Maintenance (O&M) (Excluding Digestate Composting and Residue Disposal Cost) ($) 1,905,000 1,905,000 2,281,000 1,905,000 1,341,000Annual Digestate Composting and Residue Disposal Cost ($) 0 0 0 0 0

Amortized Capital Per Ton ($/Ton) 29.24 11.53 32.85 29.24 26.29Annual O&M Per Ton ($/Ton) 19.05 19.05 22.81 19.05 26.82Annual Digestate Composting and Residue Disposal Cost Per Ton ($/Ton) 0.00 0.00 0.00 0.00 0.00Total Annual Cost Per Ton ($/Ton) 48.29 30.58 55.66 48.29 53.11Annual Electricity Revenue Per Ton (If Electricity Rate is $0.065/kWh) ($/Ton) (5.58) (5.58) (7.38) (7.59) (7.59)Net Cost Per Ton ($/Ton) 42.71 25.00 48.29 40.70 45.52Cost per kWh Input (If Input Tipping Fee is set at $25/ton) 0.271 0.065 0.270 0.199 0.241 A summary of costs of all the options explored is provided in Table 7.8. 7.13 Next Steps in Research The following options should be explored to improve the economics of the AD facility:

Identify potential sources of capital grants and also operating grants to make the AD facility viable. Both CIWMB and CEC are very interested in conversion technologies at this time and may be a potential source of some capital grants;

Explore the option of charging higher tipping fees for the garden waste. This analysis has been carried out using a composting tipping fee of $25/ton as the value needed for AD to be competitive. However, there may be local policy reasons why a higher tipping fee would be tolerated in exchange for green energy purchases. Also, new air quality requirements are likely to increase tip fees for green waste;

Negotiate a lower tipping fee for composting of the digestate and/or co-locate the digester at a composting site;

Find a market which will take the digestate as-is without any further stabilization. Farmers can use the digestate as-is depending on local by-laws, and the nutrient content. Finding a market or outlet which does not require the digestate to be composted could reduce digestate handling costs by up to $14/ton of input. This approach is used in Europe where most of the revenues are obtained from tipping fees at the front end of the facility. Compatibility with future air quality requirements need to be explored;

Negotiate free tipping of residue with SWA. This only saves $250,000/year, but the issue should be raised. The material could possibly be used as alternative daily cover

7-32 April 2005


(ADC) at the county landfill. Explore possibility of using digestate as ADC at a reduced tipping fee with SWA; and

Explore sources of other feedstocks such as food and paper wastes, biosolids and animal manures which could be co-digested and both increase the AD facility revenues and increase gas production rates.

Table 7.8 Financial Analysis Summary

Option 1 Option 2 Option 3 Option 4 Option 5 Option 6

Feedstock Garden Waste Garden Waste Garden Waste Garden WasteGarden and Food Waste


AD Technology Dry Dry Dry Dry Wet WetSize (TPY) 100,000 200,000 100,000 100,000 100,000 100,000Location Greenfield Greenfield Co-Located Co-Located Greenfield Co-LocatedCapital Grants ($) 0 0 0 16,760,000 0 0Capital Cost ($) 30,960,000 54,970,000 27,670,000 10,910,000 34,400,000 31,090,000Annual Capital Cost ($) 3,271,562 5,808,713 2,923,906 1,152,866 3,635,069 3,285,299Annual Operating and Maintenance (O&M) (Excluding Digestate Composting and Residue Disposal Cost) ($) 2,460,000 3,957,000 1,905,000 1,905,000 2,836,000 2,281,000Annual Digestate Composting and Residue Disposal Cost ($) 1,650,000 3,300,000 0 0 1,775,000 0

Amortized Capital Per Ton ($/Ton) 32.72 29.04 29.24 11.53 36.35 32.85Annual O&M Per Ton ($/Ton) 24.60 19.79 19.05 19.05 28.36 22.81Annual Digestate Composting and Residue Disposal Cost Per Ton ($/Ton) 16.50 16.50 0.00 0.00 17.75 0.00Total Annual Cost Per Ton ($/Ton) 73.82 65.33 48.29 30.58 82.46 55.66Annual Electricity Revenue Per Ton (If Electricity Rate is $0.065/kWh) ($/Ton) (5.58) (5.58) (5.58) (5.58) (7.38) (7.38)Net Cost Per Ton ($/Ton) 68.23 59.75 42.71 25.00 75.08 48.29Cost per kWh Input (If Input Tipping Fee is set at $25/ton) 0.568 0.470 0.271 0.065 0.506 0.270

7-33 April 2005


8.0 Conclusions and Recommendations 8.1 Conclusions Anaerobic digestion of garden waste is technically feasible. It produces a low energy yield compared to anaerobic digestion of other materials such as food, paper and animal manures. The energy yield can be improved by adding these materials to the digester. Anaerobic digestion of garden waste is expensive compared to open windrow composting, which is the traditional technology used. However, new air quality regulations for open windrow composting sites (not finalized) will increase costs of composting making AD more cost competitive. There is very little experience with anaerobic digestion of solid wastes in North America. Most of the existing and planned digestion facilities are in Europe, with a few in Asia. The On-Site Power Systems pilot project at UC Davis provides a valuable opportunity to carry out research on an AD technology. Construction of the pilot project is expected to be complete by summer, 2005, with research results by the end of 2005. Dry anaerobic digestion technologies are more suited to treating garden waste, which is a relatively clean waste stream. Wet technologies are more suitable for situations where contaminant removal (particularly plastic bag removal) is a key requirement. Dry anaerobic digestion technologies produce more net energy per ton than wet technologies, when in-plant energy demands are satisfied; therefore, dry AD technologies are more suitable for a situation where energy production is a key objective. On the basis of the preliminary screening, four dry AD technologies were considered viable options for a future SMUD –supported facility:

Kompogas, Dranco, Valorga, and Linde.

North American municipalities lack vital operating experience with anaerobic digestion of organic wastes. All existing information is sketchy at best, and is based on facilities operating in Europe, where the economic conditions are very different to North America. Therefore, if AD technology is to be seriously considered as a long term energy source in California or elsewhere, more domestic operating experience is needed. For this reason, it is important to discuss the viability of capital assistance from various funding and research agencies to make construction of the first few AD facilities in California economically viable to the project proponents. Co-locating an AD facility at an existing waste management facility (transfer station, MRF, composting or landfill) is considered the most viable approach in the short to medium term, as this reduces both capital and operating costs of the AD facility. This analysis shows considerable benefits of co-located site options. If co-located at a MRF, the facility can share staff and other facilities. If co-located at composting site, curing can take place on site, and

8-1 April 2005


facilities such as the admin building and scale house can be shared. If co-located at a landfill, the existing LFG engines can burn biogas directly, saving considerable costs. It would also be very beneficial to locate the facility near an industrial heat customer who can purchase excess heat. If air emissions regulations are imposed on open windrow composting sites, the cost to upgrade aerobic composting facilities could likely increase the tipping fee to $35- $40/ton. This situation will make anaerobic digestion more competitive with aerobic composting. 8.2 Recommendations Anaerobic digestion is a technology that should be pursued by SMUD. It is being established as a component of most green energy strategies in Europe, and is suitable for application in the US. Any anaerobic digestion facility contemplated needs to incorporate the flexibility to operate using a range of feedstocks such as animal manures, etc. SMUD should investigate an anaerobic digestion facility, which would process other waste streams (food, paper, animal manure, food processing wastes, etc) in addition to garden waste. Addition of these other waste streams would increase gas yield. The only way for SMUD to get reasonable, reliable cost estimates for a future AD facility in the Sacramento area is to initiate a Request for Proposal process to obtain quotes from qualified AD vendors. SMUD should explore capital funding sources for an AD facility. An amount of $17 million is needed for a 100,000 tpy facility in order to make it cost competitive with today’s composting prices. The AD facility should pursue options to co-locate the AD facility at an existing landfill, transfer station, MRF or composting facility to maximize the co-benefits. Establishing the AD facility at a greenfield location should not be pursued due to higher costs involved. SMUD should explore project partners, which would provide an existing waste management site (preferably a transfer station, MRF, composting facility or landfill), which would provide 6-8 acres on which an AD facility could be located. This will save considerable capital and operating costs. Project partners who would take digestate and dispose of AD facility residue at no cost are also needed.

8-2 April 2005


Appendix A

100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site

A-1 April 2005


A-2 April 2005

sub total: 1,200,000

Total of above: 23,820,000Unforeseen and Estimating Allowance (20%): 4,760,000

Engineering and Contract Administration (10%): 2,380,000Total: 30,960,000

Plant Capital Cost Estimate100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield site)

Main and Post-Processing Equipment

MiscellaneousResidue compactor, bins, containers Platforms, catwalks, ladders, other misc. metal worksWastewater treatment package allowance

4,180,000sub total:

Electrical and Steam Generation Steam Generation package (digester preheating)Electrical Generation package - Engine Generator Set ($2,100/kW x 1,800kW)

525,000sub total:

Flaring and Odor ControlFlare and gas train Biofilter (concrete walls, media support, media, etc.)Blower, ducting, humidity control, other controls, etc.

6,650,000sub total:

Feed pumps, mixing units, conveyors Screw Presses (2), centrifugeVibrating ScreenOther process piping, valves, pumps, small tankage

1,700,000sub total:

Pre-Processing EquipmentComminuting drums, trommel screen

3,700,000sub total:

Digesters (2 x 3,500 m3 glass lined steel) Gas Storage Tank (500 m3)Liquid (feedstock) Storage Tank (200 m3) Process water storage tank

Major Tankage (including foundations) 5,015,000sub total:

New BuildingsTip floor (1,800 m2 x $800/m2) Pre-Processing Building (675 m2 x $1,000/m2)Main and Post-Processing Building (1,700 m2 x $1,000/m2)Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Scalehouse and 2 scales Miscellaneous structures (at tanks, etc.)

850,000sub total:

Land Costs (assume land available at no cost)General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater managementUtility connections, buried piping (sewer, gas, water)

General Site Works$ U.S.


A-3 April 2005

Staff Requirements (based on 3 shift operation) $ U.S./yr

1 Plant Manager (60k)3 Process Control Operators (35 k)2 Tip Floor Operators (30 k)2 Maintenance Technicians (30 k)2 Scale House Operators (25 k)1 Reception (25 k)1 Marketing Mgr (35 k)6 General laborers (25 k)1 lab technician (30 k)Sub total including 1.5 factor for O'head/benefits sub total: 863,000

Utilities and Fuel

Fuel for rolling equipment (2 vehicles x 10 L/hr x 16 hrs/d x 250 d/yr x $0.5/L)Water (1,000 m3/yr x $1/m3) Electricity (assumes parasitic load addressed through on-site power generation)Start-Up Natural Gas (assumes biogas used to satisfy heat loads)

sub total: 42,000Maintenance

Equipment (~16 M at 4%)Buildings and Site Works (~7 M at 0.5%)Tankage and Odor Control (~ 5M at 1%)

sub total: 725,000Other

Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table 7-3Residue Disposal (10% residue assumed) - see Table 7-3Greenhouse gas credits

sub total: 420,000

Total: 2,050,000Unforeseen at 10%: 205,000

Estimating Allowance at 10%: 205,000Grand Total: 2,460,000

Plant Operating & Maintenance Cost Estimate 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield site)


A-4 April 2005

Input Assumptions & DataAnnual Mass Material Balance

- Net O & M Costs 2,460,000

Capital Costs 30,960,000 See Table 7-2

Capital Grant - Net Capital Cost 30,960,000

Capital FinancingBefore Tax Cost of Capital 6.4% Used to calculate annual capital charge

Amortization Period 15 Years Used to calculate annual capital charge

Annual Capital Charge 3,271,562 Net cap. cost amortized over 15 Yrs. at cost of cap.

Annual Inflation Rate 2% Used in NPV analysis

Financial Analysis: Input Assumptions and Data 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield site)

See Table 7-1 2,460,000Facility CostsAnnual O & M CostsAnnual O & M Grant

Based on 45% thermal conversion, 90% availabilityMMBTU 5 0,050Engine Heat Available for Sale

Assuming 90% annual availabilitykWkWh

1 ,0898,587,663

Net Power OutputAnnual Electricity Available for Sale

Based on electrical load required per ton of wasteBased on 35% electrical conversionkW

kW

1 ,766677

Gross Electrical Output PowerParasitic Plant Power Load

Assuming 45% engine heat efficiency, 90% availabilityBased on thermal load required per ton of wasteMMBTU

MMBTU

1 1,0386 1,088

Gross Annual Plant Heat Load Annual Engine Heat Recovered

3Assuming 522.1 BTU/ftConverted from metric unit above

gas/tonne waste3Mass Balance, mm3/Tonneft3/TonMMBTU

9 2 ,889

1 50,835

0Gas Generation Rate (metric)Gas Generation Rate (imperial) Total Gas Heat Energy Produced

Annual Energy Balance

Received by facility for sale of process heatReceived by facility for sale of electricityPaid by facility for disposal of residuesPaid by facility for composting of digestatePaid to facility to process garden Waste$/Ton

$/Ton$/Ton$/kWh$/MMBTU

252525

0.0650

Unit Prices Input Material Tipping Fee Digestate Composting Fee Residue Disposal FeeElectricity Selling PriceProcess Heat Selling Price

TonsTonsTons

1 00,0001 0,0005 6,000

Input Quantity to facilityResidue to DisposalDigestate To Composting


A-5 April 2005

a) Input Tip Fee Calculation if Electricity Priced @ 0.065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table 7-3)

O & M Costs 2,460,000 See Table 7-1 Digestate Composting Cost 1,400,000 Quantity of digestate times composting priceResidue Disposal Cost 250,000 Quantity of residue times residue disposal price

Sub Total Annual Operating Cost 4,110,000

Annual Capital Charge 3,271,562 Net cap. cost amortized over 15 Yrs. at cost of cap.Gross Annual Cost 7,381,562 Sum of annual operating & capital charge

Heat Sales Revenue - Electricity Sales Revenue (558,198) Quantity of electricity times electricity price

Net Annual Cost 6,823,364 Gross annual cost less electricity revenue

Cost per Input Ton 68.23 Net annual cost divided by input quantity

b) Electricity Price Calculation If Input Tipping Fee Set @ 25$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table 7-3)

O & M Costs 2,460,000 See Table 7-1 Digestate Composting Cost 1,400,000 Quantity of digestate times composting priceResidue Disposal Cost 250,000 Quantity of residue times residue disposal price



Gross Annual Cost 7,381,562 Sum of annual operating & capital charge

Heat Sales Revenue - Tipping Fee Revenue (2,500,000) Input quantity times input material tipping fee

Net Annual Cost 4,881,562 Gross annual cost less tipping fee revenue

Cost per Output kWh 0.568$ Net annual cost divided by annual electricity sold

Tipping Fee & Power Price Calculation 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield site)


Appendix B

200,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) on a Greenfield Site

A-6 April 2005


A-7 April 2005

Table B-1 - Plant Capital Cost Estimate200,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

$ U.S.General Site WorksLand Costs (assume land available at no cost) General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater management Utility connections, buried piping (sewer, gas, water)

sub total: 850,000

New BuildingsTip floor (2,800 m2 x $800/m2) Pre-Processing Building (1,350 m2 x $1,000/m2) Main and Post-Processing Building (2,800 m2 x $1,000/m2)Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Scalehouse and 2 scalesMiscellaneous structures (at tanks, etc.)


Major Tankage (including foundations) Digesters (4 x 3,500 m3 glass lined steel) Gas Storage Tank (2 x 500 m3)Liquid (feedstock) Storage Tank (200 m3) Process water storage tank


Pre-Processing Equipment Comminuting drums, trommel screen


Main and Post-Processing EquipmentFeed pumps, mixing units, conveyorsScrew Presses (2), centrifuge Vibrating ScreensOther process piping, valves, pumps, small tankage

sub total: 12,100,000

Flaring and Odor Control Flare and gas traneBiofilter (concrete walls, media support, media, etc.)Blower, ducting, humidity control, other controls, etc.

sub total: 875,000

Electrical and Steam GenerationSteam Generation package (digester preheating)Electrical Generation package - Engine Generator Set ($2,100/kW x 3,600kW)


MiscellaneousResidue compactor, bins, containersPlatforms, catwalks, ladders, other misc. metal worksWastewater treatment package allowance


Total of above:Unforeseen and Estimating Allowance (20%):

Engineering and Contract Administration (10%):

42,280,0008,460,0004,230,000

Total: 54,970,000


Table B-2 - Plant Operating & Maintenance Cost Estimate200,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)


1 Plant Manager (60k)6 Process Control Operators (35 k)4 Tip Floor Operators (30 k)2 Maintenance Technicians (30 k)2 Scale House Operators (25 k)1 Reception (25 k)1 Marketing Mgr (35 k)9 General laborers (25 k)1 lab technician (30 k)Sub total including 1.5 factor for O'head/benefits sub total: 1,223,000

Utilities and Fuel





Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table A-3Residue Disposal (10% residue assumed) - see Table A-3Greenhouse gas credits

sub total: 645,000


Estimating Allowance at 10%: 330,000

Other

3,957,000Grand Total:

A-8 April 2005


Table B-3 - Financial Analysis: Input Assumptions and Data200,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

Input Assumptions & DataAnnual Mass Material Balance

Years Used to calculate annual capital chargeAnnual Capital Charge 5,808,713 Net cap. cost amortized over 15 Yrs. at cost of cap.


Input Quantity to facility Residue to Disposal Digestate To Composting

2 00,0002 0,000

1 12,000

TonsTonsTons

Unit Prices Input Material Tipping Fee Digestate Composting Fee Residue Disposal Fee Electricity Selling Price Process Heat Selling Price

252525

0.0650

$/Ton$/Ton$/Ton$/kWh$/MMBTU

Paid to facility to process garden WastePaid by facility for composting of digestatePaid by facility for disposal of residuesReceived by facility for sale of electricityReceived by facility for sale of process heat

Annual Energy Balance m

3ft

3/Tonne Mass Balance, m3Gas Generation Rate (metric)Gas Generation Rate (imperial) Total Gas Heat Energy Produced

9 2,889

3 01,669

0 gas/tonne waste /Ton Converted from metric unit above

Assuming 522.1 BTU/f t3 MMBTU


2 2,0761 22,176

MMBTUMMBTU

Based on thermal load required per ton of waste Assuming 45% engine heat efficiency, 90% availability


3,5321,354

kWkW

Based on 35% electrical conversion Based on electrical load required per ton of waste


2,1791 7,175,326

kWkWh

Assuming 90% annual availability

Engine Heat Available for Sale 1 00,100 MMBTU Based on 45% thermal conversion, 90% availability

Facility Costs Annual O & M Costs Annual O & M Grant

3 ,957,000-

See Table A-1

Net O & M Costs 3 ,957,000

Capital Costs Capital Grant

5 4,970,000-

See Table A-2

Net Capital Cost 5 4,970,000

Capital Financing Before Tax Cost of Capital Amortization Period

6.4%15

Used to calculate annual capital charge

A-9 April 2005


A-10 April 2005

a) Input Tip Fee Calculation if Electricity Priced @ 0.065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table A-3)

O & M Costs 3,957,000 See Table A-1Digestate Composting Cost 2,800,000 Quantity of digestate times composting priceResidue Disposal Cost 500,000 Quantity of residue times residue disposal price



Heat Sales Revenue - Electricity Sales Revenue (1,116,396) Quantity of electricity times electricity price



b) Electricity Price Calculation If Input Tipping Fee Set @ 25$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table A-3)

O & M Costs 3,957,000 See Table A-1Digestate Composting Cost 2,800,000 Quantity of digestate times composting priceResidue Disposal Cost 500,000 Quantity of residue times residue disposal price






Cost per Output kWh 0.470 Net annual cost divided by annual electricity sold

Table B-4 - Tipping Fee & Power Price Calculation200,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)


Appendix C

100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Co-located Site

A-11 April 2005


A-12 April 2005

$ U.S.General Site WorksLand Costs (assume land available at no cost)General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater managementUtility connections, buried piping (sewer, gas, water)

sub total: 425,000

New BuildingsPre-Processing Building (675 m2 x $1,000/m2)Main and Post-Processing Building (1,700 m2 x $1,000/m2)Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Miscellaneous structures (at tanks, etc.)


Major Tankage (including foundations) Digesters (2 x 3,500 m3 glass lined steel) Gas Storage Tank (500 m3)Liquid (feedstock) Storage Tank (200 m3) Process water storage tank





Feed pumps, mixing units, conveyors Screw Presses (2), centrifugeVibrating ScreenOther process piping, valves, pumps, small tankage


Flaring and Odor ControlFlare and gas traneBiofilter (concrete walls, media support, media, etc.)Blower, ducting, humidity control, other controls, etc.

sub total: 525,000


4,180,000





Table C-1 - Plant Capital Cost Estimate 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Co-Located Facility)



1 Plant Manager (60k)3 Process Control Operators (35 k)1 Maintenance Technicians (30 k)1 Marketing Mgr (35 k)6 General laborers (25 k)1 lab technician (30 k)Sub total including 1.5 factor for O'head/benefits sub total: 615,000

Utilities and Fuel

Water (1,000 m3/yr x $1/m3) Electricity (assumes parasitic load addressed through on-site power generation)Start-Up Natural Gas (assumes biogas used to satisfy heat loads)

sub total: 2,000


sub total: 710,000

Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table B-3Residue Disposal (10% residue assumed) - see Table B-3Greenhouse gas credits

260,000



Table C-2 - Plant Operating & Maintenance Cost Estimate100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

Maintenance

Other

A-13 April 2005


A-14 April 2005

Table C-3 - Financial Analysis: Input Assumptions and Data100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

Input Assumptions & DataAnnual Mass Material BalanceInput Quantity to facility 100,000 TonsResidue to DisposalDigestate To Composting

10,00 56,00

00

TonsTons

Unit Prices Input Material Tipping Fee Digestate Composting Fee Residue Disposal Fee Electricity Selling Price Process Heat Selling Price

25 $/Ton0 $/Ton0

0.0650

$/Ton$/kWh$/MMBTU

Paid to facility to process garden WastePaid by facility for composting of digestatePaid by facility for disposal of residuesReceived by facility for sale of electricityReceived by facility for sale of process heat

Annual Energy Balancem3/Tonneft3/TonMMBTU

Mass Balance, m3Gas Generation Rate (metric)Gas Generation Rate (imperial) Total Gas Heat Energy Produced

9 2,889

150,835

0 gas/tonne waste Converted from metric unit aboveAssuming 522.1 BTU/ft3


11,03 61,08

88

MMBTUMMBTU

Based on thermal load required per ton of waste Assuming 45% engine heat efficiency, 90% availability


1,766 677

kWkW

Based on 35% electrical conversion Based on electrical load required per ton of waste


1,089 638,587,6

kWkWh

Assuming 90% annual availability

Engine Heat Available for Sale 50,05 0 MMBTU Based on 45% thermal conversion, 90% availability

Facility Costs Annual O & M CostsAnnual O & M Grant

1 ,905,000-

See Table B-1

Net O & M Costs 1 ,905,000

Capital Costs Capital Grant

27,67 0,000-

See Table B-2

Net Capital Cost 27,67 0,000

Capital FinancingBefore Tax Cost of CapitalAmortization PeriodAnnual Capital Charge

6.4%15

06

Used to calculate annual capital chargeYears Used to calculate annual capital charge

2,923,9 Net cap. cost amortized over 15 Yrs. at cost of cap.



A-15 April 2005

a) Input Tip Fee Calculation if Electricity Priced @ 0 .065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table B-3)

O & M Costs 1 ,905,000 See Table B-1

Digestate Composting Cost - Quantity of digestate times composting price

Residue Disposal Cost -

4,828,906 Sum of annual operating & capital charge




Table C-4 - Tipping Fee & Power Price Calculation100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

Gross Annual CostNet cap. cost amortized over 15 Yrs. at cost of cap. 062,923,9 Annual Capital Charge

Sub Total Annual Operating Cost

1 ,905,000 -

Quantity of residue times residue disposal priceQuantity of digestate times composting price

- 1,905,0 00

See Table B-1O & M CostsDigestate Composting CostResidue Disposal Cost

b) Electricity Price Calculation If Input Tipping Fee Set @ 25$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table B-3)

Capital grant used to achieve $25/ton cost per input16,76 0,000Capital Grant Required for $25/ton

Net annual cost divided by input quantity42.71 Cost per Input Ton

Gross annual cost less electricity revenueNet Annual Cost

- Quantity of electricity times electricity price

( 558,198)

4,270,7 07

Heat Sales Revenue Electricity Sales Revenue

Sum of annual operating & capital chargeNet cap. cost amortized over 15 Yrs. at cost of cap.2,923,9 06

4,828,9 06Annual Capital Charge

Gross Annual Cost

1,905,0 00Sub Total Annual Operating CostQuantity of residue times residue disposal price


Appendix D

100,000 ton/yr Garden Waste with Food Waste AD Facility (Wet, Mesophilic) at a Greenfield Site

A-16 April 2005


A-17 April 2005

$ U.S.General Site WorksLand Costs (assume land available at no cost)General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater management Utility connections, buried piping (sewer, gas, water)

sub total: 850,000

New BuildingsTip floor (1,800 m2 x $800/m2) Pre-Processing, dewatering Building (1,800 m2 x $1,000/m2)Wet Processing Building (675 m2 x $1,000/m2) Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Scalehouse and 2 scalesMiscellaneous structures (at tanks, etc.)


Major Tankage (including foundations) Digesters (3 x 4,500 m3 glass lined steel) Gas Storage Tank (500 m3) Liquid (feedstock) Storage Tank (200 m3) Process water storage tank


Pre-Processing Equipment Trommel screen

sub total: 400,000

Wet Processing EquipmentPulpers, tanks, degritters, conveyors, digester preheating, etc.Screw Presses (4)Compressors, mixersOther process piping, valves, pumps, small tankage



sub total: 525,000

Electrical and Steam GenerationSteam Generation package (digester preheating) Electrical Generation package - Engine Generator Set ($2,100/kW x 2,200kW)






Table D-1 - Plant Capital Cost Estimate100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Greenfield Site)



1 Plant Manager (60k)3 Process Control Operators (35 k)2 Tip Floor Operators (30 k)2 Maintenance Technicians (30 k)2 Scale House Operators (25 k)1 Reception (25 k)1 Marketing Mgr (35 k)6 General laborers (25 k)1 lab technician (30 k)Sub total including 1.5 factor for O'head/benefits sub total: 1,088,000

Utilities and Fuel




sub total: 755,000

Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table C-3Residue Disposal (10% residue assumed) - see Table C-3Greenhouse gas credits

sub total: 470,000



Table D-2 - Plant Operating & Maintenance Cost Estimate100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Greenfield Site)

Other

A-18 April 2005


Table D-3 - Financial Analysis: Input Assumptions and Data100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Greenfield Site)

Input Assumptions & DataAnnual Mass Material Balance Input Quantity to facility 100,000 TonsResidue to Disposal 15,000 TonsDigestate To Composting 56,000 Tons

Unit PricesInput Material Tipping Fee 25 $/Ton Paid to facility to process garden Waste

Digestate Composting Fee 25 $/Ton Paid by facility for composting of digestate

Residue Disposal Fee 25 $/Ton Paid by facility for disposal of residues

Electricity Selling Price 0.065$/kWh Received by facility for sale of electricity

Process Heat Selling Price

0 $/MMBTUReceived by facility for sale of process heatAnnual Energy Balance

Gas Generation Rate (metric) 110 m3/Tonne Mass Balance, m3 gas/tonne waste

Gas Generation Rate (imperial) 3,531 ft3/Ton Converted from metric unit above

Total Gas Heat Energy Produced 184,354 MMBTU Assuming 522.1 BTU/ft 3

Gross Annual Plant Heat Load 27,638 MMBTU Based on thermal load required per ton of waste

Annual Engine Heat Recovered 74,663 MMBTU Assuming 45% engine heat efficiency, 90% availability

Gross Electrical Output Power 2,159 kW Based on 35% electrical conversionParasitic Plant Power Load 719 kW Based on electrical load required per ton of waste

Net Power Output 1,440 kWAnnual Electricity Available for Sale 11,349,033 kWh Assuming 90% annual availability

Engine Heat Available for Sale 7,0254 MMBTU Based on 45% thermal conversion, 90% availability

Facility Costs2,836,000

- 2,836,000

Annual O & M CostsAnnual O & M GrantNet O & M Costs

See Table C-1

Capital CostsCapital GrantNet Capital Cost

3 4,400,000-

4,400,000

See Table C-2

3

Capital FinancingBefore Tax Cost of CapitalAmortization PeriodAnnual Capital Charge

6.4%15

3,635,069

Used to calculate annual capital charge

Years Used to calculate annual capital charge

Net cap. cost amortized over 15 Yrs. at cost of cap.


A-19 April 2005


A-20 April 2005

Table D-4 - Tipping Fee & Power Price Calculation 100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Greenfield Site)

a) Input Tip Fee Calculation if Electricity Priced @ 0.065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table C-3)

O & M Costs 2 ,836,000 See Table C-1

Digestate Composting Cost 1 ,400,000 Quantity of digestate times composting price

Residue Disposal Cost 3 75,000

- ( 2,500,000)

,746,0695

Heat Sales Revenue Tipping Fee Revenue

Net Annual Cost

3 ,635,0698 ,246,069

Annual Capital Charge Gross Annual Cost

4

2 1

,836,000,400,0003 75,000,611,000

O & M Costs Digestate Composting Cost Residue Disposal Cost


b) Electricity Price Calculation If Input Tipping Fee Set @ 2 5$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table C-3)

Net annual cost divided by input quantity5.087 Cost per Input Ton

Gross annual cost less electricity revenue

Quantity of electricity times electricity price-

( 7

737,687),508,382

Heat Sales Revenue Electricity Sales Revenue

Net Annual Cost

Sum of annual operating & capital chargeNet cap. cost amortized over 15 Yrs. at cost of cap.3 ,635,069

8 ,246,069Annual Capital Charge

Gross Annual Cost

,611,0004 Sub Total Annual Operating Cost Quantity of residue times residue disposal price

See Table C-1Quantity of digestate times composting priceQuantity of residue times residue disposal price


Sum of annual operating & capital charge

Input quantity times input material tipping fee

Gross annual cost less tipping fee revenue

Cost per Output kWh 0 .506$ Net annual cost divided by annual electricity sold


Appendix E

100,000 ton/yr Garden Waste with Food Waste AD Facility (Wet, Mesophilic) at a Co-located Site

A-21 April 2005


A-22 April 2005


Table E-1 - Plant Capital Cost Estimate100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Co-Located Facility)

23,920,0004,780,000


1,400,000sub total:

Residue compactor, bins, containers Platforms, catwalks, ladders, other misc. metal worksWastewater treatment package allowance

Miscellaneous

5,020,000


525,000sub total:

Flare and gas traneBiofilter (concrete walls, media support, media, etc.)Blower, ducting, humidity control, other controls, etc.

Flaring and Odor Control

6,900,000sub total:

Wet Processing EquipmentPulpers, tanks, degritters, conveyors, digester preheating, etc.Screw Presses (4)Compressors, mixers Other process piping, valves, pumps, small tankage

400,000sub total:

Pre-Processing EquipmentTrommel screen

6,250,000sub total:

Major Tankage (including foundations) Digesters (3 x 4,500 m3 glass lined steel) Gas Storage Tank (500 m3) Liquid (feedstock) Storage Tank (200 m3) Process water storage tank

3,000,000sub total:

New BuildingsPre-Processing, dewatering Building (1,800 m2 x $1,000/m2)Wet Processing Building (675 m2 x $1,000/m2) Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Miscellaneous structures (at tanks, etc.)

425,000sub total:

Land Costs (assume land available at no cost)General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater managementUtility connections, buried piping (sewer, gas, water)

General Site Works$ U.S.




Water (10,000 m3/yr x $1/m3) Electricity (assumes parasitic load addressed through on-site power generation)Start-Up Natural Gas (assumes biogas used to satisfy heat loads)

sub total: 11,000


sub total: 740,000

Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table D-3Residue Disposal (10% residue assumed) - see Table D-3Greenhouse gas credits

310,000



Table E-2 - Plant Operating & Maintenance Cost Estimate100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Co-Located Facility)

Other

Utilities and Fuel

Maintenance

A-23 April 2005


Input Assumptions & Data Annual Mass Material BalanceInput Quantity to facility 100,000 TonsResidue to Disposal 15,000 TonsDigestate To Composting 56,000 Tons

Unit PricesInput Material Tipping Fee 25 $/Ton Paid to facility to process garden Waste

Digestate Composting Fee 0 $/Ton Paid by facility for composting of digestate

Residue Disposal Fee 0 $/Ton Paid by facility for disposal of residues

Electricity Selling Price 0.065$/kWh Received by facility for sale of electricity

Process Heat Selling Price 0 $/MMBTUReceived by facility for sale of process heat

Annual Energy BalanceGas Generation Rate (metric) 110 m3/Tonne Mass Balance, m3 gas/tonne waste

Gas Generation Rate (imperial) 3,531 ft3/Ton Converted from metric unit above

Total Gas Heat Energy Produced 184,354 MMBTU Assuming 522.1 BTU/ft 3

Gross Annual Plant Heat Load 27,638 MMBTU Based on thermal load required per ton of waste

Annual Engine Heat Recovered 74,663 MMBTU Assuming 45% engine heat efficiency, 90% availability




Facility CostsAnnual O & M Costs 2,281,000 See Table D-1Annual O & M Grant - Net O & M Costs 2,281,000

Capital Costs 31,090,000 See Table D-2Capital Grant - Net Capital Cost 31,090,000

Capital FinancingBefore Tax Cost of Capital 6.4% Used to calculate annual capital chargeAmortization Period 15 Years Used to calculate annual capital chargeAnnual Capital Charge 3,285,299 Net cap. cost amortized over 15 Yrs. at cost of cap.


Table E-3 - Financial Analysis: Input Assumptions and Data100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Co-Located Facility)

A-24 April 2005


a) Input Tip Fee Calculation if Electricity Priced @ 0.065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table D-3)

O & M Costs 2,281,000 See Table D-1

Digestate Composting Cost - Quantity of digestate times composting price

Residue Disposal Cost - Quantity of residue times residue disposal price




Heat Sales Revenue - Electricity Sales Revenue (737,687) Quantity of electricity times electricity price



b) Electricity Price Calculation If Input Tipping Fee Set @

100,000 ton/yr Garden Waste with Food Waste (Wet, Mesophilic AD Plant, Co-Located Facility)

Table E-4 - Tipping Fee & Power Price Calculation

2 5$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table D-3)

O & M Costs Digestate Composting Cost Residue Disposal Cost


2 ,281,000- -

2 ,281,000

See Table D-1Quantity of digestate times composting priceQuantity of residue times residue disposal price

Annual Capital Charge Gross Annual Cost

3 ,285,299,566,2995


Sum of annual operating & capital charge

Heat Sales Revenue Tipping Fee Revenue

Net Annual Cost

- (2,500,000)

,066,2993 Input quantity times input material tipping fee

Gross annual cost less tipping fee revenue

Cost per Output kWh 0 $ .270 Net annual cost divided by annual electricity sold

A-25 April 2005


Appendix F

100,000 ton/yr Garden Waste with Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site

A-26 April 2005


A-27 April 2005

$ U.S.

21,280,0004,260,0002,130,000


Engineering and Contract Administration (10%):

1,200,000sub total:


4,180,000


525,000sub total:

Flaring and Odor ControlFlare and gas traneBiofilter (concrete walls, media support, media, etc.)Blower, ducting, humidity control, other controls, etc.

6,650,000sub total:

Main and Post-Processing EquipmentFeed pumps, mixing units, conveyors Screw Presses (2), centrifugeVibrating ScreenOther process piping, valves, pumps, small tankage

1,700,000sub total:


3,700,000sub total:

Major Tankage (including foundations) Digesters (2 x 3,500 m3 glass lined steel) Gas Storage Tank (500 m3)Liquid (feedstock) Storage Tank (200 m3)Process water storage tank

2,900,000sub total:

New BuildingsPre-Processing Building (675 m2 x $1,000/m2)Main and Post-Processing Building (1,700 m2 x $1,000/m2)Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Miscellaneous structures (at tanks, etc.)

425,000sub total:

General Site WorksLand Costs (assume land available at no cost)General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater managementUtility connections, buried piping (sewer, gas, water)

Table F-1 - Plant Capital Cost Estimate100,000 ton/yr Garden and Food Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

27,670,000Total:


A-28 April 2005

Table F-2 - Plant Operating & Maintenance Cost Estimate100,000 ton/yr Garden and Food Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

Staff Requirements (based on 3 shift operation)

1,587,000159,000159,000

1,905,000

Total:Unforeseen at 10%:

Estimating Allowance at 10%:Grand Total:

260,000

Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table E-3Residue Disposal (10% residue assumed) - see Table E-3Greenhouse gas credits

Other 710,000sub total:

Equipment (~16 M at 4%) Buildings and Site Works (~4 M at 0.5%)Tankage and Odor Control (~ 5M at 1%)

Maintenance2,000sub total:

Water (1,000 m3/yr x $1/m3)Electricity (assumes parasitic load addressed through on-site power generation)Start-Up Natural Gas (assumes biogas used to satisfy heat loads)

Utilities and Fuel

615,000sub total:

1 Plant Manager (60k)3 Process Control Operators (35 k)1 Maintenance Technicians (30 k)1 Marketing Mgr (35 k)6 General laborers (25 k)1 lab technician (30 k)Sub total including 1.5 factor for O'head/benefits

$ U.S./yr


Input Assumptions & DataAnnual Mass Material BalanceInput Quantity to facility 100,000 TonsResidue to Disposal 15,000 TonsDigestate To Composting 56,000 Tons

Unit PricesInput Material Tipping Fee 25 $/Ton Paid to facility to process garden WasteDigestate Composting Fee 0 $/Ton Paid by facility for composting of digestateResidue Disposal Fee 0 $/Ton Paid by facility for disposal of residuesElectricity Selling Price 0.065 $/kWh Received by facility for sale of electricityProcess Heat Selling Price 0 $/MMBTU Received by facility for sale of process heat

Annual Energy BalanceGas Generation Rate (metric) 110 m3/Tonne Mass Balance, m 3 gas/tonne waste

Gas Generation Rate (imperial) 3,531 ft3/Ton Converted from metric unit aboveTotal Gas Heat Energy Produced 184,354 MMBTU Assuming 522.1 BTU/ft 3

Gross Annual Plant Heat Load 11,038 MMBTU Based on thermal load required per ton of wasteAnnual Engine Heat Recovered 74,663 MMBTU Assuming 45% engine heat efficiency, 90% availability




Facility CostsAnnual O & M Costs 1,905,000 See Table E-1Annual O & M Grant - Net O & M Costs 1,905,000

Capital Costs 27,670,000 See Table E-2Capital Grant - Net Capital Cost 27,670,000



Table F-3 - Financial Analysis: Input Assumptions and Data100,000 ton/yr Garden and Food Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

A-29 April 2005


a) Input Tip Fee Calculation if Electricity Priced @ 0.065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table B-3)

O & M Costs 1,905,000 See Table E-1Digestate Composting Cost - Quantity of digestate times composting priceResidue Disposal Cost - Quantity of residue times residue disposal price



Heat Sales Revence - Electricity Sales Revenue (759,332) Quantity of electricity times electricity price



Capital Grant Required for $25/ton 16,760,000 Capital grant used to achieve $25/ton cost per input

b) Electricity Price Calculation If Input Tipping Fee Set @ 25$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table E-3)

O & M Costs 1,905,000 See Table E-1Digestate Composting Cost - Quantity of digestate times composting priceResidue Disposal Cost - Quantity of residue times residue disposal price







Table E-4 - Tipping Fee & Power Price Calculation100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

A-30 April 2005


Appendix G

50,000 ton/yr Garden Waste with Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site

A-31 April 2005


A-32 April 2005

$ U.S.

Feed pumps, mixing units, conveyorsScrew Presses (2), centrifuge Vibrating ScreenOther process piping, valves, pumps, small tankage



sub total: 425,000

Electrical and Steam GenerationSteam Generation package (digester preheating)Electrical Generation package - Engine Generator Set ($2,100/kW x 1,080kW)

2,568,000


sub total: 900,000



Table G-1 - Plant Capital Cost Estimate50,000 ton/yr Garden and Food Waste (Dry, Thermophilic AD Plant, Co-Located Facility)


1,100,000sub total:

Pre-Processing Equipment Comminuting drums, trommel screen

1,850,000sub total:

Major Tankage (including foundations) Digesters (1 x 3,500 m3 glass lined steel)Gas Storage Tank (250 m3) Liquid (feedstock) Storage Tank (100 m3) Process water storage tank

1,950,000sub total:

New BuildingsPre-Processing Building (400 m2 x $1,000/m2) Main and Post-Processing Building (1,200 m2 x $1,000/m2)Other (admin areas, electrical/mechanical, maintenance, laboratory, etc.)Miscellaneous structures (at tanks, etc.)

425,000sub total:

General Site WorksLand Costs (assume land available at no cost)General (clearing, dewatering, geotechnical investigations, etc.)Roadworks, paving, roadway lighting, signage, fencing/gatesStormwater management Utility connections, buried piping (sewer, gas, water)


A-33 April 2005

Staff Requirements (based on 2 shift operation)$ U.S./yr


Utilities and Fuel

Water (1,000 m3/yr x $1/m3)Electricity (assumes parasitic load addressed through on-site power generation)Start-Up Natural Gas (assumes biogas used to satisfy heat loads)


Equipment (~10 M at 4%) Buildings and Site Works (~3 M at 0.5%)Tankage and Odor Control (~3M at 1%)

sub total: 445,000Other

Rolling Equipment Leases and maintenanceWastewater TreatmentLicensing FeesLab analysis costsAdministration, Legal, Accounting costsService ContractsProduct haul and Tip Fees at Curing Site - see Table F-3Residue Disposal (10% residue assumed) - See Table F-3Greenhouse gas credits

220,000



Table G-2 - Plant Operating & Maintenance Cost Estimate50,000 ton/yr Garden and Food Waste (Dry, Thermophilic AD Plant, Co-Located Facility)


Input Assumptions & DataAnnual Mass Material BalanceInput Quantity to facility 50,000 TonsResidue to Disposal 7,500 TonsDigestate To Composting 28,000 Tons

Unit PricesInput Material Tipping Fee 25 $/Ton Paid to facility to process garden WasteDigestate Composting Fee 0 $/Ton Paid by facility for composting of digestateResidue Disposal Fee 0 $/Ton Paid by facility for disposal of residuesElectricity Selling Price 0.065 $/kWh Received by facility for sale of electricityProcess Heat Selling Price 0 $/MMBTU Received by facility for sale of process heat

Annual Energy BalanceGas Generation Rate (metric) 110 m3/Tonne Mass Balance, m 3 gas/tonne waste

Gas Generation Rate (imperial) 3,531 ft3/Ton Converted from metric unit aboveTotal Gas Heat Energy Produced 92,177 MMBTU Assuming 522.1 BTU/ft 3

Gross Annual Plant Heat Load 5,519 MMBTU Based on thermal load required per ton of wasteAnnual Engine Heat Recovered 37,332 MMBTU Assuming 45% engine heat efficiency, 90% availability


Net Power Output 741 kWAnnual Electricity Available for Sale 5,841,016 kWh Assuming 90% annual availability


Facility CostsAnnual O & M Costs 1,341,000 See Table F-1Annual O & M Grant - Net O & M Costs 1,341,000

Capital Costs 17,440,000 See Table F-2Capital Grant 5,000,000 Net Capital Cost 12,440,000



Table G-3 - Financial Analysis: Input Assumptions and Data50,000 ton/yr Garden and Food Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

A-34 April 2005


a) Input Tip Fee Calculation if Electricity Priced @ 0.065$ per kWh(Other inputs and assumptions, except tip fee as set out in Table B-3)

O & M Costs 1,341,000 See Table F-1Digestate Composting Cost - Quantity of digestate times composting priceResidue Disposal Cost - Quantity of residue times residue disposal price



Heat Sales Revence - Electricity Sales Revenue (379,666) Quantity of electricity times electricity price



Capital Grant Required for $25/ton 16,760,000 Capital grant used to achieve $25/ton cost per input

b) Electricity Price Calculation If Input Tipping Fee Set @ 25$ Per Ton(Other inputs and assumptions, except electricity price, as set out in Table F-3)

O & M Costs 1,341,000 See Table F-1Digestate Composting Cost - Quantity of digestate times composting priceResidue Disposal Cost - Quantity of residue times residue disposal price







Table G-4 - Tipping Fee & Power Price Calculation50,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Co-Located Facility)

A-35 April 2005

Download - Feasibility of Generating Green Power through Anaerobic Digestion

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