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  • Cooperative Extension Lewis County

    Final Report June 2010 (updated)

    Feasibility Study of Anaerobic Digestion and Biogas Utilization Options for the Proposed Lewis County Community Digester

    www.manuremanagement.cornell.edu

  • Feasibility Study of Anaerobic Digestion and Biogas Utilization Options for the Proposed Lewis County Community Digester

    By:

    Curt Gooch, P.E.1, Senior Extension Associate

    Jennifer Pronto1, Research Support Specialist

    Brent Gloy, Ph.D2, Professor

    Norm Scott, Ph.D1, Professor

    Steve McGlynn1, Research Support Specialist

    Christopher Bentley1, Undergraduate Student

    1Biological and Environmental Engineering Department

    2Department of Applied Economics and Management

    334 Riley-Robb Hall

    Cornell University

    Ithaca, New York 14853

    June 11, 2010

    Updated June 30, 2010

  • Foreword

    The Feasibility Study of Anaerobic Digestion and Biogas Utilization Options for the Proposed Lewis

    County Community Digester project is not a feasibility study in its strictest definition, but rather an

    assessment of the farm and non-farm biomass resources available in and around the village of Lowville,

    an investigation into the available options for co-digesting them (various combinations of materials and

    site locations), an estimation of the biogas that could be produced by the various scenarios, the resulting

    energy produced, and net energy available for use, and an economic profitability assessment for each of

    the options investigated. The scope of work for this project was somewhat dynamic as adjustments

    were continually made based on progress of evaluating the information at hand. This report was

    written to provide the findings and recommendations of the feasibility study to the client, the Lowville

    Digester Workgroup, and also to serve as an educational tool for the stakeholders of this and future

    proposed centralized anaerobic digester projects.

    The proposed Lewis County Community Digester project exemplifies the full potential of a centralized

    anaerobic digester. Manure and, waste biomass materials (processing byproducts from multiple

    sources), are mixed together and heated to produce biogas; a locally generated, clean burning,

    renewable energy. Waste biomass is generated daily by food processing plants and restaurants, public

    facilities and institutions such as schools and hospitals, and at private residences. Co-digesting manure

    and these materials reduces the burden on landfills and reduces greenhouse gas (GHG) emissions. The

    U.S. dairy industry has formally committed to reducing its GHG emissions by 25% by 2020 and this

    project is an example of how this can be effectively accomplished, from a technical/applied perspective.

    In fact, the Lewis County Community Digester project demonstrates the vision behind Dairyville 2020

    the Innovation Center for U.S. Dairys Dairy Power Initiative flagship project. The major shortcomings

    at this point are high capital costs and less than required energy purchase prices needed to make such

    systems economically feasible.

  • Acknowledgements This document is the culmination of a team effort by the authors and many others who provided their

    assistance and support. The authors wish to acknowledge and thank the following individuals/groups

    for their contributions:

    Senator Joseph Griffo, 47th District in New York State, for funding this project and for his continued

    interest.

    The dairy farmers of Lewis County who completed the farm surveys.

    Representatives for the non-farm biomass suppliers who completed the non-farm surveys.

    Drs. Dave C. Ludington and Michael B. Timmons, Professor Emeritus and Professor, respectively, of

    Biological and Environmental Engineering at Cornell University for their efforts in reviewing drafts of the

    feasibility study and for their constructive inputs and suggestions.

    Members of the Lowville Digester Workgroup for their confidence in the Cornell team to provide a

    feasibility study that would contain unbiased information and for their teamwork and collaboration

    while the feasibility study was being conducted.

    Ms. Christine Ashdown (Cornell Office of Sponsored Programs) for her timely efforts in developing the

    contract for this project and for her continued support to funded project opportunities pursued by

    members of the Cornell PRO-DAIRY program.

    Ms. Michele Ledoux (Cornell Cooperative Extension Lewis County) for her trust in the Cornell team

    and for her work in securing the funding and performing contract administration tasks that resulted in a

    workable means to performing this work.

    Ms. Norma McDonald (North American Sales Manager, Organic Waste Systems, Inc.) for providing key

    information on energy crop digesters suitable for U.S. applications needed to perform the annual

    economic profitability analysis for the energy crop digester scenarios investigated.

  • Mr. Todd Vernon (Senior Sales Manager, GE Energy Jenbacher) for providing key information on the

    Jenbacher engine-generator sets needed to perform the annual economic profitability analysis.

    Mr. Frans Vokey (Cornell Cooperative Extension Lewis County) for his overall leadership of the

    Lowville Digester Workgroup and Cornell collaboration, and for all of his efforts in planning and running

    project meetings.

    Mary Beth Anderson (community resident) for her assistance in collecting samples from non-farm

    biomass suppliers and for work on distributing and collecting non-farm biomass surveys.

    Mike Durant (Soil and Water Conservation District) for designing the project map.

  • Table of Contents

    Foreword

    Acknowledgements

    Table of Contents

    Table of Figures

    Table of Tables

    Abbreviations and Acronyms

    Executive Summary p. 1

    Introduction p. 15

    Chapter 1. Basics of Centralized Dairy Manure-based Anaerobic Digestion, Biogas Utilization, and Nutrient Recovery Systems

    p. 23

    Chapter 2. Literature Review of Centralized AD Projects p. 39

    Chapter 3. Farm and Community Biomass Survey p. 49

    Chapter 4. Biomass Sample Collection and Analysis p. 61

    Chapter 5. Biomass Transportation p. 71

    Chapter 6. Preliminary Investigation of Five AD Scenarios p. 77

    Chapter 7. Final AD Scenario Selection and Details p. 93

    Chapter 8. Next Steps and Recommendations p. 115

    References p. 117

    Appendix

    A. Glossary of terms p. 121

    B. Farm-based Survey p. 127

    C. Non Farm-Based Survey p. 131

    D. Substrate Sampling Report p. 133

    E. Biochemical Methane Potential; Laboratory Procedure p. 137

    F. Projected Farm Survey Responses p. 139

  • Table of Figures Page Figure 1. New York State map showing location of project-site ................................................................. 16 Figure 2. Typical CAD system process flow diagram ................................................................................... 23 Figure 3. A CAD in Jutland, Denmark .......................................................................................................... 24 Figure 4. Danish above-grade complete mix vertical digesters in background .......................................... 29 Figure 5. Thermal to electric conversion efficiency of six NYS on-farm engine-generator sets. (Source: Gooch, Pronto, Ludington, Unpublished, 2010) ......................................................................................... 32 Figure 6. Basic process flow diagram for advanced biogas clean-up for biomethane production. ........... 34 Figure 7. Advanced digestate treatment to segregate and concentrate nitrogen, phosphorus, and potassium. ................................................................................................................................................... 38 Figure 8. Landfill tipping fees ($/ton) by region of the U.S. (Repa, 2005) .................................................. 47 Figure 9. Landfill tipping fees ($/ton), developed from Figure 8 (Repa, 2005). ......................................... 47 Figure 10. Lowville regional map with collaborating dairy farms superimposed along concentric circles of various radii centered on downtown Lowville............................................................................................ 54 Figure 11. Quantity (millions lbs/yr.) of substrates (wet weight). ............................................................. 57 Figure 12. Biochemical Methane Potential (BMP) data (cumulative biogas yield) for substrate 4. ........... 62 Figure 13. Graphical representation of biochemical methane potentials for all substrates tested. .......... 63 Figure 14. Estimated annual minimum, maximum, and average methane production by substrate. ....... 66 Figure 15. Estimated aggregated annual minimum, maximum, and average methane production of non-farm biomass substrates and manure. ....................................................................................................... 66 Figure 16. Nutrient concentrations for pre- and post-digestion conditions for N, P, K.............................. 70 Figure 17. Diagram of estimating a break-even tipping fee for non-farm biomass substrate suppliers. ... 75 Figure 18. CAD Site 1 for Scenario Nos. 1 and 2. ........................................................................................ 78 Figure 19. Remote AD Site 2 for Scenario Nos. 3, 3a, and 3b. .................................................................... 79 Figure 20. Remote AD Site 3 for Scenario Nos. 3, 3a, and 3b. .................................................................... 80 Figure 21. Process flow diagram for Scenario No. 1 using the average annual total volume of the seven non-farm biomass substrates. .................................................................................................................... 81 Figure 22. Process flow diagram for Scenario No. 2 using the average annual total volume of the three non-farm biomass substrates. .................................................................................................................... 83 Figure 23. Process flow diagrams for Scenario No. 3 using the average annual total volume of the three non-farm biomass substrates for Site 2 and Site 3. All manure and digestate are trucked. ..................... 85 Figure 24. Process flow diagram for Scenario No. 3a using the average annual total volume of three non-farm biomass substrates for Site 2 and Site 3. Manure and digestate are pumped and trucked. ............ 87 Figure 25. Process flow diagram for Scenario No. 3b using the average annual total volume of three non-farm biomass substrates for Site 2 and Site 3. ........................................................................................... 89 Figure 26. Final Scenario No. 2 process flow diagram. ............................................................................... 94 Figure 27. Energy crop anaerobic digester process flow diagram. ............................................................. 94 Figure 28. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received, by farm. ....................................................................................................................................................... 96 Figure 29. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received, by farm, taking into account each farm's nutrient balance situation....................................................... 112 Figure 30. Image of residential food waste sample collected. ................................................................. 134 Figure 31. Meat and butcher waste from substrate number 4. ............................................................... 135

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  • Table of Tables Page Table 1. Typical fuel-to-power efficiency values (adapted and updated from Wright, 2001). .................. 33 Table 2. St.Albans/Swanton, VT project statistics ...................................................................................... 39 Table 3. LREC project statistics ................................................................................................................... 41 Table 4. Dane County, WI (Waunakee cluster) project statistics ............................................................... 42 Table 5. Cornell project statistics ................................................................................................................ 43 Table 6. York, NY project statistics .............................................................................................................. 43 Table 7. Salem, NY project statistics ........................................................................................................... 44 Table 8. Perry, NY project statistics ............................................................................................................ 45 Table 9. Port of Tillamook project statistics................................................................................................ 46 Table 10. Summary of current (2009) farm survey data ............................................................................. 51 Table 11. Summary of nutrient balance information as provided in farm surveys ................................... 53 Table 12. Summary of non-farm biomass survey results............................................................................ 56 Table 13. Select Lewis County crop farm data ............................................................................................ 58 Table 14. BMP analysis results for all substrates tested ............................................................................. 63 Table 15. Biogas production potential of non-farm biomass substrates and manure ............................... 65 Table 16. Potential biogas production of available energy crop acreage ................................................... 65 Table 17. CES lab results for each non-farm biomass substrate: nutrients ................................................ 67 Table 18. CES lab results for each non-farm biomass substrate: solids...................................................... 67 Table 19. Estimated annual mass of nitrogen series for raw AD feedstock .............................................. 68 Table 20. Estimated annual mass of phosphorus and potassium series for raw AD feedstock ................ 68 Table 21. Predicted annual mass of nitrogen for post-digested AD feedstock ......................................... 69 Table 22. Predicted annual mass of phosphorus and potassium for post-digested AD feedstock ........... 70 Table 23. Capital and annual cost estimates for a project-owned trucking fleet ....................................... 72 Table 24. Contracted trucking fleet example schedule .............................................................................. 73 Table 25. Scenario No. 3a means of manure and digestate transport ....................................................... 87 Table 26. Comparison of the five AD scenarios .......................................................................................... 91 Table 27. Scenario No. 2 participating farms and associated manure generation ..................................... 94 Table 28. Scenario No. 2 feedstock volumes .............................................................................................. 97 Table 29. Potential methane and biogas production volumes for each feedstock in Scenario No. 2 CAD 98 Table 30. Capital costs ($) for Scenario No. 2 CAD system, engine-generator set, and biogas clean-up

    system, and totals for two different energy sale options ............................................................... 101 Table 31. Annualized capital costs ($) for the Scenario No. 2 CAD system based on minimum, maximum,

    and average biogas production quantities...................................................................................... 102 Table 32. Scenario No. 2 CAD, annual operating and maintenance expenses ($) .................................... 103 Table 33. Scenario No. 2 CAD, total annual costs ($) ................................................................................ 103 Table 34. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various biomethane sale prices

    and biogas production volumes (no tipping fees received) ............................................................ 104 Table 35. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various electrical energy sale

    prices and biogas production volumes (no tipping fees received) ................................................. 104 Table 36. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various biomethane sale prices

    and biogas production volumes, including current tipping fee paid by substrate supplier #8 ...... 105 Table 37. Scenario No. 2 CAD net annual economic profitability ($) 2,3 for various electrical energy sale

    prices and biogas production volumes, including current tipping fee paid by substrate supplier #8 ......................................................................................................................................................... 105

  • Table 38. Scenario No. 2 CAD net annual economic profitability ($)2 for various biomethane sale prices and tipping fee revenues ................................................................................................................ 106

    Table 39. Scenario No. 2 CAD, net annual economic profitability ($)2 for various electrical energy sale prices and tipping fee revenues ...................................................................................................... 106

    Table 40. Annualized capital costs ($) for energy crop digester system .................................................. 108 Table 41. Net annual economic profitability ($) for various electricity prices and feedstock costs ......... 109 Table 42. Capital cost estimate for construction of on-farm short-term manure storage per farm ........ 111 Table 43. Scenario No. 2 CAD nitrogen series annual masses by feedstock source and totals ................ 111 Table 44. Scenario No. 2 CAD phosphorus and potassium series masses by feedstock source and totals

    ......................................................................................................................................................... 111 Table 45. Farm survey responses based on projections for two years ..................................................... 139 Table 46. Farm survey responses based on five year projections ............................................................ 140

  • Abbreviations and Acronyms AD Anaerobic digestion BMP (1) Best Management Practice BMP (2) Biochemical Methane Potential Btu British thermal unit (mmBtu = 1 x 106 Btu), (TBtu = 1 x 1012 Btu) CAD Centralized anaerobic digester CAFO Concentrated Animal Feeding Operation cfm Cubic feet per minute CCE-LC Cornell Cooperative Extension of Lewis Count CIP Clean-in place wastewater CMMP Cornell Manure Management Program CNMP Comprehensive Nutrient Management Plan CBM Compressed biomethane CH4 Methane CHP Combined heat and power CNG Compressed natural gas CO2 Carbon dioxide COD Chemical oxygen demand Decatherm = 1 million Btu ESP Electrical service provider FOG Fats, oils, and greases ft3 Cubic foot gal US gallon (3.8 liters) GE General Electric Company GHG Greenhouse gas GWh Giga-Watt hours GWP Global Warming Potential gpm Gallons per minute H2 Hydrogen H2S Hydrogen sulfide HRT Hydraulic retention time kg Kilogram kW Kilowatt kWh Kilowatt-hour L Liter LCE Lactating cow equivalent LWWTP Lowville Wastewater Treatment Plant Lb(s) US pound LNG Liquefied natural gas m3 Cubic meter mmscf Million standard cubic feet MW Megawatt MWh Mega-Watt hours N2 Nitrogen N2O Nitrous oxide NH3 Ammonia

  • NPK Nitrogen, phosphorus and potassium content of fertilizer/organic matter NRCS Natural Resources Conservation Service NYS New York State OLR Organic loading rate O&M Operations and maintenance PPA Power Purchase Agreement REC Renewable energy credit RNG Renewable natural gas STP Standard Temperature and Pressure TSS Total suspended solids SCFM Standard cubic feet per minute (adjusted for temperature and pressure) SLDM Sand-Laden Dairy Manure SLS Solid-liquid separator SPDES State Pollutant Discharge Elimination System VFA Volatile fatty acids VS Volatile solids VSS Volatile suspended solids yd3 Cubic yard

  • 1

    Executive Summary The region surrounding Lowville, New York has multiple existing large scale renewable energy systems,

    including wind and hydro-power. In the spirit of broadening the areas renewable energy systems,

    members of the Lowville Digester Work Group (comprised of representatives from Cornell Cooperative

    Extension of Lewis County (CCE-LC), Kraft Foods, Lewis County Economic Development Office,

    residents, dairy farmer representatives, Lewis County Farm Bureau, and the Soil and Water Conservation

    District) desire to develop a locally-owned and operated biomass-based renewable energy system. The

    energy produced would stay local and the system would provide direct benefits to Lewis County

    farmers, businesses, and residents. This desire prompted an investigation of anaerobic digestion

    technology and its application in a centralized anaerobic digester (CAD) system that would use both

    farm and non-farm biomass feedstock sources as input materials.

    The Lowville Digester Work Group, in June of 2009, commissioned Cornell University (Ithaca, New York)

    to conduct this feasibility study through funding provided by Senator Joseph Griffo of the 47th District in

    New York State. Cornell worked closely with the Lowville Digester Work Group to develop the feasibility

    study scope of work and key parts of its implementation.

    The scope of the feasibility study consisted of multiple biomass related components including: resource

    assessments, sampling and laboratory analyses (biochemical methane potential and nutrient

    concentration investigation), methane production estimations and trucking analyses. The scope of work

    also included biogas to energy conversion quantifications, digester site option investigations, and

    economic profitability analyses. The major findings pertinent to each of these areas investigated are

    provided below; the report contains additional information and details.

    Biomass Resource Assessment

    Many potential sources of farm and non-farm biomass in and around Lowville were initially identified by

    members of CCE-LC. Project specific surveys, one for use in assessing the dairy farms and one for

    assessing the non-farm biomass sources, were developed by Cornell University and CCE-LC. Identified

    farms were surveyed by members of CCE-LC while non-farm biomass sources were surveyed by the

    Lewis County Economic Development office.

  • 2

    The farm survey results revealed that there are 25 dairy farms (herd size ranges from 62 to 787 cows)

    within an 18-mile radius of downtown Lowville with a total of 5,327 lactating cow equivalents (LCEs). All

    of these farms have long-term manure storages (6-month or longer), and use organic bedding material

    to bed their cow stalls. Five of the farms reported they have excess organic nutrients (nitrogen,

    phosphorus, and potassium), while nine farms indicated that they are nutrient deficient, and 11 are in

    balance. An opportunity exists for this project to help farms better manage their nutrients and lessen

    the need to purchase commercial fertilizers. The survey responses also showed that the number of LCEs

    would increase by approximately 675 cows over two years, and then by 150 more cows after five years.

    It should be noted that the actual change in cow numbers in the future (increase or decrease) will be

    driven primarily by dairy farm profitability.

    The non-farm survey results revealed there are 11 potential sources of biomass (local food processors,

    food vendors and residents were surveyed) in the local area that could be aggregated and co-digested

    with manure. The minimum estimated useable quantity of substrates from the six non-farm biomass

    sources with the highest volumes, was 110 million lbs/year, and the maximum quantity of useable

    substrate was 160 million lbs/year. Two of the potential sources (whey mixed with CIP water and post-

    digested sludge) provide the bulk (largest volume) of the non-farm biomass available for digestion.

    Initial survey results prompted investigation into additional sources of biomass for co-digestion to

    further increase potential biogas production. This included manure from sand-bedded dairy farms,

    which was ruled not to be an option at this time due to the small farm sizes and comparatively large

    capital equipment cost to effectively separate bedding sand from manure. Potential biomass sources

    from Fort Drum, a nearby United States Army base, Reed Canary grass from fallow ground along the

    Black and Beaver Rivers, and sludge from the Lowville Wastewater Treatment plant (LWWTP) were also

    considered and investigated but due to availability, harvesting, and handling issues, all were deemed not

    feasible for inclusion at this time, and therefore were not included in further analysis.

    Energy crops (corn silage and haylage) fed directly to an energy crop digester were also considered. Two

    farms, one north of Lowville and the other south of Lowville, that are currently solely cash crop farms

    were included, but kept separate, in the overall analysis.

  • 3

    Biomass Sampling and Laboratory Analysis

    Based on the information available from the 10 completed non-farm biomass surveys1, the decision was

    made to obtain samples from five of the 10 potential feedstock sources, with one source having two

    different materials analyzed, for a total of six potential feedstock materials analyzed. These included

    waste grease, meat processing by-products, mixed food scraps, post-digested sludge, and diluted whey.

    Sub-samples of the collected materials were analyzed in triplicate at the Cornell Agricultural Waste

    Management Laboratory to quantify the biogas and methane (CH4) produced by these materials, on a

    unit basis. As expected, the laboratory results showed that the waste grease material produced the

    highest unit yield (363 L CH4/kg raw substrate2) and the diluted whey the least (2 L CH4/kg raw

    substrate2). Sub-samples were also analyzed at an EPA certified laboratory, to quantify their nutrient

    composition.

    Biogas and methane production estimates for dairy manure were obtained from previous work

    conducted at the Cornell Agricultural Waste Management Laboratory where several manure samples

    had previously been obtained from commercial New York State dairy farms and analyzed using the same

    procedure (Labatut and Scott, 2008).

    Methane Production Estimation

    The methane (CH4) production for dairy manure and each identified non-farm biomass substrate was

    estimated by multiplying the methane production (on a unit mass basis) by the annual estimated

    biomass quantity provided in each of the completed surveys. Using this approach, the estimated

    minimum annual methane production was 10 thousand ft3 CH4/yr for waste grease (due to its

    comparative low quantity available) and the maximum was 157 million ft3 CH4/year for manure (due to

    the comparatively high quantity available).

    Energy crop methane production estimates were developed using typical yields (wet tons/acre) for corn,

    grass, and alfalfa silage for Lewis County, applied to the cropland currently farmed by the two

    potentially collaborating cash crop farmers (2,000 and 400 acres). Total biomass yields were multiplied

    by unit methane yields for each crop; overall, the estimated annual methane yield from the energy crop

    digester was 97 million ft3 CH4/year.

    1 Substrate supplier #11 was not initially surveyed; it was discovered subsequent to the conclusion of the survey period. 2 Expressed on a wet weight basis

  • 4

    Energy Potential Quantification

    Assuming that manure from 15 selected farms3 and the three non-farm biomass substrates with the

    highest volumes are co-digested, and using the average estimated gross and parasitic electrical energy

    values, the resulting potential net electrical energy available from the CAD facility would be

    approximately 8,880 MWh/year. Assuming a typical residence uses 7,250-kWh/year, approximately

    1,225 homes could be powered by the CAD facility. If all net energy available were used for biomethane

    sale, the CAD facility would be capable of producing 80,800 million Btus, which would have a residential

    value (at a price of $13.81/1,000 ft3 natural gas) of $1,115,900.

    Trucking Analysis

    The proposed project would encompass facilitating the transport of raw manure to the centralized

    anaerobic digester (CAD) facility (30 million gallons per year), and CAD effluent (42-48 million gallons per

    year), back to the collaborating farms at no cost to the collaborating farms. The CAD effluent is a higher

    volume than the manure proportion of the influent due to the inclusion of non-farm biomass substrates

    at the CAD facility, which would be transported to the CAD by each substrate supplier at their cost. Two

    options for the transport of manure and CAD effluent were analyzed; initiating a project-owned trucking

    fleet, or contracting with an existing trucking company. A 6,000-gallon manure tanker truck was

    assumed for all trucking-related analyses.

    The analysis of a project-owned trucking fleet, with an estimated initial capital cost of $1.5 million and

    estimated annual expenses of more than $420,000, was deemed not economically feasible at this time.

    Contracting with an existing trucking company is the recommended option to pursue in order to simplify

    the overall CAD facility start-up by lessening the capital cost and reducing the risks. Although this option

    entails higher annual costs, (estimated to be $1.3 million dollars in total annual expense), the project-

    run fleet is a possibility to pursue at any time following project start-up.

    3 These 15 farms referred to are the selected farms under Scenario No. 2

  • 5

    Digester Site/Configuration Scenarios Investigated

    Five different digester site/configuration scenarios were initially analyzed and presented, along with

    other interim project findings, to the Lowville Digester Work Group at a December 2009 meeting. The

    five scenarios explored were:

    Scenario No. 1: Co-digest manure from all (25 farms) dairy farms surveyed, and seven (out

    of 11 total) non-farm biomass substrates at a central location adjacent to the LWWTP.

    This option makes use of all manure and most non-farm biomass substrates discovered by

    the completed surveys.

    Scenario No. 2: Co-digest manure from 14 dairy farms, and three non-farm biomass

    substrates at a central location adjacent to the LWWTP. This option was explored to

    reduce trucking costs by reducing the number of collaborating farms.

    Scenario No. 3: Co-digest manure from only 12 dairy farms, and one non-farm biomass

    substrate at one of two remote sites, and co-digest manure from four dairy farms and two

    non-farm biomass substrates at a second remote site. This option was explored to

    determine the impacts of having multiple, smaller, regional digesters to further reduce

    trucking costs.

    Scenario No. 3a: Identical to Scenario No. 3, except that 33% of the manure would be

    piped to each remote digester site, and the remainder would be trucked. This option was

    also pursued to determine impacts on trucking costs.

    Scenario No. 3b: Identical to Scenario No. 3, but includes 400 acres of energy crops

    digested at one remote site and 2,000 acres of energy crops digested at the second

    remote site. This option was explored to investigate the impacts of including an energy

    crop digester on overall biogas production and profitability.

    The Lowville Digester Work Group chose Scenario No. 2 CAD, as described above, for complete

    investigation at the December, 2009 meeting, and it was decided that one additional farm would be

    included in the scenario before performing an economic profitability analysis.

  • 6

    The remainder of the Executive Summary provides details and the results of a complete analysis

    performed for the Scenario No. 2 CAD, and since the Lowville Work Group also requested a detailed

    analysis of an energy crop digester co-located with the Scenario No. 2 CAD manure and non-farm

    biomass digester, this information is also provided below.

    Scenario No. 2 CAD System Overview

    The estimated annual average volume of non-farm biomass substrates available for co-digestion by

    three local suppliers was 16 million gallons per year (range 13 to 19 million gallons per year) and the

    manure volume available from the 15 targeted collaborating farms was 30 million gallons per year.

    Therefore, the CAD should be sized to handle at least on average 122,400 gallons of influent per day.

    Using a digester hydraulic retention time of 22.54 days, the digester treatment volume needed was

    calculated to be 2.8 million gallons. A digester configuration of one or multiple tanks can be used to

    accomplish this overall size requirement. The average estimated capital cost for a complete mix digester

    system of this size was $5.89 million (range $4.73 to $7.14 million).

    The annual cost to transport manure to the CAD site (adjacent to the existing LWWTP) and digester

    effluent back to the collaborating farms was estimated to be on average $1.12 million annually (range

    $1.07 million to $ 1.17 million). It was assumed that the trucking cost for the non-farm biomass material

    to the CAD site would be paid by the substrate suppliers, as is currently the case.

    The average estimated gross volume of biogas produced was 188 million ft3/year (range 140 million to

    237 million ft3/year). Using a biogas methane concentration of 60%, the annual estimated volume of

    methane produced was 113 million ft3/year (range 84 million to 142 million ft3/year).

    4 22.5 days is the average of 20 and 25 days, which are common retention times for similarly sized systems

  • 7

    Two of the most commonly implemented biogas utilization options were investigated:

    1) Use biogas to fuel a reciprocating engine-generator set5

    2) Sell cleaned biogas as renewable natural gas, biomethane, by first removing

    impurities (carbon dioxide, hydrogen sulfide, and moisture) using pressure-swing

    adsorption gas clean-up technology6.

    For option 1, it was assumed that thermal energy harvested from the engine-generator set would be

    used to meet all of the digester heating requirements (warming the CAD influent to target operating

    temperature and then maintaining it); field experience has shown that this is an appropriate assumption

    to make. For option 2, it was assumed that 20 percent of the biogas produced by the digester would be

    needed to meet this demand; this assumption needs to be confirmed, based on information about the

    design of each digester system considered, specifically, how well the vessel is insulated and the

    exposure it has to winter wind and temperature. The overall estimated annual parasitic heating

    requirement was 20,200 million Btus per year (range 15,000 to 25,500 million Btus per year). Using the

    average estimated parasitic heating requirement, the annual cost to provide this heat ranged from

    $81,000 to $282,000 per year for a natural gas purchase price range of $4 to $14 per decatherm,

    respectively.

    For parasitic electrical requirements, for both biogas utilization options, the average estimated parasitic

    electrical energy requirement of the CAD system was determined the same way. Calculations were

    performed using data from vendor information obtained for other similar sized systems to determine

    the electrical energy requirement per gallon of influent material; the results were that the average

    electrical energy requirement was found to be 0.0313 kWh per gallon of influent7 (range 0.0121 to

    0.0505 kWh per gallon of influent). Applying these energy values to the CAD system, the estimated

    average annual parasitic electrical energy requirement was 1,400,000 kWh per year (range 540,000 to

    2,257,000 kWh per year). Using the average estimated parasitic energy requirement, the estimated

    annual cost to provide this energy ranged from $112,000 to $252,000 for an electrical energy purchase

    price range of $0.08 to $0.18 per kWh, respectively.

    5 Other, less commonly used methods exist for converting biogas to electrical energy (e.g. microturbines) 6 Other methods are available for scrubbing biogas to make biomethane (e.g. membrane separation, regenerative amine wash)

    7 Influent is defined as the biomass on the in-flow side of a treatment, storage, or transfer device

  • 8

    Nutrient Management Implications

    Assuming the non-farm biomass imported for co-digestion supplies excess nutrients to the post-

    digestion product that would be available for sale to area crop farms, the project could potentially

    receive $226,000/year in total revenue. Of the $226,000/year, $86,000/year would be derived from the

    sale of nitrogen, $121,000/year would be derived from the sale of phosphorus, and $19,000/year would

    be derived from the sale of potassium.

    Economic Profitability Analysis- Scenario No. 2 CAD

    A net annual economic profitability analysis was performed for the Scenario No. 2 CAD to determine if

    this scenario was economically viable considering the options of: 1) selling electrical energy at a price

    range of $0.08 to $0.18 per kWh, or 2) selling biomethane (cleaned biogas) at a price range of $4 to $14

    per decatherm. For both of these options, separate net annual economic profitability analyses were

    performed, which included a tipping fee equal to the tipping fee being paid by one of the three non-

    farm biomass suppliers whose substrate was selected for co-digestion (the other two tipping fees were

    not provided by the completed surveys).

    For all of the analyses, the cost of capital (discount rate) used was 5%, the economic life of the digester

    was 20 years, and the replacement cycle of the engine-generator set was 10 years. Trucking costs to

    haul manure to the CAD site and effluent to collaborating farms was included as an annual cost. Other

    annual costs included operation and maintenance of (1) the CAD system (based on data obtained from

    vendor quotes for other similar systems), (2) the engine-generator set ($0.018 per kWh) and (3) the

    biogas clean up system.

    The results of the net annual economic analysis showed that for all energy sale options investigated it

    was more costly to own and operate the system each year, than the system would receive in revenue

    annually. In other words, no option was found to be economically profitable.

    Based on these results, a final net annual economic profitability analysis was conducted to determine

    the tipping fees needed for the two energy sale options investigated to result in a Scenario No. 2 CAD

    financially break-even situation. For the option of selling electrical energy at a price ranging from $0.08

    to $0.18 per kWh, the break-even tipping fee range was determined to be $21 to $9 per ton,

  • 9

    respectively. For the option of selling biomethane at a price range of $4 to $14 per decatherm, the

    break-even tipping fee range was determined to be $29 to $16 per ton, respectively.

    The calculated break-even tipping fee ranges were substantially below the average tipping fee of over

    $70 per ton currently charged by landfills for the northeastern U.S., but somewhat higher than the

    calculated tipping fee currently being paid by the non-farm biomass supplier considered for this

    project with the most biomass available annually.

    Energy Crop AD System Overview

    The proposed Lowville energy crop digester is an anaerobic digester designed to process high solids

    energy crop materials (corn silage and/or haylage). Such digesters are widely used in Germany and

    other European countries and produce about eight times the biogas as digesters fed manure only

    (Effenberger, 2006).

    Silage corn and grass hay would be harvested and ensiled as if they were going to be fed to dairy cattle.

    Sufficient quantities would be stored to enable the energy crop digester feed hopper (usually a walking

    floor bin) to be filled once-a-day, year round, normally with a pay loader. Several times per day, the

    control system would automatically transfer a portion of the feedstock into the digester; screw

    conveyors (augers) are normally used due to the high solids content of corn silage and haylage.

    The energy crop digester economic analysis performed for this feasibility study used in-the-bunk silage

    prices ranging from $30 to $55/ton, meaning that the costs to grow and harvest the crops and ensile

    and store them are covered by the purchase price.

    In addition to the energy crop feedstock, a small portion of manure is also normally added to the energy

    crop digester, about 10 percent by weight, to help stabilize digester pH and to provide some dilution

    water to lessen the power required to provide in-vessel mixing.

    Energy crop digester effluent, laden with organic nutrients, is the consistency of digested manure. For

    this feasibility study, it is assumed the effluent would be stored on-site for a short period of time and

    periodically trucked to the energy crop source farms for longer-term storage and for subsequent use as

    fertilizer to grow the next rotation of energy crops. Some of the surplus nutrients from the Lowville CAD

  • 10

    system could also be trucked to the collaborating farms to meet the overall fertilizer requirements for

    the crops grown on those farms.

    Economic Profitability Analysis - Energy Crop AD System

    The same net annual economic profitability analysis was performed for the energy crop AD system. For

    this analysis, the only energy sale option investigated was the sale of electrical energy8, using a sale price

    range of $0.08 to $0.18 per kWh with varying feedstock (fermented corn silage and haylage) prices

    between $30 and $55 per wet ton.

    Again, the cost of capital (discount rate) used was 5 percent, the economic life of the digester was 20

    years, and the replacement cycle of the engine-generator set was 10 years. Trucking costs to haul

    digester effluent to collaborating farms was included as an annual cost, as it would be paid by the

    project. Other annual costs included operation and maintenance of: (1) the CAD system (based on data

    obtained from industry vendors), (2) the engine-generator set ($0.018 per kWh) and (3) biogas clean up

    system.

    The results of the net annual economic analysis showed that for all digester feedstock and energy sale

    price options investigated it was more costly to own and operate the system each year than the

    system would receive in revenues annually. This is the same result that was found for the Scenario No.

    2 CAD options investigated.

    Recommendations and Future Work

    The recommendation for a CAD system is based on conducting thorough and complete technical and

    economic feasibility analyses, as well as the vision of the Lowville Digester Work Group. Based on this,

    the recommendation is to further investigate one centrally-located complete mix AD, sited adjacent to

    the LWWTP that would co-digest manure from 15 targeted collaborating dairy farms and targeted non-

    farm biomass substrates (currently the following three substrates: whey, post-digested sludge, and

    glycerin) that are by-products generated nearby.

    8 Biogas clean-up to biomethane was not investigated, since economic profitability analysis results for the Scenario No. 2 CAD showed little difference in the bottom line when compared to electrical energy sales.

  • 11

    The future net annual economic profitability behind this recommendation is encouraging, given that, (1)

    the calculated tipping fee needed for the system to break-even is well below the average tipping fee

    charged in the northeastern U.S. and many predict regulations will be instituted in the near future

    restricting the land-filling of organic matter, (2) future regulations aimed at reducing the impact of fossil-

    fuel derived energy (specifically GHG emissions and climate change) would likely positively impact

    renewable energy projects, (3) energy produced from such projects would have less price volatility than

    fossil fuel-based energy products, and (4) the annual economic profitability will improve with reductions

    in capital cost by receiving grants and/or premium payments for renewable energy.

    If future efforts are put forth to further investigate one CAD, it is recommended that the two major

    areas provided below be addressed in the order presented below and that the bullet items under each

    be included.

    A. Address Economic Barriers to Project Implementation

    Identify other potential sources of non-farm biomass that are currently being land-

    filled or otherwise disposed of that could be received by the CAD with a tipping fee

    paid by the supplier.

    Continue the education and outreach efforts concerning this project and the goals and

    objectives of local community members, targeted at collaborating and non-

    collaborating dairy farmers and non-farm biomass substrate suppliers to develop

    project support targeted towards securing public funding.

    Secure grant funding or subsidies that could help offset the capital cost of the CAD

    and/or supplement the revenue(s) received for system outputs (raw biogas,

    electricity, biomethane, and/or organic nutrients).

    Validate the trucking analysis and farm biomass pick-up options determined under

    this effort.

    Investigate the willingness of non-farm biomass suppliers to enter into reasonable

    long-term contracts , with a negotiated tipping fee.

    Investigate the willingness of the end user(s) of the net energy produced by the CAD

    facility to enter into reasonable long-term contracts.

    Explore the potential for selling raw biogas to a local end user.

  • 12

    Investigate the possibility of the sale of CAD surplus heat combined with woody

    biomass heat to local industry or the community (district heating).

    B. Advanced Project Due Diligence

    Perform more complete laboratory testing of the targeted substrates mixed

    proportionally with manure to better solidify the quantity of biogas that would be

    produced by the system.

    Perform a value engineering/economic analysis that includes looking at the digester

    treatment volume vs. biogas production potential.

    Conduct an in-depth site and environmental impact assessment for the targeted

    construction site.

    Investigate the legal issues for various digester ownership options.

    Determine the permit(s) that will be required by the New York State Department of

    Environmental Conversation (NYSDEC)9.

    Conduct an in-depth investigation into the site improvements that will be required at

    each farm in order to participate in the project, and develop an associated budget.

    Investigate contracting with an existing trucking company to provide transportation of

    farm biomass.

    Assess renewable energy credits (RECs) and carbon credits as applied to centralized

    digesters.

    Conduct a net energy analysis for the proposed system.

    Develop a request for proposals (RFP) package to be distributed to AD system

    designers.

    Validate the economic profitability analysis using the results of the proposed RFP.

    Continue investigation into future opportunities, such as manure nutrient extraction

    equipment and resulting product marketing opportunities for organic nitrogen,

    phosphorus, and potassium.

    Continue assessment of alternative biogas market opportunities such as the sale of

    biomethane as a vehicle fuel.

    9 There are currently no operating dairy manure-based CAD systems in NYS, and an initial inquiry made by Cornell to NYSDEC on

    behalf of this project revealed that NYSDEC is not readily prepared to state what permit(s) is/are needed.

  • 13

    Nomenclature

    Effort was made to make terminology throughout this report consistent to allow for a more clear

    understanding of the information presented. Please refer to this list as necessary.

    Centralized Anaerobic Digester (CAD) facility The term used to describe the proposed manure and substrate co-digestion AD system, and all of the integrated components.

    Energy crops Field crops grown specifically as a feedstock source for an energy crop AD system

    Feedstock Describes the entire influent to the CAD

    Lewis County Community AD project The name of the proposed project

    Lowville Digester Work Group The local volunteer group of decision-making stakeholders on behalf of the project

    Manure

    Effluent from a dairy housing barn made up of cow urine and feces, bedding, and other minor components such as gravel, undigested feed, and/or milking system gray water.

    Methane production potential Quantification of a biomass substrate to produce methane

    Non-farm biomass substrates Organic by-product material from local processors of farm products; otherwise referred to as food waste

    Non-farm biomass substrate suppliers

    Local food processors and vendors who have, upon initial survey, shown interest in supplying organic material for co-digestion; otherwise known as food waste sources

  • 14

  • 15

    Introduction

    The proposed Lewis County community anaerobic digester (AD) project (see Figure 1) was initiated in

    early 2008. Cornell University was contracted to perform a feasibility study of the proposed project in

    May 2009, with a targeted completion of December 2009. Three interim project meetings were held by

    the Cornell team to present interim project findings and assess progress in October and December, 2009

    and March, 2010. After some changes in scope of the project, the final feasibility report was completed

    in May 2010.

    Lowville goals and objectives

    Interest in a community AD from several Lewis County, NY constituents grew from the initial set of goals

    developed from multiple community viewpoints. The Lowville Digester Work Group was formed from a

    group of local stakeholders interested in determining the application of anaerobic digestion technology

    to meet the goals set forth, and to oversee development of the proposed project. The following are the

    initial project goals developed by the Lowville Digester Work Group (committee document, 2008):

    Goals for the community:

    Encourage continued economic growth

    Lessen the negative impact of farms on county residents (e.g., farm-based odor)

    Reduce the environmental footprint

    Goals for the regions dairy industry:

    Provide greater flexibility in manure handling and nutrient management that results in an

    economic advantage versus today

    Reduce odor associated with manure storage and land application

    Allow a greater number of animals per unit of land area with less environmental risk

    Goals for local industry:

    Gain access to sustainable energy at lower (versus today) cost.

  • 16

    Figure 1. New York State map showing location of project-site

    Scope of Work

    The following questions were posed in the scope of work document developed prior to the beginning of

    the feasibility study, and used throughout the study by Cornell University and the Lowville Digester

    Work Group to guide the project.

    Biomass

    1) What is the annual on-farm (manure) and Village of Lowville non-farm biomass potentially

    available for anaerobic digestion, by source?

    2) How much biomass can be secured, by source?

    3) How many farms are currently prepared (on an infrastructure basis) to store raw manure

    short- term and digester effluent long-term?

    4) What infrastructure upgrades are needed for those farms not currently prepared to store

    raw manure short-term and/or digester effluent long-term?

    Biomass/biogas transportation

    5) What options exist for transporting manure from the farms to the digester location(s) and

    digestate back to the farms and what is the estimated cost associated with this?

  • 17

    6) What options exist for transporting non-farm biomass to the digester location(s) and what

    is the estimated cost associated with this?

    7) What are the results of an economic sensitivity analysis on biomass transportation cost?

    8) What is the feasibility of transporting biogas or biomethane (processed biogas) to a

    utilization site?

    Anaerobic digestion

    9) What are the AD technology options available?

    10) Which option is best suited for the application?

    11) What are the estimated capital and operating and maintenance costs associated with the

    AD and associated equipment?

    12) Is it best to truck all biomass destined for digestion to one site or to have an array of

    digesters strategically located within the county?

    Biogas/energy conversion

    13) How much biogas can potentially be produced with the secured biomass?

    14) Is biogas clean-up required and if so what option is best?

    15) How much energy can be extracted from the biogas?

    16) What are the results of a sensitivity analysis performed on the sale price for the energy?

    Nutrients

    17) What is the expected nutrient value of the manure once digested (tons total-N, ammonia-

    N, total-P, ortho-P, and potassium)?

    18) What is the anticipated increase in digester effluent volume and nutrient composition

    with the importation of securable non-farm biomass sources?

    Impacts on the community

    19) How many truck loads of manure will be transported to the digester site(s) per day?

    20) What labor force is anticipated to operate the overall facility?

  • 18

    Economics

    21) What is the estimated total annual cost for various digester/biogas utilization scenarios?

    Designated responsibilities

    In addition to the questions set forth in the scope of work, the same document designated which tasks

    each group involved in the project would be responsible for. It was decided that the Cornell Manure

    Management Program Team (CMMPT) would provide leadership and overall project coordination to

    facilitate the completion of the feasibility study. CMMPT developed and maintained a project schedule

    identifying specific tasks, responsible parties and targeted completion dates. Specific responsibilities are

    outlined below.

    CMMPT

    o Deliverables: CMMPT will complete and provide the following items to Cornell

    Cooperative Extension of Lewis County:

    Initial Findings (written report and oral presentation)

    Interim Report (written report and oral presentation)

    Final Report (written report and oral presentation)

    o The work tasks and components of the feasibility study include:

    Gather information from existing centrally located community ADs or

    completed feasibility studies that are relevant.

    Develop a survey for completion by select dairy farms within Lewis County

    Develop a survey to all potential substrate suppliers within Lewis County

    Aggregate and analyze results of the above surveys

    Perform all calculations required to answer the questions outlined above

    Prepare all reports and make oral presentations

    Lewis County Cornell Cooperative Extension (CCE)

    o Identify farms within a specified radius of possible digester site(s)

    o Implement the farm survey and provide reports/summaries to CMMPT

  • 19

    o Organize project meetings

    Lewis County Soil and Water Conservation District (SWCD)

    o Using data provided by the Cornell Cooperative Extension, create a map identifying all

    potential participating dairy farms within the selected radius of the Village of Lowville

    Wastewater Treatment Plant (LWWTP) and other potential digester sites. Incorporate

    information on road infrastructure into map so that feasible transportation routes can

    be considered.

    o Using data provided by the Cornell Cooperative Extension, create a map identifying all

    potential substrate suppliers within the selected radii of the LWWTP and other

    potential digester sites.

    Village of Lowville

    o Implement a survey to quantify all potential non-farm biomass substrates within Lewis

    County

    o Provide completed surveys and results to CMMPT for analysis and use

    Lowville Digester Work Group

    o Assist with the identification of potential sites for the proposed central AD

    o Assist in identifying potential buyers of final products

    o Inform community about the project and generate support

    Project approach

    Cornell University, in agreeing to perform the feasibility study for the Lewis County community AD,

    responded to the Lowville Digester Work Groups request with the following plan of action:

    Develop a plan of necessary work to be accomplished on the local level

    Aggregate and analyze results of local work

    Calculate total quantity and characteristics of digester inputs

    o Farm

  • 20

    o Kraft

    o Other

    Assist local creation of a map of cooperating farms and other biomass sources

    Calculate costs and feasibility of farm-based biomass transportation

    Measure biogas producing potential of assumed substrate inputs and calculate projected

    biogas production

    Review biogas clean up options

    o Cost

    o Scale

    o Availability

    Determine the best use of biogas produced

    o Generation of electricity

    Cost of interconnection

    Sale to grid or private

    o Sale of cleaned biogas

    Sale to Kraft

    Sale to community

    Sale of energy back to farms

    Used to power vehicles/farm trucks

    o Market price of each option

    o Cost of implementing each option

    Analyze all final products from digester and determine marketability

    o Solids

    Bio-security issues

  • 21

    o Heat

    o Electricity

    o Nutrient-laden liquid effluent

    o Compost

    o Other

    o Determine revenue from each potential sale

    Devise a strategy to return organic material/nutrients to farms

    o Solids and/or liquids

    o Transportation

    o Delivery infrastructure feasibility on a farm level

    Overall cost benefit analysis for project

    Formulate questions for Lewis working group before proceeding, based on initial findings

    Incorporate new visions to final recommendation

    Develop a mid-study interim report

    Develop a final feasibility study report

  • 22

  • 23

    Chapter 1. Basics of Centralized Dairy Manure-Based Anaerobic Digestion, Biogas Utilization, and Nutrient Recovery Systems A centralized dairy manure-based anaerobic digestion and biogas utilization system is one where dairy

    manure, the systems stable feedstock, is aggregated from multiple farms, blended together, and co-

    digested in a heated vessel for 15 to sometimes more than 30 days. In many cases, non-farm biomass

    substrates such as food processing and bio-fuel processing by-products, organic industrial wastes, and

    culled and leftover human foods are co-digested with dairy manure. Digestate (digester effluent) is

    generally stored short-term on-site at the centralized facility, and then transported back to source farms

    for storage until it is used to replenish cropland with nutrients (nitrogen (N), phosphorus (P), and

    potassium (K)) and organic matter. Digestate can be further treated, as described later in this chapter,

    to achieve various undigested fiber recovery and nutrient conservation and management goals and

    objectives. A typical process flow diagram for a centralized digestion system is shown in Figure 2.

    Figure 2. Typical CAD system process flow diagram

    Centralized digesters are best located where they are strategically placed to minimize transportation of

    manure and non-farm biomass substrates and to maximize output energy and digestate utilization. CAD

  • 24

    can effectively improve fertilization of cropland by returning CAD effluent to a strategically located site

    at the farm, for ease of use in spreading on cropland.

    Centralized digestion systems are common-place in Denmark and other European countries; a

    centralized digester in Jutland, Denmark is shown in Figure 3.

    Figure 3. A CAD in Jutland, Denmark

    Overall, centralized digestion of manure provides the opportunity for economies of scale to come into

    play that generally cannot happen on individual farms. The capital and operating costs per unit of

    influent treated (i.e., cents per gallon) is generally less in larger systems than smaller systems. Another

    reason centralized digestion is given due consideration is that it is likely to have the size needed to

    justify and pay for a full-time crew to operate the facility. Further, centralized digestion provides the

    opportunity for more efficient use of organic nutrients by the collaborating farmers. Digestate can be

    sampled more frequently than on-farm, thus better quantifying the nutrients sent back to each

    collaborating farm. Also, anaerobic digestion provides a steady and consistent material that is well

    suited for secondary or tertiary treatments that can include enhanced nutrient management by

    farmers.

  • 25

    A common concern with centralized anaerobic systems is biosecurity (disease control). Commingling

    of source farm manure and non-farm biomasses is part of the centralized digestion model that

    cannot be avoided. Farmers can be especially concerned about biosecurity since manure that may

    contain infectious disease causing organisms can be brought onto their farms. However, the risk of

    this is lessened when manure is digested; further risk reductions occur when influent or digestate is

    pasteurized before being returned to the farm.

    Additional information about dairy manure-based centralized digestion systems is provided in this

    chapter with the goal of preparing the reader for the following chapters where the work and feasibility

    study findings are presented. More in-depth information about on-farm and centralized anaerobic

    digestion can be obtained by reviewing the references cited herein.

    Centralized digester feedstock materials

    Centralized digesters are generally fed two or more of the three different types of biomass materials.

    The three types are categorized based on availability, specifically those that are:

    Continuously available such as manure, certain food processing wastes like whey, etc.

    or at least almost continuously (e.g. some slaughterhouse waste sources)

    Seasonally available such as grape puree, onion tops, carrot skins, etc.

    Available year-round but not consistently such as processed foods that have exceeded

    their shelf life

    Manure

    For most centralized digestion systems, manure is the stable feedstock material. Not only is it

    continuously produced by dairy cattle, it also provides a key role in co-digestion with other, more

    biologically convertible materials as it moderates pH due to its buffering capacity.

    The average U.S. dairy cow produces 150 lbs. of raw manure per day that contains 20 lbs. of total

    solids (TS), 17 lbs. of volatile solids (VS), 1 lb. of (N), 0.17 lbs. of (P), and 0.23 lbs. of (K) per day while

    a dry cow and a replacement (heifer) produces measurably less (ASABE, 2005). A portion of the

    manure VS are biologically converted to biogas. Digestion of raw manure from a dairy cow produces

    on average, 80 ft3 biogas per cow-day (Ludington, 2008).

  • 26

    Non-farm biomass sources

    Any biomass can be digested. Digestion of various biomass materials is largely a function of materials

    handling (conveying material from storage into a digester), biodegradability, maintaining a balanced

    state within the digester vessel, and economics. Many of the suppliers of non-farm biomass substrates

    available for anaerobic digestion currently pay significant tipping fees to the local landfill authority in

    order to dispose of their unwanted processing by-products.

    In New York State, many farmers are interested in mixing non-farm biomass substrates with manure

    due to:

    1. The increased biogas production potential the mixture produces

    2. The associated tipping fees for allowing substrate suppliers to unload their by-product

    on the farm.

    Non-farm biomass can have lower solids content than raw manure, so when combined with manure

    the resulting mixture needs to be mixed within the digester to keep the solids in suspension.

    Some materials, like fats, oils, and greases readily break down in an AD while others like corn silage take

    much longer to fully do so. Many non-farm biomass substrates have the potential to produce several

    orders of magnitude of biogas per unit of influent mass compared to manure. An example of biogas

    production from co-digesting manure with food wastes is between 368 and 560 ft3 biogas per cow-

    day, as found on one New York State dairy farm (Gooch et al., 2007).

    Like manure, non-farm biomass generally contains measurable levels of nutrients (N, P, and K) that

    must be considered when assessing the impact centralized digestion will have on a collaborating

    farms ability to comply with their Comprehensive Nutrient Management Plan (CNMP).

    A centralized anaerobic digester (CAD) that looks to co-digest measurable volumes of non-farm

    biomass substrates needs to have reasonable assurance that these are available and securable by

    long-term contract or are able to be replaced with alternate biomass sources. This is important

    because the capital cost of the centralized digester will be directly affected by the volume of non-

    farm biomass sources digested and the associated biogas production potential.

  • 27

    Anaerobic Digestion

    Direct environmental benefits of an anaerobic digestion system include conservation and phase

    transformation of manure nutrients (N), (P), and (K) during digestion resulting in an effluent rich in

    organic, crop available-nutrients needed to grow feed for livestock and people alike. Since the digestion

    process significantly reduces odors associated with untreated biomass stored long-term, digestate can

    more effectively be used to fertilize crops. This reduces the need to purchase synthetic fertilizers that

    require large amounts of fossil fuels to produce, thus reducing the greenhouse gas (GHG) emissions

    associated with crop production. Improvements in water quality are also associated with less use of

    synthetic fertilizers.

    Anaerobic digesters can be thought of as an extension of a cows stomach. Both rely on operative

    microbes that flourish in the absence of oxygen to transform foodstuff into useable energy. Operative

    microbes are most successful at doing this when they are consistently fed a diet that meets their

    nutritional needs and the digester temperature and pH are maintained at target values.

    The anaerobic digestion process overall involves three groups of anaerobic microbes. First, hydrolytic

    bacteria initiate a process called hydrolysis. These bacteria use extra cellular enzymes to convert

    organic insoluble fibrous material into soluble material; however, inorganic solids and hard-to-digest

    organic material are not able to be converted.

    Next, acid forming bacteria convert the soluble carbohydrates, fats, and proteins to short-chained

    organic acids. The acids produced in step two become the food source for the methanogens, which

    produce methane gas in the third step.

    Various methanogenic species grow in different temperature regimes.

    1. Psychrophilic methanogens grow in the lowest of the temperature ranges, less than 68F.

    Methanogens in this range grow slowest and produce the least biogas per unit of time.

    Covered lagoon systems, especially those in northern climates, will be in this range much

    of the year (Wright, 2001).

  • 28

    2. Mesophilic methanogens grow in an optimum temperature of about 100F which is the

    most common operational temperature for digesters in the U.S.

    3. Thermophilic methanogens grow in an optimum temperature of about 130F. The higher

    operating temperature increases the rate of biomass degradation, increases pathogen

    reduction, and allows for shorter retention times thus reducing the capital cost of the

    digester vessel.

    Digester Types

    In the U.S. there are basically three different types of anaerobic digestion systems used today to process

    dairy manure. They are: plug-flow, complete mix, and covered lagoon. Of these three, a complete mix

    system is the system of choice for use in a centralized digester because the likelihood of co-digestion of

    dairy manure with non-farm biomasses is very high. (Digester influent concentrations less than 10

    percent total solids are common when co-digesting manure with most food processing by-products

    and require mixing to minimize solids settling.)

    Complete mix digesters can be either horizontal flow or vertical flow systems. Each is briefly discussed

    below.

    Complete Mix Digester, Horizontal Flow System

    Horizontal-mix digesters incorporate agitation systems in digester vessels. The mixing system is

    mainly utilized in scenarios that have influent total solid concentrations greater than 12 percent (not

    common with dairy manure-based systems) or less than 10 percent.

    Complete Mix Digester, Vertical System

    Vertical mixed digester tanks can be either below-grade (atypical) or above-grade (typical) as shown

    in Figure 4. Cast-in-place concrete, welded steel, bolted stainless steel, and bolted glass-lined steel

    panels are all used to construct vertical tanks.

    The mixing process is achieved by various methods, depending on the preference of the system

    designer and the overall goals of the system. In one method, an external electrical motor (about 10-

    20-Hp) turns a vertical shaft, concentric with the digester tank, which has several large paddles

  • 29

    attached. The shaft speed is about 20 RPMs. This system is common for solid top tanks.

    Another method uses submersed impeller agitators each driven by either an electrical motor or a

    centrally located hydraulic motor. These systems have a much higher blade speed, perhaps 1,750

    RPMs, and can be used with both flexible top and solid top applications. One clear advantage of the

    first method is the electrical motor is easy to service and replace.

    Vertical tanks are insulated during the construction process to reduce the maintenance heating

    requirement (heat to maintain digester operating temperature). Significant heat can be lost from

    vertical tank digesters if they are not properly insulated. Applicable insulation options are to spray

    the tank with foam insulation or to use rigid board insulation attached to the tank and then covered

    with metal cladding.

    Figure 4. Danish above-grade complete mix vertical digesters in background

    Biogas

    Anaerobic digestion produces a continuous supply of biogas in quantities sufficient to not only power

    the digestion plant but also to utilize the excess in various ways. Producing electricity and/or thermal

  • 30

    heat from biogas results in a net reduction of greenhouse gases (GHG). Anaerobic digestion of dairy

    manure also mitigates methane emissions otherwise caused by traditional manure handling and storage

    practices.

    Production of biogas is dependent mainly on the digester hydraulic retention time (HRT), digester

    operating temperature, and the biochemical energy potential of the influent. Higher biomass

    conversion efficiencies by thermophilic (~135F) methanogens allow for shorter hydraulic retention

    times and consequently reduced capital costs as compared to mesophilic (~100F) systems. Biochemical

    energy of an influent material is most accurately evaluated by conducting long-term (6-month) bench-

    top reactor tests (Angenent, 2009) but is generally estimated by measuring the VS content in the

    influent. Biochemical methane trials can also be conducted in the laboratory to estimate the biogas

    production potential of a biomass sample. Jewell (2007) reported that an appropriate estimation of the

    methane (CH4) production is to use a value of 0.5 L CH4/gram of VS degraded. If the dry biogas is 60

    percent CH4 this is equivalent to 13.4 ft3 biogas/lb. of VS degraded.

    Composition and energy value

    On-farm digester monitoring has shown that biogas is comprised mainly of ~60% methane and ~40%

    carbon dioxide (CO2), with trace levels of 0.2 to 0.4 percent hydrogen sulfide (H2S). Even though H2S

    concentrations are low, biogas is highly corrosive and prudence is needed to avoid pre-mature biogas

    transport and utilization equipment failures.

    Pure (dry) methane has a low heating value of 896 Btu/ft3 (at standard temperature and pressure: 68F

    and 1 atm) (Marks, 1978). Since biogas is only ~60% methane, its heating value is ~40% lower or about

    540 Btu/ft3. Raw biogas is considered to be saturated with water vapor.

    Utilization: fuel source for engine-generator sets

    Using biogas as an energy source to fuel on-site engine-generator set(s) is the most common use of

    biogas today. Large engines that had been adopted for landfill biogas years ago are now widely

    available for use at centralized digestion sites. Most are spark-ignited systems with a few compression

    ignited systems that also use about 10 percent diesel fuel concurrently as a fuel source.

  • 31

    Overall, these low Btu or dirty gas engines work well with the exception of difficulties arising from

    hydrogen sulfide (H2S). Hydrogen sulfide is very corrosive at low temperatures since it converts to

    sulfuric acid. To date, most on-farm biogas-fired engines combat the corrosiveness by running the

    engine nearly continuously (keeps the temperature high) and changing oil more frequently than for

    cleaner fuel source scenarios.

    Recently, some U.S. farmers have implemented methods to reduce H2S concentrations from biogas prior

    to utilization. Methods include chemical reaction and biological reduction systems. Scrubbers are

    mainstream equipment on European digester systems.

    Overall, there are two basic types of generators:

    1. Induction generators run off the signal from the utility and are used to allow parallel hook

    up with the utility. Induction generators cannot be used as a source of on-farm backup

    power since the system needs the signal from the utility line to operate properly.

    2. Synchronous generators could be run independently of the utility but matching the

    utilities power signal would be very difficult so these types of generators would be used if

    the system were not connected to the utility grid.

    Most generator systems manufactured today have controls that will allow the engine-generator set to

    synchronize with the utilitys electrical frequency and still operate in island mode when there is a

    disruption of the grid power. These systems can be set up to black start if desired.

    Thermal-to-electrical conversion efficiencies for biogas-fired internal combustion engine-generator sets

    are less than desirable, but are about the same as other fuels. On-farm digester monitoring has shown

    that the conversion efficiency ranged from 22 to 28 percent, as shown in Figure 5.

    The electricity production depends on the amount and quality of gas as well as the efficiency of the

    engine-generator. Typically, 33-38 kWh/day will be produced per 1,000 ft3/day of biogas produced

    (Koelsch et al., undated and EPA, 1997). Some engine-generator set manufacturers show biogas-to-

    electrical energy conversion efficiencies as high as 42% in their advertisement literature. As with all

  • 32

    large capital purchases, careful evaluation of those systems is needed to ensure they are economically

    feasible.

    As already mentioned, engine water jacket heat, and sometimes exhaust heat as well, is harvested and

    used as the primary means to heat the digester. In the winter, most if not all of this harvested heat is

    needed, while in the summer a good portion of it is dumped to the ambient via forced-air/water heat

    exchanger.

    Figure 5. Thermal to electric conversion efficiency of six NYS on-farm engine-generator sets.

    (Source: Gooch, Pronto, Ludington, Unpublished, 2010)

    Utilization: fuel source for microturbines

    Two New York State dairy farms have microturbines in operation to power generators to produce

    electricity. The main interest in microturbines is the premise that they require less maintenance on a

    daily basis and also on a long-term basis, and most recently that they potentially produce less exhaust

    emissions. Biogas pressure needs to be increased from typical digester pressure values to about 60 psi

    before being injected into a microturbine. Corrosion-resistant small-scale compressors are available to

    compress raw biogas to this pressure thus lessening the need for an H2S scrubber.

    The typical fuel-to-power efficiencies of various biogas utilization options are shown in Table 1. These

    efficiency figures do not account for increases due to the use of co-generated heat.

  • 33

    Table 1. Typical fuel-to-power efficiency values (adapted and updated from Wright, 2001).

    Prime Mover Type Efficiency

    Spark ignition engine 18-42%

    Compression ignition

    engine (Diesel)

    30-35% above 1 MW

    25-30% below 1 MW

    Gas turbine 18-40% above 10 MW

    Microturbine 25-35% below 1 MW

    One source states the operation and maintenance cost of $0.015 per kWh are estimated for engine-

    generators (EPA, 1997). On-going engine-generator set service contracts are offered by one company

    that sells them for $0.015 to $0.02 per kWh produced depending on the pre-existing maintenance

    performed on the set and presence of an H2S scrubber.

    Utilization: fuel source for boilers

    On-farm biogas utilization by a boiler is the second most popular use of the energy. Natural gas boilers

    can be modified to use biogas as a fuel source. The main modification involves increasing the pipe

    delivery size and orifices in the burners to accommodate the lower density fuel. Decreasing the

    concentration of H2S in the biogas can extend the life of the boiler equipment. Boilers are mainly used

    to provide primary or secondary heating of the digester and in some cases also to provide domestic

    heating of farm offices and lounge areas. One farm used boiler heat to heat a calf barn, but this use is

    limited.

    Utilization: fuel source for other uses

    Raw biogas can also be used as a fuel source for drying equipment such as grain dryers, separated

    manure solids dryers, evaporators, etc. Other possible uses fall under the category of those needing

    fully cleaned (scrubbed) biogas, commonly known as biomethane. These possible uses include any

    that currently use natural gas (almost pure methane) and as a vehicle fuel. There are two primary

    methods to process biogas into biomethane. They are: 1) chemical and, 2) physical removal of

    impurities (CO2, H2S, and water vapor). Details of these processes are beyond the scope of this report

    but the general flow process diagram is shown in Figure 6.

  • 34

    Figure 6. Basic process flow diagram for advanced biogas clean-up for biomethane production.

    Advanced Centralized Digester Information

    Specific information on a CAD system is presented below.

    System electrical demand

    Modern CADs require electrical energy to operate with the highest electrical demand normally

    associated with the pumps and agitation equipment. The electrical energy used to operate a system

    is known as parasitic electrical energy. With all centralized digester systems it is important to

    implement a design that is energy efficient. Electrical energy efficiency can be expressed in various

    ways including as a function of the: 1) influent volume (annual kWh/annual influent), 2) vessel

    treatment volume (annual kWh/tank size), and 3) energy production (kWh consumed/kWh

    produced). All systems that are not electrically efficient result in reduced sale of electrical power

    and/or increased purchase of electrical energy from the utility.

    System thermal (heat) demand

    Anaerobic digesters require a controlled heating system for operation. There are two different heat

    demands in most systems; they are: 1) differential heat, and 2) maintenance heat. Differential heat is

    the heat needed to raise the influent temperature to digester target operating temperature and

  • 35

    represents by far the largest heating requirement of the system. Maintenance heat is needed in

    most, but not all systems, to maintain digester contents at target operating temperature.

    When an engine-generator set is used to convert biogas to electricity, the heat of combustion is

    harvested from the engine and used to heat the digester. In this scenario, the heating efficiency of

    the digester heating system is less important than if heat is provided by a biogas-fired boiler. Under

    the later scenario, a primary goal of the digester system is normally to sell raw or processed biogas

    and thus the need exists to minimize the parasitic heating requirement. Installations where heat

    sales are important can utilize digester effluent/influent heat exchangers can be used to minimize the

    parasitic heating requirement by preheating digester influent.

    Biosecurity/disease control

    Dairy manure is known to contain various pathogens that survive outside the cow. Not all cows on all

    farms have the same contagious pathogens. The centralized digestion model involves commingled

    digested manure and non-farm feedstock(s) being returned to the source farms resulting in justified

    biosecurity concerns.

    The hydraulic retention time (HRT) of complete mix digesters varies at the microscopic level from

    manure particle to manure particle. Some manure particles will remain in the digester for greater

    than the theoretical HRT while some will short-circuit due to the agitation process and exit sooner.

    Data collected from one New York State dairy farm that co-digested dairy manure with several non-

    farm biomass sources using a complete mix digester showed that the average reduction of the

    commonly measured fecal coliform (an indicator organism) and Mycobacterium paratuberculosis

    (Johnes disease) was 98.4 and 94.8 percent, respectively (Wright et al., 2003).

    In Denmark, mixing of non-farm biomass materials with manure is common practice and when this is

    done, the Danish government requires the food waste/manure mixture to be pasteurized (70C for

    one hour) prior to being land applied in order for the farm to be in compliance with standard manure

    application laws. Observation has shown that pasteurization normally occurs at the centralized

    digester site, prior to digestion.

  • 36

    Operational considerations

    Experience has shown that well-designed centralized digesters can be operated successfully for long

    uninterrupted periods of time continuously (24 hours per day, seven days per week, and 365 days per

    year) when adequate management and maintenance is provided. Centralized digesters are complex and

    involve:

    Physical systems including containment vessels and influent /effluent pits

    Mechanical systems including pumps, agitators, and sensors

    Biological systems including methanogens

    The daily success of such a system is deeply rooted in personnel who take ownership in the system

    and are provided the resources needed to make it successful.

    General operational challenges for a CAD system include:

    Changes in influent composition; Adding variable qualities or quantities of influent can

    allow the acid-forming bacteria to out-produce the methanogens. Acidic conditions can

    then develop, compromising the stable environment and production of methanogens.

    Foaming; Foaming can occur when rising biogas bubbles do not pop when reaching the

    manure/biogas headspace interface in the AD. Foaming can be a major issue when

    feedstock composition or feeding rates change, most notably on farms when new corn

    silage and/or haylage is fed to cows. Excessive foaming can plug the biogas outlet or enter

    the biogas line and gum up pressure regulators or other equipment.

    Temperature; Maintaining the temperature of the AD is critical to ensure efficient,

    operative microbes and consequently consistent quantity and quality (composition) of

    biogas. Attention to design of the digester heating system is important to the success of

    the overall system.

    Frozen manure; Slushy or frozen manure is common in much of the winter in New York

    State. Tremendous energy (about 144 Btus/lb) is needed to thaw frozen manure and

    then to increase the temperature from 32F to digester operating temperature (~68

    Btus/lb manure for a mesophilic digester operating at 100F). In fact, the requirement

  • 37

    can be so high that there is not enough heat to bring the manure up to operating

    temperature. With lowered temperatures, biogas production decreases, resulting in even

    less heat being available. In a CAD system, frozen manure should not pose any problems,

    since the manure must be able to be picked up and transported from the farms to the

    CAD, within one day.

    Control systems; Automatic controls are essential for continuous performance of a

    centralized digester system. Proper control equipment selection will allow the system to

    be monitored remotely thus providing the opportunity for employees to have a rotating

    schedule of weekends off and being on call. The digester should have a preventative

    maintenance schedule that includes monitoring equipment that creates input data for the

    automated control system.

    Safety; Centralized digester employees and managers need to be properly trained for the

    safety hazards present in the system. There are safety issues of asphyxiation, fire, and

    explosion associated with the production of biogas. Methane can explode when mixed

    with air in concentrations of 5 to 15% and a fire hazard exists when there are leaks

    present in biogas containment materials. Dangerous levels of ammonia and hydrogen

    sulfide may also be present. The same hazards associated with large engines and

    electrical generation equipment are also present in these systems.

    Digestate nutrient recovery

    As previously mentioned, anaerobic digestion provides excellent pre-treatment for subsequent

    processes to separate and concentrate N, P and K as shown in Figure 7. A centralized anaerobic digester

    system can provide more economies of scale thus presenting increased opportunity to do this over

    individual farm-based anaerobic digesters.

    Separating nutrients into concentrated materials can provide farmers more flexibility in selecting

    nutrients that are needed for specific crops and soil conditions. This will further the environmental

    benefit of the project by providing such fertilizers in a form that the farmer can more efficiently apply to

    cropland and result in higher crop utilization and less environmental impact. Higher application

    efficiencies can be obtained by way of 1) reduced trips to the field, thus decreasing the time required to

  • 38

    apply organic fertilizer to cropland, and 2) increased timeliness of application resulting in reduced

    nutrient loss to the environment.

    Figure 7. Advanced digestate treatment to segregate and concentrate nitrogen, phosphorus, and potassium.

    Technologies originally developed for treating municipal wastewater are readily available for

    removing excessive phosphorous from manure (and a manure- non-farm biomass blend), but the

    economics of the implementation of such systems on-farm are not well established.

  • 39

    Chapter 2. Literature Review of Centralized AD Projects

    A literature review was conducted to assess and identify centralized (AD) feasibility studies for projects

    of similar scope as the proposed Lewis County project. There are a number of existing studies that have

    been performed to assess the feasibility of large-scale AD projects; a synopsis of the eight most relevant

    reports is presented below. The values presented in this chapter for energy production, cow numbers,

    and economics, among others, were taken directly from the feasibility reports and were not verified by

    those reviewing them. Some of the values taken from these studies do not follow the logic used to

    develop these same values throughout the remainder of this report.

    St. Albans/Swanton, Vermont Cooperative Dairy Manure Management Project

    The St. Albans/Swanton, Vermont area has a high concentration of dairy farms, and was also the site of

    Vermonts Northwest State Correctional Facility. These key considerations, in addition to environmental

    concerns such as a need to improve manure-based odors and reduce nutrient run-off (namely

    phosphorous reduction) prompted an investigation into the feasibility of a centralized anaerobic

    digestion system (Bennett, 2003). This project has not yet been initiated; the results of the feasibility

    study have been circulated for additional input. Basic statistics determined in the feasibility study are

    included in Table 2.

    Table 2. St. Albans/Swanton, VT project statistics

    Proposed input material quantity 226,0001 tons dairy manure/year

    Proposed number of farms involved 26 farms

    Proposed number of cows involved 10,200 cows

    Estimated electrical energy production 2,000 kWh/day

    Estimated capital cost $6,000,000 ($581/cow)

    Expected cash flow + $0.71/ton of manure 1this number, taken directly from the report calculates to 121 lbs manure/cow-day, and a value of 150 lbs/cow-

    day was used for this work done in this feasibility report

    This project was initially proposed with a specific end user identified. The nearby Northwest State

    Correctional Facility housing 250 inmates, consumed 1.28 million kWh/year of electricity at a cost of

    $122,000 per year, and used nearly 11.55 billion ft3 of natural gas per year. The report states:

    At first glance, the transportation cost exceeds the value of the electricity produced by the

    digester. Only when all the benefits and revenues are compared to the expenses can this project

    be fully appreciated. Then, the large environmental and public impacts are added to the

    electricity, heat, and by-products to make this a compelling project.

  • 40

    The project feasibility study considered four general designs:

    One central digester

    Three mini-central digesters (each serving between 2,000 to 5,000 cows)

    Several local cooperative digesters (for farms with over 300 animal units10)

    Individual farm digesters

    The report advocated one central digester for best economies of scale and knowledge sharing, and

    because it best fit the needs of the end user in terms of energy usage. Transportation costs were

    paramount in making this assessment. The report stated that: reaching additional farms would involve

    dramatic increases in mileage with minimal increases in electricity generated; transportation is a major

    on-going expense. Project trucking requirements estimated nine truck drivers, 6-10 facility personnel,

    and 2-3 administrators for a total of 17-22 new jobs created by the project (Bennett, 2003).

    Lane Renewable Energy Complex

    The Lane Renewable Energy Complex (LREC) was a municipal biogas plant and centralized AD facility

    proposed in light of environmental and economic concerns in the Eugene and Springfield, Oregon areas

    (Weisman, 2008). The LREC was proposed to be The United States first Kyoto-compliant municipal

    biogas power plant and public transportation refueling facility. In addition to biogas, the AD facility was

    proposed to provide organic fertilizer for 200,000 acres throughout Lane County and Oregon. The LREC

    project has not yet been implemented; adequate funding is currently being sought.

    Pollution in the Willamette River and high fertilizer prices were key concerns to be addressed through

    the reduction of runoff from un-incorporated manure. In addition, electricity and a nutrient-laden

    fertilizer are claimed to be produced by the AD facility. Basic statistics determined in the feasibility

    study are included in Table 3.

    10

    An animal unit equivalent or animal unit is generally defined as 1,000 pounds of live animal weight. Note: this is an out of date method of expressing animal equivalents; for dairy applications, expressing parameters on a lactating cow basis is appropriate.

  • 41

    Table 3. LREC project statistics

    Proposed input material quantity 400 tons1 of agricultural waste, food waste (commercial and residential), and municipal wastewater

    Estimated gross biogas production 5.5 million ft3 biogas/year

    Estimated electrical energy production 8,300 kWh/day

    Estimated capital cost $256,000,000

    Projected O&M costs $8,400,000/year

    Projected annual net revenue $19,500,000 1No units of time provided in report, i.e. tons/year

    The proposed biogas plant would consist of 15 two-stage, 1 million-gallon mesophilic digesters with

    slurry recirculation. Biogas would be scrubbed to reduce hydrogen sulfide (H2S) and siloxanes (siloxanes

    may originate from municipal sources) before being sent by a blower to five Caterpillar 3520 engine-

    generator sets, each with a generating capacity of 1,660-kW, or to a vehicle fuel upgrading system.

    The proposed project was planned to be a collaboration between: Lane County, EPA, U.S. Economic

    Development Administration, USDA, Oregon Department of Energy, Lane Transit District,

    ENERGYneering Solutions Inc., Swedish Biogas International, Union Pacific, Lane Community College,

    and the Biogas Institute of the Ministry of Agriculture in Chengdu, Sichuan, Peoples Republic of China.

    It was anticipated the facility would take 24 months to come online, and it was estimated the project

    would create 125 high-quality, full-time positions and 400 construction jobs (Weisman, 2008). The

    proposed site for the LREC has several important advantages: it is publicly owned, zoned industrial,

    located near a natural gas transmission pipeline, and has an existing 5.5 mile sewage pipeline for

    wastewater transfer. The project anticipated receiving $65 million in state and federal grants for the

    project.

    Dane County, Wisconsin Community Manure Facilities Plan

    The feasibility study for the Dane County, Wisconsin project examined two clusters of farms in

    Waunakee and Middleton, Wisconsin. Within these clusters, two options were considered: anaerobic

    digestion and combustion. The County decided to move forward with plans for the anaerobic digestion

    option for the Waunakee cluster (Strand, 2008). Basic statistics determined in the feasibility study for

    the Waunakee cluster approach are included in Table 4.

  • 42

    Table 4. Dane County, WI (Waunakee cluster) project statistics

    Proposed input material quantity 152,000 gallons per day

    Proposed number of farms involved 5

    Proposed number of cows involved 6,000 animal units

    Estimated electrical energy production 9,700 kWh/day

    Estimated capital cost1 $6,400,000

    Projected O&M costs1 $1,000,000

    Estimated GHG reduction 19,800 TCO2e/year 1Based on the lowest levels of phosphorus removal

    The Waunakee cluster included five farms with a total of approximately 6,000 animal units. The farms

    were located within approximately one-half mile of each other, with additional farms located nearby.

    The main goals of the study were to strengthen the livestock industry in the county and to protect

    water quality as related to manure management. The scope of the study included a survey of area

    farms, identification and selection of farms to be used in the analyses as well as a selection of

    management alternatives to be studied, technical and economic analyses of these alternatives, and

    discussions of financing methods, non-monetary evaluation, and potential business structures of the

    proposed project.

    In March 2009, Wisconsin Governor Jim Doyle announced that he would allocate $6.6 million to the

    Waunakee area digester and a second digester in Middleton. This is in addition to the $1.2 million

    already allocated in the 2009 County budget for construction costs associated with the project.

    Additional federal money is currently being sought.

    Cornell Universitys Proposed Anaerobic Digester

    The feasibility study examining an AD facility at Cornell University was completed as part of an

    undergraduate class research project examining sustainable development on the Cornell University

    campus in Ithaca, New York. This study considered two options for biogas use: introduction to a natural

    gas pipeline or use of the biogas to power a hydrogen fuel cell. The report advocates the more

    expensive fuel cell option over a natural gas pipeline, for its environmental benefits as well as its

    educational opportunities on the Cornell University campus (Casey et al., 2007). While this project may

    represent only a small reduction in Cornells actual carbon emissions it provides an important early step

    on the long and difficult journey to carbon neutrality, the report states. Basic project statistics

    determined in the feasibility study are included in Table 5.

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    Table 5. Cornell project statistics

    Proposed input material quantity 6,300 tons organic waste/year, including veterinary school manure, greenhouse wastes, and dining hall food waste.

    Estimated biogas production 1.45 x 107 ft3 biogas/year

    Estimated capital cost $5,500,000 (over 20 years)

    Cornell University hired Stearns & Wheler GHD to further develop the findings of the report, and the

    firm has published their feasibility study findings in, Cornell University Renewable Bioenergy Initiative

    (CURBI) Feasibility Study.

    Evaluation of Anaerobic Digestion Options for Groups of Dairy Farms in Upstate New York

    This feasibility study assessed the potential viability of constructing a CAD in York, New York in

    Livingston County, to serve several small farms in the region. The suggested measures of the study were

    never implemented, the reason(s) is not known. Basic project statistics determined in the feasibility

    study are included in Table 6.

    Table 6. York, NY project statistics

    Proposed input material quantity 164,000 tons manure/year

    Proposed number of farms involved 16 farms

    Proposed number of cows involved 4,700

    Estimated electricity production 650 kWh/day

    Estimated capital cost $1,550,000

    Projected O&M costs $317,000/year

    Projected annual revenue $235,000/year

    While several potential project sizes were examined, the projections above consider 4,700 cows

    supplying manure to the CAD, since this resulted in the lowest estimated transportation costs. Break-

    even benefit at 4,700 cows was $150/cow, derived from the sale of post-digestion products. Since the

    value of these products per cow ranged from $200 - $400, revenue was estimated to be $50/cow,

    assuming the conservative $200 value per cow ($235,000/year profit in 1997) (Jewell et al., 1997).

    Effects of economies of scale were examined in this report. As the dairy size decreased to 600 milk

    cows, the net cost of managing manure increased to over $200 per cow per year (net cost or value

    equals fertilizer value less the cost of land application), the report states. The study recommended

    construction of a 4,000 - 6,000 - cow facility as a first step in the York, NY area. Initially, stabilized waste

    would be returned to farms. The report advocated for efforts that would reclaim other by-products,

    such as fiber, in a cost-effective manner. The report projected a total annual value of the recovered

  • 44

    fiber for bedding to be $50 - $200/cow-year (Jewell et al., 1997).

    Feasibility Study of a Central Anaerobic Digester for Ten Dairy Farms in Salem, NY

    A Salem-based dairy farmer group contracted with Stearns & Wheler, LLC, and Dr. Stanley A. Weeks to

    conduct a feasibility study for constructing a centralized AD to cost-effectively treat manure from 10

    dairy farms in Washington County New York (Bothi and Aldrich, 2005). Basic project statistics

    determined in the feasibility study are included in Table 7.

    Table 7. Salem, NY project statistics

    Proposed input material quantity 113,000 tons dairy manure/year

    Proposed number of farms involved 10 farms

    Proposed number of cows involved 3,700 cows

    Estimated electricity production 6,600 kWh/day

    Estimated capital cost $2,105,000

    Projected O&M costs $1,043,000/year

    The study considered three design options:

    1. Pre-treatment with solid-liquid separation, digestion and separated solids composting

    2. Option one with the addition of a centrifuge process to remove additional solids and

    nutrients prior to digestion

    3. Solid-liquid separation and digestion with no on-site composting

    The report recommended option number three, since the per-cow costs were lowest for this option.

    Construction of a centralized AD was deemed not economically feasible at the time the report was

    written. Trucking costs were a significant component of the total annual cost for all scenarios. Within

    each alternative, several options for material transport were examined. The costs of trucking manure

    for these scenarios ranged from $384,000/year for one-way trucking (given that the effluent was

    pumped off-site to 6-month storage) to $604,000/year for raw manure trucking and effluent trucking

    (given 5 days on-site storage) (Bothi and Aldrich, 2005). Furthermore, the potential energy generation

    was beyond the electrical needs of the target end-user. Finding a use for the excess power generated

    could improve the economic feasibility of this project.

  • 45

    Feasibility Study of Anaerobic Digestion Options for Perry, New York

    The New York State Energy Research and Development Authority (NYSERDA) provided partial funding

    for a feasibility study to assess anaerobic digestion potential among four of the larger neighboring dairy

    operations in the Town of Perry, Wyoming County, NY. Wyoming County is the largest milk-producing

    county in New York State. The four CAFOs involved in the study cited odor reduction as their primary

    goal in pursuing an alternative manure management system (CCE, 2002). Basic project statistics

    determined in the feasibility study are presented in Table 8.

    Table 8. Perry, NY project statistics

    Proposed input material quantity 90,400 gallons dairy manure/day

    Proposed number of farms involved 4 farms

    Proposed number of cows involved 3,804 lactating cow equivalents

    Estimated biogas production 323,500 ft3 biogas/day

    Estimated electricity production 519 kW

    Estimated capital cost $1,187,000

    Projected annual revenue $91,490

    The study examined four options: (1) one centralized digester shared by all farms, (2) one digester

    shared by two nearby farms, (3) one digester on each farm with collaboration in other ways, such as

    through collaborative marketing or joint composting, and (4) collaboration to recruit an independent

    business to provide digestion services for farms. The project statistics presented in Table 8 represent

    the centralized digestion option considered. The economic analysis for this option was the least

    feasible, due to logistical concerns, low energy benefits, and high transportation costs. The report noted

    that if electricity could be sold back to the grid as a premium, the economics of the study would change

    significantly. The option considering one digester installed on each farm was found to be the most

    economically and logistically feasible option at the time of the study. Two digesters were constructed in

    2006, one at Sunny Knoll Farm and one at Emerling Dairy (CCE, 2002), and remain operational today.

    Feasibility Study for a Port of Tillamook County Dairy Waste Treatment and Methane

    Generation Facility

    This report was assembled for the Tillamook Methane Energy and Agricultural Development Policy

    Committee. In light of the Tillamook Creamerys capacity to double its cheese production, local dairies

    sought to improve manure waste management. Pathogens, water quality issues, and public health

    issues resulting from mostly nitrogen-based pollution were cited as important motivators for a

  • 46

    reassessment of manure management practices (Edgar, 1991). Basic project statistics are provided in

    Table 9.

    Table 9. Port of Tillamook project statistics

    Proposed input material quantity 57-128 tons dairy manure solids/day

    Proposed number of farms involved 191 dairies

    Proposed number of cows involved 25,996 cow-units

    Estimated electricity production 123,600 kWh/day; 5.15 MW

    Estimated capital cost $1,300,532 $5,739, 674

    Projected annual O&M $25,558 $1,233,186

    Projected annual revenue $52,300

    Initial inquiries into accepting sludge from waste treatment plants at both the City of Tillamook and the

    Tillamook Creamery found that regulatory complications outweighed the marginal production benefit of

    this added waste stream. The report considered several scenarios with varying degrees of three key

    variables: percent total solids of the raw waste being hauled (10% or 13%), the extent of manure

    collection (50%, 100%), and the percent of the total number of cows manure collected (15%, 25%, 50%,

    100%, 200%). The report also considered varying scenarios involving one, two, or three digesters.

    Ultimately, the best case for net cost was two plants (Edgar, 1991). The facility was ultimately built and

    is in operation under the direction of George DeVore at the time of this writing. In 2007, it seemed the

    project had transitioned to using heat produced by the system to dry solids and then to sell organic

    material (Scott, 2010).

    Economic Feasibility Study for a Centralized Digestion System

    A web-based model was developed to be used in performing an economic sensitivity analysis for

    centralized anaerobic digester projects (Minchoff, 2006). The model found that tipping fees were a

    crucial component of overall CAD economic viability. Average landfill tipping fees ($/ton) for

    different regions in the United States are presented in Figure 8, and the data is also presented

    graphically in Figure 9. As of the last survey, the Northeast had the highest tipping fees when

    compared with the rest of the country, at $70.53/ton (Repa, 2005).

  • 47

    Figure 8. Landfill tipping fees ($/ton) by region of the U.S. (Repa, 2005)

    Figure 9. Landfill tipping fees ($/ton), developed from Figure 8 (Repa, 2005).

    Summary

    The centralized digester feasibility studies reviewed were mostly initiated due to local concern over

    improved manure management, odor reduction, and/or improved nutrient management. For the

    studies that involved co-digestion of dairy manure with non-farm biomass substrates, the amount of

    energy produced was higher per dollar of capital investment. While many of the studies were not

    deemed economically feasible or were otherwise not implemented, several mentioned that valuation of

    environmental benefits could potentially improve the economic outlook for some projects, depending

  • 48

    on initial goals of the project. Of the feasibility studies reviewed here to look at the practice and

    economics of centralized digestion, the common findings of these feasibility studies were:

    Economics: Many of the proposed systems were not found to be economically feasible

    at the time the studies were conducted. Manure trucking costs were a prohibitively

    large component of the estimated annual operating cost. However, the approaches

    taken to analyze transportation expenses generally did not include a line item for

    tipping fees received by the digester from non-farm biomass suppliers. Several studies

    also found the need to develop a valuation system for benefits that are not readily

    perceived, i.e., odor reduction or water quality improvement. Many centralized

    digester projects take advantage of additional biomass, beyond manure, for co-

    digestion which greatly enhances energy production and can usually generate a tipping

    fee for the project. Most of the projects described in this chapter were never pursued,

    as many sought grant funding to cover capital costs.

    Energy production: Most projects reviewed here planned to generate electricity for

    sale to, in most cases, one end user/buyer.

    Odor: Concern was expressed about the potential for significant odor emissions from

    trucking raw manure to the centralized digester site, and the potential of on-site odors

    from the centralized digestion facility. Experience has shown that odors associated

    with influent materials stored short-term can be mitigated with systems that collect the

    off-gases and process them in a bio-filter. Odor reduction was one of the most

    common reasons for pursuing centralized AD.

    Biosecurity concerns: There is no way to prevent the commingling of sourced manure

    and centralized digester effluent needs to be returned to the source farms. Here it is

    important to point out that research has shown that anaerobic digestion of dairy

    manure significantly reduces viable populations of two tested pathogens that are a

    concern for cattle and humans (Wright et al., 2003).

  • 49

    Chapter 3. Farm and Community Biomass Survey

    The Lowville community AD project was conceived through discussions about what could be done locally

    to preserve and preferably to increase the strength of the agriculture industry in Lewis County. A

    community manure treatment and processing center was proposed, including an AD centrally located in

    Lowville, New York with the goal of providing benefits to three key groups in Lewis County: dairy

    farmers, local industry, and residents.

    In order to accurately assess the needs of these key groups and to determine the feasibility of meeting

    those needs, two surveys were developed by Cornell Universitys Manure Management Program and

    Cornell Cooperative Extension of Lewis County (CCE-LC).

    The dairy farm manure and non-farm biomass surveys served three purposes:

    1. Determine the useable quantity, availability, and general composition of existing

    biomass (waste) streams

    2. Assess the willingness to cooperate among local farmers and businesses

    3. Make contacts and compile data for future community involvement

    The first survey, distributed by CCE-LC, was a survey of dairy farms that: (1) fell within a 20-mile radius of

    Lowville, (2) did not use sand bedding, and (3) had long-term storage. The presence of a long-term

    storage at each farm was a key item that was used to select collaborating farms, as farms with a long-

    term storage could participate in the project with little additional capital expense.

    CCE-LC representatives administered the dairy farm-based surveys by mail in fall 2008. To improve the

    response rate, the farm-based surveys were administered again face-to-face in Spring/Summer 2009.

    The second survey was a non-farm biomass survey distributed to select local businesses by the Village of

    Lowville. Officials from the village of Lowville administered the non-farm surveys in-person in

    Spring/Summer 2009. A blank copy of each survey is provided in Appendix B and C.

  • 50

    Dairy farm survey

    While it was ultimately decided that those farmers who took the time to fill out a survey could be

    considered interested or supportive simply because of their decision to participate in the survey, most

    of the farmers responded to the perspective questions with caution. If it benefits me, was a

    common reply of the respondents' willingness to provide the proposed CAD project with their manure.

    Delivery of nutrient-laden effluent back to each participating farm will likely prove to be an important

    determinant of the projects ultimate success with the farmers. Overall, willingness to cooperate is

    heavily dependent on perceived benefits to the farmer.

    A summary of the data obtained through the farm survey is shown in Table 10. Information regarding

    each farms existing manure storage(s), road access, and bedding type(s) is included. Storage, access,

    and bedding are all farm characteristics needed to help determine the degree to which a dairy farm

    would be able to participate in a community digester project.

  • 51

    Table 10. Summary of current (2009) farm survey data

    Farm ID number

    Distance from

    center of Lowville (miles)

    Number of

    mature cows

    Number of

    heifers

    Lactating cow equivalents (LCE) (total

    solids basis)1

    Days of short-term

    storage available

    Months of long-

    term storage

    available

    Bedding type

    1* 2 200 150 262 3-4 6 Bedded

    pack/shavings

    2 6 0 150 62 1 6 Chopped

    hay/shavings

    3 6 66 10 70 1-3 5 chopped hay

    4 7 105 75 136 0 7 chopped hay

    5 7 420 40 436 0 2 mattresses, hay

    shavings

    6* 7 85 70 114 1-3 6 chopped hay

    7* 8 150 100 191 1 6 mattresses,

    sawdust

    8 8 80 80 113 0 6 chopped hay

    9 8 620 407 787 2 4 sand, chopped

    hay

    10 9 145 115 192 1-3 6 chopped hay

    11 9 190 160 256 0 6 Sawdust

    12* 9 195 160 261 1-3 5 sand, sawdust

    13 9 155 150 217 1 6 chopped hay

    14* 9 175 80 208 0 5 flat hay

    15 10 70 30 82 0 6 Hay

    16 10 62 62 87 0 4 chopped hay

    17 11 80 70 109 3 12 chopped hay

    (sawdust)

    18* 11 500 150 562 2 24 dust hay

    19 11 400 430 576 0 10 Sawdust

    20 12 54 36 69 0 6 chopped hay

    21 13 91 60 116 0 6 mattresses, hay

    22 13 91 60 116 0 6 chopped hay

    23 15 130 35 144 0 6 Sawdust

    24 15 85 10 89 0 6 Sawdust

    25 18 50 60 75 0 16 Hay

    SUM 4,199 2,750 5,327 Farms with an asterisk (*) next to their ID number have either gravel, stone, or paved road access. No asterisk indicates the presence of a dirt road. All farms in the table have on-farm long-term storage. 1LCE values were not provided on the surveys, but were calculated using survey data.

  • 52

    Using information provided in the American Society of Agricultural and Biological Engineering (ASABE)

    Practices Standard (ASABE, 2005) along with information from the farm surveys, estimates were made

    of the daily mass of manure production and composition by farm.

    In order to account for the fact that dry cows and heifers produce less manure and volatile solids per

    day than lactating cows, the manure quantity and composition produced by each animal management

    group is expressed on a lactating cow equivalent (LCE) basis. ASABE Standards (ASABE, 2005) were used

    to establish the baseline manure and total solids production for each management group and

    adjustments were made for the dry cow and heifer management groups in such a way that their manure

    production and total solids were expressed on a lactating cow equivalent basis.

    The survey inquired not only about the present situation of each farm, but also requested answers to

    each of the questions based on projections of two years (2011) and five years (2014). Based on

    responses from the 25 farms that completed the survey, the number of LCEs is projected to increase by

    675 cows over two years, and 150 more after five years. When considering a project such as a CAD with

    a significant project life (in this case 20 years), it is important to consider the availability of all feedstocks

    on a long-term basis. The overall dairy population in Lewis County is expected to increase over the next

    two to five years (Vokey, 2010). The survey results based on two and five year projections are provided

    in Appendix F.

    The survey also asked farms to describe their nutrient balance situation; the responses regarding

    nutrient balance are provided in Table 11. The responses showed that nine farms lack the three key

    nutrients (N, P, and K), eleven farms have a balanced nutrient situation, and five farms have excess of at

    least one of the three key nutrients. Farms with a lack of nutrients, for example, would likely be more

    interested in the nutrient-laden effluent produced as a by-product of anaerobic digestion. Select survey

    results from the 25 dairy farms who responded to the survey are superimposed on a map of Lewis

    County, NY and shown in Figure 10.

  • 53

    Table 11. Summary of nutrient balance information as provided in farm surveys

    Farm ID number Nitrogen (N) Phosphorus (P) Potassium (K)

    1 lack lack lack

    2 lack lack lack

    3 lack lack lack

    4 lack lack lack

    5 balanced balanced balanced

    6 lack lack lack

    7 excess excess excess

    8 excess excess excess

    9 balanced balanced balanced

    10 lack lack lack

    11 excess excess excess

    12 balanced balanced balanced

    13 lack lack lack

    14 lack lack lack

    15 balanced balanced balanced

    16 balanced balanced balanced

    17 balanced balanced balanced

    18 lack lack lack

    19 excess excess excess

    20 balanced balanced balanced

    21 balanced excess balanced

    22 balanced balanced balanced

    23 balanced balanced balanced

    24 excess excess excess

    25 balanced balanced balanced

  • 54

    Figure 10. Lowville regional map with collaborating dairy farms superimposed along concentric circles of various radii centered on downtown Lowville.

  • 55

    Non-Farm Survey

    The non-farm biomass survey asked businesses what type and how much of each waste stream they had

    available, and what they currently pay to dispose of it. Also asked in the survey, was how much

    contamination (non-biodegradable materials, i.e., plastic forks or aluminum foil) might be found in each

    waste stream, which is important to consider when aggregating non-farm biomass for co-digestion.

    Eleven local food processors and businesses responded to the survey; however only a few were found to

    have a measurable supply of food waste. Results from all eleven respondents are shown in Table 12,

    with sources italicized to indicate they were later sampled for laboratory analysis.

    A graphical representation of the annual quantity available from select non-farm biomass substrates,

    manure from the 25 dairy farms, and manure from the 15 farms selected for the final scenario, is shown

    in Figure 11. It is apparent from the figure that the quantity of most of the non-farm biomass substrates

    is insignificant when compared to the quantity of manure available. The two non-farm biomass

    substrates with the most meaningful quantities are substrates 8 and 10.

  • 56

    Table 12. Summary of non-farm biomass survey results

    Non-farm biomass

    ID Biomass Description Quantity

    Estimated annual quantity available (lbs/year)

    Approximate disposal costs

    ($/year) Minimum Maximum

    1 mixed food, milk,

    napkins, paper plates, straws

    3 yd3/day,

    September-June 1,009,000 1,009,000 5,000

    2 mixed food, liquid, paper

    plates

    40 gallons pre-consumer/day,

    225 gallons post-consumer/day

    790,000 806,000 19,400

    3 mixed food, oil, grease 25 lbs/day 9,100 9,100 4,100

    4 meat, fat, guts 800 - 2,000 lbs/week December-October

    17,000 72,000 N/A

    5A mixed food

    1-5 gallons pre-consumer/day,

    5-10 gallons post-consumer/day

    13,200 37,500

    4,200

    5B waste grease 8 gallons/week 2,200 3,750

    6 flowers, stems, petals 50 lbs/week, more in December, February,

    May 2,400 2,700 N/A

    7 mixed food 3 gallons/week, more in

    Summer 1,000 1,250 N/A

    8

    whey/water 28,800 to 36,000

    gallons/day 62,400,000 109,500,000 251,000

    Clean in Place (CIP) Wastewater

    14,400 gallons/week 4,400,000 6,200,000 26,000

    9

    oil 5 gallons/week 2,000 2,000

    2,300 vegetables 2 gallons/week 800 800

    meat 1 gallons/week 400 400

    mixed product 5 gallons/week 2,000 2,000

    10 post-digested sludge 5,037,261

    gallons/year 41,900,000 41,900,000 N/A

    111 glycerin

    150 gallons/day, 5 days/week

    339,000 409,000 N/A

    Totals 110,000,000 160,000,000 $312,000

    Italicized sources denote samples tested for biochemical methane potentials 1The source for non-farm biomass substrate 11 was discovered further along in the project and the information in the table was

    provided directly by the substrate supplier

  • 57

    Additional biomass sources

    The lower than expected quantity of manure discovered in the completed dairy farm surveys, prompted

    investigation of additional sources of biomass for co-digestion, in order to increase the gas producing

    potential of the AD system. Co-digestion with additional non-farm biomass substrates provides more

    benefits to project economics than additional dairy manure. The other biomass sources investigated are

    outlined below. Currently, non-farm surveys have been distributed to other local businesses in an

    attempt to supplement the currently low available quantities of non-farm biomass substrates.

    Sand-bedded and daily-spread dairy farms

    The Lowville Digester Work Group inquired about the inclusion of sand-bedded farms in the area, as

    potential candidates to increase manure available for digestion. However, for almost all of the farms in

    the region of the proposed CAD project, the economies of scale are not present to allow for sand-

    manure separation systems to be economically feasible, and for those that it does, sand-manure

    separator effluent is too dilute to warrant transporting to a CAD site.

    Several relatively small farms within a 15-mile radius of the proposed digester site in downtown Lowville

    were not included since they currently practice daily manure spreading and do not currently have

    manure storage capabilities.

    Figure 11. Quantity (millions lbs/yr.) of substrates (wet weight).

  • 58

    Residential food waste

    Residential food waste was considered as a potential non-farm biomass substrate, but serious

    investigation was postponed in light of the lack of technologies to make this option feasible. Feasibility

    of the large-scale collection of residential organic waste would need to be assessed independently, as it

    is outside the scope of this project.

    Fort Drum

    Fort Drum, a large military base north of Lowville, NY is a potential source of organic substrates that was

    investigated; however, a phone conversation with a Fort Drum official revealed that they intend to

    develop their own waste management system to handle food waste from their centralized dining

    facilities.

    Energy crops

    The availability of growing energy crops for inclusion to the CAD system was also investigated. Lewis

    County has few strictly crop farms; those that do exist total approximately 2,400 acres (Lawrence, 2009).

    Details about the two farms surveyed are included in Table 13.

    Table 13. Select Lewis County crop farm data

    Crop farm Farm acreage Crops grown Location relative to central Lowville

    A 2,000 1,000 acres corn 500 acres grass 500 acres alfalfa

    15 miles north

    B 400 150 acres corn

    50 acres soybeans1 200 acres alfalfa/grass

    12 miles south

    1Not considered as an energy crop for this study; the 50 acres of soybeans were added to the acreage of corn, for estimates associated with this study.

    Lowville Wastewater Treatment Plant

    The Lowville Wastewater Treatment Plant (LWWTP) was suggested as a potential site for the Lewis

    County community AD system; therefore, output solids from the LWWTP were investigated as a possible

    organic waste input for the CAD facility. The plant has two aerobic lagoons, one with 23 million gallons

    of capacity and the second with 21 million gallons of capacity. The average influent to the LWWTP is 1.1

    million gallons per day (gpd), but can be as high as 5 million gpd during high precipitation events (Tabolt,

    2009). Lagoon number one was drained in 1998, and 2,860 tons of sludge was removed. The plant

  • 59

    manager estimated the sludge removal process would take place approximately every 26 years.

    According to previous sludge sample analysis, the sludge contains high concentrations of heavy metals

    such as lead (Tabolt, 2009). Due to the intermittent availability, heavy metal concentration, and

    unknown impact on the AD process, the solids from the LWWTP were not considered to be feasible for

    inclusion to the AD facility.

    Fallow Ground

    Finally, the possibility of digesting several hundred acres of reed canary grass that grows along the Black

    and Beaver Rivers in Lewis County was considered. Historically, this acreage has been harvested for

    bedding hay, however, difficulties that prevent utilizing this land base on a reliable basis include:

    flooding, debris, fragmented ownership, accessibility, timeliness of harvesting and logistics (Lawrence,

    2009). For these reasons, this option was ultimately not included in final biomass source estimates.

  • 60

  • 61

    Chapter 4. Biomass Sample Collection and Analysis

    In this chapter, the collection and analysis of the non-farm biomass samples is described in detail. After

    these samples were collected, they were used in analyses to determine their biochemical methane

    potential (BMP). In addition to the BMP analysis, sub samples were sent to a laboratory in Syracuse, NY

    for nutrient analysis. The results from both analyses are presented, as well as the implications of the

    laboratory results. Laboratory test results from BMP analysis were translated to total volume of biogas

    that can be expected to be produced by digesting each of the feedstocks available on an individual basis.

    These values are important in assessing energy production capabilities and digester vessel sizing

    estimates. Also, nutrient implications are presented based on the laboratory nutrient results. Values

    such as the annual mass of nutrients returning to collaborating farms are important for nutrient

    management and therefore overall digester facility design.

    Sample collection

    In order to quantify the methane production potential of available non-farm biomass substrates,

    samples were collected from the substrate suppliers on July 15, 2009. Six select non-farm biomass

    substrates (2, 4, 5A, 5B, 8, and 10) with the highest available volumes, based on survey results, were

    chosen to perform biochemical methane potential (BMP) tests. Samples were stored in 1L plastic screw-

    top containers, and placed on ice until refrigerated. All efforts were made to obtain a representative

    sample under normal operating conditions. A full substrate sampling report is available in Appendix D.

    Laboratory Biochemical Methane Potential test (BMP trials)

    Six select non-farm biomass substrates from five sources11 were analyzed for biochemical methane

    potential (BMP) at Cornell Universitys Agricultural Waste Management Laboratory. All samples

    collected were analyzed in triplicate for 30 days, with the exception of substrate 4, which was analyzed

    with six replicates, due to the high variability of the substrate sample, resulting in seven individual BMP

    trials conducted, as listed below. A synopsis of the laboratory procedures for conducting the BMP trials

    are provided in Appendix E developed from Labatut and Scott (2008).

    11

    Substrates 5A and 5B are from the same source

  • 62

    Substrate 2

    Substrate 4 (six replicates)

    Substrate 5A

    Substrate 5B

    Substrate 8

    Substrate 10

    Results

    An example of the biogas production data from a 30-day BMP assay depicting biogas yield for substrate

    4 is shown in Figure 12. The results from the BMP trials are shown in Table 14 in liters of CH4 per kg of

    raw substrate for each of the non-farm biomass substrates, and also represented graphically in Figure

    13. The minimum and maximum values are one standard deviation below and above the mean,

    respectively. The same information (L CH4/kg substrate) was found for manure from Experimental and

    Predicted Methane Yields from the Anaerobic Co-Digestion of Animal Manure with Complex Organic

    Substrates (Labatut and Scott, 2008).

    Figure 12. Biochemical Methane Potential (BMP) data (cumulative biogas yield) for substrate 4.

    1only four of six replicates shown; other two replicates contained outlying data points.

  • 63

    Table 14. Cornell University Agricultural and Waste Management Laboratory BMP analysis results (2009) for all substrates tested

    Non-farm biomass substrate ID

    Non-farm biomass substrate description

    Yield (L CH4/kg raw substrate)

    Minimum Maximum Average

    5B Waste grease 258 468 363

    4 Meat, fat, guts 149 177 163

    5A Mixed food scraps 110 118 114

    2 Mixed food scraps, liquid 78 85 81

    Raw manure1 Dairy farm manure 20 33 27

    10 Post-digested sludge 5 10 7

    8 Diluted whey and CIP 2 3 2 1Data from Labatut and Scott, 2008

    As can be expected, the grease and meat substrates have the highest methane producing potential.

    Pre- and post-consumer food scrap wastes were the second highest producers. As observed through

    many manure sampling analyses, the biogas producing potential of manure is expected to be low as

    compared with many organic substrates. The whey sample was very dilute, which accounts for the low

    methane yields, and the post-digested sludge has already undergone a digestion process, which

    accounts for the low methane yields from that substrate.

    Figure 13. Graphical representation of biochemical methane potentials for all substrates tested. 1Data from Labatut and Scott, 2008.

    After the BMP trials concluded at day 30, two of the substrates showed indications that biogas

    production could continue substrates 2 and 5B. The number of days that CH4 was produced by each

    substrate is listed below. Although it is unlikely that a community digester would have a hydraulic

    1

  • 64

    retention time of more than 30 days, it is worth noting the additional biogas producing capabilities of

    certain non-farm biomass substrates.

    Substrate 8: 28 days CH4 production complete

    Substrate 5A: 30 days CH4 production complete

    Substrate 5B: CH4 production could continue past 30 days

    Substrate 2: CH4 production could continue past 30 days

    Substrate 4: 28 days CH4 production complete

    Substrate 10: 22 days CH4 production complete

    It should be noted that co-digestion of certain organic substrates with manure has the potential to

    create a synergistic effect on biogas production; therefore, simply adding the biogas producing potential

    of raw manure and each substrate may underestimate potential total biogas production. However,

    there can also be antagonistic effects of non-farm biomass substrates as well, due to inhibitory

    characteristics that might disrupt the function of the methanogens, responsible for methane production.

    Therefore, minimum, maximum, and average values are presented to show a potential range of biogas

    producing capabilities. More in-depth laboratory analyses, such as co-digestion studies using bench-

    scale reactors, are necessary to determine the expected behavior of each substrate in an operational

    CAD.

    Glycerin

    Non-farm biomass substrate 11 glycerin was discovered after the BMP trials had already been

    performed. Therefore, the methane potential of glycerin was calculated using theoretical values and

    the following values from Lopez (2009): 1,010 g COD/kg substrate, 292 ml CH4/g COD removed, and 85%

    biodegradability of glycerin.

    Biogas production estimates

    The potential quantity and availability of each of the AD feedstocks along with laboratory analyses were

    used to calculate the potential total annual biogas production volume. The results of this analysis,

    including minimum and maximum values for biogas production, are shown in Table 15.

    The results presented in Table 15 for the biogas production projections of each non-farm biomass

    substrate, is shown graphically in Figure 14. Non-farm biomass substrates 8 and 10, although low in

  • 65

    methane yields, are high in available quantity and therefore result in the highest overall biogas

    production potential on an annual basis for the non-farm substrates. The aggregated minimum,

    maximum, and average annual biogas production potential for these seven non-farm biomass substrates

    and for manure from 25 farms are shown in Figure 15. It is apparent from

    Figure 15 that the impact of the non-farm biomass substrates on overall biogas production is very small

    in relation to manure, not due to methane yields per unit of influent, but due to the sheer volume

    available.

    Table 15. Biogas production potential of non-farm biomass substrates and manure

    Methane production potential

    (million ft3/year)

    Feedstock source ID Minimum Maximum Average

    2 0.99 1.10 1.04

    4 0.04 0.20 0.12

    5A 0.02 0.07 0.05

    5B 0.01 0.03 0.02

    8 1.86 4.77 3.15

    10 3.42 6.60 5.01

    11 1.36 2.89 2.13

    Raw manure 94 156 125

    Energy crops

    A total of 2,400 acres of energy crops, including alfalfa, grass hay, and silage corn, are estimated to be

    available for use in co-digesting with manure for the proposed Lewis County community AD system. A

    summary of the biogas production information is presented in Table 16. Unit biogas yields were

    provided by Norma McDonald at Organic Waste System, Inc.

    Table 16. Potential biogas production of available energy crop acreage

    Tons per year Unit biogas yield1

    (scf/ton as fed) Annual biogas production

    (million ft3/year)

    Corn 22,200 5,550 128

    Alfalfa and grass 5,400 5,780 30 1Source: McDonald (2010)

  • 66

    Figure 14. Estimated annual minimum, maximum, and average methane production by substrate.

    Figure 15. Estimated aggregated annual minimum, maximum, and average methane production of non-farm biomass substrates and manure.

  • 67

    Laboratory nutrient testing

    Sub samples of the six substrates analyzed for co-digestion were sent to the Certified Environmental

    Services Laboratory (CES), an EPA certified lab, in Syracuse, NY for nutrient analysis. The laboratory

    results are shown in Table 17 and Table 18.

    Table 17. CES laboratory results for each non-farm biomass substrate: nutrients

    Non-farm biomass substrate ID

    Constituent

    TKN1 (mg/kg)

    NH3-N1

    (mg/kg) Organic N1

    (mg/kg) TP1

    (mg/kg) OP1

    (mg/kg) K1

    (mg/kg)

    2 5,024 496 4,528 571 181 1,234

    4 20,493 8,551 11,941 975 979 2,200

    5A 14,394 1,200 13,194 1,295 375 2,334

    5B 4,122 291 3,831 393 117 1,096

    8 195 28 179 187 78 143

    10 3,931 796 3,235 1,971 83 593 1TKN: Total Kjeldhal Nitrogen, NH3-N: Ammonia, Organic N: by subtraction (TKN-NH3-N), TP: Total Phosphorus, OP:

    Ortho Phosphorus, K: Potassium

    Table 18. CES laboratory results for each non-farm biomass substrate: solids

    Non-farm biomass substrate ID Constituent

    TS1

    (%)

    TVS1

    (%) pH1

    VAAA1

    (mg/kg)

    COD1

    (mg/kg)

    2 16 15 4.05 1,602 201,192

    4 25 22 6.95 13,317 382,992

    5A 35 31 4.29 2,075 385,416

    5B 97 92 6.00 653 187,860

    8 0.51 0.35 5.22 98 3,636

    10 6 4 7.83 359 44,844 1TS: Total Solids, TVS: Total Volatile Solids, VAAA: Volatile acids as acetic acid, COD: Chemical oxygen

    demand

    Glycerin

    Since this non-farm biomass substrate was not identified until after the testing phase of the project was

    completed, the total annual mass of N, P, and K imported to the CAD site from this material was

    estimated by using nutrient concentration data from an un-publishable source. Since glycerin products

    vary widely depending upon source and purity, further analysis of the glycerin product specific to this

    project is recommended. Nutrient concentrations for the three key nutrients, N, P, and K in glycerin

    used in this analysis were: 100, 1, and 0 pounds per 8,000 gallons glycerin, respectively.

  • 68

    Manure

    Manure nutrient concentrations were estimated using ASABE standard manure production values, as

    provided in Chapter 1. The mass of the three key nutrients, N, P, and K in manure are: 0.99, 0.17, and

    0.23 pounds per cow per day, respectively (ASABE, 2005).

    Nutrient implications

    The estimated minimum and maximum quantities available (Table 12) and the laboratory data for each

    non-farm biomass substrate were used to determine the total mass of each nutrient parameter in the

    raw non-farm biomass substrates on an annual basis. The total number of LCEs available from the 25

    farm surveys received was used in conjunction with the standard values for nutrient concentrations in

    manure. The resulting mass of nutrients from both manure and non-farm biomass sources, on a pre-

    digestion basis, are provided in Table 19 for the N series, and Table 20 for the P and K series.

    Table 19. Estimated annual mass of nitrogen series for raw AD feedstock

    Non-farm biomass substrate

    Raw Substrate TKN (lbs/year)

    Raw Substrate Ammonia-N (lbs/year)

    Raw Substrate Organic Nitrogen (lbs/year)

    Minimum Maximum Minimum Maximum Minimum Maximum

    2 3,980 4,050 390 400 3,580 3,650

    4 350 1,480 150 620 200 860

    5A 190 540 16 45 170 500

    5B 10 15 1 10 15

    8 13,050 22,600 1,870 3,240 11,980 20,740

    10 165,100 33,430 135,920

    11 490 - -

    Raw manure1

    1,925,000 - - 1manure from 25 farms

    Table 20. Estimated annual mass of phosphorus and potassium series for raw AD feedstock

    Non-farm biomass substrate

    Raw Substrate Total Phosphorus (lbs/year)

    Raw Substrate Ortho Phosphorus (lbs/year)

    Raw Substrate Potassium (lbs/year)

    Minimum Maximum Minimum Maximum Minimum Maximum

    2 450 460 140 150 980 1,000

    4 20 70 17 70 40 160

    5A 20 50 5 14 30 90

    5B 1 0 2 5

    8 12,540 21,700 5,220 9,040 9,590 16,600

    10 82,790 3,470 24,930

    11 5 - 0

    Raw manure1

    330,500 - 447,160 1manure from 25 farms

  • 69

    Since the values shown in Table 19 and Table 20 are for raw non-farm biomass substrates, estimates

    must be used to quantify the post-digestion concentration of the same nutrients; these values are

    shown for the nitrogen series in Table 21 and for the phosphorus and potassium series in Table 22. The

    values for post-digested nutrient concentrations were estimated using a percent change value for each

    nutrient parameter from previous manure and substrate sampling and monitoring of five digester

    systems including one co-digestion system (Gooch et al., 2007). Results indicate that on average,

    ammonia-N increases in concentration by 23.4%, organic nitrogen decreases in concentration by 15.9%

    and ortho-phosphorus increases in concentration by 14.4% (Gooch et al., 2007). It is assumed that the

    mass of total nitrogen, total phosphorus and potassium do not change as a result of the anaerobic

    digestion process. A comparison of pre- and post-digestion nutrient concentrations is shown in Figure

    16 for the N, P, and K nutrient series for the non-farm biomass substrates. As can be observed there is

    no change in the concentration of the major forms of these nutrients, however, for ammonia-N, organic

    nitrogen, and ortho-phosphorus, there is a slight increase in concentration due to the digestion process.

    Table 21. Predicted annual mass of nitrogen series for post-digested AD feedstock

    Non-farm biomass substrate

    Post Digestion TKN (lbs/year)

    Post Digestion Ammonia-N (lbs/year)

    Post Digestion Organic-N (lbs/year)

    Minimum Maximum Minimum Maximum Minimum Maximum

    2 3,980 4,050 480 490 4,150 4,230

    4 350 1,480 180 760 230 1,000

    5A 190 540 20 60 200 570

    5B 10 15 1 10 15

    8 13,050 22,590 2,310 4,000 13,880 24,020

    10 165,140 41,240 157,460

    11 490 - -

    Raw manure1

    1,924,730 - - 1manure from 25 farms

  • 70

    Table 22. Predicted annual mass of phosphorus series and potassium for post-digested AD feedstock

    Non-farm biomass substrate

    Post Digestion Total Phosphorus (lbs/year)

    Post Digestion Ortho Phosphorus (lbs/year)

    Post Digestion Potassium (lbs/year)

    Minimum Maximum Minimum Maximum Minimum Maximum

    2 450 460 160 170 980 1,000

    4 20 70 20 80 40 160

    5A 20 50 10 20 30 90

    5B 1 0 2 5

    8 12,540 21,700 5,970 10,340 9,590 16,610

    10 82,790 3,970 24,930

    11 5 - 0

    Raw manure1

    330,510 - 447,160

    1manure from 25 farms

    Figure 16. Nutrient concentrations for pre- and post-digestion conditions for N, P, K.

  • 71

    Chapter 5. Biomass Transportation The literature search performed for existing centralized digester feasibility studies (see Chapter 1)

    revealed that transportation costs are usually the largest operating cost component of a CAD. The

    approach used in these studies to determine the overall transportation costs were 1) unit cost per gallon

    and 2) unit cost per gallon-mile.

    For the purposes of this feasibility study, transportation of material to and from each participating farm

    and the CAD facility was explored in two different ways, through the use of a project-owned and

    operated trucking fleet, and by contracting with an existing trucking company. Each option was

    investigated for the proposed Lewis County CAD facility feasibility study and is discussed below. Overall,

    it was determined that the best option would be to contract with an existing trucking company.

    Transportation costs were based on a methodology that used the estimated time required to pump and

    to load or unload a 6,000-gallon truck with a 500 gallon per minute (gpm) truck-mounted pump. The

    comparison of trucking options presented is based on participation of all 25 dairy farms who responded

    to the survey, however, regardless of which final digestion scenario is chosen, the final determination

    remains the same, that it is less costly to contract with an existing trucking company for the proposed

    project.

    Whether choosing a contracted or an owned trucking fleet, the process and assumptions that are made

    for transporting manure from the farms and CAD effluent back, are the same. Manure is picked up from

    the short-term storage at each farm, and transported to the CAD facility, at a cost to the project; this

    service would be of no cost to the farms. Non-farm biomass substrates incorporated for co-digestion

    are not transported through the same means as manure from farms. It is assumed that the substrate

    suppliers would continue to be responsible for trucking their waste and paying a tipping fee to the

    project. Effluent from the CAD facility would be trucked by the project back to the participating farms,

    and deposited in a long-term storage at each farm. The return trucking volumes would consist of both

    the manure and non-farm biomass substrates delivered by the substrate suppliers. There is the

    possibility to further explore delivery of CAD effluent to satellite storages for each farm, where the

    effluent would be delivered to a location more central to the farms cropping activities.

  • 72

    Owned Trucking Fleet

    The first option regarding material transportation to and from participating farms is to create an in-

    house trucking division to be owned and operated by the project. In order to handle the manure from

    participating dairy farms, it was determined that six 6,000-gallon truck-mounted tanker trucks would be

    needed with a 500 gpm truck-mounted pump, with a capital cost of $165,000 per truck (Mack Trucks,

    2009), for a total initial cost of $990,000. In addition, it would cost approximately $450,000 (estimated

    at $30/ft2) to construct a 15,000 ft2 building to house a maintenance shop, clerical support, employee

    amenities (locker and break rooms), and $75,000 (estimated at $5/ft2) for start-up equipment, tools and

    computers.

    Necessary staff includes six drivers, one clerical person, and one maintenance person for a total of eight

    project-related jobs that would be created. Annual labor expenses for the in-house fleet drivers were

    calculated using a draft schedule for collection and delivery to/from each farm and the proposed CAD

    facility located in downtown Lowville. Costs for fuel, truck maintenance, parts, utilities, insurance and

    general overhead are also included in the annual operating cost estimate, which is shown in Table 23.

    Table 23. Capital and annual cost estimates for a project-owned trucking fleet

    Capital cost ($) Annual Cost ($)

    One 6,000 gallon truck 165,000 8,500

    6 trucks 990,000 51,000

    Fuel cost 19,500

    Maintenance Building 450,000 12,000

    Equipment/Furnishings 75,000

    Driver salary 45,000

    6 drivers 270,000

    Administrative salary (1) 30,000

    Maintenance person salary (1) 40,000

    Total $1,515,000 $422,500

    In summary, the capital cost estimate for the project-owned trucking fleet scenario is $1,515,000 and

    annual operating costs are estimated to be $422,500.

  • 73

    Contracted Trucking Fleet

    The second option regarding material transport to and from participating farms is to enter into a

    contract with a private waste hauler. Shue Trucking based in Port Leyden, NY was contacted to obtain

    cost estimates and to provide technical feasibility information. Shue provided a quote of $82 per hour

    for a driver and truck with all required accessories. The annual cost projections were based upon a

    6,000-gallon truck with a 500 gpm truck-mounted pump. Projected total annual volumes of manure and

    non-farm biomass substrates were utilized to determine the number of trips required per year to service

    all 25 participating farms. The same loading and unloading time requirements were used as for the

    project-owned fleet calculations in determining the necessary annual trucking time. An example used to

    calculate costs for the contracted fleet scenario is shown in Table 24.

    Table 24. Contracted trucking fleet example schedule

    Farm ID

    Distance from

    digester (miles)

    Volume manure

    to digester (gal/day)

    Volume influent

    to digester annually

    (gal/year)

    No. of trips from farm to

    digester annually

    miles influent trucked annually

    Hours per trip

    Hours per year

    Cost ($/hour)

    Annual cost to

    transport influent

    1

    to AD ($/year)

    1 2 4,710 1,804,680 300 600 0.75 230 $82 $18,500

    2 6 1,110 424,430 70 420 1 70 $82 $5,800

    5 7 7,860 3,011,710 500 3,510 1 500 $82 $41,160

    7 8 3,440 1,318,140 220 1,760 0.75 170 $82 $13,510 1Only influent trucking costs represented in this table

    In summary, there is no trucking-related capital costs associated with the contracted trucking fleet

    scenario. The estimated annual operating cost based on 25 farms for the contracted fleet scenario is

    $1,260,000 if using the minimum volume of manure and non-farm biomass substrates available (110

    million lbs/year). The estimated annual operating cost based on 25 farms for the contracted fleet

    scenario is $1,350,000 if using the maximum volume of manure and non-farm biomass substrates

    available (160 million lbs/year).

    Manure and Digestate Trucking

    The location of the 25 collaborating farms can be revisited in Figure 10. When developing scenarios with

    a reduced number of farms, the criteria used was whether those farms produced at least 3,000 gallons

    of manure per day. It was assumed that a mass of 3,000 gallons of manure stored for one day in the

    winter would not be likely to freeze, whereas a smaller amount might, as indicated by several of the

  • 74

    farm-based surveys. Collaborating farms would not be charged a transportation fee for trucking

    material between their farm and the digester; this cost would be covered by revenue (tipping fee)

    received from non-farm biomass disposed of at the digester site.

    It is important to note that a 5% increase in the calculated volume of manure associated with each farm

    was assumed, to account for washwater and other biomass co-mingled with manure at the farm prior to

    project pick-up. Also, the assumption was made that there is a 3% reduction of overall influent volume

    due to the digestion process, and that effluent from the CAD would consist of digested manure and non-

    farm biomass substrates. Assuming less than a 3% reduction would result in higher trucking costs. The

    CAD effluent would be a higher volume than the manure initially trucked to the CAD facility, and each

    participating farm would receive a weighted amount of this additional volume as digester effluent. The

    resulting aggregated volume would be trucked back to participating farms.

    Non-farm Biomass Substrate Trucking

    It is assumed that substrate suppliers would provide transportation of their biomass by-products from

    their business location to the AD facility at their expense. This is a safe assumption to make since the

    substrate suppliers currently have to pay trucking costs to transport their organic by-products to a

    disposal site. Tipping fees, needed to cover manure transportation expenses, are intended to be

    charged to substrate suppliers only, and not to participating farms, as can be seen in Figure 17.

  • 75

    Figure 17. Diagram of estimating a break-even tipping fee for non-farm biomass substrate suppliers.

  • 76

  • 77

    Chapter 6. Preliminary Investigation of Five AD Scenarios One apparent reason for many proposed CAD facilities not being implemented is the cost to transport

    manure and digestate between collaborating farms and the CAD site. Therefore, the following five

    scenarios were developed based on the survey data from the initial feasibility investigation with specific

    emphasis on transportation costs, biogas production, and biogas utilization options. The information

    contained in this chapter was presented as an interim report to the Lowville Digester Work Group at a

    December 2009 meeting.

    Scenario No. 1: co-digest manure from 25 dairy farms (see Figure 10), and seven non-farm

    biomass substrates (2, 4, 5A, 5B, 8, 10, 11) at a central location (Site 1) adjacent to the

    Lowville wastewater treatment plant (see Figure 18)

    Scenario No. 2: co-digest manure from 14 dairy farms, and three non-farm biomass

    substrates (8, 10, 11) at a central location (Site 1) adjacent to the Lowville wastewater

    treatment plant (see Figure 18)

    Scenario No. 3: co-digest manure from 12 dairy farms, and one non-farm biomass

    substrate (8) at Site 2 (see Figure 19), and co-digest manure from four dairy farms and two

    non-farm biomass substrates (10, 11) at Site 3 (see Figure 20)

    Scenario No. 3a: identical to Scenario No. 3, except that at Site 2 manure from five of the

    12 farms would be piped to the digester site, and at Site 3 manure from two of the four

    farms would be piped to the digester site

    Scenario No. 3b: same as Scenario No. 3 with 400 acres of energy crops digested at Site 2

    and 2,000 acres of energy crops digested at Site 3

    Each scenario and the investigation results were the core of an interim project report presented to the

    Lowville Digester Work Group on December 18th, 2009 (details in the remainder of this chapter). As a

    result of that presentation, the Lowville Digester Workgroup decided that Scenario No. 2 should be

    more fully investigated and the results of that complete investigation are detailed in Chapter 7.

  • 78

    The remainder of this Chapter provides baseline information used in evaluating all five scenarios,

    additional details about each scenario analyzed, and analysis results (transportation cost, biogas

    production, and biogas utilization options) used in part to select one scenario to perform a full economic

    evaluation. The corresponding process flow diagram(s) for each scenario includes average feedstock

    and effluent volumes, trucking cost, biogas production, electricity and heat generation that represent

    the average of the minimum and maximum values.

    Figure 18. CAD Site 1 for Scenario Nos. 1 and 2.

    Proposed CAD site

  • 79

    Figure 19. Remote AD Site 2 for Scenario Nos. 3, 3a, and 3b.

    Proposed CAD site

  • 80

    Figure 20. Remote AD Site 3 for Scenario Nos. 3, 3a, and 3b.

    Background for All Scenarios

    In each scenario, biogas produced could be used as:

    A thermal heat source to fuel a boiler to produce hot water

    A fuel source for an engine-generator set to produce electrical power

    A renewable alternative to natural gas after being scrubbed

    For the centralized scenarios (Scenario Nos. 1 and 2), biogas that has been processed by gas-clean up

    equipment could also potentially be injected into a natural gas pipeline as biomethane. Any of the

    resulting forms of energy could be sold to one or more buyers; however, for the de-centralized regional

    digesters scenarios, sale of energy to one main buyer may not be practical. Biogas production volumes

    were determined at STP (0C and 1 atm), and heat content was calculated using the lower heating value

    of methane at STP which is 896 Btu/ft3 and a concentration of 60% CH4 (Marks, 1978).

    Proposed CAD site

  • 81

    Scenario No. 1

    Scenario No. 1 consists of one CAD system located at Site 1, adjacent to the Lowville Wastewater

    Treatment Plant (LWWTP) in downtown Lowville, as shown in Figure 18. Manure from 25 nearby dairy

    farms would be trucked by the project from each farm to the proposed Lewis County community CAD

    facility (See Table 10 for details of the 25 farms). Seven non-farm biomass substrates with the highest

    volumes (2, 4, 5A, 5B, 8, 10, 11) out of the 11 non-farm biomass sources initially surveyed would be co-

    digested. Figure 21 shows a simplified process flow diagram for Scenario No. 1.

    Figure 21. Process flow diagram for Scenario No. 1 using the average annual total volume of the seven non-farm biomass substrates.

    The following are additional project values determined according to the details of Scenario No. 1:

    Average annual mass of non-farm biomass substrates: 134 million lbs/year (16 million gallons/year)

    o Minimum: 110 million lbs/year (13 million gallons/year)

    o Maximum: 160 million lbs/year (19 million gallons/year)

    Average annual total AD feedstock mass: 440 million lbs/year (53 million gallons/year)

    o Minimum: 416 million lbs/year (50 million gallons/year)

    o Maximum: 465 million lbs/year (56 million gallons/year)

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    Average annual manure influent and CAD effluent transportation costs: $1,305,000

    o Minimum: $1,260,000

    o Maximum: $1,350,000

    Average annual volume biogas produced: 228 million ft3/year

    o Minimum: 170 million ft3/year

    o Maximum: 287 million ft3/year

    Average annual volume methane produced: 137 million ft3/year

    o Minimum: 102 million ft3/year

    o Maximum: 172 million ft3/year

    Substrate tipping fee needed: $0.08 per gallon

    Scenario No. 2

    Scenario No. 2 consists of a centralized digester located at Site 1, as in Scenario No. 1, however with

    select farms and select non-farm biomass substrates. Instead of the 25 dairy farms, Scenario No. 2

    would involve digesting manure from 14 surveyed dairy farms, chosen for those farms ability to

    produce at least 3,000 gallons of manure per day. The three non-farm biomass substrates with the

    highest volumes (8, 10, 11), out of the 11 sources initially surveyed, would be co-digested with the

    manure. Figure 22 shows a process flow diagram for Scenario No. 2. For complete details on the final

    Scenario No. 2, please also see Chapter 7.

  • 83

    Figure 22. Process flow diagram for Scenario No. 2 using the average annual total volume of the three non-farm biomass substrates.

    The following are additional project values determined according to the details of Scenario No. 2:

    Average annual mass of non-farm biomass substrates: 134 million lbs/year (16 million gallons/year)

    o Minimum: 109 million lbs/year (13 million gallons/year)

    o Maximum: 158 million lbs/year (19 million gallons/year)

    Average annual total AD feedstock mass: 372 million lbs/year (45 million gallons/year)

    o Minimum: 348 million lbs/year (42 million gallons/year)

    o Maximum: 397 million lbs/year (48 million gallons/year)

    Average annual manure influent and CAD effluent transportation costs: $1,120,000

    o Minimum: $1,070,000

    o Maximum: $1,170,000

  • 84

    Average annual volume biogas produced: 188 million ft3/year

    o Minimum: 140 million ft3/year

    o Maximum: 237 million ft3/year

    Average annual volume methane produced: 113 million ft3/year

    o Minimum: 84 million ft3/year

    o Maximum: 142 million ft3/year

    A substrate tipping fee needed: $0.07 per gallon

    Scenario No. 3

    Scenario No. 3 consists of two decentralized regional digesters, one located north of Lowville (Site 2) and

    one located south of Lowville (Site 3). Site 2 would digest manure trucked by the project from 12 of the

    25 dairy farms, chosen for their proximity to AD Site 2. Site 3 would digest manure trucked by the

    project from four of the 25 dairy farms chosen for their proximity to AD Site 3. Site 2 would co-digest

    substrate number 8, the highest volume non-farm biomass substrate that is closest to AD Site 2. Site 3

    would co-digest substrate numbers 10 and 11, the highest volumes of non-farm biomass substrates, in

    proximity to AD Site 3. A simplified process flow diagram for Scenario No. 3 is shown in Figure 23.

  • 85

    Figure 23. Process flow diagrams for Scenario No. 3 using the average annual total volume of the three non-farm biomass substrates for Site 2 and Site 3. All manure and digestate are trucked. The following are additional project values determined according to the details of Scenario No. 3:

    Minimum annual mass of non-farm biomass substrates for both sites: 109 million lbs/year (13 million

    gallons/year)

    o Site 2: 67 million lbs/year (8 million gallons/year)

    o Site 3: 42 million lbs/year (5 million gallons/year)

    Maximum annual mass of non-farm biomass substrates for both sites: 158 million lbs/year (19 million

    gallons/year)

    o Site 2: 116 million lbs/year (14 million gallons/year)

    o Site 3: 42 million lbs/year (5 million gallons/year)

  • 86

    Minimum annual manure influent and CAD effluent transportation costs for both sites: $684,000/year

    o Site 2: $477,000/year

    o Site 3: $207,000/year

    Maximum annual manure influent and CAD effluent transportation costs for both sites: $740,000/year

    o Site 2: $533,000/year

    o Site 3: $207,000/year

    Average annual volume biogas produced for both sites: 191 million ft3/year

    o Site 2: 125 million ft3/year

    o Site 3: 66 million ft3/year

    Average annual volume methane produced for both sites: 114 million ft3/year

    o Site 2: 75 million ft3/year

    o Site 3: 39 million ft3/year

    Average substrate tipping fee needed:

    o Site 2: $0.05 per gallon

    o Site 3: $0.04 per gallon

    Scenario No. 3a

    All aspects of Scenario No. 3a are identical to Scenario No. 3, except that Scenario No. 3a utilizes

    a combination of pumping and trucking manure and digestate to/from collaborating farms and

    the remote digester sites. Certain farms appear near enough to the proposed remote AD sites

    to logically envision that manure may be piped, with the hopes that overall transportation cost

    would be lessened by pumping approximately 33% of the total available manure. Table 25

    shows which farms would potentially pipe and truck manure according to Scenario No. 3a.

    Figure 24 shows a process flow diagram for Scenario No. 3a.

  • 87

    Table 25. Scenario No. 3a means of manure and digestate transport

    Remote Site 2 (Northern site) Remote Site 3 (Southern site)

    Farm ID lbs/day 3a. Transport Farm ID lbs/day 3a. Transport

    5 65,460 Trucked 4 20,363 Trucked

    6 17,055 Trucked 9 118,031 Trucked

    7 28,650 Piped 10 28,823 Piped

    8 16,920 Piped 11 38,340 Piped

    12 39,090 Piped 205,556

    13 32,475 Piped

    14 31,170 Piped

    17 16,305 Trucked

    18 84,225 Trucked

    19 86,445 Trucked

    21 17,340 Trucked

    23 21,653 Trucked

    456,788

    Figure 24. Process flow diagram for Scenario No. 3a using the average annual total volume of three non-farm biomass substrates for Site 2 and Site 3. Manure and digestate are pumped and trucked.

  • 88

    The following are additional project values determined according to the details of Scenario No. 3a, a

    hybrid scenario of manure both piped and trucked from 16 farms to two regional digesters in different

    locations.

    Minimum annual manure influent and CAD effluent transportation costs for both sites: $539,000/year

    o Site 2: $375,000/year

    o Site 3: $164,000/year

    Maximum annual manure influent and CAD effluent transportation costs for both sites: $599,000/year

    o Site 2: $435,000/year

    o Site 3: $164,000/year

    A substrate tipping fee needed:

    o Site 2: $0.04 per gallon

    o Site 3: $0.03 per gallon

    The costs associated with piping manure and digester effluent between selected farms, shown in Table

    25, were not calculated prior to the Dec. 18, 2009 project meeting, and based on the selection by the

    Lowville Digester Workgroup to focus on Scenario No. 2, no effort was subsequently made to finish out

    the preliminary investigation of this option.

    Scenario No. 3b

    Scenario No. 3b was developed to examine the effect of including a separate energy crop digester at

    each of the two regional digester sites. The same dairy farms and non-farm biomass substrates would

    be used to provide material to each of the decentralized regional AD locations as was outlined in

    Scenario No. 3. Field crops from crop farm A would be ensiled and digested at Site 2, while field crops

    from crop farm B would be digested at Site 3. There would be two digester systems at each de-

    centralized site. Figure 25 shows a simplified flow diagram for Scenario No. 3b, with some details

    removed for clarity; these details are provided in bullet form following the figure.

  • 89

    Figure 25. Process flow diagram for Scenario No. 3b using the average annual total volume of three non-farm biomass substrates for Site 2 and Site 3. The following are additional project values determined according to the details of Scenario No. 3b; all

    other substrate volumes are identical to Scenario No. 3:

    Average annual volume of effluent for Site 2: 35 million gallons/year

    o Manure/substrate AD: 31 million gallons/year

    o Energy crop AD: 4 million gallons/year

    Average annual volume of effluent for Site 3: 15 million gallons/year

    o Manure/substrate AD: 14 million gallons/year

    o Energy crop AD: 1 million gallons/year

  • 90

    Minimum annual manure influent and CAD effluent transportation costs for both sites: $704,000/year

    o Site 2: $491,000/year

    o Site 3: $213,000/year

    Maximum annual manure influent and CAD effluent transportation costs for both sites: $759,000/year

    o Site 2: $546,000/year

    o Site 3: $213,000/year

    A substrate tipping fee needed:

    o Site 2: $0.05 per gallon

    o Site 3: $0.04 per gallon

    A summary of the initial investigation of the five scenarios is provided in Table 26. As was mentioned at

    the beginning of this chapter, the Lowville Digester Work Group selected Scenario No. 2 to perform

    additional investigation and a complete economic analysis. The two main reasons that Scenario No. 2

    was selected by the Workgroup were, it provided:

    1. Increased opportunities for energy utilization produced by the CAD system, and

    2. Increased opportunities for post-digestion treatment of effluent that would benefit

    collaborating farms.

    There is less risk involved with a centralized AD option as opposed to the de-centralized regional

    digesters described in Scenario No. 3, since the project could likely still proceed even if a few of the

    farms decided at some point to discontinue participating. Scenario No. 2 would allow for energy

    capture from one system, which could be sold to one main buyer. Also, if it is discovered that nutrient

    concentrations in the effluent stream need to be adjusted, this scenario allows there to be one point

    where this could be done. The Work Group requested that an energy crop digester, located at Site 1 be

    included in the full analysis.

  • 91

    Table 26. Comparison of the five AD scenarios

    Scenario No.

    No. of feedstock sources

    Average AD feedstock mass

    (million lbs/year)

    Average volume biogas

    produced (million

    ft3/year)

    Average raw manure and CAD effluent

    transportation costs

    Tipping fee

    needed ($/gallon)

    1 25 farms,

    7 non-farm biomass substrates

    440 228 $1,303,000 $0.08

    2 14 farms,

    3 non-farm biomass substrates

    372 188 $1,120,000 $0.07

    3

    Site 2: 12 farms, 1 non-farm biomass substrate

    Site 3: 4 farms, 2 non-

    farm biomass substrates

    375 191 $684,000 $0.05

    3a Same as Scenario

    No. 3 375 191 $599,0001 $0.04

    3b

    Site 2: 12 farms, 1 non-farm biomass substrate,

    crop farm A

    Site 3: 4 farms, 2 non-

    farm biomass substrates, crop farm B

    420 344 $732,000 $0.05

    1Does not include cost to pump manure and digestate.

  • 92

  • 93

    Chapter 7. Final AD Scenario Selection Analysis and Results

    Overview

    As mentioned in the previous chapter, the Lowville Digester Work Group decided during the December,

    2009 interim report meeting that Scenario No. 2 was the best scenario of those initially developed and

    investigated based on the initial goals they had outlined at the onset of the project (see Introduction)

    and the findings developed to date for presentation at that meeting.

    Scenario No. 2 as described in the previous chapter was slightly altered to include one additional farm

    for the final analysis (15 total farms). During the December meeting, the Lowville Digester Work Group

    also requested an analysis of an energy crop digester (co-located at the same site but as a separate

    system, due to AD design specifications based on material handling requirements) be performed to

    determine the increase in biogas available from the facility. Both the Scenario No. 2 manure/non-farm

    biomass CAD and the energy crop digester analysis are based on two separate systems co-located at Site

    1, adjacent to the LWWTP.

    Scenario No. 2 manure/non-farm biomass CAD is based on manure from the 15 identified

    collaborating dairy farms (listed by farm ID in Table 27) and 3 non-farm biomass

    substrates with the highest volumes available (8, 10, and 11) out of the 11 surveyed. The

    15 farms were chosen for their ability to produce at least 3,000 gallons of manure per day

    (justification in Chapter 5). A process flow diagram for Scenario No. 2 is shown in Figure

    26.

    The energy crop digester is based on two crop farms (A, B) that would supply corn silage

    and grass and alfalfa to the site and ensile it for use in constantly feeding the energy crop

    digester. A process flow diagram for the energy crop digester is shown in Figure 27.

  • 94

    Figure 26. Final Scenario No. 2 process flow diagram.

    Figure 27. Energy crop anaerobic digester process flow diagram.

    Table 27. Scenario No. 2 participating farms and associated manure generation

    Farm ID LCEs lbs/day

    1 262 39,225

    2 62 9,225

    5 436 65,460

    7 191 28,650

    9 787 118,031

    10 192 28,823

    11 256 38,340

    12 261 39,090

    13 217 32,475

    14 208 31,170

    16 87 13,113

    18 562 84,225

    19 576 86,445

    21 116 17,340

    23 144 21,653

    4,355 653,264

  • 95

    Transportation

    The Lowville CAD project includes transporting manure from collaborating dairy farms to the CAD site

    and digestate back to the farms. Non-farm biomass substrates would be trucked to the CAD facility at

    the suppliers expense. The initial transportation assessment for the project centered on whether to

    contract with an existing trucking company, or to initiate a trucking division as part of the overall

    centralized AD project (details in Chapter 5). It was determined that initially contracting with an existing

    trucking company would be more cost effective to the project and provide lower financial risk. At some

    point after project start-up, when the economic implications of the project are clear, it will be prudent

    to re-evaluate the option of a project-owned trucking fleet to transport material between the farms and

    the Scenario No. 2 CAD site.

    Based on contracting with an existing fleet, the trucking costs were estimated based on transporting

    manure from the dairy farms to the CAD site, and effluent back to participating dairy farms. The

    estimated annual trucking costs for Scenario No. 2 manure/non-farm biomass CAD are between

    $1,100,000 (minimum substrate assumed) and $1,200,000 (maximum substrate assumed).

    As explained in Chapter 5, each dairy farm would receive a higher volume of CAD effluent as compared

    with the manure volume provided, as determined by using a weighted basis calculation for each farm;

    this is shown in Figure 28.

  • 96

    Figure 28. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received, by farm.

    It is important to consider the impacts of additional traffic a project of this magnitude would have on

    the community. For the manure and non-farm biomass CAD, there would be an estimated 13,000 loads

    per year brought by the 6,000-gallon manure tankers; this amounts to approximately 35 loads per day

    transported through town. It is not known at this time the specific impacts to certain routes, or

    upgrades that would be necessary to local infrastructure, i.e., bridges.

  • 97

    Anaerobic Digestion

    The feedstock volumes for Scenario No. 2 are shown in Table 28. Under Scenario No. 2 manure/non-

    farm biomass CAD, there are three non-farm biomass substrates that would be co-digested with manure

    from 15 collaborating farms. The mass of feedstock available for inclusion to the proposed energy crop

    digester was proposed to be co-digested with a portion of the manure (10% of that in the manure/non-

    farm biomass CAD), and is also presented in Table 28. Minimum and maximum potential substrate

    volumes for all feedstocks were quantified in order to develop a range in quantities available.

    Table 28. Scenario No. 2 feedstock volumes

    1Based on varying specific gravities, since the purity of the glycerin substrate is unknown

    Table 29 contains the minimum, maximum and average values for the potential methane and biogas

    production for each individual feedstock, as well as for the total substrate quantity, in the Scenario No. 2

    manure/non-farm biomass CAD. The CAD in this scenario is projected to produce on average, 113

    million ft3 of methane annually with a thermal value of 101,000 million Btus.

    Potential quantity

    (gal/day) Potential quantity

    (lbs/day) Availability (days/year)

    Potential quantity available

    (million lbs/year)

    Feedstock source

    Min Max Min Max Min Max Min Max Ave

    8 31,000 38,000 257,000 317,000 260 365 66.8 115.7 91.2

    10 13,800 13,800 115,000 115,000 365 365 42 42 42

    11 150 150 1,300 1,6001 260 260 0.34 0.41 0.37

    Subtotal 110 160 135

    crop farm A 100,000

    100,000 365 365 37 37 37

    crop farm B 20,000 20,000 365 365 7.4 7.4 7.4

    Subtotal 44.4 44.4 44.4

    100% Manure 78,000 78,000 653,000 653,000 365 365 238 238 238

    Total 392 441 416

  • 98

    Table 29. Potential methane and biogas production volumes for each feedstock in Scenario No. 2 CAD

    Feedstock source

    Minimum methane (million ft

    3/year)

    Maximum methane (million ft

    3/year)

    Average methane (million ft

    3/year)

    Minimum biogas

    (million ft

    3/year)

    Maximum biogas

    (million ft

    3/year)

    Average biogas

    (million ft

    3/year)

    8 1.9 4.8 3.3 3.1 8 5.5

    10 3.4 6.6 5 5.7 11 8.4

    11 1.4 2.9 2.1 2.3 4.8 3.5

    Total substrate 6.7 14.3 10.4 11.1 23.8 17.2

    Raw manure 77.1 127.8 102.4 128.5 212.9 170.7

    Total 83.8 142 112.7 139.6 236.7 187.9

    CAD facility sizing

    The Scenario No. 2 manure/non-farm biomass CAD was sized based on providing a 22.5 day12 hydraulic

    retention time to co-digest the aggregate daily manure volume from the 15 collaborating farms and the

    average daily volume of the three non-farm biomass substrates. It was assumed all manure and

    substrates generated at each source would be made available for co-digestion.

    Ideally, the system would include a separate influent holding tank for each substrate. A heated

    substrate holding tank would be needed if any fats, oils or greases (FOG) were secured in the future for

    co-digestion. The size of the substrate holding tank(s) needs to be determined based on each suppliers

    need for disposal of biomass.

    The energy crop digester sizing estimates were based on:

    1. Farm data for the two identified energy crop farms

    2. Average yields for corn, alfalfa and grass hay for the types of farms provided by the

    Lewis County Field Crops Educator (Lawrence, 2009)

    3. Energy crop digester specifics from a representative of Organic Waste Systems, Inc.

    (McDonald, 2010), a company that is currently engaged in the energy crop digester

    business.

    12

    22.5 days is the average of 20 and 25 days, which are the most common retention times for similarly sized systems

  • 99

    Economics

    An economic analysis was conducted to estimate the annual profitability of the Scenario No. 2

    manure/non-farm biomass CAD system using data developed by this study and other available

    information needed to perform the calculations. The economic analysis considered the costs and

    revenues that would be generated by the system. The major cost categories include capital costs,

    operating and maintenance costs, and feedstock transportation. The capital costs were converted to

    annual economic costs using an annual equivalent cost approach (includes economic depreciation),

    using Equation (1).

    Equation (1): AEC = PV/ ( 1/r 1/(r*(1+r)^n) )

    With AEC = annual economic cost PV = present value (initial capital investment) r = interest rate

    n = time (years) This approach uses discounted cash flow principles to annualize the up-front investment costs. After

    annualizing these costs, a series of annual budgets for the system were developed by estimating the

    annual income and expenses associated with the project. The analysis did not consider any potential

    grants or direct subsidies; these would have the impact of improving the economic results. Similarly, the

    analysis did not include items such as insurance or tax implications.

    As previously stated, the Scenario No. 2 manure/non-farm biomass CAD and the energy crop digester

    system were analyzed independently, since they are mutually exclusive digester systems. The biogas

    produced by the two systems could be combined immediately after production to gain economies of

    scale for pre-utilization/utilization equipment, but our analysis was not performed with this assumption.

    The economic analysis of each system is presented below, starting with the Scenario No. 2 CAD system.

  • 100

    Scenario No. 2 Manure/Non-Farm Biomass CAD

    Capital costs

    The capital costs for the three main components of the Scenario No. 2 CAD system are shown in Table

    30; these costs were determined by multiplying values for project specific items by a unit cost for each

    of the items. The unit costs for the digester system were based on analyses of competitive proposals

    received between 2007 and 2009 for previous digester system projects of a similar size and adjusted for

    inflation. The unit cost used was $1.84 (minimum), $2.43 (maximum), and $2.14 (average) per gallon of

    digester treatment volume. The capital cost for the Scenario No. 2 CAD system is also based on a HRT of

    22.5 days13.

    The engine-generator set capital cost is based on a unit cost of $800/kW for all GE Jenbacher engine-

    generator sets (Vernon, 2010). The size of the engine was determined based on projected quantity and

    quality of biogas produced and the nearest sized engine-generator set available14 that best matched the

    projections. Other manufacturers of engine-generator sets that are also well-suited for biogas plant

    applications exist and data for their systems could also be used in the analysis. The capital costs for the

    engine-generator sets shown in Table 30 are for minimum, maximum, and average projected biogas

    production volumes.

    The capital cost for a biogas clean-up system (hydrogen sulfide and carbon dioxide removal) to produce

    pipeline quality biogas (biomethane) was provided by a vendor representative for Guild Associates, Inc.

    (Mitariten, 2009) for their Molecular Gate technology SPEC plant that we understand is appropriate for

    all ranges of projected biogas productions for this CAD project, at $796,000.

    13

    22.5 days is the average of 20 and 25 days, which are the most common retention times for similarly sized systems 14

    The theoretical size of the engine-generator set needed was compared with that commercially available, which was not an exact match

  • 101

    Table 30. Capital costs ($) for Scenario No. 2 CAD system, engine-generator set, and biogas clean-up system, and total cost for two different energy sale options

    CAD system Engine-generator

    set Biogas cleanup

    system

    Total Cost: biomethane sale

    option1

    Total Cost: electricity sale

    option2

    Minimum 4,730,000 678,000A 796,000 5,526,000 5,408,000

    Maximum 7,140,000 1,146,000B 796,000 7,936,000 8,285,000

    Average 5,887,000 905,000C 796,000 6,683,000 6,792000

    1Assumes total biogas production used in production and sale of biomethane; no electricity sale

    2Assumes total biogas production used to generate electricity; no biomethane sale

    AFor a 848-kW GE Jenbacher Type 3 engine-generator set

    BFor a 1,432-kW GE Jenbacher Type 6 engine-generator set

    CFor a 1,131-kW GE Jenbacher Type 4 engine-generator set

    The estimated total capital costs of the Lowville CAD system ranged from $4.7 million to $7.1 million.

    Annualized capital costs

    The total capital investment was converted to an annual equivalent capital investment based upon the

    total investment required, the cost of capital invested in the project, and the expected life of the

    equipment. The cost of capital was estimated at 5 percent. The cost of capital reflects the opportunity

    cost for funds invested in the project. The approach used in this analysis was to treat the discount rate

    as a real discount rate. In other words, this discount rate does not include the impact of inflation. As

    a result, no-inflation factors were applied to the future cash flows. Consistent with the request of the

    Lowville Digester Work Group, the 5% cost of capital is relatively low. Increases to the discount rate

    would have the impact of increasing the annual economic capital costs of the project. There are two

    large capital investments associated with the project, one for the digester itself and one for either the

    electrical generation equipment or the biogas clean-up equipment.

    The estimated life of the digester system was assumed to be 20 years, and the estimated life of the

    engine-generator set and biogas clean-up system were assumed to be 10 years, meaning the set was

    replaced on a 10-year replacement cycle and for this analysis the set was replaced at the same price as it

    was when the first purchase was made. In other words, the real costs of the generator are expected to

    remain the same. The analysis did not inflate cash flows associated with income and expenses. This

    approach is consistent with using a relatively low discount rate (5%) that is meant to reflect the real cost

    of capital. A future analysis could incorporate inflation expenses into the replacement of the electrical

    generation equipment. Similarly, a future analysis could shorten or lengthen the replacement cycle for

    the electric generation equipment. In general, lengthening the replacement cycle will improve the

    profitability of the system and shortening the cycle will decrease the profitability.

  • 102

    The annualized capital costs for the Scenario No. 2 CAD system are shown in Table 31. Energy sales via

    electricity and biomethane were considered for the three scenarios of minimum, maximum, and

    average biogas production quantities. The total annual capital costs for the entire system necessary for

    each energy sale option are shown in the two furthest right columns of Table 31. The costs of the

    electrical generation equipment are annualized based upon a 10-year replacement cycle. The annual

    total capital costs for the system under electrical energy generation range from $468,000 to $721,000.

    The total annual capital costs for the system under biomethane production range from $483,000 to

    $676,000.

    Table 31. Annualized capital costs (ACC) in dollars for the Scenario No. 2 CAD system based on minimum, maximum, and average biogas production quantities.

    CAD

    system Engine-Generator

    set Gas Clean-Up

    system

    Total ACC: biomethane sale option

    1

    Total ACC: electricity sale

    option2

    Minimum 380,000 88,000A 103,000 483,000 468,000

    Maximum 573,000 148,000B 103,000 676,000 721,000

    Average 472,000 117,000C 103,000 575,000 589,000

    1Assumes total biogas production used in production and sale of biomethane; no electricity sale

    2Assumes total biogas production used to generate electricity; no biomethane sale

    AFor a 848-kW GE Jenbacher Type 3 engine-generator set

    BFor a 1,432-kW GE Jenbacher Type 6 engine-generator set

    CFor a 1,131-kW GE Jenbacher Type 4 engine-generator set

    Annual operating and maintenance costs

    Estimates for the annual operating and maintenance (O&M) costs were calculated for the Scenario No. 2

    CAD, the engine-generator set, and the biogas clean-up system and the results are shown in Table 32.

    The O&M costs for the engine-generator set were estimated using 1.7/kWh of energy produced for a

    GE Jenbacher unit (Vernon, 2010). The O&M costs for the gas clean-up system were estimated

    assuming 5% of capital expenses for annual maintenance and repair costs. The average total O&M costs

    assuming biomethane production and sale were estimated at $227,000, and assuming electricity

    production and sale, were estimated at $348,000.

  • 103

    Table 32. Scenario No. 2 CAD, annual operating and maintenance expenses ($)

    O&M Digester O&M Generator Biogas Clean-Up Total: biomethane

    sale option1

    Total: electricity sale option

    2

    Minimum 87,000 120,000A 40,000 126,000 207,000

    Maximum 301,000 203,000B 40,000 341,000 503,000

    Average 188,000 160,000C 40,000 227,000 348,000

    1Assumes the net biogas production (20% of total for parasitic heating) used in production and sale of biomethane; no

    electricity sale 2Assumes total biogas production used to generate electricity; no biomethane sale

    AFor a 848-kW GE Jenbacher Type 3 engine-generator set

    BFor a 1,432-kW GE Jenbacher Type 6 engine-generator set

    CFor a 1,131-kW GE Jenbacher Type 4 engine-generator set

    Total annual cost

    The total annual cost, based on total annualized capital costs and annual O&M costs, are shown in Table

    33. The average total annual costs assuming biomethane production and sale were estimated at

    $803,000, and assuming electricity production and sale, were estimated at $937,000.

    Table 33. Scenario No. 2 CAD, total annual costs ($) for options of selling biomethane and electricity

    Digester system

    Engine-Generator set

    Biogas Clean-Up system

    Total: biomethane sale

    option1

    Total: electricity

    sale option2

    Minimum 466,000 208,000A 143,000 609,000 674,000

    Maximum 874,000 351,000B 143,000 1,016,740 1,225,000

    Average 656,000 277,000C 143,000 803,000 937,000

    1Assumes the net biogas production (20% of total for parasitic heating) used in production and sale of biomethane; no

    electricity sale 2Assumes total biogas production used to generate electricity; no biomethane sale

    AFor a 848-kW GE Jenbacher Type 3 engine-generator set

    BFor a 1,432-kW GE Jenbacher Type 6 engine-generator set

    CFor a 1,131-kW GE Jenbacher Type 4 engine-generator set

    Net economic profitability

    The total annual costs (annual capital costs plus annual O&M costs) were compared to the estimated

    revenues that could be generated by the Scenario No. 2 CAD system, and are presented for varying

    biogas production volumes and revenues for biomethane sale in Table 34 and for electric power sale in

    Table 35. The values in both tables indicate the annual economic gain or loss (when the numbers are in

    parenthesis) associated with the system. For the option of biomethane sale, the analysis assumes that

    20% of the energy generated by the system will be used to meet the parasitic heat needs of the Scenario

    No. 2 CAD.

    These results indicate that there is no reasonable gas or electricity price at which currently projected

    biogas production volumes would allow for the revenue needed to meet capital and O&M costs. The

  • 104

    annual profitability of the system is highly negative under even the most optimistic energy price

    scenarios. This includes the sale of biomethane associated with non-farm biomass co-digested with

    manure; it was assumed that the substrate suppliers would cover costs associated with non-farm

    biomass transportation from the business to the CAD facility. It is important to note that these are

    annual economic costs. In other words, operating the digester with electricity production and sale at

    $0.10 per kWh and average gas production would result in an annual economic loss of nearly $1.3

    million dollars.

    Table 34. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4 for various biomethane sale prices and biogas production volumes (no tipping fees received)

    Biomethane sale1 price

    ($/Decatherm) 4 6 8 10 12 14

    Low Biogas Production (1,971,000) (1,861,000) (1,752,000) (1,642,000) (1,532,000) (1,423,000)

    High Biogas Production (1,819,000) (1,605,000) (1,391,000) (1,177,000) (963,000) (749,000)

    Average Biogas Production (1,906,000) (1,745,000) (1,583,000) (1,421,000) (1,260,00) (1,098,000) 1Assumes net biogas production (20% of total for parasitic heating) used for biomethane sale; no electricity sale

    2Assumes average capital and O&M cost estimates

    3Includes manure and CAD effluent transportation costs

    4Does not include pipeline injection costs

    Table 35. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4,5 for various electrical energy sale prices and biogas production volumes (no tipping fees received)

    Electric sale1 price

    ($/kWh) 0.08 0.10 0.12 0.14 0.16 0.18

    Low Gas Production (1,620,000) (1,507,000) (1,394,000) (1,281,00) (1,167,000) (1,054,000)

    High Gas Production (1,231,000) (1,021,000) (811,000) (600,000) (390,000) (179,000)

    Average Gas Production (1,431,000) (1,271,000) (1,111,000) (951,000) (791,000) (630,000) 1Assumes total biogas production used to generate electricity; no biomethane sale

    2Assumes average capital and O&M cost estimates

    3Includes manure and CAD effluent transportation costs

    4Does not include interconnection costs

    5 Assumes no revenue from the sale of engine-generator set surplus thermal energy

    The above results show that the Scenario No. 2 CAD is not economically viable for either energy sale

    option, even with the most optimistic energy sale prices.

    When tipping fees currently paid are included, the economic profitability overall becomes less negative;

    this is shown in Table 36 and 37. For this analysis, an annual tipping fee of $277,000 ($6/ton)15 was

    used, which represents the annual cost for non-farm biomass substrate supplier #8 to dispose of their

    by-products. The other two non-farm substrate providers whose by-products were included in this

    analysis did not provide the current tipping fees they pay to dispose of their processing by-products.

    15

    An updated value provided in May 2010 to correct a wrong value shown in the non-farm biomass survey

  • 105

    Table 36. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4 for various biomethane sale prices and biogas production volumes, including current tipping fee paid by substrate supplier #8

    Biomethane sale1 price

    ($/Decatherm) 4 6 8 10 12 14

    Low Gas Production (1,694,000) (1,585,000) (1,475,000) (1,365,000) (1,256,000) (1,146,000)

    High Gas Production (1,542,000) (1,328,000) (1,114,000) (900,000) (686,000) (472,000)

    Average Gas Production (1,630,000) (1,468,000) (1,306,000) (1,145,000) (983,000) (821,000) 1Assumes total biogas production used for biomethane sale; no electricity sale

    2Assumes average annual capital and average O&M cost estimates

    3Includes manure and CAD effluent transportation average cost and tipping fee paid to project

    4Does not include pipeline injection costs

    Table 37. Scenario No. 2 CAD net annual economic profitability ($) 2,3,4,5 for various electrical energy sale prices and biogas production volumes, including current tipping fee paid by substrate supplier #8

    Electric sale1 price ($/kWh) 0.08 0.10 0.12 0.14 0.16 0.18

    Low Gas Production (1,343,000) (1,230,000) (1,117,000) (1,004,000) (891,000) (778,000)

    High Gas Production (955,000) (744,000) (534,000) (323,000) (113,000) 97,000

    Average Gas Production (1,155,000) (995,000 (834,000) (674,000) (514,000) (354,000) 1Assumes total biogas production used to generate electricity; no biomethane sale

    2Assumes average capital and O&M cost estimates

    3Includes manure and CAD effluent transportation costs and tipping fee paid to project

    4Does not include interconnection costs

    5 Assumes no revenue from the sale of engine-generator set surplus thermal energy

    Since the economic profitability of the Scenario No. 2 CAD remained negative even when including the

    tipping fee paid by non-farm biomass substrate supplier #8, and realizing the other two suppliers also

    already pay a tipping fee to dispose of their by-products, we determined the tipping fees needed to

    result in a break-even economic profitability for both energy sales options. The results of these analyses

    are shown in Table 38 and 39.

    The tipping fee revenue (column 1) represents the range in aggregated annual tipping fees received and

    the correlating fee in ($/ton). The price per ton was determined by dividing the tipping fee received

    (column 1) by the average total mass of all non-farm biomass received from substrates 8, 10, and 11. If

    biogas prices received were $10 per decatherm, the net annual tipping fee revenues required to make

    the project break-even would be $1,421,000 per year, at $21/ton. If electrical energy prices received

    were $0.14 per kWh, the net annual tipping fee revenues required to make the project break-even

    would be $951,000 per year.

  • 106

    Table 38. Scenario No. 2 CAD net annual economic profitability ($)2,3 for various biomethane sale prices and tipping fees charged for non-farm biomass substrates

    Biomethane sale1 price ($/decatherm)

    Tipping Fee 4 6 8 10 12 14

    ($/year) ($/ton)

    0 0 (1,906,000) (1,745,000) (1,583,000) (1,421,000) (1,260,000) (1,098,000)

    200,000 3 (1,706,000) (1,545,000) (1,383,000) (1,221,000) (1,060,000) (898,000)

    400,000 6 (1,506,000) (1,345,000) (1,183,000) (1,021,000) (860,000) (698,000)

    600,000 9 (1,306,000) (1,145,000) (983,000) (821,000) (660,000) (498000)

    800,000 12 (1,106,00) (945,000) (783,000) (621,000) (460,000) (298,000)

    1,000,000 15 (906,000) (745,000) (583,000) (421,000) (260,000) (98,000)

    Breakeven ($/year)

    1,906,000 1,745,000 1,583,000 1,421,000 1,260,000 1,098,000

    Breakeven

    ($/ton) 29 26 24 21 19 16

    1Assumes total biogas production used for thermal energy sale; no electricity sale

    2Assumes average capital and O&M cost estimates

    3Assumes no revenue from the sale of engine-generator set surplus thermal energy

    Table 39. Scenario No. 2 CAD, net annual economic profitability ($)2,3 for various electrical energy sale prices and tipping fees charged for non-farm biomass substrates

    Electric sale1 price ($/kWh)

    Tipping Fee 0.08 0.10 0.12 0.14 0.16 0.18

    ($/year) ($/ton)

    0 0 (1,432,000) (1,271,000) (1,111,000) (951,000) (791,000) (630,000)

    200,000 3 (1,232,000) (1,071,000) (911,000) (751,000) (591,000) (430,000)

    400,000 5 (1,032,000) (871,000) (711,000) (551,000) (391,000) (230,000)

    600,000 8 (832,000) (671,000) (511,000) (351,000) (191,000) (30,000)

    800,000 11 (632,000) (471,000) (311,000) (151,000) 9,000 169,700

    1,000,000 13 (432,000) (271,000) (111,000) 49,000 209,000 369,700

    Breakeven ($/year)

    1,432,000 1,271,000 1,111,000 951,000 $791,000 630,299

    Breakeven

    ($/ton) 21 19 17 14 12 9

    1Assumes total biogas production used to generate electricity; no thermal energy sale

    2Assumes average capital and O&M cost estimates

    3Assumes no revenue from the sale of engine-generator set surplus thermal energy

    The above shows that the Scenario No. 2 CAD can be economically viable when a moderate tipping fee

    is charged to the suppliers of the non-farm biomass that is significantly less than that charged by the

    local landfill, which was reported to be approximately $60/ton by the Lowville Digester Work Group but

    more than the calculated tipping fee being paid by non-farm biomass substrate supplier #8. It appears

    that a tipping fee range of $17 to $24/ton is needed to break-even, depending on the energy sale option

    chosen.

  • 107

    Energy Crop AD System The Lowville energy crop digester would be an anaerobic digester designed to process high solids energy

    crop materials (corn silage and or haylage). Such digesters are widely used in Germany and other

    European countries and produce about eight times the biogas as digesters fed manure only

    (Effenberger, 2006).

    Silage corn and grass hay would be harvested and ensiled as if they were going to be fed to dairy cattle.

    Sufficient quantities would be stored to enable the energy crop digester feed hopper (usually a walking

    floor bin) to be filled once-a-day, year round, normally with a pay loader. Several times per day, the

    control system would automatically transfer a portion of the feedstock into the digester; screw

    conveyors (augers) are normally used due to the high solids content of corn silage and haylage. The

    energy crop digester economic analysis performed for this feasibility study used in-the-bunk silage

    prices ranging from $30 to $55/ton, meaning that the costs to grow the crops and harvest and ensile

    them are covered by the purchase price.

    In addition to the energy crop feedstock, a small portion of manure is also normally added to the energy

    crop digester, about 10 percent by mass, to help stabilize digester pH and to provide some dilution

    water to lessen the effort required to provide in-vessel mixing.

    Energy crop digester effluent, rich in organic nutrients, is the consistency of digested manure. For this

    feasibility study, it is assumed the effluent would be stored on-site for a short period of time and

    periodically trucked to the energy crop source farms for longer-term storage and for subsequent use as

    fertilizer to grow the next rotation of energy crops. Some of the surplus nutrients from the Lowville CAD

    system could also be trucked to the source farms to meet the overall fertilizer requirements for the

    crops grown on those farms.

    Capital Costs

    The total capital cost of the energy crop digester was estimated to be $4.5 million dollars. This price was

    developed using the same fashion as the capital cost of the Lowville CAD system was determined; unit

    price information calculated from data provided by a company involved in energy crop digesters,

    Organic Waste Systems, Inc. (McDonald, 2010), was used in conjunction with project specific

    information.

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    The estimated total capital cost for the GE Jenbacher Type 4 engine-generator set that most closely

    matches (1,131 kW) the biogas available to fuel the set is $904,800. For this option, the biogas clean-up

    to biomethane was not investigated, since economic profitability analysis results for the Scenario 2 CAD

    showed little difference in the bottom line when comparing biomethane sale vs. electrical energy sale.

    Annualized capital costs

    Using the same procedure and assumptions for determining the annualized capital costs for the Scenario

    No. 2 CAD system, the annual capital cost for the energy crop digester and engine-generator set is

    $361,000 and $117,000, respectively for a total annual capital cost of $478,000.

    Annual operating and maintenance costs

    The annual operating and maintenance (O&M) costs were calculated using the same procedure and the

    assumptions for the Scenario No. 2 CAD system, with one notable difference being that the energy crop

    digester O&M costs were based on the recommendation to use 2.5% of the capital cost of the system

    (McDonald, 2010). The energy crop digester and engine-generator set annual O&M costs are $113,000

    and $123,000, respectively, for a total annual O&M cost of $236,000.

    Digester feedstock cost

    The energy crop digester feedstock cost is an important item to consider since it is a major cost of the

    system and will have the biggest impact of all costs on profitability. This cost will likely annually be

    reflective of the cost to supply corn silage and haylage to dairy cows. Based on farm data and average

    crop yields for the area, 27,600 tons of crops would be ensiled at Site 1 and the energy crop digester

    project would purchase corn silage and haylage out of the bunker. The annual estimated cost for

    feedstock is shown in Table 40 for a unit price range of $30 to $55/wet ton.

    Table 40. Annualized capital costs ($) for energy crop digester system

    Feedstock Unit Cost ($/wet ton) out of a

    bunker on-site 30 35 40 45 50 55

    Annual Feedstock Cost ($) 828,000 966,000 1,104,000 1,242,000 1,380,000 1,518,000

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    Net economic profitability

    The net annual economic profitability for the energy crop digester is presented in Table 41 for the

    situation only producing electricity for sale, over a range of feedstock and electricity sale prices. The

    economic profitability was determined by subtracting the following values from the total average

    electricity production: total annual capital costs, total O&M costs, the lowest potential feedstock costs,

    and the cost to transport energy crop digester effluent back to collaborating crop farms.

    Table 41. Net annual economic profitability ($) for various electricity prices and feedstock costs

    Electric sale price

    ($/kWh) 0.08 0.10 0.12 0.14 0.16 0.18

    Energy Crop Digester

    Feedstock Unit Cost ($/wet

    ton)

    30 (967,000) (807,000) (646,000) (486,000) (326,000) (165,000)

    35 (1,105,000) (945,000) (784,000) (624,000) (464,000) (304,000)

    40 (1,243,000) (1,083,000) (922,000) (762,000) (602,000) (442,000)

    45 (1,381,000) (1,221,000) (1,060,000) (900,000) (740,000) (580,000)

    50 (1,519,000) (1,359,000) (1,198,000) (1,038,000) (878,000) (718,000)

    55 (1,656,000) (1,497,000) (1,336,000) (1,176,000) (1,016,000) (856,000)

    The net annual economic profitability is negative for all combinations of feedstock purchase price and

    electrical energy sale price considered, meaning that the energy crop digester system would cost more

    to own than the value of the annual revenue received. Therefore, consideration of an energy crop

    digester is not recommended at this time.

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    Farm Impacts

    Capital improvements

    In order to successfully implement the Scenario No. 2 CAD system, some of the targeted collaborating

    farms will need to make on-farm modifications. Based on the farm survey results (Table 10) seven of

    the 15 collaborating dairy farms (Nos. 5, 11, 14, 16, 19, 21, and 23) would need to construct short-term

    manure storages in order to hold at least 6,000-gallons of manure to be collected by the 6,000-gallon

    manure tanker truck with an on-board pumping system. A short-term manure storage was defined by

    the project as a storage with the ability to hold one to three days worth of manure generated by that

    farm. Constructing a manure storage larger than 6,000-gallons will give a farmer the flexibility to store

    manure for additional time, should there be a reason that the manure cannot be picked up from the

    farm.

    A manure bypass system will also need to be included to be used when the manure tanker truck cannot

    access the farm manure storage site; this is unlikely to happen often, but could arise as an issue due to

    poor road conditions. The ideal manure bypass system would include a pump capable of pumping

    manure not only directly to the farms long-term manure storage, but also into the manure tanker for

    times when its on-board pumping system may fail and also into the farms manure spreader.

    Other farm improvements may include access roads and utility upgrades; these are all site specific and

    the capital cost associated with them will vary from farm to farm.

    The estimated capital cost to construct a 10,000-gallon short-term manure storage with bypass pump is

    shown in Table 42. The storage construction cost is based on poured-in-place concrete construction;

    the walls are 10 thick and the floor is 6 thick, as recommended by the local Soil and Water

    Conservation District office (Durant, 2008). Costs include a manure storage gravel access pad for more

    reliable access to the 6,000-gallon manure tanker truck upon collection. These specifications would

    require about 40 yd3 of concrete, at a price of $86/yd3 (Durant, 2008). The access pad is assumed to be

    6 thick concrete (NRCS, 2008). A centrifugal pump is specified for use as the bypass pump, with an

    estimated cost of $16,000 (NRCS, 2008).

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    Table 42. Capital cost estimate per farm for construction of a 10,000-gallon on-farm short-term manure storage

    Total cost of concrete $3,450

    Labor $6,900

    Gravel $900

    Excavation/site prep $1,500

    Pump in short-term storage $16,000

    Electrical service/upgrade $2,000

    Access road $3,500

    Total $34,250

    Nutrients

    Chapter 4 contains the results of the laboratory nutrient concentration testing of the non-farm biomass

    substrates. The raw manure nutrient values shown in Table 43 represent the 15 collaborating farms for

    Scenario No. 2. Total post-digestion nutrient mass of nitrogen, phosphorus and potassium series are

    provided in Table 43 and Table 44.

    Table 43. Scenario No. 2 CAD estimated post-digestion nitrogen series and total annual masses by feedstock source

    Digestate source

    Post Digestion TKN (lbs/year)

    Post Digestion Ammonia-N (lbs/year)

    Post Digestion Organic-N (lbs/year)

    Minimum Maximum Minimum Maximum Minimum Maximum

    8 17,420 25,230 3,090 4,470 18,520 26,830

    10 165,140 165,140 41,240 157,460

    11 490 - -

    Manure 1,573,710 - -

    Total 1,756,760 1,764,570 44,330 45,710 175,980 184,290

    Table 44. Scenario No. 2 CAD estimated post-digestion phosphorus and potassium series and total masses by feedstock source

    Digestate source

    Post Digestion Total Phosphorus (lbs/year)

    Post Digestion Ortho Phosphorus (lbs/year)

    Post Digestion Potassium (lbs/year)

    Minimum Maximum Minimum Maximum Minimum Maximum

    8 16,730 24,240 7,970 11,540 12,800 18,540

    10 82,790 3,970 24,930

    11 5 - 0

    Manure 270,230 - 365,610

    Total 369,755 377,265 11,940 15,510 403,340 409,080

    The land base used to grow the crops for the proposed energy crop digester could be used to receive

    the nutrients contained in CAD effluent. Discussions between the Lowville Digester Work Group and

    owners of area crop farms have shown the willingness of some crop farmers to receive digested effluent

    at their farms to replace some or all of the commercial fertilizers currently used. One of the initial goals

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    of the project was to improve the nutrient balance situation in the region; re-distributing nutrients from

    farms with excess to farms that are deficient would significantly advance this goal.

    Similar to Figure 28, a comparison of the volume of manure provided to the CAD by each farm and the

    volume of digested effluent the farm in turn would receive back is shown in Figure 29; however, in this

    case, each farms individual nutrient balance situation is taken into account. The farms that have either

    a balanced or excess nutrient situation would receive an amount of CAD effluent equivalent to the

    amount of manure they provide to the CAD project, contrary to the increased amount of effluent they

    would receive in the weighted scenario, shown in Figure 28. Assuming farms receive effluent in this

    manner, there would be an estimated 11 million gallons/year of excess CAD effluent available for sale to

    area crop farms.

    Figure 29. Comparison of the volume of manure sent to the CAD and volume of CAD effluent received, by farm, taking into account each farm's nutrient balance situation.

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    Assuming the non-farm biomass imported for co-digestion supplies excess nutrients to the post-

    digestion product that would be available for sale to area crop farms, the project could potentially

    receive $226,000/year in total revenue. Of the $226,000/year, $86,000/year would be derived from the

    sale of nitrogen, $121,000/year would be derived from the sale of phosphorus, and $19,000/year would

    be derived from the sale of potassium16.

    16

    Based on fertilizer sale prices for N,P,and K of $0.46/lb, $0.51/lb, and $0.40/lb, respectively.

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    Chapter 8. Future Work and Recommendations The recommendation for a CAD system is based on conducting thorough and complete technical and

    economic feasibility analyses, as well as the vision of the Lowville Digester Work Group. Based on this,

    the recommendation is to further investigate one centrally-located complete mix AD, sited adjacent to

    the LWWTP that would co-digest manure from 15 targeted collaborating dairy farms and targeted non-

    farm biomass substrates (currently the following three substrates: whey, post-digested sludge, and

    glycerin) that are by-products generated nearby.

    The future net annual economic profitability behind this recommendation is encouraging, given that, (1)

    the calculated tipping fee needed for the system to break-even is well below the average tipping fee

    charged in the northeastern U.S. and many predict regulations will be instituted in the near future

    restricting the land-filling of organic matter, (2) future regulations aimed at reducing the impact of fossil-

    fuel derived energy (specifically GHG emissions and climate change) would likely positively impact

    renewable energy projects, and (3) the annual economic profitability will improve with reductions in

    capital cost by receiving grants and/or premium payments for renewable energy.

    If future efforts are put forth to further investigate one CAD, it is recommended that the two major

    areas provided below be addressed in the order presented and that the bullet items under each be

    included.

    A. Address Economic Barriers to Project Implementation

    Identify other potential sources of non-farm biomass that are currently being land-

    filled or otherwise disposed of that could be received by the CAD with a tipping fee

    paid by the supplier

    Continue the education and outreach efforts concerning this project and the goals and

    objectives of local community members, targeted at collaborating and non-

    collaborating dairy farmers and non-farm biomass substrate suppliers to develop

    project support targeted towards securing public funding.

    Secure grant funding or subsidies that could help offset the capital cost of the CAD

    and/or supplement the revenue(s) received for system outputs (raw biogas,

    electricity, biomethane, and/or organic nutrients)

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    Investigate the willingness of non-farm biomass suppliers to enter into reasonable

    long-term contracts , with a negotiated tipping fee

    Investigate the willingness of the end user(s) of the net energy produced by the CAD

    facility to enter into reasonable long-term contracts

    B. Advanced Project Due Diligence

    Perform more complete laboratory testing of the targeted substrates mixed

    proportionally with manure to better solidify the quantity of biogas that would be

    produced by the system

    Conduct an in-depth site and environmental impact assessment for the targeted

    construction site

    Investigate the legal issues for various digester ownership options

    Determine the permit(s) that will be required by the New York State Department of

    Environmental Conversation (NYSDEC)17

    Conduct an in-depth investigation into the site improvements that will be required at

    each farm in order to participate in the project, and develop an associated budget

    Validate the trucking analysis and farm biomass pick-up options

    Investigate contracting with an existing trucking company to provide transportation of

    farm biomass

    Develop a request for proposals (RFP) package to be distributed to AD system

    designers

    Validate the economic profitability analysis using the results of the proposed RFP

    Continue investigation into future opportunities, such as manure nutrient extraction

    equipment and resulting product marketing opportunities for organic nitrogen,

    phosphorus, and potassium

    Continue reassessment of market opportunities such as the sale of biomethane as a

    vehicle fuel.

    17

    There are currently no operating dairy manure-based CAD systems in NYS, and an initial inquiry made by Cornell to NYSDEC on behalf of this project revealed that NYSDEC is not readily prepared to state what permit(s) is/are needed.

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    References

    Angenent, Lars. 2009. Associate Professor of Biological and Environmental Engineering, Cornell University. Personal Communication.

    American Society of Agricultural and Biological Engineering (ASABE) Standards, 52nd ed. 2005. ASAE

    D384.2 Manure Production and Characteristics. ASABE, Joseph, Michigan. Bennett, S. 2003. Feasibility Report of a Cooperative Dairy Manure Management Project in St.

    Albans/Swanton, VT.

    Bothi, K.I. and B.S. Aldrich. Fact sheet: Feasibility Study of a Central Anaerobic Digester for Ten Dairy

    Farms in Salem, NY. www.manuremanagement.cornell.edu 2005.

    Casey, J., L. Gerson, A. Smith, N.R. Scott, and L. Albright. 2007. Cornells Proposed Anaerobic Digester. Cornell Cooperative Extension (CCE) of Wyoming County. 2002. Feasibility Study of Anaerobic Digestion

    Options for Perry, New York. Web address: http://counties.cce.cornell.edu/wyoming/agriculture/programs/anaerobic_digestion/files/FeasabilityStudyFinalReport.doc

    Durant, Mike. Natural Resources Conservation Service (NRCS). 2008. Draft engineering drawings for on-

    farm manure storage.

    Edgar, Thom G., and Andrew G. Hashimoto. 1991. Feasibility Study for a Tillamook County Dairy Waste Treatment and Methane Generation Facility. Department of Bioresource Engineering, Oregon State University.

    Effenberger, Mathias. 2006. Dipl. Ing. M.Sc. Mathias Effenberger. Bavarian State Research Center for Agriculture (LfL) Institute of Agricultural Engineering and Animal Husbandry.

    Energy Information Administration (a), 2009. How much electricity does a typical American home use? Website: www.tonto.eia.doe.gov/ask/electricity_faqs.asp#electricity_use_home

    Energy Information Administration (b), 2009. Natural gas navigator

    Website: http://tonto.eia.doe.gov/dnav/ng/ng_sum_top.asp United States Environmental Protection Agency (USEPA). 1997. A Manual for Developing Biogas Systems

    at Commercial Farms in the United States. EPA-430-B-97-015. Gooch, C.A., S.F. Inglis, and P.E. Wright. 2007. Biogas Distributed Generation Systems Evaluation and

    Technology Transfer Project Interim Report. Prepared for: The New York State Energy Research and Development Authority. NYSERDA Project No. 6597. Albany, New York.

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    Gooch, C.A., and J.L. Pronto. 2009. Unpublished graph; Data from NYSERDA Project Nos. 6597 and 9446, Digester Assessment following the protocol developed by Association of State Energy Research and Technology Transfer Institutions.

    Jewell, W.J. 2007. Professor Emeritus of Biological and Environmental Engineering, Cornell University.

    Personal Communication. Jewell, W.J., et al. 1997. Evaluation of Anaerobic Digestion Options for Groups of Dairy Farms in Upstate

    New York. Prepared for: USDA-NRCS. Koelsch, R.K., E.E. Fabian, R.W. Guest, J.K. Campbell. Undated. Anaerobic Digesters for Dairy Farms.

    Agricultural and Biological Engineering Extension Bulletin 458. Cornell University, Ithaca, NY 14853.

    Labatut, R.A. and N.R. Scott. 2008. Experimental and Predicted Methane Yields from the Anaerobic Co-

    digestion of Animal Manure with Complex Organic Substrates. ASABE Paper No. 08-5087. Lawrence, Joe. 2009. Field crop extension educator, Cornell Cooperative Extension of Lewis County.

    Personal Communication. Lewis County Digester Work Group. 2008. A Partnership of the Supply Chain with Benefits to the

    Community and the Dairy Industry. Committee working document. Lopez, J.A., et al. 2009. Anaerobic digestion of glycerol derived from biodiesel manufacturing.

    Bioresource Technology 100 (2009) 5609-5615. Ludington, D.C. and S.A. Weeks. 2008. The Characterization of Sulfur Flows in Farm Digesters at Eight

    Farms. Mack Trucks, Canada. 2009. Personal communication. . Marks, L.S. 1978. Mechanical Engineers Handbook, 4th Edition. McGraw-Hill Book Company, Inc.

    McDonald, Norma. 2010 North American Sales Manager, Organic Waste Systems, Inc. Personal Communication.

    Minchoff, CJ, and Kifle G. Gebremedhin. 2006. Economic Feasibility Study for a Centralized Digestion System. Proceedings of the 2006 ASABE Annual International Meeting. Portland, Oregon, July 9-12. American Society of Agricultural and Biological Engineers, St. Joseph, Michigan. Paper No. 064198.

    Mitariten, Michael. Senior Engineer. Guild Associates, Inc. 2009. Personal Communication.

    Public Interest Energy Research. 2006. Glossary of energy terms. Website: www.pierminigrid.org/glossary.html

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    Repa, Edward W. 2005. NSWMAs 2005 Tip Fee Survey. National Solid Wastes Management Association Research Bulletin 05-3.

    Roka, F.M., R.M. Muchovej, and T.A. Obreza. 2001. Assessing Economic Value of Biosolids. Florida

    Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Scott, Norm. 2010. Personal Communication. Strand Associated, Inc. 2008. Community Manure Management Facilities Plan, Dane County, WI. Tabolt, Mark. Lowville Wastewater Treatment Plant Manager. Personal communication. December 15,

    2009. Weisman, W. 2008. Lane Renewable Energy Complex, Lane County, Oregon. Vernon, Todd. 2010. Senior Sales Manager, GE Energy - Jenbacher

    Vokey, Frans. Cornell Cooperative Extension, Lewis County. Personal communication. 2010. Wright, P.E. 2001. Overview of Anaerobic Digestion Systems for Dairy Farms. Proceedings of Dairy

    Manure Systems, Equipment and Technology Conference; Rochester, New York, March 20-22. NRAES-143. Natural Resource, Agriculture, and Engineering Service. Cornell University, Ithaca, New York.

    Wright, P.E., Inglis, S.F, Stehman, S.M, and J. Bonhotal. 2003. Reduction of Selected Pathogens in Anaerobic Digestion. Proceedings of the Ninth International Symposium, Animal, Agricultural and Food Processing Wastes IX. Raleigh, North Carolina, Oct. 12-15. American Society of Agricultural and Biological Engineers, St. Joseph, Michigan.

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    Appendix A. Glossary for New York State Manure-Based Anaerobic Digestion18 Anaerobic bacteria

    Microorganisms that live and reproduce in an environment containing no free or dissolved oxygen.

    Anaerobic digester

    A vessel and associated heating and gas collection systems designed specifically to contain biomass undergoing digestion and its associated microbially produced biogas. Conditions provided by the digester include: an oxygen-free environment, a constant temperature, and sufficient biomass retention time.

    Anaerobic digestion

    A biological process in which microbes break down organic material while producing biogas as a by-product.

    Anaerobic lagoon

    A holding pond for livestock manure that is designed to anaerobically stabilize manure, and may be designed to capture biogas with the use of an impermeable, floating cover.

    Annual capital cost The equivalent annual capital cost converts the total capital costs into an annual charge. The

    equivalent annual capital cost is calculated according to the formula EAC= pv/(1/r - 1/(r*(1+r)^n)) where pv is the present value or total capital investment in today's dollars, r is the discount rate, and n is the life of the capital investment.

    Barn effluent

    Material exiting a barn structure, generally consisting of animal excrement (urine and feces) and used bedding material, and may contain milking center washwater.

    Biogas

    For the purposes of this document, the raw and un-cleaned gas produced by an AD, consisting of mainly methane CH4 (~60%), carbon dioxide CO2 (~40%), water vapor, and hydrogen sulfide.

    British Thermal Unit (Btu)

    The English System standard measure of heat energy. It takes one Btu to raise the temperature of one pound of water by one degree Fahrenheit at sea level.

    18

    Reference: (Public, 2006)

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    Capital cost A one-time fixed cost incurred on the purchase of buildings and equipment. A digesters capital cost includes the purchase of land the system is on, permitting and legal costs, the equipment needed to run the digester, cost of digester construction, the cost of financing, and the cost of commissioning the digester prior to steady-state operation of the digester.

    Centralized digester

    An anaerobic vessel which uses feedstocks from several farms and/or other biomass sources, within a relatively proximate distance to the digester location.

    Co-generation

    The sequential use of energy for the production of electrical and useful thermal energy. The sequence can be thermal use followed by power production or the reverse, subject to the following standards: (a) At least 5% of the co-generation projects total annual energy output shall be in the form of useful thermal energy. (b) Where useful thermal energy follows power production, the useful annual power output plus one-half the useful annual thermal energy output equals not less than 42.5% of any natural gas and oil energy input.

    Combined Heat and Power (CHP)

    The sequential or simultaneous generation of two different forms of useful energy mechanical and thermal from a single primary energy source in a single, integrated system. CHP systems usually consist of a prime mover, a generator, a heat recovery system, and electrical interconnections configured into an integrated whole.

    Complete mix digester An anaerobic vessel that is mixed with one or more mixing techniques. Dewater

    To drain or remove water from an enclosure. Dewater also means draining or removing water from sludge to increase the solids concentration.

    Digestate

    Effluent; Material remaining after the anaerobic digestion of a biodegradable feedstock. Digestate is produced both by acidogensis and methanogenesis, and each has different characteristics.

    Discount rate The interest rate used in discounting future cash flows. Distributed generation

    A distributed generation system involves small amounts of generation located on a utilitys distribution system for the purpose of meeting local (substation level) peak loads.

    Distribution system (electric utility)

    The substations, transformers and lines that convey electricity from high-power transmission lines to consumers.

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    Effluent Digestate; Material exiting the AD vessel. Emission

    The release or discharge of a substance into the environment; generally refers to the release of gases or particulates into the air.

    End-use sectors The residential, commercial, transportation and industrial sectors of the economy. Engine-Generator set

    The combination of an internal combustion engine and a generator to produce electricity; may be single or dual fueled depending on the location and set up.

    Flare A device used to safely combust surplus or unused biogas. Greenhouse Gas (GHG)

    A gas, such as carbon dioxide or methane, which contributes to a warming action in the atmosphere.

    Grid

    The electric utility companies transmission and distribution system that links power plants to customers through high power transmission line service; high voltage primary service for industrial applications; medium voltage primary service for commercial and industrial applications; and secondary service for commercial and residential customers. Grid can also refer to the layout of gas distribution system of a city or town.

    Hydraulic retention time (HRT)

    The length of time material remains in the AD. Hydrogen sulfide (H2S)

    A toxic, colorless gas that has an offensive odor of rotten eggs. Hydrogen sulfide has serious negative implications for the wear of gas handling equipment for an anaerobic digester system.

    Hydrolysis

    A biological decomposition process involved in the anaerobic digestion of organic material. Influent Biomass on the in-flow side of a treatment, storage, or transfer device. Installed capacity The total capacity of electrical generation devices in a power station or system. Kilowatt-hour (kWh)

    The most commonly used unit of measure of the amount of electric power consumed over time. The stand-alone unit indicates one kilowatt of electricity supplied for one hour.

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    Lagoon In wastewater treatment or livestock facilities, a shallow pond used to store wastewater where biological activity decomposes the waste.

    Lost capital The portion of a capital investment that cannot be recovered after the investment is made, usually used to express the immediate loss in value of a purchased or constructed item.

    Main tier

    Distributed renewable energy systems where the electrical power produced is not used on-site but rather transported to the grid for use elsewhere. Wind generation generally falls into this category.

    Manure

    The combination of urine and feces. Methane (CH4)

    A flammable, explosive, colorless, odorless, gas. Methane is the major constituent of natural gas, and also usually makes up the largest concentration of biogas produced in an anaerobic digester.

    Methanogens

    Active in phase 3 of the digestion process, acids (mainly acetic and propionic acids) produced in phase 2 are converted into biogas by methane-forming bacteria.

    Microturbine

    A small combustion turbine with a power output ranging from 25- to 500-kW. Microturbines are composed of a compressor, combustor, turbine, alternator, recuperator, and generator.

    Net generation

    Gross generation minus the energy consumed at the generation site for use in maintaining energy needs (heat or electric).

    Net Present Value (NPV)

    The present value of an investments future net cash flow minus the initial investment. Generally, if the NPV of an investment is positive, the investment should be made.

    Operation and Maintenance (O&M) costs

    Operating expenses are associated with running a facility. Maintenance expenses are the portion of expenses consisting of labor, materials, and other direct and indirect expenses incurred for preserving the operating efficiency or physical condition of a facility.

    Plug-flow digester

    A design for an anaerobic digester in which the material enters at one end and is theoretically pushed in plugs towards the other end, where the material exits the digester after being digested over the design HRT.

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    Present value The current value of one or more future cash payments, discounted at some appropriate interest rate.

    Rate of return

    The annual return on an investment, expressed as a percentage of the total amount invested. Siloxane

    Any of a class of organic or inorganic chemical compounds of silicon, oxygen, and usually carbon and hydrogen, based on the structural unit R2SiO where R is an alkyl group, usually methyl.

    Tipping fees

    Monies that are paid to a site that is accepting outside sources of organic material (non-farm biomass).

    Ton US short ton equals 2,000 lbs Tonne Metric ton equals 1,000 kg Treatment volume

    Inside volume of an anaerobic digester that, under normal operating conditions would be full of material undergoing anaerobic decomposition.

    Turbine

    A device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical motion.

    Volatile solids

    Those solids in water or other liquids that are lost on ignition of the dry solids at 550 degrees Centigrade.

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    Appendix B. Survey data for Lewis County Anaerobic Digester Feasibility (Farm based survey)

    Farm name: ________________________________________

    Contact: ___________________________________________

    Farm mailing (or street) address: __________________________________________________

    Who is your nutritionist? _________________________________________________

    Do we need permission to contact your nutritionist? _______________________

    Cow population questions

    At the present time, what is the:

    Number of mature cows: ________________

    Number of heifers: __________________

    Housing type for both groups: _______________________________________________

    Bedding type for both groups: _______________________________________________

    2 years from now, what changes do you expect to see in the:

    Number of mature cows: ________________

    Number of heifers: __________________

    Housing type for both groups: _______________________________________________

    Bedding type for both groups: _______________________________________________

    5 years from now, what changes do you expect to see in the:

    Number of mature cows: ________________

    Number of heifers: __________________

    Housing type for both groups: _______________________________________________

    Bedding type for both groups: _______________________________________________

    Do you have off-site heifer manure? ________________

    If yes, what is the:

    Address: __________________________________________________

    Population of heifers providing manure: __________________

    Age span of off-farm heifers: _____________________________________

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    Manure composition questions

    Is milking center wastewater or other extra water included in the manure? _________________

    Estimated amount of extra water: ________________ (gallons/day)

    If water is added, is it possibly to separate it from the manure flow? (Y/N) ____________

    Does the farm use Rumensin for any of the cows (lactating or heifer)? ____________________

    Does the farm use copper sulfate for foot-baths? ___________________________________

    Is there a copy of a recent (< 2 years) manure analysis available? ________________________

    Do you have an excess OR a lack of manure nutrients on your farm? ______________________

    How much of each of the following do you have in excess, OR are lacking:

    N ________________ (lbs/year)

    P________________ (lbs/year)

    K ________________ (lbs/year)

    Manure handling and storage questions

    Manure Storage

    Size (circle units)

    Animal groups

    Wastewater included?

    Describe access

    (paved, dirt road, etc.)

    How is manure transferred?

    (pumps, gravity, etc.)

    How often is this storage spread on

    fields?

    How many acres is it

    spread on?

    1 Gal/cu ft Yes/No

    2 Gal/cu ft Yes/No

    3 Gal/cu ft Yes/No

    4 Gal/cu ft Yes/No

    5 Gal/cu ft Yes/No

    What is the approximate acreage of: (1) Corn: _____ (2) Grass hay: _____ (3) Alfalfa: _____

    (4) Other: _____

    Is there short-term (1-3 days) storage available? ________________________________

    Is there long-term storage available? _____________________________________

    If yes, how many months storage does it provide? _______________________

    Describe the access to both short-term and long-term storages; is it directly off a paved road? If possible,

    please provide a rough map describing the layout. _____________________________

    ______________________________________________________________________________

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    Where, if any, are the existing pumps located in the manure handling system? _______________

    ______________________________________________________________________________

    Is dealing with frozen manure an issue at your farm? ___________________________________

    Does your farm have significant waste feed to dispose of (ex. Feed refusal, spoiled forage, etc.)?

    _____________________________________________________________________________

    Perspective questions

    What concerns would you have in spreading manure that you receive back from a common central

    anaerobic digester system? __________________________________________________

    ______________________________________________________________________________

    Would you be willing to pay for necessary features or additions that are necessary for the

    removal/delivery of manure and digested material (this includes storage facilities, pumps, etc.)?

    ______________________________________________________________________________

    Would you be interested in discussing the formation of a cooperative to run and manage this centralized

    digester?

    ______________________________________________________________________________

    Thank you, for taking the time to complete this survey! Feel free to add any additional comments,

    concerns or questions in the space below.

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    Appendix C. Survey data for Lewis County Anaerobic Digester Feasibility (Non-farm based survey)

    Company name: ________________________________________

    Industry type: _____________________

    Contact: ___________________________________________

    Mailing address: _____________________________________________________

    Give a description of the type of organic material you would be disposing of:

    _____________________________________________________________________________________

    ___________________________________________________________

    Organic waste item

    Solid or Liquid?

    Fat, oil, or protein?

    Pre-consumer or post-

    consumer?

    Quantity or volume?

    Frequency of removal?

    Frequency of accumulation (seasonality)1

    1This means, do you only produce this waste at a certain time of year?

    Do you have any lab analysis of the organic material you would be disposing of? And could this be made

    available? _______________________________________________

    Do you currently have a method to dispose of the organic material your business produces? (Y/N)

    ___________________

    Do you pay someone to provide this service? (Y/N) ___________________________

    What is the approximate cost of this disposal? ________________________________

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    What is the setup of the storage facility for the organic material produced by your business? Please

    describe any pits, tanks, pumps, or other equipment used in conveying the organic material to disposal.

    _____________________________________________

    ________________________________________________________________________

    What are your feelings/concerns about providing this organic material to a common central anaerobic

    digester system? ____________________________________________

    ________________________________________________________________________

    Thank you, for taking the time to complete this survey! Feel free to add any additional comments,

    concerns or questions in the space below.

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    Appendix D. Substrate Sampling Report

    This report details the process of collecting samples of non-farm biomass substrates from substrate

    suppliers in Lewis County.

    Residential food waste

    A local volunteer for the Lowville digester project provided food waste samples from her home which

    consisted of residential food waste, chopped with a knife and mixed using a food processor, as shown in

    Figure 30. There are considerable logistical problems with obtaining a representative sample of

    residential food waste, which varies considerably in content and volume throughout the year and from

    home to home.

    Meat and butchers waste

    Samples of meat, fat and guts were collected from a local butcher. The offal was deposited in eight oil

    drums and included blood, intestines, hides, livers, fat and other assorted butcher wastes, as shown in

    Figure 31. To obtain a representative sample, some blood was pooled into a container along with slices

    of liver, intestine and fat that had been manually mixed using a power drill. Since the waste was not

    uniform throughout the barrels, the sample incorporated elements from several of the barrels. The

    owner of the establishment noted that during deer season (October-December), deer bones would be

    the sole by-product from the butchering plant.

    Dilute whey

    A sample of diluted whey and CIP waste water was collected from a dairy processing plant. Employees

    explained that waste whey was disposed of every day while CIP wastewater, was disposed of about

    every three days. Thus, a representative sample was taken by mixing three parts whey to one part CIP

    wastewater. It should be noted that the substrate supplier already pumps this waste to a location to be

    trucked off-site; therefore, no additional infrastructure would likely be necessary for collection and

    inclusion to the proposed digester project.

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    Grocery store scraps

    A local grocery chain was unable to provide a food waste sample, since the portion of their usable food

    waste is deposited into a catch-all dumpster that accumulates a high degree of contamination, such as

    plastic, metal and other indigestible refuse. Produce waste is currently piped through the local sewer

    system to the wastewater treatment plant after being sent through a garbage disposal. Collaboration

    between the bakery, produce, and meat departments within the grocery store need to improve in order

    to coordinate a large scale waste separation process in the future.

    Post-consumer scraps

    Samples were taken from multiple local restaurants all of which contributed samples of mixed pre- and

    post-consumer food waste in addition to samples of fryer grease. For the purpose of the biological

    methane potential (BMP) trials, food and grease wastes from two of the restaurants were combined in

    proportion to what they normally produce. Similar waste streams were provided by two local

    institutions that were comprised entirely of post-consumer scraps. One institution separated waste into

    solid and liquid portions these were re-mixed for the purpose of sampling and analysis.

    Florist shop waste

    Finally, a sample was taken from a local florist consisting of refuse flower stems, flowers, petals, and

    other plant matter.

    Figure 30. Image of residential food waste sample collected.

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    Figure 31. Meat and butcher waste from substrate number 4.

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    Appendix E. Biochemical Methane Potential Laboratory Procedure

    320-mL bottles are used in the trials, and contain 200 mL of substrate, inoculum, and nutrient medium. Inoculum is an active anaerobic mixed culture media obtained from an operating bench scale AD reactor. The nutrient medium is added for the purpose of providing the necessary nutrients and trace elements for the microorganism to thrive.

    Bottles with only inoculum were used in the set up as controls, to account for the background methane produced in the bottles by the inoculum.

    Bottles containing only water were also used in the set up as controls, to correct for internal pressure variations due to external temperature and atmospheric pressure fluctuations.

    Prior to incubation, bottles were gassed-out with a mixture of 70% N2 and 30% CO2 and sealed immediately.

    Sealed bottles were placed in a mesophilic (371C) incubator containing a shaker to constantly agitate the bottles during the trials.

    The biogas production within the bottles was determined by pressure transducers attached to a hypodermic needle inserted through the septa of each bottle.

    Pressure measurements were performed continuously over a period of 30 days using a data acquisition (DAQ) system connected to a computer. As pressure built-up in the bottles, it was periodically released by way of a valve in the top of the bottles. The instances of these pressure release events can be seen in Figure 12 by the presence of the small dips across the lines on the graph.

    Pressure data recorded by the DAQ system were converted to volume of biogas at a standard temperature and pressure (STP) according to the ideal law of gases (PV = nRT). STP is defined as 1C and 1atm.

    Temperature inside the incubator was also continuously monitored through the DAQ with a thermocouple placed inside a control bottle containing water.

    Methane and carbon dioxide content in the biogas was determined by a gas chromatograph (GC) and the methane yield was subsequently calculated.

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    Appendix F. Projected farm survey responses Table 45. Farm survey responses based on projections for two years

    Farm ID number

    Number of

    mature cows

    Number of

    heifers

    Lactating cow equivalents (LCE) (total solids basis)

    1* 200 150 262

    2 0 150 62

    3 66 10 70

    4 105 75 136

    5 620 80 653

    6* 85 70 114

    7* 195 195 275

    8 80 80 113

    9 688 448 872

    10 145 115 192

    11 190 160 256

    12* 195 160 261

    13 155 150 217

    14* 175 80 208

    15 85 35 99

    16 75 70 104

    17 80 70 109

    18* 600 0 600

    19 550 430 726

    20 54 36 69

    21 91 60 116

    22 91 60 116

    23 150 40 166

    24 85 10 89

    25 80 100 121

    SUM 4,840 2,834 6,002

  • 140

    Table 46. Farm survey responses based on five year projections

    Farm ID number

    Number of

    mature cows

    Number of

    heifers

    Lactating cow equivalents (LCE) (total solids basis)

    1* 200 150 262

    2 0 150 62

    3 66 10 70

    4 105 75 136

    5 620 80 653

    6* 85 70 114

    7* 195 195 275

    8 80 80 113

    9 688 448 872

    10 145 115 192

    11 190 160 256

    12* 195 160 261

    13 155 150 217

    14* 175 80 208

    15 85 35 99

    16 62 62 87

    17 80 70 109

    18* 500 150 562

    19 750 430 926

    20 54 36 69

    21 91 60 116

    22 91 60 116

    23 150 40 166

    24 85 10 93

    25 50 60 121

    SUM 4,897 2,936 6,151

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