development of domestic solid waste management schemes for...

Faculté des Sciences El Jadida

National Technical University of Athens

Municipality of the Urban

Community of

AZEMMOUR

Development of Domestic Solid Waste Management Schemes for Small Urban Communities in Morocco

WASTESUM (LIFE06 TCY/MA/000254)

Deliverable 3A:

Domestic solid waste management practices in EU and Internationally Best practices and success stories.

MAY 2010

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Table of Contents

Summary........................................................................................................ 1

1. Integrated Waste Management Systems ................................................ 3

1.1. Background information........................................................................................... 3

1.2. Development and Implementation of IWM Systems.............................................. 8

2. Case studies and Success stories of applied IWM Systems ................ 10

2.1 Success stories of applied MBT technologies.......................................................... 12

2.1.1. The ArrowBio Plant in Tel Aviv, Israel (Wet Anaerobic Digestion) ......... 12

2.1.2. The Västerås MBT plant in Sweden (Wet Anaerobic Digestion)............... 20

2.1.3 The Kaiserslautern MBT plant in Germany (Dry Anaerobic Digestion) .... 31

2.1.4 The Drseden MBT plant in Germany (Bio-drying) ..................................... 35

2.1.5 The Montanaso MBT plant in Italy (Bio-drying) ........................................ 39

2.1.6 The Tufino MBT plant at Italy (Composting) ............................................. 42

2.1.7 The Erbenschwang MBT plant in Germany (Composting)......................... 46

2.1.8 The Ano-Liosia MBT plant in Greece (Composting).................................. 51

2.1.9 The Edmonton BT plant in Canada (Co-composting) ................................. 63

2.1.10 The Botarell plant in Spain (Composting) ................................................. 71

2.2 Success stories of applied thermal treatment technologies ................................... 75

2.2.1 The Thun plant in Switzerland (Incineration).............................................. 75

2.2.2 The Zorbau plant in Germany (Incineration)............................................... 80

2.2.3 The Spittelau Thermal Waste Treatment Plant in Austria (Incineration) .... 84

2.2.4 The Toshima Thermal Treatment Plant in Japan (Incineration).................. 90

2.2.5 The Lidköping Waste-to-Energy Plant in Sweden (Incineration) ............... 93

2.2.6 The TIRMadrid Plant in Spain (Incineration).............................................. 95

2.2.7 The Ottawa Waste-to-Energy Plant in Canada (Plasma gasification) ......... 97

2.2.8 The Toyohashi Waste Treatment of Recovery and Resources Centre in Japan (Pyrolysis gasification) ............................................................................. 102

3. Remarks ................................................................................................. 108

References.................................................................................................. 110

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List of Tables Table 1: MSW generated - kg per capita in EU countries from 1997 to 2008 (Eurostat, 2010).... 3 Table 2: Output material of processing 70.000 tpa mixed MSW at Tel Aviv plant (Juniper, 2005).............................................................................................................................................. 18 Table 3: Outputs material from the MBT Västerås plant in Sweden............................................ 30 Table 4: Outputs based on a plant processing 20.000 tpa of grey waste, Kaiserslautern plant .... 34 Table 5: Composition of SRF produced at Dresden plant in Germany (Juniper, 2005) .............. 37 Table 6: Outputs of processing 85.000 tpa mixed MSW at Dresden plant (Juniper, 2005)......... 38 Table 7: Outputs of processing 60.000 tpa MSW at Montanaso at Italy (Juniper, 2005) ............ 41 Table 8: Indicative energy requirements for a VKW composting plant (Juniper, 2005) ............. 44 Table 9: Projected outputs of processing 150.000 tpa MSW from a VKW plant (Juniper, 2005)44 Table 10: Indicative costs for VKW MBT process for 150.000 tpa mixed–MSW (Juniper, 2005)....................................................................................................................................................... 45 Table 11: Projected outputs of processing 40.000 tpa MSW from Erbenschwang plant in Germany (Juniper, 2005) .............................................................................................................. 50 Table 12: Outputs from Ano – Liosia MBT plant in Greece (Eleftheriades, 2010)..................... 62 Table 13: Outputs of the Edmonton Composting Facility in Canada ........................................... 70 Table 14: Outputs from Botarell in Spain .................................................................................... 73 Table 15: Cost of the Baix Camp Separation, Collection and Composting Scheme for the Year 1998 (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf). ....................... 74 Table 16 : Capital and Running Cost of the Botarell Composting Scheme (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf). ................................ 74 Table 17: Output data from the Thun waste incineration plant in Switzerland ............................ 79 Table 18: Output data from the Zorbau incineration plant in Germany ....................................... 83 Table 19: Output data from the Spittelau Thermal Waste Treatment Plant in Austria................. 89 Table 20: Output data from the Toshima Thermal Waste Treatment Plant in Japan (IEA, 2000) 92 Table 21: Output data from the Lidköping Waste-to-Energy Plant in Sweden (IEA, 1999) ........ 94 Table 22: Output data from the TIRMadrid Plant in Spain (Granatstei, 2001) ........................... 96 Table 23: Output data from the Ottawa Waste –to-Energy Treatment Plant in Canada............. 101 Table 24: Output data from the Toyohashi Waste Treatment of Recovery and Resources Center in Japan........................................................................................................................................ 107

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List of Figures Figure 1: MSW generated - kg per capita in EU, 1997 and 2007 (Eurostat, 2010) ........................ 4 Figure 2: Map presentation-MSW generated (kg per capita) in EU 1997 and 2007(Eurostat, 2010)......................................................................................................................................................... 5 Figure 3: Elements of IWM system (McDougall et al., 2003)........................................................ 7 Figure 4: The ArrowBio plant at Tel Aviv (Finstein, 2006) ......................................................... 12 Figure 5: MSW pre-treatment in the ArrowBio process at Tel Aviv (Juniper, 2005) .................. 13 Figure 6: The Interior of the Hydro-mechanical material recovery unit at Tel Aviv (Fienstein, 2006).............................................................................................................................................. 14 Figure 7: Front end of the MRF at Tel Aviv (Fienstein, 2006)..................................................... 15 Figure 8: Anaerobic digestion ArrwBio process at Tel Aviv MBT plant (Juniper 2005)............. 16 Figure 9: Anaerobic digestion unit at Teli Aviv, (http://www.oaktech-environmental.com/description.htm) ............................................................................................. 17 Figure 10: The Västerås plant at Sweden (Heiskanen, 2006)........................................................ 20 Figure 11: The schematic flow of the Västerås plant at Sweden (Växtkraft, 2006) ...................... 21 Figure 12: Equipment used in each section of Västerås plant at Sweden ..................................... 22 Figure 13: The receiving hall of Västerås plant at Sweden (Växtkraft, 2006)............................... 23 Figure 14: Equipment of pre-treatment unit of Västerås plant at Sweden (Växtkraft, 2006) ........ 25 Figure 15: Plastic hoses in the Västerås plant at Sweden (Växtkraft, 2006) ................................. 26 Figure 16: Close vies of Plastic hoses in the Västerås plant at Sweden (Växtkraft, 2006)............ 26 Figure 17: Feeding silage system (Växtkraft, 2006)...................................................................... 26 Figure 18: Anaerobic digester the Västerås plant at Sweden (Växtkraft, 2006)............................ 27 Figure 19: Gas storage interior (a) and the flare (b) at the Västerås plant (Växtkraft, 2006) ........ 28 Figure 20: The centrifuges (a) and the containers for the storage of solid digestate (b) at the Västerås plant in Sweden (Växtkraft, 2006) .................................................................................. 28 Figure 21: Storage basin of the liquid digestate fraction at the Västerås plant (Växtkraft, 2006) . 29 Figure 21: The scrubber (a) and the biofilter (b) at the Västerås plant (Växtkraft, 2006) ............. 29 Figure 22: The Kaiserslautern plant in Germany (OWS, 2000)..................................................... 31 Figure 23: Full stream digestion process in Kaiserslautern (Juniper, 2005) ................................. 32 Figure 24: Dranco Digester (CIWMB, 2008)................................................................................. 33 Figure 25: MBT Dresden Plant (Herhorf 2010)............................................................................ 35 Figure 26: Herhof bio-drying process at Dresden plant (Juniper, 2005) ...................................... 36 Figure 27: The Montanaso plant in Italy (Juniper, 2005) ............................................................. 39 Figure 28: Process flow diagram of Montanaso plant at Italy (Juniper, 2005) ............................. 40

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Figure 29: The Tufino plant in Italy (Juniper, 2005) .................................................................... 42 Figure 30: Baled RDF at Tufino plant in Italy (Juniper, 2005)..................................................... 43 Figure 31: Part of the ‘CTM’ compost turning machine at Tufino plant in Italy (Juniper, 2005) 43 Figure 32: The Erbenschwang MBT plant in Germany ................................................................ 46 Figure 33: Flow diagram of Erbenschwang MBT process in Germany, (1997-2004 & 2005) (Juniper, 2005) .............................................................................................................................. 47 Figure 34: The Erbenschwang MBT plant in Germany (Juniper, 2005) ...................................... 48 Figure 35: The composting bays at Erbenschwang plant in Germany (sutco, 2010) .................... 49 Figure 36: The mobile “Biofix” windrow turning device at Erbenschwang plant in Germany (sutco, 2010) .................................................................................................................................. 49 Figure 37: The Ano-Liosia MBT plant at Greece ......................................................................... 51 Figure 38: Waste Reception Facility at Ano-Liosia in Greece...................................................... 52 Figure 39: Waste reception trench at Ano-Liosia in Greece ......................................................... 53 Figure 40: Mechanical separation unit at Ano-Liosia in Greece................................................... 53 Figure 41: Components of mechanical separation unit at Ano-Liosia in Greece.......................... 55 Figure 42: View of the building with the composting tunnels at Ano-Liosia in Greece............... 55 Figure 43: View of composting tunnel .......................................................................................... 56 Figure 44: Shredder employed for shredding green waste at Ano-Liosia in Greece..................... 57 Figure 45: Refinery unit at Ano-Liosia in Greece......................................................................... 58 Figure 46: Recycling of coarse material from the refinery unit to the composting unit at Ano-Liosia ............................................................................................................................................. 58 Figure 47: Open-air windrows where 85% of the compost is cured at Ano-Liosia in Greece ...... 59 Figure 48: Warehouse where curing of 15% of the compost takes place at Ano-Liosia in Greece....................................................................................................................................................... 60 Figure 49: Wastewater Treatment Unit at Ano-Liosia in Greece................................................. 60 Figure 50: Scrubbers Employed for Air Treatment at Ano-Liosia in Greece ............................... 61 Figure 51: Panoramic View of the Edmonton Composting Facility in Canada (http://en.wikipedia.org/wiki/File:MRF_Composter03.jpg) ......................................................... 63 Figure 52: Flow diagram of Edmonton waste processing plant in Canada ................................... 64 Figure 53: View of the Tipping Floor where Solid Waste is Collected of the Edmonton Composting Facility in Canada ..................................................................................................... 65 Figure 54: Manual Selection of Oversized Waste of the Edmonton plant ................................... 65 Figure 55: Placement of Remaining Waste Inside the Mixing Drums of the Edmonton plant .... 65 Figure 56: Centrifugal Pumps Utilized for Dewatering Sewage Sludge of the Edmonton Composting Facility in Canada ..................................................................................................... 66 Figure 57: Storage Hopper of the Edmonton Composting Facility in Canada.............................. 66 Figure 58: View of one of the Mixing Drums of the Edmonton Composting Facility in Canada 67

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Figure 59: Conveyor Belts of the Edmonton Composting Facility in Canada plant .................... 67 Figure 60: Aeration Building of the Edmonton Composting Facility in Canada .......................... 68 Figure 61: Mobile Compost Augers of the Edmonton Composting Facility in Canada................ 68 Figure 62: Compost Refining System of the Edmonton Composting Facility in Canada (http://www.edmonton.ca/for_residents/CompostingFacility.pdf) ................................................ 69 Figure 63: Biofilters of the Edmonton Composting Facility in Canada........................................ 70 Figure 64: Botarell Composting System in Spain ......................................................................... 71 Figure 65: Biofilter in the Composting Plant of Botarell in Spain ................................................ 73 Figure 66: The Thun incineration plant in Switzerland ............................................................... 75 Figure 67: Schematic operation of the Thun waste incineration plant in Switzerland .................. 78 Figure 68: The Zorbau incineration plant in Germany ................................................................ 80 Figure 69: Schematic operation of the Zorbau waste incineration plant in Germany ................... 82 Figure 70: The Spittelau Thermal Waste Treatment Plant in Austria .......................................... 84 Figure 71: Schematic operation of the Spittelau Thermal Waste Treatment Plant in Austria....... 88 Figure 72: Ottawa plasma gasification plant in Canada ................................................................ 97 Figure 73: Schematic operation of the Ottawa Waste - to - Energy Treatment Plant in Canada 100 Figure 74: The Toyohashi Waste Treatment of Recovery and Resources Centre in Japan......... 102 Figure 75: Process diagram of the Toyohashi Waste Treatment of Recovery and Resources Centre in Japan........................................................................................................................................ 105 Figure 76: Schematic operation of the Toyohashi Waste Treatment of Recovery and Resources Centre in Japan ............................................................................................................................ 106

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Summary

This report was prepared for the purposes of WasteSUM Project (http://www.uest.gr/wastesum/). WasteSUM (LIFE06 TCY/MA/000254) is a Life-Third Countries Project co-funded by the European Community with title “Management and Valorisation of Solid Domestic Waste for the Small Urban Communities in Morocco” with benefiting country that of Morocco. The report constitutes the outcome (Deliverable 3) of the completion of Task A under the title: Assessment of the existing situation in Morocco concerning domestic solid waste generation and management.

The objectives of this report is to provide basic knowledge on engineered technologies applied for mixed municipal solid waste treatment and to collect, classify and present information on best practices and known success stories of mixed municipal solid waste disposal schemes in the EC and internationally.

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Abbreviations and Acronyms

AD Anaerobic Digestion BMT Biological Mechanical Treatment BOD Biochemical Oxygen Demand BOD5 5-day Biochemical Oxygen Demand CH4 Methane CO2 Carbon Dioxide COD Chemical Oxygen Demand d day EEA European Environment Agency g gram GWh Gigawatt hours (1 million megawatt hours) H2S Hydrogen Sulfide hr hour HRT Hydraulic Retention Time IWM Integrated Waste Management kW kilowatt kWe kilowatts of electricity kWh kilowatt hour L liter m meter m3 cubic meter (gas volumes assume 0°C and 1.101 bar) MBT Mechanical Biological Treatment MC Moisture Content MS-OFMSW Mechanically Sorted Municipal Solid Waste MSW Municipal Solid Waste MW megawatt MWe megawatts of electricity MWh megawatt hour OFMSW Organic Fraction of Municipal Solid Waste ppm parts per million RDF Refuse Derived Fuel SRT Solids Retention Time tons short ton tpa ton per annum tph ton per hour TP Total Phosphorous TS Total Solids UASB Upflow Anaerobic Sludge Blanket VFAs Volatile Fatty Acids VS Volatile Solids

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1. Integrated Waste Management Systems

1.1. Background information

Waste is an inevitable product of society. Solid waste management practices were initially developed to avoid the adverse effects on public health that were caused by the increasing amounts of solid waste being discarded without appropriate collection or disposal (McDougall et al., 2003).

Based on EEA, on average, each European citizen generated 460 kg Municipal Solid Waste (MSW) in 1995. This amount rose to 520 kg per person in 2004, and a further increase to 680 kg per person is projected by 2020. In total, this corresponds to an increase of almost 50 % in 25 years (EEA, 2008). Detailed data concerning MSW generated per capita per annum in EU countries from 1997 to 2008 are presented in Table 1 (Eurostat, 2010).

Table 1: MSW generated - kg per capita in EU countries from 1997 to 2008 (Eurostat, 2010)

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

EU (27) 499 496 511 523 522 527 515 514 517 523 525 524 EU (15) 537 540 555 569 572 577 564 564 558 564 567 565 Belgium 463 (e) 457 (e) 463 (e) 476 (e) 471 (e) 487 468 487 481 484 497 (e) 493 (e)

Bulgaria 577 495 503 516 491 500 499 471 475 (i) 446 (i) 468 (i) 467 CzechRepublic 318 (e) 293 327 334 273 (i) 279 280 278 289 296 294 306 Denmark 588 593 627 665 658 665 672 696 737 741 801 (e) 802 (s)

Germany 658 (s) 647 (s) 638 (s) 643 (s) 633 (s) 640 601 587 564 563 582 581 (e)

Estonia 422 400 413 440 372 (b) 406 418 (e) 449 436 (e) 466 (e) 507 (e) 515 (s)

Ireland 547 (e) 557 581 (e) 603 705 698 736 745 740 804 788 733 Greece 363 378 393 408 417 423 428 433 438 443 448 453 Spain 561 566 615 662 658 645 655 608 (e) 597 599 590 575 (e)

France 497 508 509 516 528 532 508 521 532 538 544 543 (e)

Italy 468 472 498 509 516 524 524 538 542 553 550 561 (s)

Cyprus 650 664 670 680 703 709 724 739 739 745 754 770 (e)

Latvia 254 (e) 247 (e) 256 (e) 270 (e) 302 338 298 311 310 411 377 331 Lithuania 421 443 350 (b) 363 377 401 383 366 376 390 400 407 Luxembourg 607 629 650 658 650 656 684 683 678 688 694 (e) 701 (e)

Hungary 487 484 482 445 (b) 451 457 463 (e) 454 460 468 456 453 Malta 437 (e) 470 (e) 477 547 542 543 581 625 624 624 652 696 Netherlands 590 593 599 616 615 622 610 (i) 625 624 622 630 622 (e)

Austria 532 532 563 581 578 609 609 620 620 654 598 601 (e)

Poland 315 (i) 306 (i) 319 (i) 316 (i) 290 (i) 275 (i) 260 (i) 256 (i) 319 (e) 321 (e) 322 (e) 320 (e)

Portugal 405 423 442 472 472 439 (b) 447 436 446 454 (i) 472 (e) 477 (e)

Romania 333 277 314 355 336 383 350 (e) 345 (e) 377 (e) 388 (e) 378 (e) 382 (e)

Slovenia 589 (e) 584 551 (e) 513 (e) 479 407 (b) 418 417 423 432 441 459 Slovakia 275 259 261 254 239 283 (b) 297 274 289 301 309 328 Finland 448 466 485 503 466 459 466 470 479 495 507 522 Sweden 416 431 428 428 442 468 471 464 482 497 518 515 UK 533 543 570 578 592 600 593 (i) 605 585 587 572 565 (s)

Turkey 503 510 463 (e) 458 (e) 457 450 445 421 (b) 438 (e) 415 430 (s) 428 (s)

Iceland 445 452 457 466 469 478 485 506 521 570 566 (e) 555 (s)

Norway 619 647 596 615 362 (b) 393 403 416 427 461 494 490 Switzerland 609 613 637 657 662 678 670 662 (b) 663 711 724 741 :=Not available e=Estimated value i=See explanatory text s=Eurostat estimate b=Break in series Hyperlink to the table: http://epp.eurostat.ec.europa.eu/tgm/table.do?tab=table&init=1&plugin=1&language=en&pcode=tsdpc210

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This indicator presents the amount of MSW generated in EU countries. It consists of waste collected by or on behalf of municipal authorities and disposed of through the waste management system. The bulk of this waste stream is from households, though similar wastes from sources such as commerce, offices and public institutions are included. For areas not covered by a municipal waste scheme an estimation has been made of the amount of waste generated. The quantity of waste generated is expressed in kg per person per year. For a more comprehensive understanding, graphical and mapping presentation of MSW indicators for years 1997 and 2007 are given in Figure 1 and Figure 2, accordingly (Eurostat, 2010).

1997 2007 Figure 1: MSW generated - kg per capita in EU, 1997 and 2007 (Eurostat, 2010)

Hyperlink to the figure: http://epp.eurostat.ec.europa.eu/tgm/graph.do?tab=graph&plugin=1&pcode=tsdpc210&language=en&toolbox=sort

EU (27) EU (15) Belgium Bulgaria Czech Republic Denmark Germany Estonia Ireland Greece Spain France Italy Cyprus Latvia Lithuania Luxembourg Hungary Malta Netherland Austria Poland Portugal Romania Slovenia Slovakia Finland Sweden United Kingdom Turkey Iceland Norway Switzerland

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Figure 2: Map presentation-MSW generated (kg per capita) in EU 1997 and 2007(Eurostat, 2010)

It is observed that differences in MSW composition indicate the effect of urbanization and development. In urban areas, the major fraction of MSW is compostable materials (40–60%) and inerts (30–50%). The relative percentage of organic waste in MSW is

1997

2007

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generally increasing with the decreasing socio-economic status; so rural households generate more organic waste than urban households.

Morocco currently produces about 5.0 Mtpa MSW, a figure that could reach 6.2 million tons by 2020. In the absence of an active and strategic role at the central government level, most municipalities equate solid waste management only with the removal of waste from visible public areas. Waste disposal in sanitary landfills has been entirely neglected by municipalities, and waste is generally disposed in open dumps (>95%) (WorldBank, 2009). Organic fraction of Morocco’s MSW exceeds 70%.

Managing MSW more effectively is now a need that society has to address. In dealing with the waste, there are two fundamental requirements: less waste, and then an effective system for managing the waste still produced (McDougall et al., 2003).

The Brundtland report of the United Nations, Our Common Future, clearly explained how sustainable development could only be achieved if society in general, and industry in particular, learned to produce ‘more from less’; more goods and services from less of the world’s resources (including energy), while generating less pollution and waste. In this era of ‘green consumerism’, this concept of ‘more from less’ has been taken up by industry. This has resulted in a range of concentrated products, light-weighted and refillable packaging, reduction of transport packaging and other innovations. Production as well as product changes have been introduced, with many companies using internal recycling of materials as part of solid waste minimisation schemes. All of these measures help to reduce the amount of solid waste produced, either as industrial, commercial or domestic waste. In essence, they are improvements in efficiency, i.e. ‘eco-efficiency’, whether in terms of materials or energy consumption.

‘Waste minimisation’, ‘waste reduction’ or ‘source reduction’ are usually placed at the top of the conventional waste management hierarchy. In reality, however, source reduction is a necessary precursor to effective waste management, rather than part of it. Source reduction will affect the volume, and to some extent, the nature of the waste, but there will still be waste for disposal. What is needed, beyond source reduction, is an effective system to manage this waste (McDougall et al., 2003).

In Europe, decisions on waste management strategies have often been based on “The Waste Management Hierarchy”. This is a ranking of different waste management options that is intended to give a broad indication of their relative environmental benefits. This hierarchy of preferred options has varied, but usually gives the following order of preference: waste reduction, re-use, recycling, composting, biogasification (anaerobic treatment), incineration with energy recovery, incineration without energy recovery and landfill. Taken as a rigid hierarchy rather than as only an indicator, it does not allow for the

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flexibility required when selecting the most environmentally effective and economically efficient method of waste management for any specific scenario (Franke et al., 1999; McDougall et al., 2003).

The limitations of the Hierarchy of Waste Management are becoming increasingly apparent, especially in relation to Integrated Waste Management (IWM) systems. Rather than a hierarchy of preferred waste management options a holistic approach is proposed, which recognises that all options can have a role to play in Integrated Waste Management (see Figure 3). The model illustrates the interrelationships of the parts of the system.

Energy Recovery

Figure 3: Elements of IWM system (McDougall et al., 2003).

Unlike the hierarchy, this approach does not predict what would be the ‘best’ system due to the fact that best scenario for each case depends on geographic differences in both the composition and the quantities of waste generated, in the availability of some waste management options (such as landfill), and in the size of markets for products derived from waste management (such as recovered materials, compost and energy). This approach allows comparisons to be made between different waste management systems for dealing with the solid waste of the local regions. The best system for any given region will be determined locally. In essence what is needed is less waste to deal with in the first instance, and then an Integrated Waste Management system to manage the waste that is still produced in an environmentally effective, economically affordable and socially acceptable way (McDougall et al., 2003).

Collection

& Sorting Fuel

burn

Mass burn

Biological Treatment

Materials Recycling

Thermal Treatment Landfill

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1.2. Development and Implementation of IWM Systems

McDougall et al propose the following definition for Integrated Waste Management systems: “IWM systems combine waste streams, waste collection, treatment and disposal methods, with the objective of achieving environmental benefits, economic optimisation and societal acceptability. This will lead to a practical waste management system for any specific region”.

The Key features of IWM are:

1. an overall approach

2. uses a range of collection and treatment methods

3. handles all materials in the waste stream

4. environmentally effective

5. economically affordable

6. socially acceptable.

Solid waste management systems need to assure human health and safety. In addition to these prerequisites, a sustainable system for solid waste management must be environmentally effective, economically affordable and socially acceptable.

More precisely, in order to achieve best environmental effectiveness, the waste management system must minimise possible environmental impacts of waste management (emissions to land, air and water, such as CO2, CH4, SOx, NOx, BOD, COD and heavy metals). Environmental pillar should be in balance with economic and social considerations. Thus, the costs of operating an effective solid waste system will depend on existing local infrastructure, but ideally should be little or no more than existing waste management costs. A vary crucial aspect is the social acceptance. There are numerous of examples where IWM systems did not succeed due to low public participation. If an IWM system ensures acceptance for the majority of people in a community, it is very likely to succeed. This will definitely require an extensive dialogue with many different groups to inform and educate, develop trust and gain support.

Clearly it is difficult to minimise three variables – cost, social acceptability and environmental burden – simultaneously. There will always be a trade-off. The balance that needs to be achieved is to reduce the overall environmental burdens of the waste management system as far as possible, within an acceptable level of cost (McDougall et al., 2003).

IWM systems for mixed MSW include mechanical processing followed by biological or thermal treatment. Solid waste processing that combines a mechanical treatment (sort, size classification) with a form of biological treatment such as composting or anaerobic

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digestion are classified under the acronym ‘MBT’ - Mechanical Biological Treatment technologies. In some cases, the entire raw waste input is first processed in the biological stage, followed by mechanical separation systems to provide an overall treatment process, hence the acronym ‘BMT’ - Biological Mechanical Treatment technologies. Biological treatment includes anaerobic digestion and/or composting. Anaerobic digestion (AD) differs from aerobic composting in that the degradation of biodegradable matter occurs in the absence of oxygen. During AD biogas is produced which is a mixture of methane (CH4) and carbon dioxide (CO2). Usually, the biogas is cleaned to reduce its moisture content and remove H2S (hydrogen sulphide) before it is pressurised and injected into gas engines. The gas engines generate electricity (Juniper Consultancy Services, 2005).

Thermal methods for waste management aim at the reduction of the waste volume, the conversion of waste into harmless materials and the utilization of the energy that is hidden within waste as heat, steam, electrical energy or combustible material. They include all processes converting the waste content into gas, liquid and solid products with simultaneous or consequent release of thermal energy (Moustakas et al., 2010). Most well known thermal treatment is incineration accompanied by energy recovery andburning of Refuse-Derived Fuel (RDF).

Landfilling can also be considered as a disposal scenario. In a landfill the organic fraction of solid waste is broken down under appropriate conditions by aerobic and then anaerobic bacteria. Methane emissions arise from the breakdown of organic matter and groundwater pollution may occur due to leaching of toxic materials from the solid waste. Landfilling operations also require large amounts of space. Use of the other options prior to landfilling can both divert significant parts of the waste stream and reduce the volume and improve the physical and chemical stability of the final residue. This will reduce both the space requirement and the environmental burdens of the landfill (McDougall et al., 2003).

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2. Case studies and Success stories of applied IWM Systems

In this chapter, success case studies applied in EU countries and worldwide for MSW treatment are presented. Special attention is given on the core process as well as on the performance of the systems. These systems include mechanical processing (sort, size classification) followed by a biological (composting or anaerobic digestion) or thermal treatment (incineration, pyrolysis, gasification etc).

Classification and definitions are given below:

Mechanical Biological Treatment, MBT refers to solid waste processing that combines a mechanical treatment with a form of biological treatment. In some cases, the entire raw waste input is first processed in the biological stage, followed by mechanical separation systems to provide an overall treatment process, hence the acronym ‘BMT’ - Biological Mechanical Treatment technologies.

Mechanical separation is the separation of waste into various components using mechanical means, such as cyclones, trommels and screens. Refuse-derived fuel (RDF) is a product of mechanical separation. RDF is a combustible, or organic, portion of municipal waste that has been separated out and processed for use as fuel (Tchobanoglous, 2002).

Biological treatment processes

Anaerobic Digestion is the degradation of organic matter by microorganisms in the absence of air (oxygen) to produce methane and carbon dioxide (biogas). Anaerobic digestion is taking place in chemical reactors, called anaerobic digesters, in which anaerobic bacteria are used to decompose biomass or organic wastes to produce methane and carbon dioxide (ASTM, 2005).

Composting is the controlled biological decomposition of organic material in the presence of air to form a humic product called compost (ASTM, 2005). A very important term in the definition of composting is "controlled". It is the application of control that distinguishes composting from the natural rotting, putrefaction, or other decomposition, that takes place in an open dump, a sanitary landfill, in a manure heap, or in an open field (http://www.lagoonsonline.com/composting.htm). Composting can be accomplished in windrows, static piles, and enclosed vessels (known as in-vessel composting).

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Thermal treatment processes

Incineration is the controlled burning of waste products or other combustible material carried out at constructed devices in which waste materials are burned (ASTM, 2005).

Pyrolysis is the thermal degradation of carbon-based materials through the use of an indirect, external source of heat, typically at temperatures of 250 to 700°C, in the absence or almost complete absence of free oxygen. In contrast to gasification and incineration, pyrolysis is an endothermic process which requires a permanent external heat source for the chemical decomposition of the organic fraction of MSW. Under these conditions, organic vapours, pyrolysis gases and charcoal are produced. During pyrolysis waste is transformed into a medium calorific gas, liquid and a char fraction (coke) in the absence of oxygen, through the combination of thermo-cracking and condensation reactions. (BALKWASTE, 2010).

Gasification is the thermal process that converts carbon-containing materials, such as coal, petcoke, biomass, sludge, domestic solid waste to a syngas which can then be used to produce electric power, valuable products, such as chemicals, fertilizers, substitute natural gas, hydrogen, steam, and transportation fuels. Gasification is a partial oxidation process which produces a composite gas (syngas) comprised primarily of hydrogen (H2) and carbon monoxide (CO). It is not a complete oxidation (combustion) process, which produces primarily thermal energy (heat) and solid waste, air pollutants (NOx and SO2), and carbon dioxide (CO2) (BALKWASTE, 2010).

Plasma Gasification Technology is the thermal process that converts the organic fraction into synthesis gas and the inorganic fraction into molten slag through an electric discharge similar to a lightning called plasma. Typically temperatures are greater than 3.870°C achieving complete conversion of carbon-based materials, including tars, oils, and char, to syngas composed primarily of H2 and CO while the inorganic materials are converted to a solid, vitreous slag. The syngas can be utilized in boilers, gas turbines, or internal combustion engines to generate electricity while the slag is inert and can be used as gravel (BALKWASTE, 2010).

Landfill is the engineered method of solid waste disposal on land in a manner that protects human health and the environment. Waste is spread in thin layers, compacted to the smallest practical volume, and covered with soil or other suitable material at the end of each working day, or more frequently, as necessary (Tchobanoglous, 2002).

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2.1 Success stories of applied MBT technologies

2.1.1. The ArrowBio Plant in Tel Aviv, Israel (Wet Anaerobic Digestion)

Overview

The plant in Tel Aviv, Israel was commissioned in January 2003 to treat mixed MSW through ArrowBio process. ArrowBio Process1 recovers over 90% of the material and energy resources from mixed MSW, leaving less than 10% to be landfilled (Finstein et al.2003). The typical process module has a capacity of 200 tpd (∼70.000 tpa). The ArrowBio process utilises a combination of wet pre-processing and mechanical separation to process mixed MSW to produce a suspension of biodegradable materials. The suspension is treated in a two-stage anaerobic digestion (AD) process to produce biogas for use in gas engines and a digestate, which is currently being used as a ‘fertiliser’ in Israel (Juniper, 2008). On 2008, the plant was renewed after the signing of a new contract with the Dan Region Association of Municipalities (headed by Tel Aviv).

The plant is housed in a partially open building, situated alongside the pre-existing Transfer Station of the municipality which is operated under the Dan Region Association of Municipalities. The main treatment units of the plant are: a) the transfer station of MSW, b) the pre-treatment unit and c) the biological unit (anaerobic treatment) as shown in Figure 4.

Figure 4: The ArrowBio plant at Tel Aviv (Finstein, 2006)

1 The ArrowBio Process, which holds a United States patent, is adevelopment of Arrow Ecology Ltd., Haifa, Israel (Finstein et al, 2003).

Hydro- Mechanical Unit Transfer Station Biological Treatment Unit

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Process and technology involved

ArrowBio is a water-based mechanical biological treatment process including two (2) separate units, namely: i) a hydro-mechanical material recovery unit and ii) an advanced anaerobic digestion unit (Marshall et al., 2006).

Hydro-mechanical material recovery unit

Process flow diagram of the hydro-mechanical treatment unit is given in Figure 5.

Figure 5: MSW pre-treatment in the ArrowBio process at Tel Aviv (Juniper, 2005)

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Legend

a) Conveyor belt b) Paddle wheel c) Main body of water tank d) Bag breaker

e) Magnetic separator f) Eddy current separator g) Air suction system h) Ductwork

i) Enclosed trommel screen j) Lifters k) Shredder l) Large trommel screen

Figure 6: The Interior of the Hydro-mechanical material recovery unit at Tel Aviv (Fienstein, 2006)

MSW delivered to the transfer station is tipped from the waste trucks, through a conveyor belt (Figure 6a), into a water-filled tank. The waste is passed through a submerged paddle wheel (Figure 6b) at the head of this tank into the main body of water (Figure 6c) which is continuously replenished by water recovered from the dewatering of the digestate in downstream screw and filter presses. In the tank concurrent flotation, sedimentation and dispersion of the waste materials take place. As a result, dense material (which sink to the lower part of the tank) is separated from lighter material (which floats in top), while most of the biodegradable materials disperse to form a suspension of fine solids. Dense material is diverted to the left part of the unit by a conveyor system and pass through a bag opening system (Figure 6d) and afterwards through magnetic (Figure 6e) and eddy current separators (Figure 6f) in order to recover ferrous and non-ferrous metals respectively. The remaining materials pass to a secondary water pool. Light materials from this pool are returned to the inlet tank and the denser materials are sent to landfill.

i

j

h

ge

b

l

c

f

d

a

k

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Dispersed solid suspension is removed along with light fraction, from the top of the pre-inlet tank through a paddle wheel. This overflow stream passes through a aller enclosed trommel screen (Figure 6i). The larger materials collected on the enclosed trommel are screened via an air suction system (Figure 6g) which removes mainly light plastics which are baled (see Figure 7a) (Juniper, 2005). From air system film plastic is swept into ductwork (Figure 6h). Ducts from several such stations converge on the cyclone (see Figure 7b). The remaining larger material are lifted (Figure 6j) to a slow speed shredder (Figure 6k) and then to the large trommel screen (Figure 6l). The “overs” from this trommel consist mostly of film plastic and are removed to the air suction system. The “unders” (material that have passed through screen) are washed into a settling tank (see Figure 7b) for further solubilization and size reduction (Finstein, 2006). The overflow from the settling tank is pumped to a sand filter and the overflow passed through a drum screen. The sediments from the settling tank, the materials collected in the sand filter and the drum screen oversize are sent to landfill. The fraction passing the drum screen (containing particles <10-15mm) is pumped to the first stage of the two-step anaerobic digestion process. This fraction contains about 3% TS. The entire waste preparation stage takes about thirty (30) minutes to complete.

7A

Bales of plastic recovered from mixed MSW

7B (a) the settling tank (b) the cyclone at the terminal end of a plastic film

plastic removal system which leads to a baler (7a) (c) the large trommel screen (d) the control room

Figure 7: Front end of the MRF at Tel Aviv (Fienstein, 2006)

b d

ac

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Biological treatment (anaerobic digestion process)

The process of the anaerobic treatment unit is given in Figure 8.

Figure 8: Anaerobic digestion ArrwBio process at Tel Aviv MBT plant (Juniper 2005)

As shown in Figure 4, the biological unit is located in a separate place close to the transfer station. The digestion process is carried out in two stages which are taking place in separate digestion tanks, under meshophilic conditions (35-40oC).

Degradable waste, separated during hydro-mechanical processing, is first entered into the first bioreactor where hydrolysis and acidogenesis processes take place. During hydrolysis, organic polymers (proteins, carbohydrates, lipids) are hydrolyzed to

17

monomeric or dimeric substances (amino acids, sugars, organic acids etc) by hydrolytic microorganisms. Following, acidogenesis is occurred during which the simple substances are biologically converted mostly to volatile fatty acids (VFAs). The inflow of fresh suspension to this stage and the outflow of the hydrolysed suspension are continuous with a Hydraulic Retention Time (HRT) and Solids Retention Time (SRT) of about four (4) hours.

Figure 9: Anaerobic digestion unit at Teli Aviv, (http://www.oaktech-

environmental.com/description.htm)

The suspension from the first stage is heated to about 35 - 400C (to facilitate the meshophilic digestion) and pumped continuously to the second stage reactor. In the second reaction stage, acetogenesis and methanogenesis reactions take place in an Upflow Anaerobic Sludge Blanket (UASB) digester. In this type of digester the suspension is introduced from the bottom of the digester, where it flows upward through a sludge blanket composed of biologically formed granules. UASB digestion is widely used for the treatment of sludge. Treatment occurs as the suspension comes into contact with the granules. The HRT in this digester is 1-3 days but the average SRT is about 80-90 days. One potentially significant advantage in using this type of digester is the long SRT that can be achieved through recycling undigested particles over a certain size. This allows materials which are harder to digest, to be broken down and ultimately increases the overall waste digestion efficiency. The products resulting from this stage are biogas, used in gas engines to generate electricity; water, a portion of which is recycled to the

2nd Stage

1st Stage

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waste pre-preparation tank; and a solid digestate, which is currently utilised as a ‘fertiliser’ in Israel (Juniper, 2005).

The two digestion stages are operated separately mainly because the optimum conditions, such as pH, are different. While on the one hand undertaking the digestion process in two stages allows each of the stages to be optimised individually, the need for additional process equipment, tanks, pumps etc., could potentially increase capital and operating costs.

Output material

Output material from the entire ArrowBio process for mixed MSW at Tel Aviv plant are given in Table 2.

Table 2: Output material of processing 70.000 tpa mixed MSW at Tel Aviv plant (Juniper, 2005)

Capacity 70.000 tpa

Input material mixed - MSW

Output material Value Application of materials

8,75 x106 – 12,25 x106 m3 per annum Biogas

125 -175 m3(biogas)/t (waste)

utilised in gas engines to produce electricity

Ferrous & Non-ferrous metals 2.100 - 2.800 tpa can be recycled Inerts (including glass, oversized materials, grit etc.) 8.400 - 9.800 tpa landfilled

Wastewater 14.000 - 17.600 tpa sent to leachate treatment plant

Digestate from AD plant 5.600 - 7.000 tpa used as a fertiliser in Israel

Biogas: The ArrowBio process produces between 125 and 175 m3 of biogas (~75% CH4) per ton of waste input to the plant depending on the waste feed. The Tel Aviv plant is configured to utilise the biogas in a gas engine to produce electricity. The biogas is passed through condensers to remove water before being sent to the on-site gas engine. No further biogas cleaning is carried out. Based on Juniper (2005), 20% of the electricity generated is used to meet the parasitic load requirements of the plant and the remainder is sent to the local grid. A small amount of biogas is also used for heating the UASB reactor. Excess biogas is flared using an ‘enclosed’ flare.

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Digestate: Due to high SRT in the digester, about 80 days, the digestate is a fully bio-stabilised product with 65-70% moisture content (MC), after pressing. For the time being, the digestate is sold without any further treatment to a farmer who further distributes the product to other farmers to be used as fertiliser in Tel Aviv. Alternative uses would be to use the digestate as fuel in boilers and cement kilns (Juniper, 2005).

Cost

Based on 2005 published data capital cost for one process module of 70.000 tpa (based on the Tel Aviv plant) reported by the company is EUR 10,4 to 12,2 million (Juniper, 2005).

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2.1.2. The Västerås MBT plant in Sweden (Wet Anaerobic Digestion)

Overview

The Västerås plant in Sweden started its operation in 2005. The capacity of the plant is approximately 14.000 tpa of sorted household waste, 4.000 tpa of sludge and 5.000 tpa of ley crops. Processing is carried out through MBT technology including mainly mechanical pretreatment and wet anaerobic digestion. Produced biogas is mainly upgraded to automotive fuel gas, corresponding to 2.000.000 L of petrol. A number of fuelling stations have been built to sell the gas produced.

The plant was the result of a jointly project (AGROPTI-gas) started in 1995 by three partners, namely local farmers, the regional waste treatment company and the municipal energy company in Sweden. The project aimed at developing a plant that would digest ley crops, organic household waste and sludge to produce biogas. The regional waste company was responsible for the project management and provided most of the expertise for the project. Local farmers involvement was of high importance because they were responsible for the ley crop cultivation and for the subsequently use of the produced digestate. The municipal energy company had the responsibility of biogas sale and distribution (Heiskanen, 2006).

Figure 10: The Västerås plant at Sweden (Heiskanen, 2006)

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Process and technology involved

The schematic flow of the Västerås plant is presented in Figure 11.

Figure 11: The schematic flow of the Västerås plant at Sweden (Växtkraft, 2006)

There are six (6) main sections in the plant:

• Receiving hall – receiving, quality control and initial preparation of the incoming bio waste.

• Pre-treatment – process water is added to create a suspension

• Silage feeding – silage is fed directly into the digester

• Biogas production – the microbial process in the digester tank in which the biogas is produced

• Digestate handling– separation and handling of digestate into a solid and a liquid fraction

• Air treatment – the outgoing air is treated in a water scrubber and in a biofilter in order to avoid

odour problems (Växtkraft, 2006).

INPUT MATERIAL OUTPUT MATERIAL

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In the above mentioned sections different processes take place using various types of

equipment. Basic equipment for each section is presented in Figure 12.

Figure 12: Equipment used in each section of Västerås plant at Sweden

Receiving hall

The Västerås plant is processing a) biowaste, b) grease trap removal sludge and c) silage. Biowaste enters the receiving hall (Figure 13) where it undergoes processing through a shredder, a star sieve and a walking floor which crush, separate and feed the waste for the processing at the pre-treatment section. More precisely, shredder (Figure 13a) (type hammer mill) is used to cut paper bags where the biowaste is collected and reduces the material in smaller pieces. Shredded material passes through a star sieve (Figure 13b), where large and light pieces, mainly plastics, are separated while the organic material is gathered to the walking floor (Figure 13c). Walking floor is used in order to facilitate biowaste’s transfer into the turbo-mixers. Slurry waste, mainly grease trap removal sludge, is also entered at the receiving hall through the deep bunker (Figure 13d) which has a volume of 100 m3. Inside the bunker there are four (4) screws that mix and force sludge to a hydraulic driven piston pump which pumps sludge to the turbo-mixers.

Västerås plant

Receiving hall

Pre- treatment

Silage feeding

Biogas production

Digestate handling

Air treatment

Shredder

Star sieve

Walking floor

Deep bunker

Turbo-mixers

Screen rake, sand trap

Macerator

Sanitation

Heat Exchangers

Feeding system

Digester

Biogas compressor

Gas storage

Flare

Centrifuges

Solid digestate

Liquid digestate

Scrubber

Biofilter

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(a) Shredder (b) Star sieve

(c) Walking floor (d) Deep bunker

Figure 13: The receiving hall of Västerås plant at Sweden (Växtkraft, 2006)

c b

a

d

c

ba

d

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Pre-treatment

The pre-treatment section includes: (a) the turbo-mixers, (b) the screen rake and the sand trap, (c) the macerator, (d) the suspension tank and (e) the sanitation tank and (f) the heat exchangers.

Processed biowaste and sludge from the receiving hall enter the turbo-mixers (Figure 14a) in which suitable treatment takes place in order to create a suspension (slurry) suitable for the digestion process. The incoming biowaste is mixed with process water (reject water from the centrifuges) resulting in a homogenous suspension of 8–10 % TS. The turbo-mixers are made of steel. Mixing and shredding is achieved by an electric impeller located on top of the mixer. The entire process is controlled through PLC-system. The retention time for one batch is approximately 20 minutes.

After the turbo-mixers, the suspension undergoes an integrated two step process in order to remove impurities. The two step process includes screening via a screen rake and trapping via a sand trap (Figure 14b). The screen rake removes particles larger than 15 mm. The screen reject mainly consists of plastic and larger pieces of organic and inorganic material. In a sand trap the heavy particles (mainly stones, glass and bones) are removed by sedimentation (Växtkraft, 2006). As a result: (i) equipment is protected from ware and abrasion, (ii) anaerobic digestion is optimized due to minimization of sedimentation and clogging problems and (iii) quality of the digestate is enhanced.

The suspension then passes through a macerator (Figure 14c) for particle size reduction. To allow continuous feeding of material to the sanitation step and to the digester the suspension is temporarily stored in the suspension tank (Figure 14d). The capacity of the tank is 270 m3 which is sufficient for continuous feeding of the digester. To avoid sedimentation in the suspension tank, it is equipped with an agitator and a pump which circulates the suspension.

Before the suspension enters the digester it undergoes a sanitation process by heating the material (>70 ºC) for at least one (1) hour. There are three (3) sanitation tanks (Figure 14e), 16 m3 each and while the suspension in one tank undergoes sanitation the other two tanks are simultaneously filled and emptied respectively. Thereby, a continuous flow to the digester is achieved. By process control it is assured that only well sanitized organic material is charged into the digester. In this way sufficient sanitation of the digestate, which is further used as fertiliser on farms, is ensured.

The heating of the suspension and heat recovery before the suspension enters the digester is done through heat exchangers. To this end, three heat exchangers (Figure 14f) of

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suspension-water type (the suspension flows inside pipes and water outside the pipes) operate. Two of them perform heat recovery and pre-heating of the suspension, while the third is used to heat the suspension to the target temperature (>70 °C).

(a) the turbo-mixers

(b) the screen rake and the sand trap

(c) the macerator

(d) the suspension tank

(e) the sanitation tank (f) the heat exchangers

Figure 14: Equipment of pre-treatment unit of Västerås plant at Sweden (Växtkraft, 2006)

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Silage treatment

Apart from biowaste and sludge, ley crop (approximately 1/3 of the organic material) is also processed at the plant. By mixing bio waste with silage the amount of gas produced per unit input material is increased. Ley crop is cultivated by local farmers and is harvested by contractors. The crop is transfered to the biogas plant where it is packed into plastic hoses (Figure 15), 90 metres long. In the hoses the crop is preserved as silage in the same way as normal cattle feed. Thereby the crop can be used in the biogas production throughout the year (Växtkraft, 2006).

Figure 15: Plastic hoses in the Västerås plant at Sweden (Växtkraft, 2006)

Figure 16: Close vies of Plastic hoses in the Västerås plant at Sweden (Växtkraft, 2006)

Based on information provided by the company (Växtkraft, 2006), a system for feeding silage directly into the digester tank is under construction. The silage will be loaded to a wagon (38 m3, approximately 15 – 20 tons). The transport capacity corresponds to the daily requirement of the plant. The silage feeder is a system of double screws which feeds the silage into a pipe where it is diluted and mixed with digestate from the digester and pumped back into the digester.

Figure 17: Feeding silage system (Växtkraft, 2006)

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Gas production

Biogas production takes place in the one stage anaerobic digester. The digester is located close to the receiving hall and the suspension tank of the pre-treatment unit, as shown in Figure 18.

Figure 18: Anaerobic digester the Västerås plant at Sweden (Växtkraft, 2006)

The digester is made of carbon steel tank with a capacity of 4.000 m3. The suspension is pumped from the sanitation step via the heat recovery step to ensure optimal temperature for the micro-organisms digesting the material. Silage is fed directly into the digester. The temperature is 37 °C (mesophilic process). The digester works continuously 24 hours/day with HRT of approximately 20 days. To avoid the use of moving parts inside the digester, mixing is performed by compressed biogas. The gas enters the digester via twelve pipes at the top of the tank and the pipes goes to the bottom of the tank, where the gas is released. Through expanding gas-bubbles the suspension is mixed. Additionally the suspension is circulated in the tank by a pump (Växtkraft, 2006).

The gas produced is led to gas storage tank including a cylindrical rubber-coated fabric bag installed in a corrugated steel, (Figure 19a) before it is upgraded to vehicle fuel. Biogas not upgraded is used for production of electricity and heat in a separate plant. In case of malfunctioning in the gas upgrading plant or the fuel station, the excess gas is burnt in the flare (Figure 19b). The flare is designed to be able to handle 150% of the gas

AnaerobicDigester

Receiving Hall Process water

tank

Biofilters

SuspensionTank

Plastic hoses - silage

28

production in order to act as a safety valve by burning excess gas and avoiding any release of methane gas to the atmosphere. Gas leakage is prevented by an automatic condensate separator.

(a) (b)

Figure 19: Gas storage interior (a) and the flare (b) at the Västerås plant (Växtkraft, 2006)

Digestate handling

The effluent from the digester tank is separated into a solid and a liquid fraction by two centrifuges (Figure 20a). The solid digestate has 25–30% TS. After the separation it is loaded directly into containers (Figure 20b) to be transported to the farmers.

(a) (b)

Figure 20: The centrifuges (a) and the containers for the storage of solid digestate (b) at the Västerås plant in Sweden (Växtkraft, 2006)

The liquid fraction from the centrifuges is initially stored in a process water buffer tank (see Figure 18) from which process water is either recycled to the turbo-mixers or discharged in a storage basin (Figure 21). In order to avoid loss of volatile substances to the atmosphere, mainly ammonia, the basin is covered. The liquid digestate, 2-3 % TS, is primarily used by the farmers as a fertilizer (Växtkraft, 2006).

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Figure 21: Storage basin of the liquid digestate fraction at the Västerås plant (Växtkraft, 2006)

Odour treatment

Odour reduction of 95% is achieved by the combination of two air treatment processes: a scrubber (Figure 22a) and a biofilter (Figure 22b). The scrubber increases the air humidity to 95 – 98 % which is necessary for optimal function of the biofilter. The scrubber also functions as pre-treatment by removing water soluble pollutants and thereby reducing the odour load to the bio filter.

(a) (b)

Figure 21: The scrubber (a) and the biofilter (b) at the Västerås plant (Växtkraft, 2006)

The inlet air to the biofilter is loaded with odour compounds which micro-organisms in the filter material use as a food source, breaking it down to carbon dioxide and water. Since the function of the filter is based on micro-organisms, it is vital that both moisture and temperature are kept at an optimal level, 30–60 % and at least 15°C respectively. In the cool winter months the air is heated before entering the filter. The bio filter consists of tree roots and is expected to be replaced every 3 - 5 years (Växtkraft, 2006).

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Output material

Outputs from the Västerås treatment plant at Sweden are given in Table 3.

Table 3: Outputs material from the MBT Västerås plant in Sweden

Capacity 23.000 tpa

Input material (a) Biowaste: 14.000 tpa Source-separated organic waste from households and institutional kitchens, 30 %TS

(b) Sludge: 4.000 tpa Liquid waste (grease trap removal sludge), 4% TS

(c) Silage: 5.000 tpa Ley crop, 35% TS

Output material Value Application of materials3,54 x106 m3 per annum

Biogas ~ 150 m3

(biogas)/t (waste) Equivalent to petrol 2,3 x106 L

upgraded to fuel

Digestate from AD plant Solid, 25 – 30% TS Liquid , 2-3% TS

6.500 15.000

tpa tpa

used as a fertiliser

Costs

Based on AGROPTI-gas project data (2006) the total investment cost for the project was calculated to EUR 16, 88 million and can be specified as follows:

Biogas plant EUR 8,67 million Gas upgrading plant, tank stations etc. EUR 3,75 million Biogas transition pipes etc. EUR 1,38 million Consultants EUR 0,65 million Energy costs during erection EUR 0,08 million Ground lease costs EUR 0,02 million Technical infrastructure EUR 0,77 million Containers EUR 0,05 million Silage storage area EUR 0,27 million Service car EUR 0,02 million Liquid digestate stores EUR 0,54 million Salaries EUR 0,63 million Miscellaneous EUR 0,05 million

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2.1.3 The Kaiserslautern MBT plant in Germany (Dry Anaerobic Digestion)

Overview

Kaiserslautern plant, located in Germany nearby the municipal landfill, is in operation since 1999. It is an MBT plant processing MSW and has a capacity of 20.000tpa. The core biological step involves dry thermophilic anaerobic digestion for treating MSW (source separated or grey waste2). The process incorporates a composting step to bio-stabilise the digestate from the anaerobic digester resulting in a range of variants. Process is operated on a commercial basis and is geared to produce biogas for use in gas engines, RDF and a bio-stabilised residue.

Figure 22: The Kaiserslautern plant in Germany (OWS, 2000)

The plant has been designed to generate 5.200 MWh per year electricity derived from the biogas. The plant consumption is about 700 MWh per year resulting in a net electricity production of 4.500 MWh per year (OWS, 2000).

The anaerobic system was provided by Organic Waste Systems (OWS). OWS markets the Dranco (Dry Anaerobic Composting) process as well as the Soridsep (Sorting Digestion Separation) integrated waste treatment system (Juniper, 2007; CIWMB, 2008).

The MBT plant in Kaiserslautern implements the Dranco process and more precisely the ‘full stream digestion’ process. In this configuration all waste <40 mm is sent for digestion after metals recovery (Juniper, 2005).

2 Grey waste is the residual organic fraction of MSW

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Process and Technology involved

The entire process is given in Figure 23.

Figure 23: Full stream digestion process in Kaiserslautern (Juniper, 2005)

Mechanical treatment

The waste is dumped in a bunker which is closed in order to limit odour emissions. Waste can be either source separated biowaste or grey waste. A walking floor at the bottom of the bunker is transporting the waste to the pre-treatment station. The pre-treatment station includes a shredder, trommel screens of 40 mm and an over-belt magnet. The oversize of the screen (waste fraction >40) mm is sent for utilisation as RDF and the output digestate stream is mechanically dewatered before being sent to landfill. The undersize, about 18.000 tpa, is sent to a 200 m³ buffer. The pre-treatment is functioning five days a week. The buffer allows the feeding of the digester during the weekend so that a continuous gas production is ensured. Before being pumped into the fermentation reactor the substrate is

33

mixed with digestate and a small amount of steam is entered in order to heat up the substrate to about 50°C. This fraction is mixed with digestate and with steam before it is pumped to the digester. The patented pre-digestion mixing process brings active anaerobes into contact with untreated waste (substrate) and the steam provides the heat to help maintain the process at thermophilic conditions. This premixing is essential in the Dranco process because the actual digester does not have a mixer (in contrast to many other designs) (OWS, 2000; Juniper, 2005).

Anaerobic Digestion

Figure 24: Dranco Digester (CIWMB, 2008)

A schematic presentation of the digester is given in Figure 24. The reactor is a downward plug-flow type reactor and has a total volume of 2.450 m³. In the reactor no mixing takes place.

Pre-treated organic material is pumbed to the top of the digester. If the waste consists of high amounts of easily degradable material, the degradation can cause liquefaction of some of the material in the reactor, preventing the plug flow principle with the risk that some particles will flow through thereactor without achieving the required retention time (Angelidaki et al., 2002).

Therefore, addition of recalcitrant ligno-cellulose material is usually recommended. The digestion takes place under thermophilic conditions, in the range of 50-55°C. The holding time in the digester is about 2-4 days but the waste can be recirculated for up to about 7-8 times, resulting in average SRT of up to about 30 days. The average dry matter content of the feed to the digester is reported to be 15-40%, which is significantly higher than that in wet systems (usually <15% TS). This gives a higher yield of biogas per ton of solids input to the digester than conventional wet digestion systems treating waste with a similar volatile biodegradable content. High solids digestion in an unmixed flow positively affects digestion efficiency due to minimisation of settling and foaming phenomena which occur during low solids digestion. The digested biomass is extracted from the bottom of the reactor by a special patented sliding frame, pulling material evenly from the reactor cross section into an extraction screw channel. The fermentation reactor itself is heated by a hot water spiral in order to minimise the amount of steam needed for maintaining the operating temperature in

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this range. The waste heat is used to evaporate wastewater. Due to the evaporation of the process water the installation is operating free of any effluent (OWS, 2000; Juniper 2005).

The gas production is about 110 Nm³ per ton of waste fed to the digester. The methane concentration is around 55% which is the expected biogas quality. The collected gas is stored in a 170 m³ gas bag and is used, together with landfill gas, to fuel biogas engines with a total installed electrical power of 1.400 kWe. The surplus of electrical energy is sold to the grid. A high temperature torch is installed in order to flare off excess biogas (OWS, 2000).

The digested residue is extracted and either recycled together with fresh substrate back into the reactor or pumped to a 20 m³ buffer in order to be dewatered. Before the dewatering process, the residue is dosed to a mixing unit and mixed with a polymer solution in order to improve the dehydration. A screw press is dewatering the residue to 50% total solids. The resulting press cake is sent to a post-composting system in order to produce a mature compost. The water effluent from the press is centrifuged and the effluent of the centrifuge is stored into a 200 m³ buffer before being evaporated by utilising the waste heat of the gas engines. The evaporating capacity is 1.100 L/h. The concentrate of the evaporator is mixed with the press cake and the centrifuge cake in order to be stabilised aerobically. The steam is sent to an acid scrubber which is capturing the evaporated ammonia and producing an ammonium sulfate solution. After the scrubber the steam is mixed with process air, and eventually clean air, and treated in an insulated container with a biofilter (OWS, 2000).

Output material

Outputs from the Dranco process of treating grey waste at Kaiserslautern plant in Germany are given in Table 4.

Table 4: Outputs based on a plant processing 20.000 tpa of grey waste, Kaiserslautern plant

Capacity 20.000 tpa Input material Grey waste


3,16x106 m3 Biogas

~ 158 m3(biogas)/t (waste)

utilised in gas engines to produce electricity

Cost

No data cost available.

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2.1.4 The Drseden MBT plant in Germany (Bio-drying)

Overview

The Dresden plant, started to operate in January 2001. The MBT Dresden plant utilises aerobic drying as the core biological technology to treat MSW into a dry stabilized product. The capacity of the plant is to treat 85.000 tpa of urban waste from the households in the region (number of affiliated residents 480.000). Process used is based on Herhof Dry-Stabilat Method, provided by Herhorf Gmbh.

Figure 25: MBT Dresden Plant (Herhorf 2010)

Herhof Dry-Stabilat method is developed as an economically viable alternative during which waste is dried using the heat from the biological degradation process (in Herhof degradation box), separating the incombustible waste stream and pelletizing the remaining waste (‘dry stabilat’ – organic material with caloric value 4,7 MWh/Mg) in order to be used as fuel in appropriate facilities (IUWMM, 2007; Juniper 2005; Herhof, 2010).


Different stages of Herhof Dry-Stabilate Method are given in Figure 26.

Waste reception

The mixed municipal solid waste is brought in the delivery area. There are 4 (four) handover shafts with a hydraulic closing system, in which the waste is unloaded directly into the bunker. A fully-automated delivery crane operates in the bunker area, which ensures both the optimum utilisation of the bunker volume by moving the waste and also that the downstream crushing machines are filled. The crushing takes place via slowly running rotary shredders. The shredding operation reduces the particle size to less than 200 mm. The shredded waste is transferred to a buffer bunker after initial separation of ferrous metals (IUWMM, 2007; Juniper, 2005).

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Figure 26: Herhof bio-drying process at Dresden plant (Juniper, 2005)

Biological drying

A second process crane takes material from the buffer bunker to load whichever biodryer (also named composting boxes or Herhof-Rotteboxes) is ready for refilling. The same crane is used to remove and replace the bio-dryer lid and to unload the bio-dried material. Each of the composting box has an effective volume of approximately 600 m3 and can take approximately 280 tons of waste. During the filling process, the level of the composting box is automatically monitored by the crane system. Once the composting box is full, the crane lifts the lid and closes the box rendering it air tight. Due to the fully automated operation no manual activities are required in the bunker and decomposition hall (IUWMM, 2007).

The waste remains in the bio-drying boxes for seven days under aerobic conditions, but no water is added to the waste so that full composting of the waste does not take place. No external heat is used. The air flow is introduced through a floor plate and is automatically adjusted from online carbon dioxide and temperature measurements. The temperature in the box rises to about 50oC in the first half day and is held between five and ten days (typically seven) depending on individual plant optimisation (Juniper, 2005). The removed condensate is fed to the wastewater treatment plant. The mass is reduced by up to 30% and residual moisture content is less than 12% (IUWMM, 2007).

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SRF Production

The bio-dried materials are conveyed to a refining mechanical treatment stage where 3 (three) basic fractions are distinguished: (a) Solid Recovered Fuel (SRF), (b) Ferrous and non-ferrous metals and (c) Inerts (stones, sand, glass).

An important characteristic of the material separation, especially the separation of the light-weight fraction, is that due to the well positioned use of several air classification and sieving processes matched to each other, a very precise separation between light (combustible) and heavy waste components (metals, inert materials) is achieved and thus a high fuel quality is guaranteed.

The remaining ferrous and non-ferrous constituents are removed from the dry, light weight material using magnetic and fluidised bed separators. This treated light-weight fraction now consists of virtually 100% combustible materials such as wood, paper, plastics, textiles and organic matter. The average composition of this SRF fraction is shown in Table 5.

Table 5: Composition of SRF produced at Dresden plant in Germany (Juniper, 2005)

Content Units Dry weight analysis, %

Contaminants (stones, glass, ceramics, metals) % dry wt. 1

Renewable substances (carboard, paper, textiles, wood, organic) % dry wt. 65

Plastic % dry wt. 9

Other fossil fuel combustibles (synthetic fabrics, rubber, laminates) % dry wt. 25

Calorific value MJ/kg 15 - 18

Moisture content % 15

Ash content % 20

Due to its dry consistency, SRF is very easy to store and can thus be used as a secondary fuel in industrial processes when it is required and independent of the amount of waste generated. The removal of heavy metals associated with the removal of metal parts and batteries is of decisive importance for the use of SRF as a secondary fuel. It reduces the heavy metal load by up to 90% compared to that of residual waste.

The Stabilat (organic material) is passed over 4 (four) pelleting presses to form around 20 mm sized pellets for reuse in Methanol plant SVZ (Sekundaerrohstoff – Vervwertungs-Zentrum). In the SVZ the pellets are mixed with a small quantity of coal and then are

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supplied to gasification reactors. At a pressure of 25 bar and temperatures above 1000 °C they form synthesis gas. The synthesis gas produced primarily consists of carbon monoxide, carbon dioxide and hydrogen. Following thorough cleaning, the synthesis gas passes into a plant that produces methanol. At a pressure of 45 bar, a temperature of 500°C and in the presence of a catalyst, the gas constituents react to form methanol. Annually, approx. 16.600 tons of methanol are produced in the SVZ using the 42.500 tons of pelleted SRF produced in the Dresden Waste Recycling Plant 15% of which is coal. This equates to 21,5 million litres. This can then replace around 16,5 million litres of petrol (IUWMM, 2007).

Output material

Outputs from the Dresden plant in Germany are given in Table 6.

Table 6: Outputs of processing 85.000 tpa mixed MSW at Dresden plant (Juniper, 2005)

Capacity 85.000 tpa

Input material mixed - MSW

Output material tpa Application of materials

SRF 42.500 co-fuel Ferrous & Non-ferrous metals 4.250 can be recycled Residues 12.750 landfilled

Wastewater Not reported cleaned and recycled in the plant as cooling water

Off-gases (including moisture) 25.500 Treated before exhausting

Cost

The investment cost (2001) was reported to be about EUR 22 million (IUWMM, 2007).

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2.1.5 The Montanaso MBT plant in Italy (Bio-drying)

Overview

The Montanaso plant (Figure 34) is designed to treat residual MSW in a single process module. Ecodeco has developed and built the MBT process utilizing aerobic drying for treating MSW. The process, which is called ‘Biocubi’ drives off moisture from the waste by using its biological activity. The ‘dried’ output is passed through a number of screening stages to produce an SRF, which is currently being used as a co-fuel in cement kilns and a fluidised bed boiler in Italy.

The plant has a capacity of 60.000 tpa and a building footprint of 80m x 20m x 14m high. It was constructed in 1999 and started operations in June 2000 taking the MSW, after source segregation (kerbside), of glass, paper, plastics and in some cases the organic waste fraction from districts in Milan.

Figure 27: The Montanaso plant in Italy (Juniper, 2005)


The process takes place in a fully enclosed building where negative air pressure is maintained to minimise environmental impacts. Waste is unloaded from refuse collection vehicles into a tipping pit which takes place in a controlled environment with water sprays and airflow management to control emissions to the atmosphere. The reception pit has sufficient storage capacity to contain more than one (1) day supply of waste and has an elevated perforated floor. Waste is picked up automatically by a programmable crane operated from the control room and transported to a shredder. The shredded waste (exit size 200-300 mm) is then transported into a buffer storage pit to produce a homogenous material. The material is then moved by crane to the aerobic fermentation area where the waste is placed in contiguous windrows. The area is divided into a virtual grid on the computerised control system which controls the crane movements and records when and where materials have been stockpiled.

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According to the pre-set computer programme the crushed and homogeneous material is formed into heaps of up to six (6) m height. The perforated floor and ductwork system allows air which is sucked in by fans, to be drawn through the waste and the void beneath the raised floor. This air is transferred to the bio-filters (a bed of woody material) mounted on the roof which neutralises odours before release. The air flow is controlled automatically by a computer system to ensure optimum temperature range (50-60oC) is maintained so that material is stabilised, sanitised and practically odour free in 12-15 days. By providing air the activity of micro organisms is stimulated and heat is released, causing the evaporation of water present in the waste (bio-drying). The most easily putrefied portion of the organic waste is decomposed, whilst the remaining material has a heating value of between 15 MJ/kg and 18 MJ/kg.

Once the material has been aerated for 12-15 days it is automatically transported by crane to the recycling and recovery process area where the dried waste is separated into fractions by using a combination of sieving, weight separation and metal extraction and secondary shredding. The stabilised waste fraction (approx 50%) can be landfilled or sent for conversion into energy as a secondary fuel. For use as Solid Recovered Fuel (SRF) the material is shredded to a suitable size i.e. dimension of around 100-150 mm. In Figure 28 process flow diagram is presented.

Figure 28: Process flow diagram of Montanaso plant at Italy (Juniper, 2005)

Output material

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Table 7 gives the quantities of outputs that can be obtained from the Ecodeco process. This gives some indication of the amounts from the various streams that have to be managed if this process is implemented for treating similar types of waste.

Table 7: Outputs of processing 60.000 tpa MSW at Montanaso at Italy (Juniper, 2005)

Capacity 60.000 tpa

Input material MSW


SRF 30.000 co-fuel in cement kiln or fluidised bed boilers

Ferrous & Non-ferrous metals 1.800-3.000 recycled

Residues 12.000 landfilled

Wastewater 600 sent to a nearby sewage treatment plant

Off-gases 14.400 treated in bio-filter before exhausting to atmosphere

Cost

No cast data available.

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2.1.6 The Tufino MBT plant at Italy (Composting)

Overview

The reference plant at Tufino (Italy), in which VKW systems are being used, produce a bio-stabilised output through a composting process, which is being used to treat approximately 135.000 tpa of mixed MSW in MBT configurations and various bio-wastes. The end product is further used as a soil improver or landfilled. The Tufino plant is shown in Figure 29. The composting process uses a patented compost turning machine which is called as the ‘CTM’ system.

Figure 29: The Tufino plant in Italy (Juniper, 2005)


The process involves a pre-treatment stage which is housed in separate building and a biological stage. During the mechanical stage two fractions are produced:

• One that is more than 100mm. This fraction is baled as RDF (Figure 30) and

• One fraction that is less than 100mm and is sent for the composting process

The waste material to be composted is loaded into bays that are aerated from below and housed in a closed building. It takes 4-6 weeks to complete this process and a further three weeks for the maturation of compost. The compost is turned automatically by the ‘CTM’ system, which is essentially a bucket wheel and conveyor system, which incorporates compost irrigation that traverses each composting bay about five times

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during the initial 4-6 weeks cycle. At the Tufino plant, no further mechanical separation of the bio-stabilized materials is carried out and this output is being landfilled.

Figure 30: Baled RDF at Tufino plant in Italy (Juniper, 2005)

Figure 31: Part of the ‘CTM’ compost turning machine at Tufino plant in Italy (Juniper, 2005)

Leachate from the composting process is collected and re-circulated as process water. The off-gases from the composting process and the fugitive emissions from the mechanical separation stage are collected and sent for treatment. The off-gases are first scrubbed to reduce the levels of ammonia (NH3) and then passed through a biofilter

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before being emitted to the atmosphere. Moreover, the off-gases from the process and the fugitive emissions from the mechanical pre-treatment plant were piped to separate scrubbers before they were treated by bio-filtration.

Data concerning indicative energy requirements for a VKW composting plant are presented in Table 8.

Table 8: Indicative energy requirements for a VKW composting plant (Juniper, 2005)

Capacity 150.000 tpa

Input material mixed-MSW and biowaste

Equipment kWh

Pre-processing equipment 1.900 Composting 900 Waste gas extraction & gas cleaning system 3.500

Miscellaneous 200

Total 6.500

As is evident from the data, the process is a net energy consumer.

Output material

Table 9 presents projected output from a VKW plant processing 150.000 tpa of MSW.

Table 9: Projected outputs of processing 150.000 tpa MSW from a VKW plant (Juniper, 2005)




Ferrous metals 3.750 can be recycled

Rejects 54.450 utilised as RDF

Bio-stabilized output (including moisture) 75.000 landfilled

Leachate none Recycled and re-used as process water

Waste gases 76.350 treated in scrubbers and bliofilters

Water addition 59.550

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Costs

According to Juniper study (2005), a full breakdown of capital and operating costs for a plant processing 150.000 tpa is presented in Table 10.

Table 10: Indicative costs for VKW MBT process for 150.000 tpa mixed–MSW (Juniper, 2005)



Cost EUR* Application of materials

Capital cost 14,70 can be recycled

Civil works 11,84 utilised as RDF

Operating costs * 3,70 landfilled

Operating costs per ton input* 25,03 Recycled and re-used as process water

* based on 2005 currency 1GBP=1,48 EUR ** cost include depreciation of 10% on machinery and 5% on civil works

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2.1.7 The Erbenschwang MBT plant in Germany (Composting)

Overview

The Erbenschwang MBT plant (Figure 32) is located at Bavaria in Germany and has first operated on 1997 while on 2005 the plant was upgraded expanding its capacity. Process used is provided by Sutco company (http://www.sutco.de/). It is an MBT process for treating MSW, based on a waste composting system, which is called ‘Biofix’. The main outputs from the process are an RDF and a bio-stabilised output, which is landfilled.

The plant that operated from 1997-2004 had a capacity of 22.000 tpa. At 2005 the plant was upgraded in order to treat all of the residual MSW and biowaste arising from Weilheim-Schongau county (total capacity to 40.000 tpa) and to meet the German regulations on bio-stability of residues going to landfill (German 30th BImSchV regulations). The original plant utilised a single pre-processing line and six composting bays. The new plant also uses a single pre-processing line but with eight bays for intensive composting and a further six bays for post-maturation. Each bay has a capacity of approximately 450 m3.

The land-take of the 40.000 tpa plant at Erbenschwang is 8.448 m2. This translates to a footprint of 0,21m2/tpa. Despite the need for compost maturation, the land-take is low compared with plants that require a considerable land area for windrow composting and maturation (Juniper, 2005).

Figure 32: The Erbenschwang MBT plant in Germany (http://www.anlagen.ebegleitschein.com/?page_id=116 ; Juniper, 2005)

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Schematic presentation of process used from 1997 to 2004 and after the upgrade of the plant on 2005 is given below.

(a) The process operated from 1997-2004 at Erbenschwang, Germany (b) The new process at Erbenschwang, Germany from 2005

Figure 33: Flow diagram of Erbenschwang MBT process in Germany, (1997-2004 & 2005) (Juniper, 2005)

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Mechanical treatment

Waste is received in a flat bunker. The waste is transported by wheel loader to a crusher, which reduces the size of the incoming materials to about 300 mm. The crushed waste is conveyed to a sieved drum that separates it into two fractions of particle sizes: >80 mm and <80 mm. The >80 mm fraction is passed through an electromagnetic separator which recovers ferrous metals. Non-ferrous metals are not separated from the waste stream at this plant as it is not considered cost effective due to the high degree of household separation conducted in Germany. After metals recovery, the remaining materials are baled and sent for use offsite as an RDF in an incineration plant. Ferrous metals are also recovered from the <80mm fraction before it passes to a homogenizing mixing drum to which water is added (Juniper, 2005).

Figure 34: The Erbenschwang MBT plant in Germany (Juniper, 2005)

Biological treatment

The homogenized materials are sent for composting, which is carried out in open-top bays as shown in Figure 35. Open-top bays are housed in an enclosed building and are aerated via a combination of pressure aeration, for 4-5 hours per day, and a suction system (suction aeration is the predominant method of aeration used for the remainder of the day). The waste is loaded by an automatic loading and turning machine and is composted for 30 to 40 days during which time the waste is turned about seven times within each bay by the mobile “Biofix” windrow turning device (Figure 36). During turning, fresh or process water can be added to the waste. After the intensive composting

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step, the materials are transferred to another set of bays where they undergo maturation for a further 30-40 days. The bio-stabilized output for the maturation bays is separated by star screen into three fractions. The <25 mm fraction is sent to landfill without any further processing. The 25-50 mm fraction passes to an air density separator, which separates the light organics (fluff) from the mostly inert materials. The fluff and >50 mm fraction is marketed as an RDF. The inerts are also sent to landfill (Juniper, 2005).

Figure 35: The composting bays at Erbenschwang plant in Germany (sutco, 2010)

Figure 36: The mobile “Biofix” windrow turning device at Erbenschwang plant in Germany (sutco, 2010)

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Output material

Table 11 presents output material from Erbenschwang plant in Germany processing 40.000 tpa of MSW.

Table 11: Projected outputs of processing 40.000 tpa MSW from Erbenschwang plant in Germany (Juniper, 2005)

Capacity 40.000 tpa

Input material mixed-MSW


RDF (>80mm from Input separation) 16.000 could be upgraded for use as a fuel

RDF (>50mm from refining of the outputs from the maturation plant) 3.680 could be upgraded for use as a fuel

Ferrous metals 1.000 recycled

‘Fluff’ 280 could be upgraded for use as a fuel

Composting losses 6.040 treated in bliofilters and in Regenerative Thermal Oxidation

Bio-stabilised output 13.000 sent to landfill

Costs

Juniper reported that the current gate fees are EUR 130 per ton and EUR 110 per ton, including and excluding landfilling respectively. The cost includes the operation of the regenerative thermal oxidiser RTO (Juniper, 2005).

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2.1.8 The Ano-Liosia MBT plant in Greece (Composting)3

Overview

The Ano-Liosia Integrated Waste Management Scheme is situated in the Western suburbs of Athens in Greece. The entire processing plant comprises of a landfill, an industrial unit of incineration of hospital waste and an MBT scheme (Figure 37) for waste. The latter includes a large composting facility.

The MBT part for mechanical recycling of waste is the largest one in Europe and one of the largest in the world. It receives waste from the Attica region. Currently, the population of Attica exceeds 4,5 million people. The plant was designed and constructed after an international tender, which was procured by the Association of Communities and Municipalities of the Attica Region (ACMAR). ACMAR is the Public Authority responsible for the management (treatment, recycling and disposal) of Solid Waste of about 95% of the population of the Attica Region. The construction of the factory of Mechanical Recycling was funded by the European Union and by the Greek government.

• 1,200 tons/day of MSW

• 300 tons/day of sewage sludge generated from the Wastewater Treatment Plant of the Attica Prefecture

• 130 tons/day of green waste (leaves) and tree branches

Figure 37: The Ano-Liosia MBT plant at Greece

3 Note: Unless otherwise stated, information (including the photos) concerning the Ano-Liosia plant has been written by Dr. Evangelos Kapetanios for the purposes of this report. Dr. Kapetanios is the Director of the Development Department of ACMAR

Composting unit Mechanical separation unit

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Useful products that is produced in this factory is compost, refuse derived fuel (RDF), ferrous metals and aluminium. The by-products of the whole process are directed to the Ano-Liosia landfill which is located nearby.


The MBT consists of the following components:

A. Entrance Facilities – Weighting of waste, Unit for the Reception of Waste

B. Unit of Mechanical Separation

C. The Composting Unit

D. The refinery unit

E. Curing Unit

F. Packaging Unit

G. Wastewater Treatment Unit

H. Unit for Treatment of Air Emissions from the Composting Unit

I. Unit for Treatment of Air Emissions from the Mechanical Separation Unit

Description of the above mentioned unit is given below.

A. Unit for the Reception of Waste, Entrance Facilities – Weighting of waste,

In the waste reception unit (Figure 38) receiving of mixed MSW and the unloading of trucks take place.

The unit has three (3) waste reception facilities (i.e. lowered reservoirs). In each reservoir eight (8) garbage trucks can unload waste simultaneously. Therefore, in total there are 24 positions from where waste can be unloaded simultaneously.

Each waste reception facility comprises the following:

Figure 38: Waste Reception Facility at Ano-Liosia in Greece

i. One crane and one electrical hook which feeds with waste the waste collection hopper (Figure 54)

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ii. Three (3) hoppers for receiving waste. Each hopper corresponds to a conveyor, upstream of which there is a device that rips the bags that contain waste

iii. The three (3) aforementioned devices that rip the waste bags

iv. One receptor of grass, greens and tree cuttings into which the trucks unload their content. A mechanically operating loader feeds the shredder with leaves and tree cuttings

v. Three (3) receptors of sludge (i.e. elevated reservoirs) into which the trucks unload sludge

Figure 39: Waste reception trench at Ano-Liosia in Greece

B. The Mechanical Separation System

The objective of the unit (Figure 40) is the separation of the incoming mixed municipal solid waste in order to produce different fractions which will be further treated according to their nature for the production of marketable products.

Figure 40: Mechanical separation unit at Ano-Liosia in Greece

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This unit includes the following components:

1. Three (3) lines of mechanical separation; each line is fed with waste from its respective receptor. Each line of mechanical separation consists of:

• A primary rotating screener

• A secondary screener

• Electrical magnets

• A bioreactor in the last compartment of which there is a tertiary screener

• Conveyor belts

2. Line for the dry fraction of waste consisting of:

• Four (4) ballistic separators (Figure 41a) in order to sort out the light weight fraction which is then shredded, the biodegradable fraction which is fed to the mixer and the remaining residues

• Four (4) shredders of the light weight fraction of waste; each shredder is fed by a conveyor belt

• Electrical magnet ballistic separators

• Conveyor belts

3. The Refuse Derived Fuel (RDF) line which is composed of the following components:

• One (1) compressor which is fed by the shredded light weight waste through conveyor belts. The light weight fraction is compressed and packaged

• Conveyor Belts

4. The Residuals Line which has:

• One (1) silo for storing the ferrous metals which are then fed to the compressor of ferrous metals

• One (1) compressor for compressing the ferrous metals into cubes

• Conveyor belts

5. The Aluminium Line which consists of:

• A layout for aluminium recycling which employs eddy currents in order to recover aluminium material from the rest

• One (1) silo where the recovered aluminium is stored. Then it is fed to a compressor

• Aluminium compressor where the recovered aluminium is formed into cubes

• Conveyor belts

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6. The homogenization line with:

• Three (3) homogenization layouts; each one corresponds to one mechanical layout and to one sludge reception system. Each layout is fed with waste through the exit of the corresponding bioreactor (after the tertiary screening, with the screener which is incorporated in the bioreactor). Furthermore, it is fed with sludge from the respective sludge receptor and with shredded tree cuttings and leaves.

• Conveyor belts (Figure 41b)

(a) Ballistic separators

(b) Elevated conveyor belt Figure 41: Components of mechanical separation unit at Ano-Liosia in Greece

Furthermore, the Factory of Mechanical Recycling of Waste has equipment which assures the protection of the environment and of the personnel. This equipment includes cyclones, air ducts and air ventilators for the suction of air.

C. The Composting Unit

The composting unit of Ano-Liosia is presented in Figure 42.

Figure 42: View of the building with the composting tunnels at Ano-Liosia in Greece

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The composting unit employs the technology of tunnel composting to treat the organics of Municipal Solid Waste sorted out through the Mechanical Separation System, sludge and green waste.

A view of the composting tunnel is given on Figure 43.

More specifically, the unit comprises of the following:

Figure 43: View of composting tunnel

a. Three (3) feeding lines: each line feeds 16 composting tunnels with biodegradable material. The total number of composting tunnels is 48. The transportation of the biodegradable material is conducted via conveyor belts. The tunnels are fed with the following material:

• The mixture exiting the homogenization unit

• The biodegradable fraction that is recovered from the ballistic separator

• The recycled material from the screening process

b. The recycled compost material. As it will be described later, the end compost is screened. The reject stream is then recycled through an elevated conveyor back to the composting unit, as a product that has not been fully composted. It is split into three (3) streams in order to be fed to the three (3) lines of the composting unit.

c. Forty-eight (48) parallel and horizontal composting tunnels (Figure 43) made of concrete. The compost mix is placed inside the tunnels up to a height of 2.1 m.

d. Six (6) electrical agitation devices. Each couple (2) of agitation devices is used to mix the sixteen (16) composting tunnels, corresponding to one feeding line. Each day the agitator agitates four (4) tunnels. Overall, twenty-four (24) composting tunnels are agitated each day. As the agitators proceed inside the composting tunnel they displace the compost mix forward towards the exit of the composting tunnel. Therefore, every two (2) days, the agitator completes one displacement of the compost mix towards the exit of the compost tunnel. This way the compost mix is gradually ‘pushed’ towards the exit of the composting tunnel. The residence time of the compost mix inside the tunnel is forty-six (4)6 days. Each agitation device is

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equipped with sprinklers for providing water to the compost mix. This is important in order to ensure that the compost mix will not dry out from the high temperatures that develop inside the compost heap. This way the moisture level of the mix is controlled and maintained at desirable levels.

e. Thirty six (36) blowers provide the required air for the composting process to take place. This corresponds to 12 blowers for each feeding line of the composting unit. Aeration is achieved (apart from agitation) with air suction from the floor of the compost tunnels. The tunnel floor has a grid; air is sucked through aeration pipes placed beneath the grid and ends up in a main pipe. In total there are six (6) main pipes; the air that is sucked is fed to each central pipe through eight (8) tunnels. Therefore, 2 main pipes correspond to each feeding line of the composting unit. At the floor of each tunnel there is a collection pipe in order to collect the produced leachate. The top part of the collection pipe is perforated so that leachate can enter inside it. All the collection pipes converge to a centralized pipe which ends up at the wastewater treatment unit of the facility. At the end of each composting tunnel there is a conveyor belt which has been installed vertically to the composting tunnels. This conveyor belt transports the end compost to the screening unit.

f. Shredder for shedding the green waste (Figure 44)

Figure 44: Shredder employed for shredding green waste at Ano-Liosia in Greece

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D. The Refinery Unit

The compost from the tunnels is fed to the refinery unit (Figure 45) through the conveyor belt of the composting tunnels. The compost is received at the reception unit. In the reception unit the compost is agitated and grinded. Agitated screws with blades speed up the simultaneous feeding, distribution and dosing of the material.

Two (2) rotating drum screens are utilized in order to produce three (3)

Figure 45: Refinery unit at Ano-Liosia in Greece

different streams of output material. The finest material is directed through a conveyor belt to the waste residuals. The coarser material, which is mainly comprised of material that has not been fully composted, is directed to a densimetric table. The middle sized stream is directed to another densimetric table.

The screening unit has in total three (3) densimetric tables. In two (2) of these tables, the separation of the middle sized stream takes place. The separation is achieved through air and through ballistic separation. Each one of the two (2) densimetric tables produces 3 different streams. The lightest and heaviest streams are directed through conveyor belts to the residual waste stream that is disposed. The third stream is directed to two flat, vibrating screens for further refinement.

Figure 46: Recycling of coarse material from the refinery unit to the composting unit at Ano-Liosia

As mentioned earlier, the third densimetric table receives the coarse material from the rotating drum screens for further refinement. This third densimetric table also produces three (3) new streams: the lighter and heavier streams go to the waste residuals in order to be disposed off; the remaining stream is directed through an elevated conveyor back to the composting tunnels in order to be composted again (Figure 46).

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Finally, the screening unit has a vibrating screen that produces two (2) streams; the coarse stream is directed to the waste residuals while the finer one goes for curing after it passes the stage of magnetic separation. 85% by weight of this stream is directed to an open-air curing place and the other 15% to a curing warehouse.

E. The Curing Unit

The curing unit consists of the open-air curing system and the warehouse where curing takes place.

In the open-air curing place, the screened compost is placed into windrows with the use of loaders. The maximum height of the windrows is 3.5 m. The residence time of the compost in the windrows is 1 month. Curing is essential in order to fully stabilize the end compost. 85% of the compost is cured in this facility (Figure 47).

Figure 47: Open-air windrows where 85% of the compost is cured at Ano-Liosia in Greece

Inside the warehouse where the compost is cured, the material is placed in windrows. The warehouse protects the compost from the outside environmental conditions. The windrows have a maximum height of 3.5 m. The residence time is 1 month. 15% of the compost is cured in this installation (Figure 48).

Following the curing stage, the loaders feed the packaging unit, in order to package the end compost.

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Figure 48: Warehouse where curing of 15% of the compost takes place at Ano-Liosia in Greece

F. The Packaging Unit

The packaging unit consists of the following:

(a) Smoothening sub-unit for ameliorating the texture of the end product

(b) Sub-unit for placing the end compost inside bags and for sealing these bags

(c) Sub-unit of palletizing the packaged end compost

G. The Wastewater Treatment Unit

The wastewater that is treated in this unitis generated from:

The reception unit for the trucks

The unit of mechanical separation

The composting unit (leachate from thefloor of composting tunnel)

Wastewater from all the sanitationareas of the factory

Figure 49: Wastewater Treatment Unit at Ano-

Liosia in Greece

A two-stage aerobic biological process takes place for the treatment of wastewater (Figure 48). The final effluent is used for irrigating the grass facilities of the installation.

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H. Unit for Treatment of Air Emissions from the Mechanical Separation Unit

This unit treats the air emissions resulting for the Unit of Mechanical Separation. The treatment unit consists of three (3) biofilters for treating air exhausts from the unit of mechanical separation. Each biofilter corresponds to one reservoir of the unit of waste reception and to one line of mechanical separation. Biofilters are made up of end compost.

I. Unit for Treatment of Air Emissions from the Composting Unit

The unit consists of six (6) sub-units for the treatment of air emissions resulting from the composting process. The treatment is performed by employing chemical means; more specifically chemical scrubbing is performed (Figure 50). Each sub-unit is fed by one of the 6 main pipes that collect the air exhaust from the composting unit. Two sub-units correspond to one line from the composting unit. Each sub-unit consists of:

i. One (1) tower for the removal of NH3 with the addition of Η2SO4.

ii. One (1) neutralization tower where NaOH is added

iii. One (1) tower for controlling the pH value and the Red/ox potential through the addition of hypochloric acid

iv. Six (6) chimneys

Figure 50: Scrubbers Employed for Air Treatment at Ano-Liosia in Greece

Furthermore, the Ano-Liosia plant has supplementary facilities (e.g. fire fighting facilities, water and acid reservoirs etc), green installations, road facilities (e.g. roundabouts) and control buildings for most units. Each building is controlled through its Local Control Building. However, the whole operation of the facility is controlled from the Main Administration Building.

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Output material In Table 12 data concerning output material of the MBT plant at Ano – Liosia is presented.

Table 12: Outputs from Ano – Liosia MBT plant in Greece (Eleftheriades, 2010)

Capacity

MSW: 440.000 tpa

Sewage sludge:110.000 tpa

Green waste: 48.000 tpa

Input material mixed-MSW including sludge and green (garden) waste


Compost 132.000 could be used as soil improver

RDF 129.000 could be upgraded for use as a fuel

Ferrous metals and non-ferrous metals 45.000 recycled

Rest 122.000 sent to nearby landfill

Costs

Estimated investment cost is approximately EUR 50 million.

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2.1.9 The Edmonton BT plant in Canada (Co-composting)4

Overview

Opened in 2000, the 38.690m2 co-composting facility of Edmonton in Canada (Figure 51) is where all MSW that is not recyclable—200.000 tpa—ends up. The organic fraction of MSW is mixed with 100.000 tpa (wet) of sewage sludge which is received from the Wastewater Treatment Plant of Edmonton in a three-week process of mixing, screening and composting. At the end of the process from 50.000 to 70.000 tpa compost is created and sold. The composting facility has been constructed by the German company COMP-ANY. The operator of the composting plant is Earth Tech Canada Inc. The Edmonton composting facility provides an affordable long-term solution for two waste streams - municipal solid waste and biosolids. With its combined recycling and composting programs, Edmonton diverts about 60 percent of its residential waste away from landfills. The facility receives thousands of visitors from around the world, creating economic spin-offs for local business. (http://www.edmonton.ca/for_residents/CompostingFacility.pdf).

Figure 51: Panoramic View of the Edmonton Composting Facility in Canada

(http://en.wikipedia.org/wiki/File:MRF_Composter03.jpg)


The entire process that takes place in the plant includes: (A) tipping, (B) sludge dewatering, (C) mixing, (D) screening, (E) composting, (F) compost refining and (G) odour treatment. The above mentioned processes are completed in different parts of the plant as shown in Figure 52.

4 Note: The above information, unless otherwise stated, has been based on material provided by the company COMP-ANY which was responsible for the design and construction of the Edmonton composting plant

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Figure 52: Flow diagram of Edmonton waste processing plant in Canada

(C) Mixing

(D) Screening

(G) Odour treatment (A) Tipping

(B) Sludge dewatering

FG

E

DC

A

(E) Composting

(F) Compost refining

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A. Tipping

In particular, the oversized items such as furniture and the house-hold hazardous waste such as propane tanks are manually removed (Figure 54). Tires and propane tanks are recycled. Most of the other oversized material is landfilled. Then the front end loaders push the remaining waste into concrete hoppers below the tipping floor. From there waste is pushed into large hollow cylinders known as the mixing drums (Figure 55).

Solid waste is received in the facility by garbage trucks which unload the waste materials onto a large indoor concrete pad. This floor is known as the tipping floor; it occupies a total area of 4,000 m2 (Figure 53) and it is where the separation process of the solid waste takes place.

Figure 53: View of the Tipping Floor where Solid Waste is Collected of the Edmonton Composting Facility in Canada

Figure 54: Manual Selection of Oversized

Waste of the Edmonton plant Figure 55: Placement of Remaining Waste Inside

the Mixing Drums of the Edmonton plant

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B. Sludge dewatering

Sewage sludge is pumped to the facility through a pipeline and is put into centrifuges where a spinning action like a washing machine on spin cycle, “dewaters” sludge (Figure 56). The biosolids are stored in a large hopper (Figure 57) and are then injected into the mixing drums together with the residential solid waste.

Figure 56: Centrifugal Pumps Utilized for Dewatering Sewage Sludge of the Edmonton

Composting Facility in Canada

Figure 57: Storage Hopper of the Edmonton Composting Facility in Canada

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C. Mixing

Hydraulic rams push the waste inside one of five parallel rotating mixing drums (Figure 58). Each drum is 74 m long and has a diameter of 4,9 m. Biosolids (sludge) are injected into the drums together with the solid waste. Composting begins as the materials tumble together while travelling for 1-2 days from one end of the drum to the other.

Figure 58: View of one of the Mixing Drums of the Edmonton Composting Facility in Canada

D. Screening

From the mixing drums the material is conveyed using conveyor belts (Figure 59) into two rotating trommel screens which remove larger materials. This material consists mainly of plastics and textiles and is diverted to landfills. Then the ferrous material is removed with magnets which are placed above the conveyor belts. The ferrous material that is removed is recycled. The biodegradable material is then conveyed through conveyor belts to the aeration building in order for the composting process to take place.

Figure 59: Conveyor Belts of the Edmonton

Composting Facility in Canada plant

Inside view

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E. Composting

The aeration building is the largest stainless steel building in North America. Inside the building the high rate aeration is performed in suitable bays where the compost mix is placed (Figure 60). In total there are 18 bays having the following dimensions: 50 m long, 8 m wide and 3m high. The residence time of the compost mix varies between 14-21 days. The material is agitated through mobile augers which pass through the compost mix (Figure 61). The augers also gradually displace the material through the compost bay. Agitation allows the required oxygen to be transferred to the whole of the compost mix. Moreover, the auger has a sprinkling system in order to supply the required oxygen so that the compost mix is not left to dry. The temperature inside the compost mix exceeds 55ºC, thus destroying the potentially harmful bacteria.

Figure 60: Aeration Building of the Edmonton Composting Facility in Canada

Figure 61: Mobile Compost Augers of the Edmonton Composting Facility in Canada (http://www.edmonton.ca/for_residents/CompostingFacility.pdf)

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F. Compost refining

The compost exiting the high-rate stage is conveyed from the aeration building to the screening unit in order to refine the compost from the larger particles (Figure 62).

Figure 62: Compost Refining System of the Edmonton Composting Facility in Canada

(http://www.edmonton.ca/for_residents/CompostingFacility.pdf)

Finally, the maturation phase takes places. The compost is placed in windrows and is left to mature for a period of 4-6 months. It is then used by farmers, landscapers, nurseries and oilfield reclamation companies.

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G. Odour treatment

Figure 63: Biofilters of the Edmonton

Composting Facility in Canada

The air inside the composting facility is hot, humid and odourized. Odourized air is produced during the composting process inside the aeration building and is exhausted through biofilters located outside the aeration building (Figure 63). The biofilters consist of one-meter layers of mature compost, woodchips and bark and effectively remove the unpleasant odours created from the composting process (www.comp-any.com).

Output material

In Table 13 data concerning output material of the Edmonton Composting Facility in Canada is presented.

Table 13: Outputs of the Edmonton Composting Facility in Canada

Capacity MSW: 200.000 tpa (that is not recycled) Sewage sludge:100.000 tpa

Input material MSW and sludge


Compost 60.000 is used as soil improver

Costs According to 2003 data of construction company, capital cost was approximately EUR 85 million (2003 currency 1USD=0,85EUR).

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2.1.10 The Botarell plant in Spain (Composting)

Overview

The Botarell composting system is located in the Baix Camp area of the province of Tarragona, in the north-east of Spain. The Baix Camp area is part of a Catalonian administrative division and provides centralized services to the nearby Municipalities. The composting system receives household biodegradable waste from 50.000 households (145.000 inhabitants) as well as biodegradable waste from hotels, schools, markets and industries. The biodegradable fraction of waste is collected through a house-to-house kerbside separate collection and is transported by lorry to the composting plant, which is located near the Botarell village.

The Botarell composting site (Figure 64) started its operation in June 1997. During the first 2,5 years of operation approximately 7.000 tons of kitchen and 3.000 tons of garden waste were composted, producing 900 tons of compost. However, the quantities of biodegradable waste received at the plant have been increasing with time, as more municipalities have undertaken separate collection (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf).

Figure 64: Botarell Composting System in Spain5

5 Note: The pictures have been taken by the NTUA team during the site visit that took place in Botarell, at Spain

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The Botarell Composting Scheme is considered one of the most successful composting sites in Spain. Apart from the technical excellence, one of the main reasons of success was the participation of a high number of individuals in the separation of the biodegradable fraction of waste. This was achieved through appropriate Catalonian legislation which imposes separate collection for Municipalities greater than 5.000 inhabitants and through an intense publicity campaign which included door-to-door distribution of leaflets and brochures, the organization of a bus road show and of radio and press campaigns (http://ec.europa.eu/environment/waste/publications /pdf/compost_en.pdf).


The technology that is employed is that of aerated static piles. The annual design capacity of the plant is 30.000 tons of biodegradable kitchen waste and 5,000 tons of garden waste. These two fractions of organics are mixed and composted in the static piles for a period of 2-3 weeks. Then the mixture is screened through an 80 mm diameter trommel screen. The rejected stream is sent to landfill and the screened fraction is placed in aerated static piles where it is left to mature for a period of 12-14 weeks. Aeration is provided through a mechanical mixer. The produced compost is screened through a 25 mm trommel screen and a densimetric table. The end compost is separated by the trommel screen into different fractions depending on demand. The aerated static piles are housed in buildings. Air treatment is provided in these buildings through biofilters (Figure 65). There are no specific standards concerning the quality of the compost, other than the legal definition of compost for agricultural purposes and the size requested by different clients. The current market for the compost is private gardens and individual farmers, mainly for fruit and olive orchards. It has also been sold for public works, like landfill closure and road revegetation. According to 2000 data the price of the compost that is sold was approximately 12 € per ton. The compost was seen as too expensive for farmers (there is excess of manure available in the area) and fairly cheap for private gardeners. Therefore efforts are made to market the product amongst retailers. (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf).

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Figure 65: Biofilter in the Composting Plant of Botarell in Spain

Output material In Table 14 data concerning output material of the composting plant at Botarell in Spain are presented.

Table 14: Outputs from Botarell in Spain

Capacity (*)

Kitchen waste: 2.800 tpa Green waste: 1.200 tpa

(**) Kitchen waste: 30.000 tpa Green waste: 5.000 tpa

Input material Kitchen and green (garden) waste

Output material tpa (*) Application of materials

Compost 360 can be used as soil improver

(*) Data from the 2,5 years operation of the plant (**) Maximum designed capacity

Costs

Table 15 summarizes the total cost of the source separation, collection and composting of organics, while Table 16 summarizes the capital and running cost (data 2000).

The running costs are covered from the flat rate which each municipality charges the households (20 €) for the treatment of the compostable biodegradable fraction and from

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the charges wastes coming from municipalities outside the Baix Camp area. The revenue obtained from compost sales is increasing as the quantities of biodegradable waste that is treated increases. During the first 2.5 years of operation, a total of 10,850 € were earned through compost selling. The price of the compost is low as there is great competition from manure which is abundant in the area (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf).

Table 15: Cost of the Baix Camp Separation, Collection and Composting Scheme for the Year 1998 (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf).

Type of Cost Amount (€)

Setting-up 6.000.000

Operating cost 45 per ton

Publicity Cost 228.000

Disposal Cost 7,2 per ton

Avoided disposal cost & revenue 1,1 per ton

Table 16 : Capital and Running Cost of the Botarell Composting Scheme (http://ec.europa.eu/environment/waste/publications/pdf/compost_en.pdf).

Type of Cost Number (€)

Total Capital Cost

Construction

Machinery

Land Purchase

5.420.000

3.600.000

1.400.000

420.000

Annual Running Cost

Operational

Staff

Assorted (insurance & treatment of rejects)

180.000

90.000

54.000

36.000

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2.2 Success stories of applied thermal treatment technologies

2.2.1 The Thun plant in Switzerland (Incineration)

Overview

only to provide reliable waste treatment, but also to minimize noise and odour pollution resulting from both delivery activities and actual operation. Emission control starts with transportation. An efficient traffic concept ensures that waste travels only short distances by truck. About 40 % is brought by rail to the plant, where it is unloaded in an enclosed hall. To prevent odor emissions, air for the combustion system is drawn in from the waste pit and the unloading area. This creates a slight negative pressure that prevents odors from escaping (http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/ application/2fdf302844a480b8b8a8505d0beabeca.pdf.).


A crane-mounted clamshell delivers the waste via a ram feeder into the incineration feed hopper. Sewage sludge (20-40% dry matter) is mixed into the waste before it reaches the incineration section. A reciprocating grate, encompassing five (5) individually

6 http://www.maurer-soehne.com/files/bauwerkschutzsysteme/images/friction_dampers_KVA_Thun_1.jpg

The Thun incineration plant, start up 2004, processes 100.000 tpa of combustible waste(MSW, dewatered sewage sludge), serving a total of 300.000 residents in 150 communities. The city, located on Lake Thun in Switzerland, is the economic hub of the Bernese Mittelland and Oberland. The plant produces about one third of the electricity consumed in the city of Thun and also provides district heating for adjacent public-sector facilities. Because of the plant’s close proximity to the city of Thun, particular attention was paid to sophisticated ecological and safety engineering concepts. It was important not

Figure 66: The Thun incineration plant in

Switzerland 6

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controllable zones for the various incineration phases (drying, ignition, combustion, and burnout), optimizes waste combustion. For maximum flexibility in terms of waste material calorific values, the first two main combustion zones were equipped with a water-cooled Aquaroll grate. Waste heat from this section is used, via a closed-loop cooling system and a heat exchanger, to preheat the primary air. Secondary air and recirculated flue gas are tangentially injected at high velocity into the secondary combustion chamber above the grate, resulting in intensive mixing and thorough burnout of combustion gases. The energy released during combustion is transferred to the water/ steam circulation loop in the downstream four-pass steam generator.

Reliable removal of contaminants and low emissions are essential. The plant’s efficient flue gas cleaning system ensures not only that these requirements are met, but that the results are in fact much better than Swiss Air Quality Ordinance (LRV) standards. The flue gas cleaning system consists of the following sections:

• electrostatic precipitator,

• SCR (selective catalytic reduction) DeNOx system,

• residual heat recovery,

• wet scrubber, and

• bag filters.

Most of the particulates and the heavy metals bound to them are removed from the flue gas in the electrostatic precipitator. In the SCR unit that follows, the catalyzer breaks down nitrogen oxides into nitrogen and water, both natural constituents of air. The flue gases, now at a temperature of about 260°C, are cooled to ca. 170°C in an economiser, and the acid gases such as sulfur dioxide and hydrogen chloride are then washed out in the wet scrubber. After reheating in the gas/gas heat exchanger, fine particulates, dioxins, and any remaining heavy metals are removed in the bag filters. An induced draft fan blows the clean flue gas into the 70-meter high stack. Before it leaves the plant, continuous measurement system checks conformity with stringent emissions requirements.

In the fly ash washing section, wash water from the wet scrubber is processed together with the fly ash. After a pre-filtration operation, mercury is first removed in a selective ion exchanger. The wash water is then transferred into the fly ash washing section, and the fly ash is extracted with the acid liquor. The fly ash, now free of heavy metals, is then separated from the wash water on a vacuum belt filter, and salts are removed from the filter cake by

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intensive rinsing. The scrubbed and dewatered fly ash is mixed in with the slag and disposed of along with it.

The dissolved heavy metals are precipitated out, dewatered in a filter press, and dried. The filter cake, consisting mostly of zinc hydroxide, is sent out for recycling. Ferrous metal scrap in the waste is also reused: the slag is passed over a magnetic separator where ferrous metals are separated from the remaining slag and then forwarded to a recycling company.

Energy recovered from combustion in the form of steam is converted into electrical power and district heat. This conversion takes place in a turbine generator set consisting of an extraction/condensation turbine with regulated low-pressure extraction and ports for district heat output. The Thun plant is designed to produce a maximum of 12 MW of electricity and 25 MW of district heat. On average, it covers about one third of the city of Thun’s electric power requirement (http://www.aee-vonrollinova.ch/var /aeeweb_site/storage/original/application/2fdf302844a480b8b8a8505d0beabeca.pdf.).

The operation of the Thun waste incineration plant in Switzerland is presented in Figure 67.

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Figure 67: Schematic operation of the Thun waste incineration plant in Switzerland

http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/application/2fdf302844a480b8b8a8505d0beabeca.pdf

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Output material

Data on output material from the Thun waste incineration plant in Switzerland are given in Table 17.

Table 17: Output data from the Thun waste incineration plant in Switzerland7

Capacity 100.000 tpa (13,1tph), max 18,4 tph

Input material Residential MSW, commercial MSW, sewage sludge


Electricity 12 MW per annum for consumption to the city of Thun

District heat 25 MW per annum to adjacent public-sector facilities

Slag 20.000 tpa disposal

Scrap iron 3.500 tpa disposal

Zinc concentrate 720 tpa recycling

Cost data

Total capital cost was approximately EUR 131 million (currency 2004, 1EUR=0,655 CHF) (http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/application/2fdf302844a480b8b8a8505d0beabeca.pdf.).

7 http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/application/2fdf302844a480b8b8a8505d0beabeca.pdf.

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2.2.2 The Zorbau plant in Germany (Incineration)

Overview

The Zorbau incineration plant (Figure 68), located some 30 km southwest of Leipzig, has been providing reliable around-the-clock treatment of household, commercial and industrial wastes since mid-June 2005. At 300.000 tpa, this plant is among the largest capacity plants in Germany.

Figure 68: The Zorbau incineration plant in Germany 8

A high-performance logistics concept regulates the efficient unloading of the 100 to 120 vehicles that arrive daily from the region. Ten tipping bays at the waste pit shorten waiting times and two cranes assure that the two combustion trains can be fed sufficiently at any time.

For times of restricted capacity, as during overhauls, Zorbau has its own interim storage for waste that cannot be treated immediately. A machine charged from the waste pit compacts these wastes into bales and wraps it in plastic film. In this way, waste can be held for several weeks. The bales are then retrieved and included in the incineration charge when the plant is running at full capacity again. (http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original /application/d487ae5620cf7b9412095f46af395e91.pdf)

8 http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/application/d487ae5620cf7b9412095f46af395e91.pdf

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The incineration plant comprises two process trains, each with a maximum waste capacity of 21 tph. Waste is combusted on a three-row reciprocating grate with water cooling in the first two zones. A “calorific value navigator” integrated into the instrumentation and control system adjusts the combustion conditions rapidly and reliably to deal with continuously changing waste fractions. This technique ensures optimal burnout of the most varied wastes.

Flue gas treatment keeps the plant in compliance with the limits of European emission regulations at all times, even when handling waste with elevated levels of pollutants. This operation takes place in two stages: destruction of nitrogen oxides by SNCR (selective non-catalytic reduction) followed by semi-dry treatment for safe removal of gaseous pollutants as well as heavy metals and dioxins. A fully automated loading system specially designed for Zorbau and operated round the clock loads slag into trucks for offsite transport.

The energy produced in the combustion process is used to supply enough electricity for currently 40.000 households. Plans call for additional use of this energy in a cogeneration scheme for district heating once the expansion of the nearby industrial park has been completed. Figure 69 presents schematically the operation of the Zorbau plant. (http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original /application/d487ae5620cf7b9412095f46af395e91.pdf)

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Waste receiving and storage Grate combustion and steam generator Flue gas treatment Consumables and residues 1. Unloading area 5 Feed hopper 11. Primary air distribution 16. SNCR injection levels 22 Ash removal 2. Waste pit 6 Ram feeder 12. Secondary air injection 17. Reactor 23 Residue conveying 3. Waste crane 7 Reciprocating incineration grate 13. Secondary air fan 18. Bag filter 24 Residue storage 4. Crane control cabin 8 Plate slag conveyor 14. Auxiliary burner 19. Induced draft fan 9 Slag pit 15. Three-pass steam generator 20. Silencer

Figure 69: Schematic operation of the Zorbau waste incineration plant in Germany

http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/application/d487ae5620cf7b9412095f46af395e91.pdf

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Output material

In Table 18 data concerning output material of the incineration plant are presented.

Table 18: Output data from the Zorbau incineration plant in Germany9


Input material Residential and commercial


Electricity 28,3 MW per annum for consumption to the city of Thun

Bottom ash 70.000 tpa

Cost data

The total investment came to EUR 120 million.

(http://www.google.gr/#hl=el&q=The+Zorbau+incineration+plant&start=20&sa=N&f

p=72d5358300396c34).

9 http://www.aee-vonrollinova.ch/var/aeeweb_site/storage/original/application/d487ae5620cf7b9412095f46af395e91.pdf

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2.2.3 The Spittelau Thermal Waste Treatment Plant in Austria (Incineration)

Overview

The thermal waste treatment plant in Spittelau, Austria (Figure 70), commissioned in 1971, has a capacity of 250.000 tpa and is linked into the network, providing an annual average of 60 MW, i.e. the base load. In addition, some 400 MW (peak load coverage) can be supplied from a further 5 gas or gas/oilfired hot water boilers. The plant provides heat to the New General Hospital which is located about two kilometres away.

In compliance with continuous adjustment to state-of-the-art flue gas cleaning technology the Spittelau Thermal Waste Treatment Plant was equipped with a flue gas scrubbing system in 1986/89, as well as an ultra-modern SCR-DeNOx and dioxin destruction facility in 1989. At the same time the outer façade of the entire district heating works was redesigned by the famous painter and architect Friedensreich Hundertwas-ser.

Figure 70: The Spittelau Thermal Waste Treatment Plant in Austria10

The Viennese municipal solid wastes, i.e. domestic waste and non-hazardous commercial wastes of similar composition, are delivered to the Spittelau Thermal Waste Treatment. Daily up to 250 delivery vehicles first pass over one of the two weighbridges to establish the weight of the waste, before emptying their loads into the 7.000 m3 waste bunker at one of a total of 8 tipping points. Following thorough mixing in the bunker (in order to homogenize the heating value) the waste is transferred to the two incineration lines by one of the two bridge cranes, whose tong grabs each have a capacity of 4 m3. (http://www.seas.columbia.edu/earth/wtert/sofos/Stern_ThespittelauWTE.pdf)

10 http://www.seas.columbia.edu/earth/wtert/sofos/Stern_ThespittelauWTE.pdf

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The thermal waste treatment plant consists of two (2) incineration lines, each with a flue gas treatment plant, with a SCRDeNOx and dioxin destruction facility serving both lines, and a treatment plant for the waste water arising from the flue gas scrubbing system.

Via the furnace feed chute and hydraulic ram feeder, the waste passes from the bunker to the firing grate situated at the lower end of the furnace. Up to 18 tph of waste can be thermally treated on the inclined, 35 m2 two-track reverse-acting stoker grate. During the transient incinerator start-up and shut-down operational phases, two(2) 9 MW gas burners ensure a furnace temperature of > 800 °C, and thus achievement of total burnout of the flue gas as required by law. In normal operation, use of the auxiliary burners is not necessary, as at 8,600 kJ/kg the lower heating value of the waste is by far sufficient to maintain an autogenous incineration process.

The 850 °C flue gas arising from the incineration process gives off its heat to the surfaces of the waste heat boiler. Both lines generate a total of 90 tons of saturated steam (33 bar) per hour. For power generation, this steam is first reduced to 4,5 bar in a back pressure turbine, before the heat is transferred to the returning water of the district heating network by means of condensation in the following heat exchanger bank.

The incombustible components (slag) arriving at the end of the firing grate are quenched by dumping into the water-filled slag discharger. From there, the cooled slag is transported to the slag bunker by a conveyor belt following removal of the ferrous scrap by overhead electromagnets. The extraction of the fresh air required for the incineration process from the waste bunker maintains the latter in a constant state of partial vacuum, thus minimizing odour and dust emissions from the tipping points into the ambient air. In addition, the use of a well-tried computerized and firing control system ensures optimum incineration along the grate, and thus maximum slag and flue gas burnout. Averaged over the year, more than 5 MW of power for internal consumption and infeed to the public grid as well as some 60 MW of district heating energy are recovered from the waste’s energy content in this way.

When commissioned in 1971, the thermal waste treatment plant already had a highly effective electrostatic precipitator, and in 1986 this was augmented by a 2-stage flue gas scrubber with downstream fine dust separator (electrodynamic Venturi). By retrofitting these 3 treatment stages and installing Europe’s first SCR-DeNOx facility downstream to a scrubber in 1989, the Spittelau plant became an international leader in flue gas cleaning

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and emission reduction for thermal waste treatment plants. From the outset, the existing process undershot by a wide margin the emission limit values for domestic waste-fired steam boiler plants imposed by the Austrian Clean Air Act a year earlier.

The flue gas leaves the first heat exchanger downstream from the waste heat boiler at a temperature of 180 °C, and is initially cleaned by the 3-stage electrostatic precipitator to a dust content of < 5 mg/nm3, the filter ash thus collected being transferred to a 125 m3 silo via a mechanical-pneumatic conveyor system.

The almost fully dedusted flue gas then enters the quencher of the first scrubber, cooling it to saturation temperature (60-65 °C) by open-circuit water injection. The first scrubber, operated at a pH value of 1, removes hydrogen chloride (HCl), hydrogen fluoride (HF) and dust, as well as particlebound and gaseous heavy metals, through intensive gasliquid contact in the cross flow.

The second scrubber stage, which is designed as a countercurrent washer and operates at a pH value of 7, is responsible for the removal of sulphur dioxide (SO2) from the flue gas. In the next treatment stage, the electrodynamic Venturi, the residual dust content is reduced to < 1 mg/nm3 by adiabatic expansion of the flue gas, followed by separation of the fine dust particles after they have been moistened and then charged by means of a central electrode. In the second heat exchanger, the flue gas is reheated to 105 °C and fed to the DeNOx and dioxin destruction facility by means of an induced-draught fan.

The DeNOx facility, as the final stage of the flue gas treatment process, utilizes selective catalytic reduction (SCR). The flue gas streams from both treatment lines are combined, mixed with vaporized ammonia water (NH3) and heated to a reaction temperature of 280 °C by a heating tube and gas duct burners.

Passing through the 3 catalytic converter stages causes the nitrogen oxides (NOx) to react with the added ammonia and the oxygen in the flue gas to form nitrogen and steam, and also results in dioxin and furan destruction. The resultant exhaust gas is then cooled to 115 °C in the third heat exchanger and finally released into the atmosphere through a 126 m high stack.

All waste water emitted by the flue gas scrubbing system is processed in a special treatment plant before being released into the receiving water (Danube channel). The heavy metal compounds dissolved in the discharge water from the first scrubber are first converted to insoluble form in a precipitation reactor, by dosinglime slurry as well as special precipitation and flocculation agents. Thereafter, separation of the heavy metal

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hydroxide suspension thus created takes place in the laminar clarifier which is connected in series. Following repetition of the precipitation and separation stages, the resultant hydroxide sludge is dewatered to a residual moisture content of approximately 30 % in a chamber filter press and filled in big bags as filter cake. After a final check of volumetric flow, temperature, pH value and conductivity, the cleaned waste water is passed into the receiving water. The sodium sulphate-laden discharge water from the second scrubber is processed in the multi-stage recycling plant. Firstly, the sodium sulphate is precipitated as calcium sulphate (gypsum) by the addition of lime slurry, sedimented in the settlement tank and, as gypsum sludge, pumped into the slag discharger. The soda lye reclaimed from the precipitation process is returned back into the water circulation system of the second scrubber.

(http://www.seas.columbia.edu/earth/wtert/sofos/Stern_ThespittelauWTE.pdf )

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Figure 71: Schematic operation of the Spittelau Thermal Waste Treatment Plant in Austria

http://www.seas.columbia.edu/earth/wtert/sofos/Stern_ThespittelauWTE.pdf

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Output material


Table 19: Output data from the Spittelau Thermal Waste Treatment Plant in Austria11


Input material Domestic waste and non-hazardous commercial wastes of similar composition


Heat 473.400 MWh per annum

Heating of 190.000 homes and 4.200 public buildings, including Vienna's largest hospital

Power 8.416 MWh per annum

Satisfaction of the plant’s electricity needs, supply the main electrical grid

Slag and gypsum 57.334 tpa Construction of border walls in landfills as a slag concrete

Ferrous scrap 6.312 tpa Returned to the material cycle (steel production)

Filter ash 4.734 tpa Construction of border walls in landfills as a filter ash concrete

Filter cake 236,7 tpa Transportation to Germany by rail in big bags, and used there as infill in a disused salt mine

Cleaned waste water 118.087 tpa Disposal into the receiving water (Danube channel)

Cleaned exhaust gas

1.472.800 m3 per annum Released into the atmosphere

Cost data

No cost data available.

11 http://www.seas.columbia.edu/earth/wtert/sofos/Stern_ThespittelauWTE.pdf

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2.2.4 The Toshima Thermal Treatment Plant in Japan (Incineration)

Overview

The incineration facility of the thermal treatment plant in the Toshima ward in Tokyo Japan, was constructed under the philosophy of disposing waste in the area in which it is generated, while minimizing the associated environmental and social burden.

Tokyo has a source separation program in effect. At each household, waste is separated into combustibles (kitchen waste, paper, clothing, etc.), noncombustibles (metals, ceramics, glass, plastics, rubber, leather, etc.) and large-sized waste (over 30 cm, furniture, appliances, etc.). Waste is required to be placed in transparent polyethylene bags containing calcium carbonate (for odor control). The large-sized and noncombustible waste goes to the Central Breakwater site in Tokyo Bay for processing (pulverization, separation of combustibles and recyclables, volume reduction and landfilling), while the small combustibles are trucked to the incinerator.

Despite the precautions taken, about 5-10% noncombustibles slip through the system and end up in the incinerator feed. The incinerator feeding system is sized to accept material less than 60 cm (IEA, 2000).


The Toshima Incineration Plant is equipped with two 200 t/d atmospheric bubbling fluidized bed (BFB) incineration boilers constructed by Ishikawajima-Harima Heavy Industries (IHI). Fluidized bed technology was chosen because of the necessity of minimizing required plant floor area (residential location). Because of the furnace’s vertical design, the incineration capacity per unit area is much greater than for a gratefired unit.

A BFB unit operates by combining fuel (in this case MSW combustibles) and combustion air in hot sand under vigorous mixing. There are basically three zones in the vertically oriented incinerator: the fluidized bed, the freeboard and the boiler. At the bottom of the vessel is the dense bed. Here fluidizing air enters through a horizontal tubing grid (distributor) just above the incinerator floor. At a higher elevation in the fluidized bed, primary combustion air (approximately 7 550 Nm3/h) is injected. Temperature in the bed is maintained at about 550-630°C, hot enough to drive off volatiles and fully combust the MSW, which is fed at the top of the bed. If the temperature should rise above 630°C, cooling water sprays are activated automatically. Ash and sand periodically migrate downward and are removed at the incinerator bottom. Sand is separated from the ash, graded, and returned to the top of the dense bed. Each incinerator contains 57 m3

of sand (90 t), some of which is lost as

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fines with the flue gases, or in the ash stream. It is estimated that periodic make-up results in a complete sand change over a period of one to two years. Above the dense bed is a tall region known as the freeboard. Here secondary combustion air (approximately 28 800 Nm3/h) is injected at several levels to completely burn off the volatiles. The temperature in this region rises steadily from about 710°C to 1030°C (automatic cooling water sprays are activated should the temperature exceed 1070°C), and gas velocity is such that a residence time (at 850°C) of at least two seconds is achieved (for dioxin destruction). In addition to fly ash, some sand fines may still be carried by the gases in the freeboard, but these are minimized by prudent velocity control.

Above the freeboard is the boiler. With no combustibles remaining in the gas, and with the aid of cooler air injection, temperatures drop rapidly prior to contact with the boiler tubes (approximately 480-580°C). This is a natural circulation water-tube boiler, equipped with a superheater. Steam is generated at a maximum rate of 33,3 tph from each unit, usually at 3.14 MPa (abs) and 300°C. The high-pressure steam is routed to a highpressure steam header, while the flue gases exit the boiler through an economizer to a quick-quench cooling tower.

Flue gas treatment begins at the exit of the economizer, where a water spray cooling tower quickly quenches the gases to 150°C, minimizing dioxin formation. At the entrance to the fabric filter baghouse, slaked lime and powdered activated carbon are injected into the flue gases to remove heavy metals, dioxins/furans and non-combusted organics, while the baghouse removes particulates. The design gas treatment rate in the baghouse is about 75 000-109 000 Nm3/h (dry). Once leaving the baghouse through an induced draft fan, the flue gases enter a wet caustic soda scrubbing tower which removes acid gases (sulphuric and hydrochloric acids), at a gas treatment rate similar to the baghouse. Upon exiting the scrubber, the flue gases are dried and heated, by heat exchange with steam generated in the plant, to 210°C before entering the selective catalytic reduction (SCR) reactor. Here, ammonia is injected into the gas stream as it passes through a honeycomb catalyst to remove nitrogen oxides (NOx).

From the SCR, flue gases enter the 210 m stack (the tallest concrete stack in Japan), containing two flues (one for each incinerator) and an elevator (for maintenance). The inlet temperature to the SCR was chosen for two reasons: to improve the rate of catalytic conversion of NOx (although a temperature of 250-350°C would have been more appropriate); and to ensure an invisible plume emanating from the stack.

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The plant is equipped with a single condensing steam turbine/generator set which can handle a maximum flow rate of 58,4 tph of 2,84 MPa steam, and produce up to 7,8 MWe. The maximum figures mentioned are based on firing 400 tpd of waste with a heating value of 13,4 MJ/kg (3200 kcal/kg), the upper design value. Under current operating conditions, however, with the feed heating value at about 9.4 MJ/kg (2.250 kcal/kg), only 5,3 MWe is generated (IEA, 2000).

Output material


Table 20: Output data from the Toshima Thermal Waste Treatment Plant in Japan (IEA, 2000)

Capacity 400 tpd

Input material Municipal solid waste (source separated)

Output material flow Value Application of materials

Heat 4,3 MWth

Satisfaction of the plant’s needs Heating, air conditioning, and water heating for the swimming pool to the adjacent Toshima Health Plaza facilities

Power 7,8 MW Satisfaction of the plant’s electricity needs, while the rest is sold to Tokyo Electric

Ferrous metal Disposal to landfills

Bed ash 0,6 tpd Disposal to landfills

Dry fly ash 6,7 tpd Disposal to landfills

Cost data

Construction costs for the facility, excluding the Toshima Health Plaza, but including all infrastructure modifications was approximately US$140 million (1997 average conversion rates). While this appears quite high by North American standards, it must be understood that: (1) the plant is in downtown Tokyo, where real estate and infrastructure costs are very high, (2) the location near the Sunshine 60 building (NEDO headquarters) has necessitated the highest concrete stack in Japan, again at great expense, and (3) the plant, stack and associated buildings were built to earthquake standards.

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2.2.5 The Lidköping Waste-to-Energy Plant in Sweden (Incineration)

Overview

This is the main production plant for district heating in the city of Lidköping, situated alongside Lake Vänern, the largest lake in Sweden. The plant is owned by the municipality of Lidköping, and consists of two 20 MW and one 8 MW oil-fired boilers and two 17 MW bio/waste-fueled boilers. Maximum capacity of the plant is 82 MWth. In addition, there are two electrically-fired boilers, rarely in operation. The bio/waste plant was originally put into operation in 1985, with two 12 MW lines for combustion of waste and biofuel using bubbling fluidized bed (BFB) technology, delivered by Kvaerner. The bio/waste plant has been gradually upgraded to meet more stringent requirements, and in 1994-95 the output was increased to 2 x 17 MW.

Today, 70.000 tpa of bio/waste fuel is combusted in the two solid fuel lines, producing 200 GWh district heat. More than half the fuel received is household and industrial waste (ISW) (maximum of 50.000 tpa), the rest being treated wood waste. The household waste is delivered from Lidköping and seven surrounding municipalities. Private companies deliver the ISW (IEA, 1999).


The furnace walls are protected with bricks up to the level of the arches, to prevent cooling and mitigate erosion. During start-up, sand (0,5-2 mm, with a bed height of 0,5 m maintained) is heated with oil burners to a temperature of 600°C. Start-up fuel is wood chips. The combustion temperature is about 800°C, and the pressure 5 kPa. Combustion takes place at an oxygen level of about 7,4 vol%, dry gas. Primary air is injected from the bottom of the bed, below the sand. Non-combustibles sink down through the bed and are removed by a cooled screw together with sand that is sieved and returned to the furnace. Approximately 1000 tons of fresh sand is added to the process each year. Total injected air is about 6,5 Nm3/s, of which 60-65 % is primary air. Ammonium bicarbonate is injected with the secondary air (300 t/a) to reduce NOx

emissions (regulated values are 250 mg/Nm3 through 2005 and 150 mg/Nm3

thereafter). In the upper part of the furnace, the temperature is about 700°C. Downstream of this, an empty draft region cools the flue gases to about 600°C. The empty draft is equipped with screens to increase the cooling surface. The free area for flue gases is 0,4x0,3 m in each passage. In the following convection drafts flue gases are further cooled to 150°C. Residence time in the convection section is kept short to minimize formation of dioxins (the regulated level of 0,1 ng/Nm3

is consistently being met). At the end of the convection section, a first economizer regulates the

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temperature into the flue gas cleaning system. The boiler works as a combined hot water/steam boiler. Hot water from the drum is exchanged at 190°C with the district heating network, and then brought through the furnace and convection section back to the drum. Saturated steam is also generated in the drum at 2.3 MPa. A maximum of 50% of the energy can be taken out as steam. Since the rebuilding in 1994/95, the boilers are equipped with superheaters that today are used as convection surface, as no electricity is generated. Flue gas cleaning consists of a dry system, with a cyclone as a first step, separating large particles, followed by a baghouse filter. Lime is added prior to the filter, as an absorbent. About 1.000 tons of lime is used for this purpose every year (for the two lines together). Lime addition is controlled by the HCl concentration in the clean flue gas. The cyclone removes about 20-25% of the heavy metals and a few percent of the acid components. After the baghouse filter, almost 100% of the heavy metals have been removed. Clean flue gas still contains 15-20% of the HCl and 40-50% of the SO2, however. Testing is ongoing with sodium bicarbonate as a replacement for lime. In addition to absorbing HCl, bicarbonate will also remove SO2, eliminating the need of a scrubber to meet the 50 mg/Nm3 SO2 regulation. From 150°C at the inlet to the flue gas cleaning system, the temperature is reduced to 110-120°C (a secondary economizer is placed at the end of the flue gas cleaning train). Finally the clean gases leave the plant through a 70 m stack (IEA, 1999).

Output material


Table 21: Output data from the Lidköping Waste-to-Energy Plant in Sweden (IEA, 1999)

Capacity 70.000 tpa

Input material Household and industrial waste (ISW), wood waste


Heat 34 MWth Animal food factory, alcohol factory, district heat

Power 7,8 MW Satisfaction of the plant’s electricity needs, while the rest is sold to Tokyo Electric

Cost data

As originally constructed (1984), capital costs were 104 million SEK (at present, 1 SEK=US$0.11), including the two incineration lines, two oil-fired boilers and buildings. As the plant has been gradually upgraded, it is difficult to estimate what the investments for the same plant would be today.

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2.2.6 The TIRMadrid Plant in Spain (Incineration)

Overview

This facility is owned by TIRMadrid (Tratamiento Integral de Residuos de Madrid s.a.) and is situated in Valdemingómez, near Madrid. In 1989 Madrid city council decided to act on waste disposal in the region, as the landfill site was becoming full. The practice at the time was to recycle as much waste as possible and compost the organic waste. In 1990, Urbaser proposed that city council develop, construct and maintain a waste-to-energy recovery facility. The TIRMadrid plant accepted 441.000 tons MSW in 1999, of which 62.000 tons was recovered for sale, 119.000 tons was landfilled or composted, and 260.000 tons RDF was fed to the three BFBs (Granatstei, 2001). Process and Technology involved

RDF is transported from each of three hoppers (10-13 t/h) by double screws into two shafts operating as the feeding system into the furnace about 3 m above the bed. The BFBs are of the Rowitec twin interchanging fluidization (TIF) design, constructed by H`lter-ABT. The TIF is similar to the Ebara design, in that the floor of the bed (4 x 6 m) slopes down from the centre to the side walls, producing circular mixing patterns in the bed. Larger particles are moved over the bed bottom to the side walls, into the ash/sand removal system. Average residence time in the bed is four minutes. To slow combustion and to keep the bed temperature at 670°C, recirculated flue gas and water (up to 2.500 kg/h) are injected above the bed. In the freeboard, temperatures of 900°C are reached. The boilers consist of two vertical radiation sections (water-cooled walls), a horizontal convection section (superheater) and a vertical economizer. Each boiler has a nominal output of 41 t/h of steam at 420ºC and 46 bar. Under design conditions, a total of 29 MWe is generated (at 19.4% overall efficiency).

Gas cleaning for each line begins in the fluidized bed, with injection of fine limestone from above via secondary air outlets. This provides partial SO2 and HCl removal and reduces fouling and corrosion in the superheater. Flue gases are then led through the three boiler passes to a pair of hot gas cyclones to remove fly ash; a semi-dry absorber (calcium hydroxide); a high-performance bag filter with dry injection of lime and activated carbon to remove the remaining fly ash, heavy metals and organic components; and an ID fan, which prevents pressure drops in the system and drives the exhaust gases into the stack (Granatstei, 2001)..

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Output material


Table 22: Output data from the TIRMadrid Plant in Spain (Granatstei, 2001)

Capacity 440.000 tpa MSW (or 260.000 tpa RDF)

Input material RDF


Power 29 MWe

Cost data

Capital cost of the plant was US$125 million, 80% for the thermal facility and 20% for waste recovery. O&M costs, including ash disposal, are US$13.5 million annually (US$30.60/t MSW) (Granatstei, 2001).

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2.2.7 The Ottawa Waste-to-Energy Plant in Canada (Plasma gasification)

Overview Plasco Energy Group, a Canadian waste conversion and energy generation company, constructed a plasma gasification demonstration plant in Ottawa, Canada.

The demonstration project receives between 75 and 85 tons per day of solid, non-hazardous municipal solid waste and produces about 5.2 MW of electricity of which 1 MW is used to power the entire Plasco facility. Plasco has secured an agreement with Hydro Ottawa for the sale of remaining electricity to the grid. The plant processed its first municipal solid waste in February 2008. (http://www.ene.gov.on.ca/envision/env_reg/er/ documents/2005/RA05E0021.pdf) Figure 72: Ottawa plasma

gasification plant in Canada


The Plasco demonstration facility has two (2) distinct processes:

1. A processing plant using plasma generators to convert the waste material into synthetic gas of quality that meets manufacturers specifications for guaranteed optimal output from gas engines, heat and an inert solid (slag); and

2. A power plant that operates in cogeneration to use the synthetic gas plus the heat from both the processing and the gas engines driving the generators to produce electricity to operate the processing plant and to sell into the grid.

The Processing Plant will operate in an enclosed building with external noise, dust and other “nuisance factors” expected to be less than the handling of the same waste into the landfill.

Residual MSW (excluding materials diverted from landfill) collected by the City of Ottawa will be brought to the processing plant by City vehicles and deposited on the tipping floor. The MSW is shredded indoors into relatively large but consistent pieces. No sorting is required for the system to be fully effective. Large metal objects will be automatically removed to permit sale by the City as scrap metal. In order to minimize release of particulate matter during shredding, air will be extracted from the vicinity of the shredder and emissions will be controlled. The Demonstration Plant will have

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the capacity to store at least four (4) days worth of MSW onsite (approximately 400 tons). Additional stockpiling of MSW will take place, to ensure that operations continue throughout long weekends.

The shredded waste is fed into the processing chamber/converter, which operates at slightly below atmospheric pressure.

Measured amounts of air and steam are fed into the converter chamber with interactive computer control to match the chemical content arising from the materials in the chamber on a real-time basis. This allows the appropriate quantities of carbon, hydrogen and oxygen to be maintained in the chamber enabling the quality of gas required for effective operation of the selected gas engines. Passing air over an electrical current produces plasma, a superheated gas that exceeds 8000°C. The MSW material fed into the chamber is reduced to its component molecules by the intense heat supported by the plasma generators and in part contributed to by the release of heat in the dissociation of the molecules in the material. Gaseous molecules exit the chamber at about 1000 degrees C and solid molecules are liquefied and entrained in the slag which hardens upon exit from the bottom of the chamber. The residual inert solid from the process, called slag, represents about ¼ of 1% of the volume of materials entering the chamber. The slag is inert, requires no controlled disposal, and has value as a construction material. The Demonstration Plant is designed to store up to one week’s production, approximately 100 tons, of slag onsite.

The gases exit the chamber into a Gas Quality Management System (GQCS). Any particulate matter that exits the chamber is caught in the GQCS and fed back to the converter for further processing. Contaminants that were in the waste exit the chamber at high temperature, and are captured and removed from the gas. Heat from the product gas is used to generate steam, which in turn is used to generate electricity.

The clean and cooled gas enters a storage tank designed to hold about 15 minutes of output from processing operations. This blends any variations in “richness” of the gas, to achieve a highly consistent gas quality flowing to the engines.

There are no air emissions from the entire processing system. All gas is cleaned and captured for use in the engines. Cleaned gases are fed to a gas engine that powers a generator to produce electricity. In the case of the Ottawa plant, gas engines designed to operate with low-BTU fuel will be used. Due to the cleaning of the gas in the GQMS, emissions from the engines are kept to levels significantly better than the existing Ontario standards.

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Heat is captured from the exhaust and used in combined cycle power generation and NO2

is maintained well within standards by an integrated control system operating along with the heat recovery unit. Heat recovered from the PGP process during the cooling stage powers a steam turbine that operates a generator to produce approximately 1.6 MW of electricity (http://www.ene.gov.on.ca/envision/env_reg/er/ documents/2005/RA05E0021.pdf).

A diagram describing the processing plant is provided in Figure 73.

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Figure 73: Schematic operation of the Ottawa Waste - to - Energy Treatment Plant in Canada

http://www.ene.gov.on.ca/envision/env_reg/er/ documents/2005/RA05E0021.pdf

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Output material

In Table 23 data concerning output material of the plasma gasification plant are presented.

Table 23: Output data from the Ottawa Waste –to-Energy Treatment Plant in Canada

Capacity 75-85 tpd

Input material Solid, non-hazardous municipal solid waste


Power 5,2 MW Satisfaction of the plant’s electricity needs (1 MW), while the rest is sold to the grid (Hydro Ottawa)

Slag 150 kg/t of waste Concrete and other applications

Residual 1 kg/t of waste Disposal to landfills

Cost data

The facility, cost construction is approximately $27 million. Plasco Energy Group will be generating revenues from fixed tipping fees projected at Canadian $40.00 per ton for up to 20 years. They will also produce income from electricity sales, carbon credits, selling of aggregate, sulfur and salt.

(1 Canadian Dollar = 0.85807 US Dollar, 2007)

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2.2.8 The Toyohashi Waste Treatment of Recovery and Resources Centre in Japan (Pyrolysis gasification)

Overview

In March 2002 next generation Pyrolysis Gasification Process Treatment Plant was completed by Mitsui Engineering & Shipbuilding Co. over its second "Mitsui Recycling 21 (R21)" and handled to Toyohashi City, Aichi Prefecture, located in Japan. This plant is the biggest kiln type gasification facility in Japan with a treatment capacity of 400 tons per day. (http://www.mes.co.jp/english/company/pdf/ 02envreport_e.pdf)

Figure 74: The Toyohashi Waste Treatment of Recovery and Resources Centre in Japan


This process is a combination of pyrolysis gasification and high temperature ash melting. Firstly, the pyrolysis gasification system produces and separates gas, carbon, iron and aluminum at temperature as low as 450°C without oxygen. Then, the melting system produces molten slag in a high temperature combustion chamber at 1,300°C with pyrolysis gas and carbon as the heat sources. In addition, this plant uses waste heat to generate electricity.

The R21 plant is designed to handle household and commercial waste. Aside from some manual sorting of bulky wastes, which may be desirable to remove large recyclable items, there is no front-end sorting. However, upstream source segregated recycling, in particular of low calorific fractions, can be beneficial to the overall energy balance of the pyrolysis plant. After bulky waste has been manually removed, the residue is shredded and thereafter delivered to the municipal solid waste (MSW)

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reception area. These waste streams are then shredded to a maximum particle size of 200 mm. The shredder’s design incorporates a fail-safe system in instances where the shredder is unsuccessful in shearing difficult items.

The pyrolysis process involves low-temperature pyrolysis (around 450°C) of MSW in a rotary drum reactor operated at a small negative pressure. Heat is provided indirectly to the rotary drum by passing hot air through a heat exchanger running along the drum’s length. Waste residence time is approximately 1 hour, resulting in large quantities of waste being present in the drum at any time - this helps to stabilise the process by smoothing out variations in MSW feed quality. The combustible ‘pyrolysis vapour’, containing condensable liquids, is carried forward through pipe work to the combustor.

Hot solids are separated from the syngas in a purpose built unit at exit from the pyrolysis drum. Solids are passed to a handling system where ferrous/non-ferrous metals can be recovered for recycling. After cooling of the solids, the metals are removed and the remaining solid residue – comprising combustible char and inert material – is crushed to a particle size of 1 mm and then conveyed pneumatically to the high-temperature combustion chamber.

The crushed material from solids handling is mixed with the syngas and combusted at high-temperature (1,300°C), in suspension, in a refractory-lined cyclone furnace. The high temperatures obtained - well in excess of those for more traditional mass-burn incineration with low excess air levels – lead to efficient combustion and are designed to minimise the potential for dioxin formation, reduce nitrogen oxides [NOx] production and convert ash into a vitrified (‘glass like’) inert ash. This ash is recovered in Japan and used in construction work.

The flue gases exiting the furnace are conveyed to the high temperature air-heater where they are used in the indirect heating of the pyrolysis drum. The heated air is circulated in a closed-loop system by a circulation fan, with a feed and return of approximately 520°C and 300°C, respectively. A support fuel is supplied for use during shutdown and start-up, and during emergency situations, otherwise the system is self-supporting.

The waste heat boiler receives heat from the high-temperature air-heater at approximately 600°C. The boiler unit generates steam at 400°C and 40 bar pressure, for supply to a turbo-generator. A percentage of the electricity is required to meet the parasitic load of the plant leaving the remainder for export. The steam requirement is

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for space heating only: in some Japanese plants council offices and other public facilities are located on the same site.

Flue gases are cleaned via two in-series bag filters: the first collects entrained fly ash and boiler ash particles. These are subsequently recycled to the high-temperature combustion unit together with ash from air-heater and boiler hoppers, removing the need to send collected fly ash streams to landfill. The second bag filter is fitted with a lime injection system to provide acid gas emission abatement. The collected material – a combination of un-reacted lime, calcium sulphate/sulphide and calcium chloride – is managed in a (hazardous waste) landfill site (Greater London Authority, 2003).

A diagram describing the processing plant is provided in Figure 75 and Figure 76.

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Figure 75: Process diagram of the Toyohashi Waste Treatment of Recovery and Resources Centre in Japan (http://www.ieabcc.nl/meetings/Tokyo_Joint_Meeting/02_Mitsui.pdf)

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Figure 76: Schematic operation of the Toyohashi Waste Treatment of Recovery and Resources Centre in Japan

(http://www.ieabcc.nl/meetings/Tokyo_Joint_Meeting/02_Mitsui.pdf)

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Output material

In Table 24 data concerning output material of the gasification Pyrolysis plant are presented.

Table 24: Output data from the Toyohashi Waste Treatment of Recovery and Resources Center in Japan12

Capacity 400 tpd (120.000 tpa)

Input material Household and commercial waste


Power 1.850 kW

Slag Reuse as an asphalt composite material

Non oxidized steel, non molten aluminium

Reuse (sold out at the market price)

Cost data

No data available.

12 http://www.ieabcc.nl/meetings/Tokyo_Joint_Meeting/02_Mitsui.pdf

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3. Remarks

MSW management is an integral but much neglected aspect of environmental management in most low and middle income countries. Despite the fact that in most of these countries the municipal solid waste expenditures is allocated to the collection and transfer of waste, solid waste management services are unreliable, provide inadequate coverage, conflict with other urban services and have adverse effects on public health and the environment. Efficient waste management approach is as valid in countries with developing economies as it is in countries with developed economies, but the actual establishment of integrated systems differs considerably (McDougall et al., 2003).

Since independence, Morocco’s municipal solid waste services have been defined only in terms of “cleanliness”, with the main focus on waste collection and limited attention and resource allocation to waste disposal. This has led to significant environmental and social impacts. Due to its impacts on the quality of life, public health, environmental and natural resources, and vital economic activities such as tourism, solid waste management is now recognized as a top priority by the Government. To this end, the Government has taken two key and significant first steps toward the reform of solid waste management. First, the Solid Waste Management Law 28-00 was passed in November, 2006. Second, it has developed and approved the Programme National de Gestion des Dechets Menagers (PNDM - the National Municipal Solid Waste Management Program), which is a 15-year, 3-phase program launched in 2008 in support of Law 28-00. The PNDM was formally adopted by the newly appointed Government in its program setting out, among other objectives, service and disposal standards for urban areas, quantitative goals for collection coverage (90 percent by 2021), the introduction of sanitary landfills (100 percent of urban areas equipped by 2021), and the closure and rehabilitation of 300 existing open dumps as well as the promotion of solid waste reduction, recovery and valorization (WorldBank, 2009). Considering the above, it is obvious that the relatively new legislative framework of Morocco will contribute to the development of integrated waste management systems of MSW.

However, apart from the legislative and institutional framework attention should be paid in order to assure individuals participation and social acceptance. There are numerous of examples where treatment systems did not succeed due to low public participation. If a treatment system ensures acceptance for the majority of people in a community, it is very likely to succeed. This will definitely require an extensive dialogue with many different groups to inform and educate, develop trust and gain support (McDougall et al., 2003). This was the case for the Botarell Composting

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Scheme which is considered one of the most successful composting sites in Spain. Apart from the technical excellence, one of the main reasons of success was the participation of a high number of individuals in the separation of the biodegradable fraction of waste. This was achieved through appropriate Catalonian legislation which imposes separate collection for Municipalities greater than 5.000 inhabitants and through an intense publicity campaign which included door-to-door distribution of leaflets and brochures, the organization of a bus road show and of radio and press campaigns (EC, 2000).

Morocco currently produces about 8,4 MTpa MSW with a generation growth of 2% per annum (METAP, 2005). In the absence of an active and strategic role at the central government level, most municipalities equate solid waste management only with the removal of waste from visible public areas. Waste disposal in sanitary landfills has been entirely neglected by municipalities, and waste is generally disposed in open dumps (>95) (WorldBank, 2009). This method of final disposal is environmentally and socially unacceptable as it does little to protect the environment or public health. Based on the evaluation of different case studies reviewed in this report, the selection of the appropriate waste management system, should take under consideration: (a) the qualitative and quantitative characteristics of MSW, (b) existing technologies such as anaerobic digestion, biodrying, composting or/and thermal treatment systems applied in waste treatment plants worldwide in relation to their capital and operational costs, (c) the desirable output i.e. biogas, heat, electricity, high quality compost, low quality compost etc and (d) the achievement of the maximum reduction of waste ending in landfills.

In conclusion, in order to implement an effective waste management scheme for the Morocco legislative and institutional, social, environmental, technological economic, aspects should be considered for each case.

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