Final Report April 2005

Transcription

1 Feasibility of Generating Green Power through Anaerobic Digestion of Garden Refuse from the Sacramento Area Final Report April 2005 Report to SMUD Advanced Renewable and Distributed Generation Program Prepared By In Association with MacViro Consultants Inc.

2 Executive Summary Glossary of Terms Table of Contents Page i vi 1.0 Introduction Quantity and Composition of Garden Refuse as Feedstock Quantity of Garden Refuse Available Composition of Garden Refuse City of Sacramento Anaerobic Digestion of Garden Refuse and Municipal Solid Waste Anaerobic Digestion Process Experience to Date with SSO, MSW and Garden Refuse Anaerobic Digestion Design Options Anaerobic Digestion Technology Designs Available Feedstock and Gas Production Energy Uses Anaerobic Digestion of Garden Waste References Technical Information on AD Technologies - DRY Methodology Kompogas Dranco/OWS Linde-DRY Biopercolat ISKA Valorga Wright Technical Information on AD Technologies - WET Methodology Onsite Power Systems Arrow Ecology Ltd BTA Waasa, WABIO and Citec Linde - WET BioConverter Entec 5-28

3 Page 6.0 Screening and Analysis of Available AD Technologies Overview Technical Screening Criteria Summary of Technical Data for AD Technologies Technical Analysis of AD Technologies By Design Parameters Gas Production and Net Energy Available From Different AD Technologies Technical Screening of AD Technologies Evaluation of Broader Concept Using SMUD Criteria Evaluation Using Sacramento Waste Authority Criteria Economic Analysis of Anaerobic Digestion of Garden Waste Overview Description of Facility Components Plant Energy Balance Costs and Financial Analysis for 100,000 ton/year Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site Option Costs and Financial Analysis for 200,000 ton/year Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site Option Costs and Financial Analysis for 100,000 ton/year Garden Waste AD Facility (Dry, Thermophilic) at a Co-located Site Options 3 & Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food Waste AD Facility (Wet, Mesophilic) at a Greenfield Site Option Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food Waste AD Facility (Wet, Mesophilic) at a Co-located Site Option Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site Option Costs and Financial Analysis for 50,000 ton/year Garden Waste with Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site Option Discussion of Costs For Greenfield Site Economic Conditions Which Make AD Viable Next Steps in Research Conclusions and Recommendations Conclusions Recommendations 8-2 Appendices Appendix A Appendix B Appendix C Appendix D 100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site 200,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site 100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Co-located Site 100,000 ton/yr Garden Waste and Food Waste AD Facility (Wet, Mesophilic) at a Greenfield Site

4 Appendix E Appendix F Appendix G 100,000 ton/yr Garden Waste and Food Waste AD Facility (Wet, Mesophilic) at a Co-located Site 100,000 ton/yr Garden Waste and Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site 50,000 ton/yr Garden Waste and Food Waste AD Facility (Dry, Thermophilic) at a Co-located Site Tables Page Table 3.1 Key Firms Generating Biogas from MSW Feedstock in Europe in Table 3.2 Communities in the United States Investigating Anaerobic Digestion for MSW 3-3 Table 3.3 Biogas Yield from MSW Materials 3-11 Table 3.4 Biogas Yield 3-12 Table 3.5 Biogas Composition 3-12 Table 3.6 Biogas Production 3-12 Table 4.1 Anaerobic Digestion Technologies Profiled 4-2 Table 4.2 Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected Kompogas Facilities 4-4 Table 4.3 Full Scale Kompogas Plants 4-5 Table 4.4 Planned Full Scale Kompogas Plants or Facilities Under Construction 4-6 Table 4.5 Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected DRANCO Facilities 4-10 Table 4.6 DRANCO Demonstration Plants 4-11 Table 4.7 Full Scale DRANCO Plants 4-12 Table 4.8 Planned DRANCO Plants 4-12 Table 4.9 Feedstocks of Linde Dry Digestion Facilities 4-16 Table 4.10 Energy Production for Selected Linde Dry AD Facilities 4-17 Table 4.11 Existing and proposed Linde Dry AD Facilities 4-17 Table 4.12 Linde Mechanical-Biological Treatment Facilities featuring Aerobic Treatment 4-18 Table 4.13 Energy Characteristics of ISKA Facilities 4-23

5 Tables Page Table 4.14 Land Requirements of Selected ISKA AD Facilities 4-24 Table 4.15 ISKA Operational and Proposed AD Facilities 4-24 Table 4.16 Typical Average Gas Yields for Different Feedstock 4-28 Table 4.17 Land Requirements for Selected Valorga Facilities 4-28 Table 4.18 Valorga AD Facilities 4-29 Table 5.1 Operating and Planned BTA Facilities 5-15 Table 5.2 Energy Information for Selected Waasa Facilities 5-18 Table 5.3 Waasa Facilities 5-19 Table 5.4 Feedstock Used in Linde Wet Facilities 5-22 Table 5.5 Energy Outputs from Selected Linde Wet Facilities 5-22 Table 5.6 Existing and Proposed Linde Wet AD Facilities 5-23 Table 5.7 Energy Information for Entec Facilities 5-30 Table 5.8 Entec Operations 5-30 Table 6.1 Summary of Key Technical Data For Thirteen Anaerobic Digestion Technologies Processing Some Garden Waste Table 6.2 Classification of AD Technologies As One Vs Two Stage Systems 6-7 Table 6.3 Classification of AD Technologies As Wet Vs Dry Systems Table 6.4 Characteristics of Mesophilic Vs Thermophilic Designs 6-8 Table 6.5 Table 6.6 Available Information on Reported Gas Production and Net Energy Available for Export For Dry Anaerobic Digestion Technologies Available Reported Information on Gas Production and Net Energy Available for Export For Wet Anaerobic Digestion Technologies Table 6.7 Screening of Anaerobic Digestion Technologies Table 7.1 Table 7.2 Table 7.3 Table 7.4 Plant Capital Cost Estimate 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site) Plant Operating and Maintenance Cost Estimate 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site) Financial Analysis: Input Assumptions and Data 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site) Tipping Fee and Power Price Calculation 100,000 ton/yr Garden Waste (Dry, Thermophilic AD Plant, Greenfield Site)

6 Tables Page Table 7.5 Summary of Costs for Options Table 7.6 Summary of Costs for Greenfield Sites 7-16 Table 7.7 Summary of Costs for Co-located Sites 7-17 Table 7.8 Financial Analysis Summary 7-19 Figures Figure 2.1 Garden Refuse Collected In the City of Sacramento By Month, 2002 and 2003 Figure 3.1 Flow Diagram for Anaerobic Digestion 3-4 Figure 3.2 Possible AD System Processes 3-5 Page 2-1 Figure 3.3 AD Technologies Supplied By Different Vendors 3-10 Figure 7-1 On-Site Cogeneration Schematic with Annual Energy Flows 100,000 Ton per Year Garden Waste Facility 7-6

7 Executive Summary Anaerobic Digestion Anaerobic digestion is a naturally occurring biological process that uses microbes to break down organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of organic waste takes place in a special reactor, or enclosed chamber, where critical environmental conditions such as moisture content, temperature and ph levels can be controlled to maximize microbe generation, gas generation and waste decomposition rates. Anaerobic digestion has been in use for several decades to treat sewage sludge, animal wastes and industrial wastewater. Only in the past decade, has the technology become a recognized method for processing solid organic waste from residential and commercial sources. The benefit of an AD process is that it is a net generator of energy which can be sold off-site in the form of heat, steam or electricity. Background To Study The Advanced Renewable and Distributed Generation Technologies (AR&DGT) group of SMUD engaged the services of IEC, with RIS International Ltd as sub-contractor, to explore the feasibility of generating green power through the anaerobic digestion of garden refuse from the Sacramento, Citrus Heights and Sacramento County areas. About 260,000 tons of garden refuse are potentially available as a feedstock for a processing facility. Sacramento Waste Authority (SWA) is currently searching for a local site for aerobic composting of garden refuse, in order to reduce transportation outside the county. SMUD s Renewable Portfolio Standard (RPS) requires 20% of SMUD s energy needs to be met with non-large hydro renewable energy by The RPS requirement can be met by conventional renewables such as wind and geothermal, as well as emerging renewable energy sources such as solar and biomass. Biomass based sources of renewable energy are seen as desirable because they use a locally generated and sustainable feedstock material (such as agricultural and municipal waste streams), and create local economic and environmental benefits. The purpose of this study was to collect and evaluate data on anaerobic digestion technologies, and assess the viability and costs of digesting garden wastes generated in the Sacramento area, and how this technology could be used to generate green energy from garden wastes. i April 2005

8 Anaerobic Digestion Technologies And Facilities Processing Solid Municipal Waste In total, 74 existing AD facilities are known to be operating at full scale and are processing some type of municipal solid waste. Most of these anaerobic digesters are located in Europe, with a few in Asia. There are two full scale digesters operating in Canada and no full scale operations in the US at this time. There are an additional 33 AD facilities planned or under construction which will process the organic fraction of the municipal solid waste stream. Distribution of 74 Existing AD Facilities Processing the Organic Fraction of MSW 28 in Germany 12 in Switzerland 7 in Spain 5 each in Austria and Italy 4 each in Japan and France 3 each in Belgium and Netherlands 2 in Canada 1 each in Finland, Sweden and Denmark (this may be closed), Libya, Korea and Portugal Distribution of 33 Planned AD Facilities Processing the Organic Fraction of MSW 8 Kompogas 6 Dranco 3 ISKA 3 APS (UC Davis, Industry, Vancouver Washington) 1 Bioconverter (Los Angeles) 3 Valorga 2 BTA 6 Linde 1 Biopercolat Some of the key points from the research conducted on the AD technologies are: Gas production for the same materials is similar for most of the AD technologies; Gas production for all technologies is lower for garden waste and higher for food waste, paper waste and MSW; Dry AD technologies appear to use 20% to 30% of the energy produced on-site for internal requirements, leaving 70% to 80% of the energy produced for export; Wet AD technologies appear to use more energy (up to 50% reported) for internal operations, and about 50% is available for export although reported values were inconsistent from one wet technology to another; and Dry technologies, therefore, are preferred where energy production is a key evaluation criterion. Europe has experienced some success handling garden waste in AD systems. Several AD facilities located throughout Europe process a feedstock consisting primarily of garden waste. Screening of AD Technologies Anaerobic digestion systems are broadly defined as wet or dry technologies. Wet AD technologies are suitable for situations where significant removal of contaminants such as plastic bags is desirable at the front end of the process. Dry AD technologies are more suited to relatively clean feedstocks which do not require significant contaminant removal. Dry AD technologies were considered more suitable for the application under consideration. Thirteen (13) commercially viable AD technologies were identified during the course of this study. Six dry AD technologies were researched and evaluated: ii April 2005

9 Kompogas (Kompogas, Switzerland) Dranco (Organic Waste Systems, Belgium) Linde (Linde-KCA-Dresden GmbH, Germany) Biopercolat (Wehrle-Werk, Germany) ISKA (U-plus Umweltservice AG, Germany) Valorga (Valorga, France) Seven wet AD technologies were evaluated: APS (Onsite Power Systems, United States) ArrowBio (Arrow Ecology Ltd, Israel) BTA (Biotechnische Abfallverwer-tund GmbH, Germany) Waasa (Citec Environmental, Finland) Linde (Linde-KCA-Dresden GmbH, Germany) BioConverter (Bioconverter, United States) Entec (Environment Technology GmbH, Austria) The viability of using these technologies to treat garden waste, or a feedstock incorporating some garden waste was assessed using a preliminary, qualitative screening process. The technical screening criteria used to assess and compare the 13 wet and dry technologies included: Proven Technology (has facilities in operation) Flexible Technology (can handle a range of feedstocks, including garden waste) Company Track Record (has a good operating record in established AD facilities) Energy Available for Export Having a local presence in the US or North America was considered an advantage, but not essential. The Onsite Power Systems pilot project at UC Davis provides a valuable opportunity to carry out local research on AD technology. However, this technology will not be ready to construct a facility with a capacity of 50,000 to 100,000 tons/year in the short term, as the pilot plant will only start operation in late 2005, and will require a number of months of operation to generate the results needed to scale to a larger unit. On the basis of the preliminary screening, four dry technologies were considered viable options for a future AD facility: Kompogas, Dranco, Valorga and Linde. Cost Estimates For AD Facilities Costs were estimated for a number of different AD options: Three facility sizes (50,000, 100,000 and 200,000 tons/year capacity); Two AD system designs (wet and dry), Two types of feedstocks (garden waste only and garden waste with food waste) and Two site situations (Greenfield site and co-located with other waste management facilities) iii April 2005

10 Costs for 8 different options are shown in Table ES.1 Table ES-1 Cost Estimates for Different AD Facility Options Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8 Feedstock Garden Waste Garden Waste Garden Waste Garden Waste Garden and Food Waste Garden and Food Waste Garden and Food Waste Garden and Food Waste AD Technology Dry Dry Dry Dry Wet Wet Dry Dry Size (TPY) 100, , , , , , ,000 50,000 Location Greenfields Greenfields Co-Located Co-Located Greenfields Co-Located Co-Located Co-Located Capital Grants ($) ,760, Capital Cost ($) 30,960,000 54,970,000 27,670,000 10,910,000 34,400,000 31,090,000 27,670,000 17,440,000 Annual Capital Cost ($) 3,271,562 5,808,713 2,923,906 1,152,866 3,635,069 3,285,299 2,923,906 1,314,542 Annual Operating and Maintenance (O&M) (Excluding Digestate Composting and Residue Disposal Cost) ($) 2,460,000 3,957,000 1,905,000 1,905,000 2,836,000 2,281,000 1,905,000 1,341,000 Annual Digestate Composting and Residue Disposal Cost ($) 1,650,000 3,300, ,775, Amortized Capital Per Ton ($/Ton) Annual O&M Per Ton ($/Ton) Annual Digestate Composting and Residue Disposal Cost Per Ton ($/Ton) Total Annual Cost Per Ton ($/Ton) Annual Electricity Revenue Per Ton (If Electricity Rate is $0.065/kWh) ($/Ton) (5.58) (5.58) (5.58) (5.58) (7.38) (7.38) (7.59) (7.59) Net Cost Per Ton ($/Ton) Cost per kwh Input (If Input Tipping Fee is set at $25/ton) The analysis showed that capital costs are highest for a greenfield site, and that co-located AD facilities result in considerable capital and operating cost savings. On this basis, a greenfield AD site was eliminated from further consideration, and the analysis focused on co-located site options. Phase 2 should explore co-located AD site options in further detail. The analysis shows that the addition of some food waste to the AD facility feedstock improves the financial performance of the facility by increasing energy revenues. Energy revenues could increase considerably from those shown in the table if the AD facility could be located close to a heat or steam customer, so that all of the energy and heat generated by the AD biogas can be sold. The cost analysis did not evaluate this option, as a specific location was not evaluated. The cost analysis shows that the highest cost component per ton of input is the amortization of capital costs, therefore efforts should be made to identify potential capital grants for construction of the AD facility. The California Energy Commission (CEC) and the California Integrated Waste Management Board (CIWMB) are both interested in supporting biomass based conversion technologies such as anaerobic digestion. Greenfield Site vs. Co-Location It was concluded that establishing an AD facility on a greenfield site (constructing an AD facility on a new, undeveloped site) was not viable economically, because of the high costs of constructing various components such as a scale house, admin building, engine generator set, wastewater treatment, tipping floor and conveyors which would already be established at other waste management facilities. Co-locating the AD facility at an existing waste management iv April 2005

11 facility was considered preferable from a cost point of view, and also because of the reduced social impacts of using an existing rather than a new site. Co-locating at an existing facility will also require less time for new permits. In addition, staff costs can be shared. Co-locating at a landfill, MRF, transfer station or composting facility is viable, and each type of site has different advantages. If the AD facility can be located at a landfill, with landfill gas recovery, the scale-house, gas engines, admin building and wastewater treatment system can be shared. If the AD facility is co-located at a composting site, the digestate (the solid material produced from the digester) can be cured on-site and stronger, more oxygen demanding wastes can be processed by the composting facility, using the digester to handle the early days of biological breakdown. The scale house and admin building can be shared, as well as wastewater treatment facilities. If the AD facility is co-located at a MRF or transfer station, the tipping floor, scale house and admin building can be shared. The net traffic impacts due to slight increases in truck traffic are likely minor. Additional benefits can be gained by locating the AD facility near any existing steam or heat customer which can use the biogas in gas boilers. Conclusions and Next Steps It is concluded that anaerobic digestion of garden waste is technically feasible. It produces a low energy yield compared to anaerobic digestion of other materials such as food, paper and animal manures. The energy yield can be improved by adding these materials to the digester. Anaerobic digestion of garden waste is also expensive compared to open windrow composting, which is the traditional technology used. However, new air quality regulations for open windrow composting sites (not finalized) will increase costs of composting, making AD more cost competitive. Co-locating an AD facility at an existing waste management facility (transfer station, MRF, composting or landfill) is considered the most viable approach in the short to medium term, as this reduces both capital and operating costs of the AD facility, and social impacts. This analysis shows the considerable benefits of co-located site options. Considerable time can also be saved if an existing site, already permitted to receive waste, is used, as modifications to the existing permit require less time than obtaining permits for a new site. Phase 2 should explore co-location options, and options to locate the AD facility close to potential heat and steam customers in more detail to identify firmer cost estimates for the AD facility. Firm costs should be obtained through a formal Request for Proposal process. Capital grants should be pursued to assist with financing of the AD facility. v April 2005

12 Glossary of Terms Biosolids Also known as sewage sludge. Biosolids are produced from primary, secondary or tertiary wastewater treatment systems. Biowaste The organic fraction of the municipal waste stream, which includes food waste and green waste. Digestate The solid organic residual produced at the end of the anaerobic digestion process. This material can be turned into compost or can be directly land applied depending on the local regulations. Garden Refuse The leaf and yard waste fraction of the municipal waste stream. Also known as green waste. Green Waste - The leaf and yard waste fraction of the municipal waste stream. Also known as garden refuse. Grey Waste The residual municipal solid waste remaining after the organic fraction and recyclables have been source separated. Grey waste contains large amounts of paper as well as other materials. MSW Municipal solid waste includes non-hazardous solid portions of residential waste (e.g. from single family and multi family households) and industrial, commercial and institutional (IC&I) waste (e.g. small, local businesses). SSO of MSW Source separated organics of the municipal waste stream includes sold organic materials collected from the residential waste stream (e.g. single family and multi-family) and the industrial, commercial and institutional (IC&I) waste stream. Typically includes food and garden waste. vi April 2005

13 1.0 INTRODUCTION The Advanced Renewable and Distributed Generation Technologies (AR&DGT) group of SMUD engaged the services of IEC, with RIS International Ltd as sub-contractor, to explore the feasibility of generating green power through the anaerobic digestion of garden refuse from the Sacramento, Citrus Heights and Sacramento County areas. About 260,000 tons of garden refuse are potentially available as a feedstock for a processing facility. Sacramento Waste Authority (SWA) is currently searching for a local site for aerobic composting of garden refuse, in order to reduce transportation outside the county. SMUDs Renewable Portfolio Standard (RPS) requires 20% of SMUD s energy needs to be met with non-large hydro renewable energy by The RPS requirement can be met by conventional renewables such as wind and geothermal, as well as emerging renewable energy sources such as solar and biomass. Biomass based sources of renewable energy are seen as desirable because they use a locally generated and sustainable feedstock material (such as agricultural and municipal waste streams), and create local economic and environmental benefits. The criteria established by SMUD to assess the options for biomass energy projects are: Potential for low cost kw-hrs; Local benefits of improved air and water quality and economic benefits; High quality fuel (BTU content, organic fraction, etc.); Sustainable supply of fuel; Proximity to SMUD distribution. The Sacramento Waste Authority is open to exploring alternatives to aerobic composting of garden refuse, if they meet the following criteria for an acceptable technology: Cost effective: Can be financed by public-private partnership to deliver costs which are in line with current costs; Durable equipment: the equipment supplier has a good track record, and the equipment or technology employed provides good warranties and serviceability; Nuisance free: There are little or no odors, litter, vectors, traffic impacts or negative effects on property values; Final Product: The technology produces a saleable residue for marketing by the private sector party involved. The purpose of this study was to collect and evaluate data on anaerobic digestion technologies, and assess the viability and costs of digesting garden wastes generated in the Sacramento area, and how this technology could be used to generate green energy from garden wastes. Data was collected on thirteen (13) anaerobic digestion technologies which are operating at various scales throughout Europe and Asia to treat solid, non-hazardous waste from residential and commercial sources, with a particular focus on facilities that processed garden wastes as part of their feedstock. 1-1 April 2005

14 The viability of using these technologies to treat garden waste, or a feedstock incorporating some garden waste was assessed, and a preliminary, qualitative screening process narrowed down the list of 13 technologies to 4 which show promise. Costs were estimated for a greenfield AD facility to process 100,000 tons/year of garden refuse. The economies of scale of constructing a 200,000 ton/year facility were also identified, as well as the cost savings associated with co-locating the AD facility as an existing waste management facility such as a transfer station, MRF, composting or landfill site. The costs of 50,000 ton colocated were identified. While this size of facility has higher capital cost per ton per year installed capacity, the capital investment required is less. Various options to decrease net operating costs were explored and identified. The study draws a number of conclusions and recommends next steps for SMUD. 1-2 April 2005

15 2.0 Quantity and Composition of Garden Refuse Available as Feedstock This section discusses the amount and composition of the garden refuse that may be processed at a future anaerobic digestion facility. 2.1 Quantity of Garden Refuse Available The research carried out for this study is based on an available feedstock of about 260,000 tons/year of garden refuse from: the City of Sacramento (83,000 tons), Sacramento County (104,000 tons), commercial and self haul (70,000 tons), and miscellaneous sources (3,000 tons). Figure 2.1 shows the tonnages of garden refuse collected and diverted through composting for the City of Sacramento for each month in 2002 and The table and figure serve to illustrate the significant variation on the amount of garden waste which is produced each month. Figure 2.1 Garden Refuse Collected In the City of Sacramento By Month, 2002 and 2003 tons 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 Jan Feb Mar Apr May June July month Aug Sept Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Total Diverted 2002 (tons) 6,526 5,029 5,965 7,212 6,699 6,464 5,366 5,641 5,538 6,153 6,145 16,591 83, (tons) 5,216 4,307 5,633 8,341 6,059 5,651 5,613 4,964 5,078 6,249 10,831 10,885 78, April 2005

16 This presents challenges for biological processes such as anaerobic digestion, where a steady rate of loading to the reactors is ideal. However, the loading rate can be equalized through stockpiling of some peak-season materials, and slowly blending these into the feedstock to the units. 2.2 Composition of Garden Refuse Typically, the garden refuse stream consists of a wide range of putrescible material including leaves, grass-clippings, perennial and annual plant material, tree and shrub branches and other woody waste, etc. The City of Sacramento and surrounding areas experience a full complement of seasons which have a great impact on the quantity and composition of their garden refuse stream. Open windrow composting sites which traditionally process garden waste are adaptable to changing waste composition, whereas anaerobic digestion processes require closer operational control to adapt to changing feedstock composition. Seasonality of garden refuse amounts and also the composition of the garden refuse present a challenge in the design of an anaerobic digestion system which must adjust to different feedstock mixtures resulting from the impact of the seasons. In order to better understand the composition of Sacramento s green refuse, a review of other relevant waste composition studies was undertaken. We did not identify residential waste composition studies from jurisdictions in California and west coast states that provided garden refuse composition and generation information. Either garden refuse specific studies had not been undertaken 1 or in the case of the California Integrated Waste Management Board (CIWMB) and the City of Portland, the waste audits targeted residential waste collected in refuse trucks and destined for disposal and focused only on the garbage picked up after recycling or composting programs. Therefore, the results were of limited value to this study. In general, the composition of the garden refuse stream varies by the following seasons: Spring high grass clippings; Summer high garden waste and grass clippings; Fall high leaf waste; Winter high woody waste (i.e. tree branches and trimmings). In the Sacramento area, the spring and summer season is characterized by the generation of mostly tree trimmings and grass-clippings; whereas leaves are generated in the fall, especially late fall (November and December). Few waste composition studies have addressed either the composition of the garden refuse waste stream which is picked up separately from garbage for separate processing and diversion, or its seasonality. Any composition studies identified during the course of this research have to date focused on the garden waste remaining in the garbage stream and do not address the composition of the garden refuse stream itself. 1 Contact with the City of Seattle, the City of San Francisco and Alameda County failed to identify relevant garden refuse composition studies that would be useful for this study. 2-2 April 2005

17 The composition and generation information identified cannot be used as a reliable substitute for the City s garden refuse composition data. Efforts should be made to establish a detailed seasonal breakdown of the garden refuse stream, through garden refuse composition studies carried out on a monthly basis for a 12-month period, to capture seasonal variations. 2.3 City of Sacramento Garden Refuse The City of Sacramento has some unique features that will impact the type and mix of garden refuse received at an anaerobic digestion facility. The City has the second highest number of trees per capita than anywhere else in the world (Paris, France takes top spot). There are an estimated 1 million trees within the City resulting in a large portion (35%) of the residential waste stream comprising of garden refuse. The City has a well established garden refuse diversion program offering separate garden refuse collection since Most of the leaf and yard waste is collected using vehicle with a claw. Residents sweep their yard waste into a bundle at the curb and a vehicle with an articulating claw picks up the green refuse pile and places the material in the back of a waiting city truck. The City is testing a lawn and garden cart service. The City actively promotes backyard composting, grasscycling 2 and mulching of yard waste. This practice reduces the amount of grass entering the garden refuse stream, although the extent to which is unknown at this time. 2 The City does not prohibit grass clippings from being collected at the curb at this time. 2-3 April 2005

18 3.0 Anaerobic Digestion of Garden Refuse and Municipal Solid Waste This section describes the different anaerobic digestion system design options available, and the key variables involved in choosing an anaerobic digestion system. 3.1 Anaerobic Digestion Process Anaerobic digestion is a naturally occurring biological process that uses microbes to break down organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of organic waste takes place in a special reactor, or enclosed chamber, where critical environmental conditions such as moisture content, temperature and ph levels can be controlled to maximize gas generation and waste decomposition rates. Landfills generating noxious odors are often demonstrations of the impact of organic waste digestion in an enclosed environment with little or no oxygen. However, in the case of anaerobic digestion technology, the gases are captured, so odors are greatly reduced. Commercial anaerobic digestion systems can replicate this natural process in an engineered reactor that produces methane gas much faster (2-3 weeks compared to years) then anaerobic conditions in a landfill. One of the by-products generated during the digestion process is biogas, which consists of mostly methane (ranging from 55% to 70%) and CO 2. The benefit of an AD process is that it is a net generator of energy. The excess energy produced by the AD facility, which is not required for in-plant operations, can be sold off-site in the form of heat, steam or electricity. The level of biogas produced depends on several key factors including the process design, the volatile solids in the feedstock (composition of the feedstock) and the carbon/nitrogen (C:N) ratio 3. Each of these factors is discussed in more detail below. 3.2 Experience to Date with SSO, MSW and Garden Refuse There are over 100,000 wastewater treatment plants around the world using anaerobic digestion to process biosolids from wastewater treatment operations. More recently, anaerobic digestion systems have been used to treat other biosolids, such as animal manures. At the lower end of the technological scale, anaerobic digestion is used at a household and community level in many developing countries, such as China and India, to generate heating and cooking fuel. Europe is generally considered to be the international leader in commercial AD technology, although their experience with digestion of solid non-hazardous municipal solid waste (MSW) is fairly recent, with most activity taking place over the past decade. Virtually all examples of anaerobic digestion facilities treating municipal waste (source separated organics or mixed waste) are located in Europe, with commercially available technologies implemented primarily in Denmark, Belgium, France, Germany and Switzerland. High capacity systems to treat mixed municipal solid waste have been introduced recently in Spain, Portugal and Italy. Japan also has some facilities. It was estimated that in 1999 European anaerobic digestion plants 3 Hackett, Colin and Williams, Robert. September Evaluation of Conversion Technology Processes and Products. Prepared for the California Integrated Waste Management Board 3-1 April 2005

19 processed about one million tons/year of mixed municipal solid waste (MSW) or source separated organics (SSO) in 53 plants. Figures for 2004 suggest that 107 AD plants are being constructed or processing the organic fraction of municipal solid waste operate worldwide. Most (95%) of these are located in Europe 4. Table 3.1 shows key AD companies processing MSW feedstock in Europe in Table 3.1 Key Firms Generating Biogas from MSW Feedstock in Europe in 2003 Company Technology Number of Plants Total Capacity (Tpy) Linde-KCA, Switzerland BRV ,500 Valgora International, France Valgora ,400 OWS, Belgium Dranco ,000 Kompogas, Switzerland Kompogas ,000 Citec Environmental, Finland Wassa ,500 Source: EurObserv ER, August 2004 Over the past decade, a number of low tech anaerobic digestion systems have been installed in the North American market to treat animal manures. In 2002, there were an estimated 40 farmscale projects in operation on swine, dairy, and poultry farms across the United States. These systems use a low-tech approach to anaerobic digestion to process and treat livestock manure and produce gas, which meets some on-farm energy needs. AgStar (a partnership of the U.S. Departments of Agriculture and Energy and the Environmental Protection Agency (EPA) to promote bio-gas projects) estimates that anaerobic digestion could be cost-effective on about 3,000 U.S. farms 8 The use of anaerobic digestion technology to treat municipal solid waste has been slow to penetrate the North American market, mostly because of high costs compared to other options. The North American market currently has only two operating anaerobic digestion plants that process municipal waste. Both are located within a one-hour drive of Toronto, Canada. The Canada Compost Inc. (CCI) facility in Newmarket, Ontario (less than one hour north of Toronto) uses BTA technology and has the capacity to process up to 150,000 tons/year of source separated organics and also some mixed waste loads. A second facility located within the City of Toronto also uses BTA technology. It has a throughput capacity of 15,000 tons/year of mixed MSW, or 25,000 tons/year of SSO. A third, two-stage digestion facility was constructed in Guelph, Ontario in the late 1990 s, but closed within the last two years because of financial problems. Currently, there are no pilot or commercial anaerobic digestion facilities operating in the United States that process municipal solid waste or source separated organic waste. In the United States, processing MSW using AD technology experienced a flurry of activity in the early 1980s. Several pilot projects were conducted in Pompano Beach, Florida; Walt Disney World, Florida; 4 Cragg, Robert. Anaerobic Digestion: Can It Be Successfully Applied to MSW Management? Recycling Association of Minnesota and Solid Waste Association of North America 9th Annual Fall Conference, Fall The Linde figure includes AD facilities processing animal liquid manure; therefore, the number of plants cited do not match those provided in this report which deal only with those facilities processing biowaste. 6 Dranco did not provide figures in the Eurobserv ER. Numbers have been added from this report. 7 Three of the facilities are demonstration plants or in the conceptual stages, which were not included in this report. 8 Balsam, John. October Anaerobic Digestion of Animal Wastes: Factors to Consider. Appropriate Technology Transfer for Rural Areas. 3-2 April 2005

20 and University of Berkley, California 9 In all three cases the organic feedstock was augmented with sewage sludge (biosolids), so that the pilots were actually testing co-digestion rather than pure digestion of MSW. More recently, the City of Greensboro, North Carolina conducted a pilot in 2000 to process 30,000 tons per year of yard waste using anaerobic digestion technology. The yard waste comprised of leaves, grass clippings, plant material and branches. The AD system was designed by Duke Engineering & Services, which invested two-thirds of the required capital, with the City investing the remaining one-third. The team intended to turn the pilot into a full scale system and to show that AD was viable for garden waste. The pilot was not successful and the plant was eventually dismantled 10. The system encountered many problems including difficulty maintaining the necessary heat in the reactor to optimize biogas generation; the lignocellulosic material failed to break down and removal of plastic bag pieces in the feedstock created problems. Over the past year, numerous large communities within the United States have entered into agreements to process source separated organic waste using anaerobic digestion technology, are in negotiations with AD suppliers or have undertaken feasibility studies examining anaerobic technology among a range of other Conversion technologies to treat municipal waste. Details are presented in Table 3.2 for details. Table 3.2 Communities in the United States Investigating Anaerobic Digestion for MSW Community Status Documents City of Los Angeles, California City of Lancaster, California City of Seattle, Washington Santa Barbara County, California Linn County, Iowa Have entered into agreement with BioConverter, United States to construct an AD plant to process 3,000 tpd (780,000 t/y) of green waste In negotiations with BioConverter to construct an AD plant to process 200 tpd (52,000t/y) of green waste. The project is waiting Council approval. Evaluated 26 food waste anaerobic digestion technologies to determine the feasibility of implementing a facility capable of processing up to 50,000 tpy of food waste AD one of a number of conversion technologies evaluated to process municipal solid waste A study was conducted to analyze the feasibility of anaerobic digestion (AD) of organic solid wastes Los Angeles Department of Water and Power Board Letter for Approval (available from LADWP) None available Summary report and supporting documents available from staff Anaerobic Digestion of Source Separated Food Study: Final Technical Memorandum Sept 2002 Study report available Alternatives to Disposal Final Report Sept 2003 Study report available Anaerobic Digestion Feasibility Study June SRI International. October Data Summary of Municipal Solid Waste Management Alternatives; Volume 1: Report Text. Prepared for National Renewable Energy Laboratory, Colorado. 10 Conversation with Ms Covington, Director of Environment, City of Greensboro, North Carolina on December 4th, April 2005

21 3.3 Anaerobic Digestion Design Options Most AD technologies use a similar approach to processing organic waste. At the front end of the process, the organic feedstock is blended to reduce the size of the material and is mixed with other materials to optimize digestion in the reactor. The blending process may involve the use of a sieve, trommel screen, chopper, magnet and/or other device to remove contaminants such as stones, metal, glass and plastic from the feedstock prior to the mixing stage. In the mixing stage, the feedstock is mixed with heated water and a starter innoculum to initiate microbial activity. The water is heated using biogas from the digestion process. Mixing with the warm water raises the temperature of the waste to increase the rate and extent of degradation within the reactor. The innoculum is supplied from either the waste stream from the reactor or from the wastewater produced during de-watering. The mixed waste is then fed into the reactor, in which digestion occurs, producing a relatively solid residue and biogas. Enough biogas will be generated to produce a self sustaining energy supply for the facility. Excess energy can be sold in the form of electricity, steam or heat. The solid waste that is produced by the digester is de-watered using a range of dewatering technologies (centrifuges and belt filter presses are the most common). The liquid from the dewatering process is directed to the wastewater treatment system, with some re-introduced back into the earlier digestion steps. The solid produced by dewatering is referred to as digestate. The digestate is at about 50% solids, is most frequently sent to composting for additional stabilization prior to sale as a compost product. In some European situations, the digestate is land applied without further stabilization. The process is illustrated in Figure 3.1. Figure 3.1 Flow Diagram for Anaerobic Digestion MSW mechanical separation Recyclables Residual Sale Disposal Source separated organic waste and garden waste kitchen and garden waste feedstock excess energy for sale Mixing or Pulping or Hydrolysis Energy - electricity - steam - heat Anaerobic Digestion Process Anaerobic Digestion Process Biogas Digestion Dewatering Wastewater Treatment Digestate Composting 3-4 April 2005

22 The key features of anaerobic design technology are: A. Digestion Stages, characterized as: - Single Stage - Two Stage B. Feed Total Solids (TS) Content, characterized as: - Wet Process (<15% TS) - Dry Process (>20%% TS) C. Operating Temperature, characterized as - Mesophilic Process (approx. 93 to 98 F or 34 to 37 C) - Thermophilic Process (approx. 131 to 140 F or 55 to 60 C) These features can be arranged in a multitude of AD systems (see Section 3.3 for details) as illustrated in Figure 3.2. Figure 3.2 Possible AD System Processes Wet Process Mesophilic Process One Stage Production Thermophilic Process Dry Process Mesophilic Process Thermophilic Process Mesophilic Process Wet Process Two Stage Production Thermophilic Process Dry Process Mesophilic Process Thermophilic Process 3-5 April 2005

23 A. Digestion Stages The production of biogas from organic waste in an environmentally controlled anaerobic digestion system involves a series separate biological processes; acidification and methanogenisis as the prominent processes. In one stage AD systems, both of these biological reactions take place at the same time in a single enclosed reactor. Two stage systems provide a separate reactor for the acidification step and one for methane production. Single Stage Process - European plants that process household organic waste are mostly onestage systems. A number of two-stage AD systems have been constructed within the past four years. The predominance of one-stage systems is in part due to this technology s relatively simple design compared to two stage or multi-stage systems, less frequent technical failures and lower capital costs 11. In addition, the overall performance of the one stage system measured in terms of the production rate of biogas is comparable to approaches that utilize more than reactor to control biological processes. Single Stage AD Process HYDROLYSIS and DIGESTER STAGE Hydrolysis (breakdown of complex organic matter into sugars and amino acids) Acidogenesis (material reduced to simple acids) Two Stage process The two stage system is based on the concept that the optimal reactor Acetogenesis environment for microbes that produce biogas is (further breakdown of material into acetate, one that is separate from environmental conditions CO 2 and H 2 ) for the other microbes that produce the acids and acetates needed for initial breakdown of the organic material. Two stage systems have been Methanogenesis used for processing biosolids in wastewater (formation of methane and CO 2 ) treatment plants for over 50 years, to optimize the environment for acid forming and methane Adapted from Ostrem, 2004 and Erickson, 2004 forming bacteria. A number of new two stage processes have been introduced, piloted and are now being offered for commercial sale to handle municipal solid waste. Some multi-stage processes feature a front-end percolation process under semi aerobic conditions to begin to break down the cellulose in the organic material over a shorter retention time. 11 Vandevivere. P. et. Al Types of Anaerobic Digesters for Solid Wastes. 3-6 April 2005

24 The key advantage of a two stage AD process is that the different processes can occur under different preferred ph conditions. The processes that occur in the first stage, the hydrolysis stage, occur most effectively under acidic conditions (below 5 ph) 12. Under these conditions, the methanogenic bacteria (methane formers) would die since they need to live in ph conditions above 6.0, with optimum ph conditions between 7.0 to 7.2 ph 13. These conditions can be achieved in the second stage, the digester stage, in a two stage process. The theory behind Two Stage AD Process First Stage HYDROLYSIS STAGE Second Stage DIGESTER STAGE Hydrolysis (breakdown of complex organic matter into sugars and amino acids) Methanogenesis (formation of methane and CO 2 ) Acidogenesis (material reduced to simple acids) Acetogenesis (further breakdown of material into acetate, CO 2 and H 2 ) Adapted from Ostrem, 2004 and Erickson, 2004 two-stage processes is that optimizing each process will lead to higher gas yield and breakdown of organic matter. However, experience to date with MSW systems is that the additional costs of the extra tankage cannot be justified in terms of the higher gas yield, therefore some companies who experimented with two stage systems in the past have reverted to one stage, or prefer one stage systems. B. Total Solid Content The total solid content within an anaerobic digester depends on the type of system employed (wet or dry). Wet System - A wet system is designed to process a dilute organic slurry with 10-15% total solids, which has the consistency of soup. This wet slurry is created by adding approximately 30cu ft of water per ton (one cubic metre of water per tonne) to the incoming waste. BTA and Wassa are two examples of wet or low solids digestion technologies. 12 Ostrem, Karena. May Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University. 13 Vermer, Shefali. May Anaerobic Digestion of Biodegradable Organics in Municipal Solid Wastes. Columbia University. 3-7 April 2005

25 Wet AD systems used to treat municipal solid waste have been adapted from well established systems used to treat wastewater treatment plant biosolids. Despite its established use in the treatment of wastewater biosolids (sludge), the wet system approach has had to overcome a number of challenges to treat municipal solid waste. The production of a wet slurry from mixed residential waste can result in the loss of volatile organics, the part of the organic waste which is required to produce biogas. A wet slurry inside the digestion reactor will tend to separate into layers of material, with a floating layer of scum at the top of the reactor. This can prevent proper mixing, while the heaviest particles will settle to the bottom where they can cause damage to the reactor s pumps 14. Short circuiting is another potential drawback associated with wet one-stage systems. This problem occurs when particles of organic waste are removed from the digestion reactor before they have been fully digested. This results in a less than optimal rate of biogas production as segments of organic waste are not processed inside the reactor for the most efficient length of time. Some systems, particularly two stage systems, have reduced the potential for short circuiting through various design modifications. One of the challenges associated with single stage wet AD systems is that the slurry inside the reactor requires frequent mixing in order to reduce the chance of over-acidification, causing a drop in ph and the potential death of the methanogenic bacteria. A number of advances have been made to address this issue. A study by Iowa Department of Natural Resources concluded that In general, the wet singlestep systems are not very well suited for digesting the OFMSW (organic fraction of municipal solid waste) alone. Besides the accumulation of sand and stone sediments in the reactor and a formation of plastic films, a fibrous material has a tendency to form strings that wind around the CSTR s (continuously stirred tank reactor) stirrer 15 Dry Systems - Dry systems mix approximately 10 cu ft of water per ton (0.3 cu m per tonne) of incoming waste to produce an organic slurry of 20-40% total solids. Examples of commercially available high solids content dry digestion systems (one stage) include Dranco, Kompogas and Valorga. Dry systems use considerably less water as part of the process than wet systems. This in turn leads to lower energy requirements for in-plant needs, because less energy is needed for heating process water, and for dewatering AD reactor contents. This in turn leads to more energy available for export. Many dry systems use plug flow reactor designs. This approach helps to maintain a balanced organic load inside the reactor by adding partially fermented slurry into the reactor while fully digested residue is extracted. One of the advantages of the single stage dry system is that it can more readily handle contaminants (i.e. stones, glass, plastic, metals) in the process compared to wet systems. 14 Vandevivere. P. et. Al Types of Anaerobic Digesters for Solid Wastes. 15 R.W. Beck. June Anaerobic Digestion Feasibility Study: Final Report. Prepared for the Bluestem Solid Waste Agency and Iowa Department of Natural Resources. 3-8 April 2005

26 C. Operating Temperature Commercial AD reactors are generally operated within either mesophilic or thermophilic temperature ranges. Mesophilic Process An mesophilic AD process operates within a temperature range of 86 o F to 95 o F (30 o C to 35 o C), and at an optimal temperature of about 35 o C (95 o F). The advantage of the mesophilic process is that the bacteria are more robust and more adaptable to changing environmental conditions 16. Thermophilic Process A thermophilic AD reactor operates at an optimal temperature of about 55 o C (130 o F) and must be maintained at a temperature ranging from 122 o F to 14 o F (50 o C to 65 o C) for most effective performance 17. The main advantage associated with a thermophilic reactor is that higher temperatures can yield a superior rate of biogas production in a shorter period of time. 3.4 Anaerobic Digestion Technology Designs Available Many AD technologies are available that claim to process municipal organic waste, either as separately collected residential organic waste (including food waste and garden waste) or as part of the municipal waste stream (MSW). Depending on the feedstock and operating restrictions (e.g. energy and water requirements), some technologies may be better suited to processing municipally sourced organic waste than others. Figure 3.3 shows the vendors which supply AD technologies in the different categories discussed above (wet, dry, single stage and two stage). 16 Ostrem, Karena. May Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University. 17 Ibid 3-9 April 2005

27 Figure 3.3 AD Technologies Supplied By Different Vendors Anaerobic Digestion Process Technologies Single Stage Production Wet Process Dry Process Waasa Linde BRT BTA BioConverter Entec Valorga Kompogas Dranco Two Stage Production Wet Process Dry Process Linde BRT APS (Onsite Pow er Systems) Arrow Bio BioPercolat ISKA Linde BRT One Stage vs. Two Stage When processing municipal solid waste, the advantages of separating biological processes into two or more reactors do not appear to yield many significant advantages. According to some sources, both single and two-stage systems perform equally well when processing municipal waste in terms of the amount of waste that can be processed on an annual basis and the rate of biogas production. Approximately 90% of all European anaerobic digestion plants that process municipal organic waste utilize one-stage technologies. The predominance of one-stage systems is in part due to this technology s relatively simple design compared to two-stage, less frequent technical failures and lower capital costs. BioPercolate and ISKA have both recently developed 2-stage systems. These systems both have a front end separation process to remove non organic materials from the organic fraction of the MSW. The organics are processed through two separate stages, a percolation (hydrolysis) stage and a digester stage. The advantage of the two stage approach is the reduced retention time (less than 8 days total retention time) due to the introduction of the intense biological activity in the percolation stage. Wet vs. Dry Wet systems used to process municipal organic waste have tended to be used in combination with more dilute feedstocks such as animal manures or sewage sludge. Where municipal solid waste is processed along with another feedstock, the process is referred to as co-digestion. This approach is popular in some municipalities in Europe, as it addresses two processing 3-10 April 2005

28 needs at the same time with the same technology. Approximately 50 of the 90 wet systems in Europe co-digest the MSW with manure Feedstocks and Gas Production Comparatively little information is available on the amount of biogas produced by different feedstocks in an anaerobic digester. The only pure research available at this time is from bench-scale studies carried out by Barlaz for the USEPA 19, where the relative contributions of different materials to landfill gas generation (through anaerobic digestion) were measured. Results of this work, which have been used extensively, are presented in Table 3.3. Material Paper Table 3.3 Biogas Yield from MSW Materials Moisture (% wt) Biogas Yield m 3 /kg of material feed* Biogas Yield ft 3 /lb of material feed Newspaper Cardboard/Boxboard Telephone Directories Office paper Mixed paper Kitchen Waste Food Yard waste Grass Leaves Brush Other organic Sources: ICF, 2001 and Hackett & Williams, 2004 The table shows that each material has a different natural moisture content, and yields a different amount of biogas through the digestion process. The amount of biogas produced by each material depends on the percentage of volatile solids available in each material. The volatile solids fraction of each material refers to the biodegradable portion of the solid content of each material, and varies from one material to another. The gas production values shown in Table 3.1 assume a methane yield of 3.52 f 3 /lb (0.22 m 3 /kg) VSS (Volatile Suspended Solids). Table 3.1 is most useful for showing the comparative gas yield from different materials under the same degradation conditions. It shows that the comparative gas yield (from most to least) is: 18 R.W. Beck. June Anaerobic Digestion Feasibility Study: Final Report. Prepared for the Bluestem Solid Waste Agency and Iowa Department of Natural Resources. 19 ICF Consulting Determination of the Input of Waste Management Activities on Greenhouse Gas Emissions. Report submitted to Environment Canada April 2005

29 Office paper, mixed paper, cardboard and boxboard, Food, Telephone directories and newspaper, Brush, Grass, and Leaves. Grass and leaves will make up most of the material which would be received at an AD facility processing only garden waste in the Sacramento area. They are the materials which yield the least biogas; therefore most digesters need a certain amount of paper and food waste to increase the gas yield to a reasonable and economic level (see Table 3.4). Table 3.4 Biogas Yield Input Digestion Nm 3 CH 4 /raw ton Biogas (m 3 /t) Biogas (ft 3 /t) Biowaste + garden waste ,800-3,200 Biowaste + low level of cardboard ,700-4,000 Biowaste + cardboard + garden waste ,700-4,000 Biowaste + cardboard ,000-4,800 MSW ,000-5,100 Typical biogas composition from the anaerobic digestion of source separated food waste is provided by in Table 3.5 and is based on the experience of BTA in Europe and their Toronto facility 20. Table 3.5 Biogas Composition Biogas Composition Average Minimum Maximum Methane Vol. % Carbon dioxide Vol. % Hydrogen sulphide ppm 50 1,800 Total chlorine mg/m Total fluorine mg/m 3 < 0.1 < Table 3.6 provides typical European experience with the production of biogas per weight of food waste processed. Table 3.6 Biogas Production m 3 /tonne Biogas Production f 3 /ton Single Stage Digestion 85 2,720 Two Stage Digestion 95 3, Source: Seattle reports Final TECHNICAL MEMORANDUM NO. 4: Biogas Markets, February April 2005

30 3.6 Energy Uses Biogas produced during anaerobic digestion is primarily composed of methane (CH 4 ) and carbon dioxide (CO 2 ) and some parts/million (ppm) of hydrogen sulfide. The biogas contains approximately 55%-70% methane, is water saturated (100% humidity), and may contain dust particles and siloxanes. Production of biogas from an anaerobic digestion process will vary depending on: The anaerobic digestion process design chosen, the extent to which volatile solids are converted to biogas (which depends on retention times and reaction temperature, etc. ) and The volatile solids content of the feedstock, which depends on the composition of the waste sent to the digester; this impacts on the amount of gas which can be produced through microbiological decomposition. Biogas Utilization Biogas from an anaerobic digester can be used as a substitute for natural gas, either in boilers producing hot water and steam for industrial processes, in combined heat and power (CHP) applications to generate electricity, as well as heat, as a pure natural gas substitute (highgraded for insertion into the natural gas supply), or for more exotic uses such as fueling a fleet of vehicles or as a fuel for fuel cells. Where biogas is used in a boiler, minimal treatment and compression is required, as the boiler is much less sensitive to sulfide and moisture levels in the fuel, and also can operate at a much lower input gas pressure. Where biogas is used for onsite co-generation, a generator of the type used in landfill gas and wastewater treatment plant applications is appropriate, as these generators are designed for digester and landfill gas, and are less sensitive to moisture and sulfides. Compression equipment would be required to boost the gas pressure to the level required by the generator. Biogas can be used as a fuel for vehicles, but significant upgrading is required to produce: A higher calorific value A consistent gas quality No enhancement of corrosion due to high levels of hydrogen sulfide, ammonia and water A gas without any mechanically damaging particles. This option is not likely of interest to SMUD, as it simply displaces traditional fossil fuels, rather than producing power from renewable sources. There are many examples in the US where landfill gas (which is similar to the biogas from an AD facility) is used for fuel in a vehicle fleet. An example of using biogas from an AD facility in a vehicle fleet is described in the Kompogas section of Section 4 of this document April 2005

31 The methane contained in biogas can also be used as a fuel for fuel cells. This combination produces a pure green energy source, as one of the criticisms of fuel cells is that they use traditional fossil fuels as their energy source and are not therefore truly green. This option can be considered by SMUD at a future time when fuel cell technology is further advanced and the AD facility is fully functional. Biogas Upgrading If biogas from the AD facility is used in the gas turbine, moisture and hydrogen sulfide must be removed, to minimize corrosion and other impacts on the equipment, which is designed for natural gas use. A boiler is much more tolerant of contaminants such as moisture and H 2 S than a gas turbine. Biogas comes out of the digester at about 1psi. If used in a gas turbine, it must enter the compression equipment at the same pressure as natural gas, which typically is supplied at psi. If used in a boiler, a pressure of 30psi is sufficient. Sulfur Removal An H 2 S scrubber uses iron to oxidize the sulfide to elemental sulfur, which precipitates out of the gas stream, and thus removes H 2 S from the biogas. The scrubber reduces the sulfide concentration by over 90%, and a removal rate of up to 99% is claimed by some manufacturers. Sulfur removal is not required if the biogas is used in a boiler. An onsite co-generation system may also be able to handle the untreated biogas if the unit is specifically designed for biogas applications (more typically landfill gas or digester gas applications). Carbon Dioxide Removal Removal of carbon dioxide enhances the energy of the biogas either to reach vehicle fuel standard or natural gas quality. At the present time, there are four methods used commercially: water scrubbing polyethylene glycol scrubbing carbon molecular sieves membrane separation. At this time, it is contemplated that SMUD will not embark on biogas applications which would need CO 2 removal, because as less technically complex options are available to meet their renewable energy production needs. Moisture Removal Moisture removal is required for transmitting biogas offsite and for use in some gas turbines. A knockout pot can be used to remove liquid water in the biogas by gravity, due to its larger diameter. A desiccant dryer or a dryer that chilled the gas would be necessary for removal of water vapor from the biogas, for transmission of the biogas by pipeline. Neither of these applications is contemplated for any SMUD AD proposals at this time. Utilization of the biogas in a boiler may not require moisture removal. Pressurization To boost the biogas pressure to the 200 psi pressure required at a co-generation unit, a large two-stage compression system is required. If the biogas is used in a boiler, compression of the gas to 30 psi is generally sufficient and necessary for transport of the biogas through a pipeline April 2005

32 Compression to 30 psi is also necessary for the gas mixing used by the wet mesophilic digestion technology. 3.7 Anaerobic Digestion of Garden Waste No AD facilities were identified which process only garden waste (100%) as the feedstock. Several Dranco and Kompogas AD facilities have garden waste as the primary feedstock (up to 75%). Suppliers contacted and interviewed for this project responded positively to supplying a system that could handle garden waste only (i.e. Linde, Kompogas, and Dranco). Some of the problems encountered trying to digest garden waste as a dedicated feedstock include: Establishing optimal nutrient, trace element and nitrogen conditions; Maintaining the heat in the reactor; Attaining optimal biogas yield; Dealing with poor biodegradation conditions of the lignocellulosic materials (woody wastes). One of the most critical factors for most anaerobic digestion processes is to maintain an optimal carbon to nitrogen (C:N) ratio. The ratio represents the amount of carbon present in the digester contents in relation to the amount of nitrogen present. The optimum C:N ratio in an anaerobic digester is between 20 and In situations where the carbon to nitrogen ratio is high, methanogens swiftly consume the nitrogen resulting in lower biogas production. When the carbon to nitrogen ratio is low, it means that there is an accumulation of ammonia in the AD reactor, and higher ph values (>8.5) are reached 22. These ph levels are toxic to the methanogens. (methanogenic bacteria), and can result in failure of the reactor. 23 In the case of garden waste, maintaining the carbon to nitrogen balance is highly dependent on the composition of the garden waste. When there is an excess of leaves in the feedstream, the digester gets too much carbon and not enough nitrogen. Nitrogen needs to be added to the digester to increase the nitrogen concentration in the reactor and restore the correct C:N ratio. This is generally done by adding chemicals (e.g. urea) or another feedstock with a high nitrogen content to the digester. Conversely, when there is a high grass content in the feed stream, the digester gets too much nitrogen and not enough carbon. In this case, additional carbon needs to be added to the digester to restore the correct balance. Discussions with AD technology suppliers indicate that a mesophilic process would best suit garden waste since the nitrogen content becomes less of an issue at mesophilic operating conditions. However, the trade off using the mesophilic process is a reduction in the amount of biogas generated. 3.8 References Balsam, John. October Anaerobic Digestion of Animal Wastes: Factors to Consider. Appropriate Technology Transfer for Rural Areas. 21 Monnet, November Ibid 23 Ibid 3-15 April 2005

33 Cragg, Robert. Anaerobic Digestion: Can It Be Successfully Applied to MSW Management? Recycling Association of Minnesota and Solid Waste Association of North America 9th Annual Fall Conference, Fall Erickson, Larry et. Al. August Anaerobic Digestion Chapter 7 from Carcass Disposal: A Comprehensive Review. National Agricultural Biosecurity Centre Consortium. EurObserv ER. August Biogas Energy Barometer. Hackett, Colin and Williams, Robert. September Evaluation of Conversion Technology Processes and Products. Prepared for the California Integrated Waste Management Board. Haight, Murray. March 9, Technical Report: Integrated Solid Waste Management Model. School of Planning, University of Waterloo. ICF Consulting Determination of the Input of Waste Management Activities on Greenhouse Gas Emissions. Report submitted to Environment Canada. Lynn, Matt. November Live and Times of an Organics Recycling Company. In Biocycle, vol. 40, pg Ostrem, Karena. May Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University. R.W. Beck. June Anaerobic Digestion Feasibility Study: Final Report. Prepared for the Bluestem Solid Waste Agency and Iowa Department of Natural Resources. Remade Scotland. November An Introduction to Anaerobic Digestion of Organic Wastes. SRI International. October Data Summary of Municipal Solid Waste Management Alternatives; Volume 1: Report Text. Prepared for National Renewable Energy Laboratory, Colorado. US Environmental Protection Agency (EPA) Greenhouse Gas Emissions from Management of Selected Materials in Municipal Solid Waste: Final Report. Prepared by ICF. EPA 530-R Vandevivere. P. et. Al Types of Anaerobic Digesters for Solid Wastes. Wise, Donald L Fuel Gas Developments. CRC Series in Bioenergy Systems. CRC Press Inc., Boca Raton, Florida. Valorga International Presentation made to the 10 th World Congress on Anaerobic Digestion In Montreal, Canada, August 29 th to September 2, Vermer, Shefali. May Anaerobic Digestion of Biodegradable Organics in Municipal Solid Wastes. Columbia University April 2005

34 4.0 Technical Information on AD Technologies - DRY 4.1 Methodology The approach to collecting information for the technical description component of the study was as follows: The list of 15 AD vendors in the Request for Proposal was used as the starting base for the study research; RIS in-house files from other AD projects were reviewed; A literature search was carried out at the outset of this study. Reports and articles were ordered and reviewed; A list of 36 AD suppliers in Biocycle magazine was used as a secondary data source. All 36 suppliers on this list were contacted to identify which technologies they represented; More detailed information was requested directly from AD suppliers. The available written information was summarized and follow-up contact was made with vendors of AD technologies to clarify the written information and to ask the following questions: - Type of technology (wet, dry, thermophilic, mesophilic one stage, two stage, etc.); - Number of facilities in operation; - Ability of the technology to process pure garden refuse; - Identification of facilities which process garden refuse and % of feedstock which garden refuse represents; - Requirement for additional feedstock in order to process garden refuse; - Extent to which additional feedstock enhances performance; - Identify all existing plants in operation, which process municipal solid waste (MSW), source separated municipal waste (SSO) or municipal waste in combination with other feedstocks (location, annual capacity, feedstocks, energy production); - Expected energy output per ton of waste (scfm biogas and MWhrs of electricity) - Amount and availability of heat or electricity required for operation (parasitic loads) - Infrastructure requirements (power, wastewater treatment); - Land requirements (footprint plus buffer); - Company track record (years in operation); - Warranties; - Parts and service support; and - Lead time required to fabricate equipment. For all technology descriptions, the information is presented in imperial units used in the United States as well as metric units used in Canada, Europe and Asia, which will enable comparison to other studies and literature, if required. The following two sections are divided into dry AD process technologies, described in Section 4.0, and wet AD process technologies, described in Section 5.0. The AD technologies profiled are summarized in Table 4.1 along with their key features. 4-1 April 2005

35 Technology DRY AD FACILITIES Kompogas (Kompogas, Switzerland) Dranco (Organic Waste Systems, Belgium) Linde (Linde-KCA-Dresden GmbH, Germany) Biopercolat (Wehrle-Werk, Germany) ISKA (U-plus Umweltservice AG, Germany) Valorga (Valorga, France) WET AD FACILITIES APS (Onsite Power Systems, United States) ArrowBio (Arrow Ecology Ltd, Israel) BTA (Biotechnische Abfallverwertund GmbH, Germany) Waasa (Citec Environmental, Finland) Linde (Linde-KCA-Dresden GmbH, Germany) BioConverter (Bioconverter, United States) Entec (Environment Technology GmbH, Austria) Total Table 4.1 Anaerobic Digestion Technologies Profiled Total* # 19 full 8 part 7 full 6 part 4 full 1 part 1 full 1 part 1 full 3 part 10 full 3part 0 full 3 neg. Facilities Processing Residential Waste <20,000 (tpy) Capacity (# of facilities in full operation only) 20,000 to 50,000 (tpy) 50,000 to 100,000 (tpy) >100,000 (tpy) full full 2 part 8 full 6 full 5 part 0 full 2 neg full full 28 part 5 neg. * full = full operation; part = under construction; neg. = under negotiations April 2005

36 4.2 Kompogas Description of the Technology Kompogas is a thermophilic process which takes place at o F (55-60 o C). Kompogas technology uses a plug flow digester with a day retention time. The The incoming waste is shredded, then sorted to remove contaminants such as plastic and glass. A magnetic separator is used to recover any ferrous metal material ahead of the digester. Waste goes to a second shredder or a sieve, then to an intermediate bunker, which is used as a storage unit for mixing and regulating the flow to the digester. The shredded waste stays in this tank for 2 days, where it warms up to some extent prior to entering the digester. Water from the dewatering unit is added to the waste in the storage unit, to adjust the feedstock moisture content to 28% dry solids content, 72% moisture content. A piston pump delivers the shredded waste to the digester, which is typically a concrete or steel tank. For a plant which processes 12,000 tons per year, a digester with a capacity of 1 ton is required. A heat exchanger heats the waste from o F (25-55 o C). The waste mass also heats while in the storage unit. The digested waste is dewatered by a screw press to 50% solids content. Management of digestate varies by location. In the Otelfingen facility in Switzerland, after 2 days, the solid digestate is sent to farmers fields for land application without curing. No revenue is received for the digestate. In some regions Kompogas pays for the transportation. The farmers like the structure of the digestate, and spread the digestate with a compost spreader. The Kompogas digestate quality is usually at half the current limits for heavy metals. Management of press-water also varies by location. For some plants, some of the water from the dewatering process goes back to plant. IN The Kompogas Otelfingen, farmers use the remainder as fertilizer (the N System and P content is of value), and some is directed to onsite aquaculture greenhouses. Kompogas have determined that for small plants, the most efficient construction approach is to pre-fabricate steel digesters elsewhere and move them to the site in one piece. The Volketswil digester is 82 feet (25 m) long and 13 feet (4m) diameter. It was welded together in the fabrication shop, and was assembled and moved to the site in one piece (on trucks, by road, at night). For big plants, digesters are made from concrete on site. Kompogas also feels that shop assembly allows better quality control for electro-mechanical equipment. Kompogas have moved to a modular approach for assembly and construction of pre-fabricated units (e.g. containers for control, heating). 4-3 April 2005

37 4.2.2 Typical Feedstocks Kompogas operates facilities using source separated biowaste (food waste and garden waste combined) as a feedstock. Some plants report biowaste and separate yard waste as feedstock (it is assumed that the two feedstocks are source separated). They also accept commercial food waste from companies such as McDonalds, or companies working in the food preparation business Energy Specifications Kompogas uses a rough rule of thumb that biogas production is 3,500 f 3 (100 m 3 ) per ton of biowaste input, and up to 5,300 ft 3 (150 m 3 ) per ton if there is a high food waste content. The process designs are based on adequate analysis of the expected input material. Table 4.2 identifies the reported energy production, internal use and export energy for selected Kompogas facilities. Table 4.2 Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected Kompogas Facilities Plant Capacity Gas Production Passau Hellersberg, 39,000 tpy 4,000 ft 3 /t (115m 3 /t) Sample facility 10,000 tpy 3,700 ft 3 /t (105 m 3 /t) Electric Energy Production 9.1million kwhr 2.1 million kwh/yr Electric Energy Use For Plant 1.6 million kwhr/year 0.3 million kwh/yr Energy available for Export 7.5 million kwhr/year 1.8 million kwh/yr Energy usage varies by site. At the Otelfingen site, Kompogas clean the biogas on-site and use it as a fuel in their fleet of cars and trucks. The gas cleaning process is proprietary, and the company have invested heavily in perfecting it Infrastructure Requirements Power Usage of biogas for electric energy production needs appropriate equipment to feed the produced power into the local grid. Wastewater from Dewatering Filter Press Kompogas have adopted an approach of directing wastewater from dewatering units to beneficial use. It is stored in a tank for use by farmers and some is also directed to aquaculture greenhouses. This approach was considered preferable to constructing pre-treatment facilities before discharging filter press wastewater to local sewers. This may or may not be viable in the Sacramento area, depending on the location of the AD facility. Other vendors (e.g. Dranco, discussed later) pre-treat the wastewater on-site through either on-site systems (e.g. a small rotating biological contactor - RBC) or add the wastewater to an existing wastewater treatment lagoon processing landfill leachate, which is also a high-strength wastewater. 4-4 April 2005

38 Land Requirements The footprint for a typical 50,000t/y digester facility is about 3 Acres 24, excluding any composting requirements. The Otelfilgen plant in Switzerland processes 12,500 tons per year and requires about 3 Acres (5,000 m 2 ) for its total footprint. It is located in an industrial area with an office building as a neighbor, and reportedly does not experience odor complaints. Lead Time to Fabricate Equipment Kompogas does not have a local agent in the US and currently handles all North and South American requests from Switzerland. If they were to become involved in a project in Sacramento, they would need to develop a local partnership, preferably with a construction company who is also involved in the waste management business. The equipment would likely be fabricated locally with engineering input from Kompogas designers Operations Elsewhere Kompogas have 19 facilities in operation, mostly in Switzerland (8), Germany (8) and Austria (3) and one pilot facility in Kyoto, Japan, with a capacity of 1,000 tons/year, which has lead to the construction of a full scale facility with a capacity of 20,000 tons/year in Another 8 facilities are scheduled to come on-line in Three of these are in Switzerland, with the others in Spain, Martinique, Japan and Germany. Table 4.3 lists the full scale Kompogas AD facilities in operation at the end of Table 4.3 Full Scale Kompogas Plants Location Weissenfels, Germany Bachenbulach, Switzerland Oetwil am See, Switzerland Feedstock (Substrate) Plant capacity Start-up Energy Use biowaste 12, Electrical and thermal energy biowaste, yard 4, Biogas fed to the national gas network biowaste 10, Electrical and thermal energy Roppen, Austria biowaste 10, Electrical and thermal energy Volketswil, Switzerland Frankfurt, Germany Alzey-Worms, Germany Niederuzwil, Switzerland Braunschweig, Germany biowaste, yard 5, Electrical and thermal energy biowaste 30, Electrical and thermal energy biowaste 26, Electrical and thermal energy biowaste 15, Electrical and thermal energy biowaste 20, Hunsruck, Germany biowaste 10, Electrical and thermal energy Lustenau, Austria biowaste 10, Electrical and thermal energy Leesternau, Austria biowaste 8, Seattle Tech Memo, April 2005

39 Location Munchen-Erding, Germany Otelfingen, Switzerland Feedstock (Substrate) Plant capacity Start-up Energy Use biowaste 26, Electrical and thermal energy biowaste 12, Electrical and thermal energy, biogas upgrading, fuel station Kempten, Germany biowaste 10, Electrical and thermal energy Simmern, Germany biowaste 10, Electrical and thermal energy Bachenbulach, Switzerland Rumlang, Switzerland Samstagern, Switzerland biowaste 4, Electrical and thermal energy, fuel, long distance heating Biowaste, yard Biowaste, yard 8, Electrical and thermal energy 10, Electrical and thermal energy, biogas upgrading, fed to the national gas network, fuel Planned Kompogas plants, and plants under construction are listed in Table 4.4 Location Weiningen, Switzerland Table 4.4 Planned Full Scale Kompogas Plants or Facilities Under Construction Feedstock (Substrate) Plant capacity Planned Opening Date Energy Use biowaste 12, Biogas upgrading, fuel Jona, Switzerland biowaste 5, Biogas upgrading, fuel Lenzburg, Switzerland biowaste 5, Electrical and thermal energy Passau, Germany biowaste 39, Electrical and thermal energy Martinique, Caribbean n.a. 20, Electrical and thermal energy Rioja, Spain n.a. 75, Electrical and thermal energy Kyoto, Japan n.a. 20, Electrical and thermal energy Dietikon, Germany biowaste 10, Electrical and thermal energy Company Standing Kompogas is a Swiss company which is an off-shoot of a construction company. The AD division has developed an anaerobic digestion technology which is about 10 years old. Kompogas have 19 AD plants in Europe; 10 in Switzerland, 8 in Germany and 3 elsewhere, and one pilot plant in Japan. The list includes 5 plants which they own and operate themselves around Zurich airport. These 5 plants allow easy access to show prospective clients. To date the company has invested US $25.3 million (30 million Swiss Francs) in the business, and have learned how to do things more efficiently as time has passed. They traditionally spent US $ 8.4 million (10 million Swiss Francs) to construct their early plants, which can now be constructed for about half of that amount. The cost savings have been achieved through a more modular and pre-fabricated approach, and building as much of their digesters outdoors, to avoid the need for construction of explosion proof buildings and fixtures. 4-6 April 2005

40 Kompogas has agents and licensing arrangements with companies in Austria, Germany, France and Japan. Current Licensees are identified on the Kompogas web site. The North and South American markets are currently serviced through their head office in Switzerland. The Austrian office is the agent for Russia as well as Eastern Europe, and the French agent serves Spain, Portugal and the UK. Kompogas prefer to make arrangements for local licensees rather than try to enter new markets themselves Descriptions of Some Kompogas Facilities Kompogas Otelfingen Facility The Otelfingen Kompogas facility was constructed in Located near Zurich airport in Otelfingen, the plant processes about 13,000 tons per year of source separated organic waste. The waste comes from both households and commercial operations (e.g. food waste from McDonalds). Three people work at the plant 5 days/week, 8 hours/day. At the weekends, one person looks after the 5 Kompogas plants in the area. There is an alarm system which alerts the operator to any problems at a specific location. The waste processed at the plant consists of 70% source separated organic waste (garden and food waste) from a population of 100,000 in small cities and villages near the plant. About 70%- 80% of the household waste is garden waste and 20% is food waste. Thirty percent of the incoming waste is commercial waste (e.g. from companies who make salads for McDonalds). McDonalds also delivers boxes of french fries and other expired foods to the facility. Two engines (180kW and 110kW) generate power on-site. Twenty five percent of the energy is required for in-plant needs; 75% is surplus energy which is sold or used for other purposes (e.g. fuel for fleets). Kompogas receive no revenues for the digestate, they receive all of their revenues from tipping fees and energy sales. They receive electricity revenues of US $0.13 (0.16 Swiss Francs) per kwhr (required by Swiss law for renewable energy), and this energy is sold into the local grid. Some of the biogas is cleaned up and used in the Kompogas car and truck fleet. Filter press effluent is directed to an aquaculture greenhouse. This facility was funded 50% by Kompogas, and 50% by the Swiss government. Schools got involved in doing research at the AD facility, figured out aeration rates for water hyacinths, etc. Volketswil Kompogas Facility, Switzerland The Volketswil AD facility is located at a composting site, and was constructed to solve an odor problem at an existing open windrow composting site. The government instructed the owner to install an AD facility to process critical components of the waste stream (mostly wet food wastes). 4-7 April 2005

41 The tipping fee at the open windrow facility is US $108 (128 Swiss Francs) per ton; this tipping fee was raised to US $125 (148 Swiss Francs) per ton to cover the costs of adding the AD facility. The AD facility cost US $2.1 million (2.5 million Swiss Francs) for equipment and buildings; it has a 5,000 t/year capacity. The digestate is directed to on-site curing in the open windrow composting area adjacent to the digester. The total site (composting plus AD) has a capacity of 15,000 t/year. The digester is made of plain steel with a thin aluminum coating covering the thermal insulation. The steel does not need to be stainless, as no corrosion occurs because there is no oxygen inside the AD tank. Mixing and storage are core parts of the fermentation process; these operations take place inside a building, but the digestion takes place outdoors. Where digesters are located within a building, all fixtures and the building itself have to be explosion proof; locating the digesters outdoors saves money. There is enough heat available within the digester contents to keep the digester at the right temperature, even in the cold winters in the area. This installation has proven that outside installation is viable in cold climates. Kompogas tried to sell the heat from the Volketswil facility, but this received much lower revenues compared to electricity. Local farmers help themselves to the wastewater produced from dewatering digester contents. This wastewater is stored in a tank on-site no data are available on the impact that this liquid has on crops but farmers like the effluent because it contains nutrients in liquid form at no cost. 4-8 April 2005

42 4.3 DRANCO Description of Technology DRANCO is a dry, thermophilic, single stage anaerobic fermentation process, followed by a short aerobic curing phase. During the AD phase, the organic material is converted into biogas in an enclosed vertical digester capable of treating a wide range of incoming material with a solids or dry matter content from 15% to 40%. Steam is injected into the incoming waste stream to raise its temperature to 122 o F (50 o C) before introduction to the digester. The steam adds moisture to the incoming feedstream, and Dranco have found that steam provides The Dranco System very efficient heat transfer. The process operates with minimal addition of water and is quite flexible in its feedstock requirements. Digestion takes place in the thermophilic range of o F (50-55 o C). Incoming feed material is fed to the top of the digester once per day. Mixing of digester contents occurs via re-circulation of the materials extracted at the bottom of the digester, mixing with fresh wastes (usually one part fresh wastes for six parts digested wastes), and pumping the material to the top of the digester. Apart from feeding and removal of the digestate, there is no further mixing or agitation needed in the digester, which works at very low pressure (less than 50 mbar). There is no internal mixing equipment within the DRANCO digestion tank; this simple process design ensures that there is little wear and tear on the digester and has proven effective for treatment of wastes ranging from 20% to 50% TS (total solids) range. The reactor retention time is between 20 to 30 days, and the biogas yield ranges between 2,800-4,200 ft 3 /t ( m 3 /t) of waste feedstock. The collected biogas is sometimes stored temporarily for further purification before it is sent to gas engines or combined heat and power (CHP) facilities. The digested material is extracted from the bottom of the digester. It is then dewatered to a total solids (TS) content of about 50%, and is stabilized aerobically for a period of about two weeks. The Humotex solid composted product is used as a soil conditioner, and can be purchased by soil blenders, landscapers or consumers. Some composting operations bag and mix their own products for sale to market; others have long standing arrangements to sell their compost to well established soil blenders. The finished compost contains some plant nutrients (nitrogen, phosphorus and potassium) but its main advantage is as a soil conditioner rather than as a fertilizer. DRANCO has also developed the SORDISEP-process which can be used prior to and after DRANCO digestion to recover metals and other materials from mixed waste (garbage). In the dry sorting step, the high-calorific fraction of the incoming waste stream (generally mixed municipal waste or grey waste) is separated for production of a Refuse Derived Fuel (RDF), and ferrous and non-ferrous metals are recovered. A wet separation step after digestion recovers sand, fibers, and inert material. 4-9 April 2005

43 4.3.2 Feedstock Specifications DRANCO digesters can digest a feedstock which is 100% garden waste, but operators prefer to have some food and paper in the waste stream also, in order to increase gas yield. The gas yield from pure garden waste is about 2,500-2,800 ft 3 /t (70 to 80m 3 /t), and is about 3,500-4,200 ft 3 /t (100 to 120 m 3 /t) for biowaste (a mixture of garden and food waste). The Brecht 2 Dranco plant in Belgium operates on a feedstream of 75% garden waste with the remaining 25% made up of food, diapers and paper. Woody materials do not contribute to gas production; therefore, they are removed from the feedstock ahead of time, or kept separate (if collected as brush) rather than using up digester capacity. The most critical factor for the Dranco process, as with other digestion processes, is to maintain the carbon to nitrogen (C:N) ratio in the optimal range. When there is an excess of leaves in the feedstream, the digester gets too much carbon, and nitrogen needs to be added to the digester (usually as urea); when there is a high grass content in the feedstream at certain periods of the year, there is too much nitrogen in the system and carbon needs to be added as wood chips to ensure optimal digestion conditions Energy Specifications Biogas consists of methane and CO 2. The methane content of the biogas is about 55%, therefore biogas production needs to be converted to energy content. The DRANCO process uses a small amount of the energy from the gas (or imported energy) for in-plant needs, therefore the net energy available for export is what is of greatest interest in this analysis. Available information on net energy exports from existing DRANCO plants is summarized in Table 4.5. Table 4.5 Reported Energy Production, Internal Energy Use and Energy Available for Export at Selected DRANCO Facilities Plant Capacity Gas Production Kaiserslautern 20,000t/y grey waste 5,600 ft 3 /t (158m 3 /t) Energy Production 5.2 million kwhr Energy Use For Plant 0.7 million kwhr Energy available for Export 4.5 million kwhr Aarberg, Switzerland 13,500 tpy garden waste 520MWhrs electricity Steam: 1120 MWhr generated; 719 MWhr used internally; 401 MWhrs sold to next door customer Electricity: 2400MWhrs sold The Aarberg plant produces anywhere from 2,800-5,300 ft 3 /t ( m 3 /t) of biogas, with an average typical value of 4,200-4,700 ft 3 /t ( m 3 /t). The Aarberg plant produces 1,120 MWhr of steam at 110 degrees C, most of this is used in the plant (719MWhr). Some is exported to a neighboring business April 2005

44 4.3.4 Infrastructure Requirements The Aarberg facility operates with 2 staff plus one manager. Wastewater produced on-site is pre-treated in a RBC (rotating biological contactor) to reduce the pollutant load to a value suitable for discharge to the local sewer. Other DRANCO facilities are located adjacent to landfills, and treat wastewaters from their facilities in the landfill lagoons Operations Elsewhere Dranco has run seven (7) demonstration facilities in Europe and Japan, and one small facility in Florida in These are listed in Table 4.6. Table 4.6 DRANCO Demonstration Plants Location Feedstock (Substrate) Volume of digester Gent, Belgium Mixed garbage and biowaste 2,100 ft 3 (60 m 3 ) Bogor, Indonesia Market waste 1,100 ft 3 (30 m 3 ) Florida, USA Mixed garbage 35 ft 3 (1 m 3 ) Graz, Austria Mixed garbage 180 ft 3 (5 m 3 ) Kagoshima, Japan Garbage and manure 1,100 ft 3 (30 m 3 ) Yaku Island, Japan Biowaste and manure 1,100 ft 3 (30 m 3 ) Graincourt Les Havrincourt, Grey waste and miscellaneous 530 ft 3 France (15 m 3 ) Year Constructed There are six full scale Dranco facilities in operation at this time: 2 in Belgium (Brecht 1 is no longer operating), 1 in Austria, 2 in Germany, and 2 in Switzerland. Most of the existing facilities are in the 10,000 to 20,000 tons/year size range. The Brecht 2 facility is the largest of the existing plants at 50,000 tons/year. Each plant incorporates design features which improve on previous efforts, hence the Salzburg plant incorporated a number of features identified through the operation of the Brecht 1 plant, etc. Full scale DRANCO plants are listed in Table April 2005

45 Table 4.7 Full Scale DRANCO Plants Location Brecht 1 Brecht, Belgium near Antwerp Brecht 2 Salzburg, Austria Bassum, Germany Aarberg, Switzerland Kaiserslautern, Germany Villeneuve, Switzerland Rome, Italy Feedstock (Substrate) Biowaste and paper waste Biowaste and waste paper Plant Capacity tpy Year Constructed and First Year of Operation 20,000 July 1992 Ceased operation by Nov 04; Brecht 2 has replaced 50,000 January 2000 Biowaste 20,000 Dec 1993 Grey Waste 13,500 June 1997 Biowaste 11,000 January 1998 Grey waste 20,000 January 1999 Biowaste 10,000 February 1999 Originally designed for mixed waste, converting to biowaste 40,000 July 2003 Planned DRANCO plants, and plants under construction are listed in Table 4.8. There are 8 plants in process (3 in Germany; 3 in Spain; 1 in Italy and 1 in South Korea). The trend is moving towards 40,000 t/year plants in Europe. Dranco provide this capacity through modular designs. Pusan, South Korea plan to construct a 75,000 tpy plant. Location Leonberg, Germany Hille (MBA Pohlsche, Heide) Terrassa, Spain (near Barcelona) Munster, Germany Pusan, South Korea Feedstock (Substrate) Table 4.8 Planned DRANCO Plants Plant Capacity tpy Planned Year of Operation Biowaste 30,000 Planned for 2004 Grey waste and dewatered sludge 38,000 Planned for 2005 Biowaste 25,000 Planned for 2005 Grey waste and industrial waste Food waste and paper sludge 24,000 Planned for ,000 Planned for 2005 Vitoria, Spain Mixed waste 20,000 Planned for 2006 Alicante, Spain unknown unknown Not constructed; being retendered 4-12 April 2005

46 4.3.6 Company Standing Organic Waste Systems (O.W.S) developed the DRANCO process (Dry Anaerobic Composting). The company was established in 1988 and is publicly owned and traded under Belgian law. The first Dranco Facility (Brecht 1) opened in 1992 with a capacity to process 20,000 t/yr of source separated organic waste and paper waste. O.W.S. has also developed the SORDISEP-process (Sorting, Digestion and Separation) for municipal and industrial waste, to recover recyclables and energy. OWS also has a laboratory and material testing business in the US, based in Dayton, Ohio. For this reason, staff from the Belgian operation travel to the US a number of times per year Short Descriptions of Full Scale DRANCO Facilities in Operation Aarberg, Switzerland At Aarberg, Switzerland there was an existing open windrow composting site for garden and food waste which experienced odor complaints. The owner needed to solve the odor problem associated with the wet fraction of waste being delivered to the site. The local municipalities of Biel, Grenchen and others produced 20,000 tpy of wet fraction waste (a combination of food and garden waste). They decided to build a 11,000 tpy digester to handle the wet fraction of incoming biowaste and send the remainder of the incoming bio-waste directly to the open windrow composting facility. This approach provided additional processing capacity and has solved the odor problems at the site. The site receives t/d, 5 days per week. Incoming waste is crushed to 1.6 inches (40mm) maximum size, followed by magnetic separator to remove any metals. The waste is then sent to a dosing unit (intermediate hopper), and from there to a loading pump, which is a heavy duty piston type, also used in the concrete industry. The carbon content of the incoming waste is 30% to 35%; it has a low organic content (65%), and an average moisture content of 37.5%. The incoming waste is heated to 131 o F (55 o C), using steam exhaust from the motor steam injection provides very efficient heat transfer and provides good temperature control, and is one of the unique elements of the DRANCO system. A small amount of the steam condenses during the heat exchange process and adds to the moisture content of the material going to the digester. DRANCO have found that heat transfer is more efficient with steam rather than using hot water. At Aalberg, 7 parts of recirculated material are mixed with 2 parts of fresh material and one part of steam to provide heat and increase the temperature of the feedstock to the digester. The incoming material is loaded into the digester at three points at the top of the digester to maintain plug flow. The retention time is days, maximum 25 days. The digester contents are at 18% to 35% solids; the ideal is to keep digester contents as dry as possible, but no drier than 40% solids. Gas is burned directly in a gas motor to generate electricity at the site. There is gas storage capacity of 13,400 ft 3 (380 m 3 ) at the site, and a flare to burn the biogas if the motor is down. Steam from the gas motors is used to heat incoming material April 2005

47 Digested material is sent to a filter press at 18% to 20% solids for dewatering to 48% to 50% solids. The same trucks which deliver the waste take the digestate back to the aerobic open windrow facility where it is stabilized and further cured through 2-3 weeks retention at the aerobic facility. The aerobic compost is given to farmers at no cost, because other revenue sources are sufficient for the facility. Filtrate from the filter press is treated in a rotating biological contactor (RBC) before discharge to the local sewer which take it to the Lyss WPCP (water pollution control plant) for further treatment in a conventional activated sludge system April 2005

48 4.4 Linde - DRY Linde-KCA-Dresden GmbH based in Germany and Linde BRV Biowaste Technologies AG based in Switzerland are fully owned subsidiaries of Linde AG, Germany. The companies supply both anaerobic and aerobic organic waste treatment systems. Linde-KCA-Dresden GmbH has been supplying biological wastewater and sludge treatment systems since 1973 and opened its first manure processing AD facility in Linde BRV Biowaste Technologies AG was founded in 1981 (formally known as BRV) and introduced the first manure AD system in Europe. In 1999, BRV became a subsidiary of Linde Description of Technology Linde offers a range of different systems, including anaerobic digestion, aerobic systems and comprehensive mechanical-biological treatment systems (MBT) for MSW (municipal solid waste). There is an increasing interest in MBT systems in the last two to three years in the UK and Europe, as it avoids the need for households to source separate organic and recyclable materials from the waste stream. The biological treatment of wastewater and sewage sludge has been part of Linde s range of services since as early as Linde started pursing anaerobic digestion for solid waste in Linde offer a complete range of AD systems, including both wet and dry digestion systems. Linde AD systems operate as single or two stage (wet) systems or as single stage (dry) processes and use both thermophilic and mesophilic digestion processes. The design of the system depends on the feedstock conditions and other factors. The dry system is described in this section and the wet system is described in Section 5.0 of this report. Dry AD System The dry AD system can treat material with a dry matter total solid (TS) content between 15-45%. The horizontal plug flow reactor uses agitators to prevent formation of floating scum and settlement of material. The organic material is fed into the digester/reactor by a compact feeding unit, which can be used to adjust the total solid content, if needed. The digested solid material is dewatered in a centrifuge and aerobically composted using a variety of approaches ranging from tunnel composting to an intensive composting module. The dry AD system is well suited to treat MSW April 2005

49 Linde Dry System Feedstock Specifications Linde state that their dry AD technology is well suited to handle organic waste, green refuse, and waste high in total solids content. Examples of existing facilities that process organic waste (including garden waste) alone or in combination with other feedstock using a dry AD system design are provided in Table 4.9. Location Baar, Switzerland Heppenheim, Germany Lemgo, Germany Table 4.9 Feedstocks of Linde Dry Digestion Facilities Feedstock Tons/year SSO 6,000 tpy Garden 12,000 tpy SSO 26,000 tpy garden waste 5,000 tpy industrial waste 2,000 tpy SSO 34,000 tpy garden waste 6,000 tpy Start-up batch process - 1 digester thermophilic batch process - 3 digester - thermophilic SSO source separated organic (biowaste or food and garden waste with non-recyclable papers) Operations Energy Specifications One source estimates that the Linde technology used to treat MSW yields biogas of 3,500 ft 3 /t (100 m 3 /t) feedstock 25. Table 4.10 shows the energy production and energy outputs for selected Linde dry facilities. 25 Ostrem, Karena. May Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University April 2005

50 Dry System Location Table 4.10 Energy Production for Selected Linde Dry AD Facilities Capacity tpy Energy output Baar, Switzerland 18,000 Biogas = 3,000 ft 3 /t (85 m 3 /t) Gross electricity production 640,000 kwh Lemgo, Germany (thermophilic) 40,000 Biogas = 3,600 ft 3 /t (102 m 3 /t) Gross electricity production 6,000,000 kwh Infrastructure Requirements Because the company offers a variety of AD technologies and waste treatment solutions, the infrastructure requirements vary by facility and plant location Operations Elsewhere Linde report that they have about 100 AD operational facilities in Europe that handle organic waste as well as sewage sludge and animal manures. Over the past two years, Linde has constructed 20 new biogas facilities in Europe. The company has been actively involved in mechanical-biological waste treatment facilities to process municipal solid waste, recently announcing several mechanical-biological treatment (MBT) ventures. Existing and proposed facilities that deal with organic wastes (including green waste) separated or as part of the municipal solid waste stream are identified in Table Location Table 4.11 Existing and Proposed Linde Dry AD Facilities Capacity tpy Feedstock Start-up Additional Information Baar, Switzerland 18,000 biowaste, garden Dry acres (10,000 m 2 ) surface - cost US $17.6 million (SFr 21 million ) operation cost SFr 90/tonne Heppenheim, Germany 33,000 SSO 31,000, garden 5,000 industrial 2, Dry, thermophilic - Retention time 21 days - Gross electricity 5.7 GWh/yr - Net electricity 4.0 GWh/yr - Heat 8.8 GWh/yr Lemgo, Germany 40,000 biowaste Dry acres (50,000 m 2 )surface - cost US $21.3 million (DM 32 million) - operation cost US $117/t (Euro 90/t) Hoppstadten- Weirsbach, Germany 23,000 Biowaste Dry Lille, France 110,000 SSO 46,000, garden 57,000 market waste 7,000 Under construction - Dry - Biogas productivity is expected to be 265 million ft 3 (7.5 million m 3 ) 4-17 April 2005

51 Lemgo, Germany - The Lemgo facility uses a thermophilic dry horizontal flow design. Some of the reactor heating is done outside the digester using a short heat exchanger, but most heating occurs within the digester walls using a heat exchanger. The feedstock is reduced in size by a screw mill and undergoes a 2 to 4 day period of anaerobic hydrolysis to facilitate inoculation. Before the material from the hydrolysis tank is fed to the digester, it is processed by a calibrator and chopped into smaller pieces. The digester has a retention time of 21 days. The digestate is cured at an aerobic composting site for 30 days As stated earlier, MBT facilities are gaining in popularity for the treatment of municipal waste, as they reportedly can handle an un-source separated waste stream. This simplifies collection for the municipality as all waste can be collected in one truck. Most of these facilities use aerobic composting technology, to break down the organic fraction of the waste stream. Some Linde aerobic facilities under construction or in the planning stages are listed in Table Location Leipzig-Crobern, Germany Table 4.12 Linde Mechanical-Biological Treatment Facilities featuring Aerobic Treatment Capacity tpy Feedstock Start-up Additional Information 300,000 MSW Under Construction Fridaff, Luxemburg MSW Ordered - will become Germany s largest mechanicalbiological treatment facility for MSW - US $89 million (68.5 million Euros) total with US $49 million (38 million Euros) for Linde's technology Linde has not constructed any AD facilities in North America to handle solid wastes materials and do not appear to have any in the planning stages Company Standing Linde is a substantial German company with well established anaerobic digestion technologies and processes to treat source separated organic waste as well as municipal solid waste. The Linde Group supplies chemical and gas processing technology, design and installation services through a number of affiliates in the United States April 2005

52 4.5 Biopercolat The Biopercolat technology, patented by Wehrle-Werk in Germany, is part of a system designed to handle the entire municipal solid waste stream and not just the source separated organic fraction Description of Technology The Biopercolat process has been developed to treat municipal solid waste and is referred to as a mechanical-biological treatment (MBT) process. The process is similar to that of the ISKA process, relying on mechanical separation to remove non-organic materials at the front end, and using a percolation method, under slightly aerobic conditions, to treat the organic matter before being processed anaerobically in a digester. Mechanical separation of the non-organic components of the municipal solid waste stream from the organic components occurs first. The organic matter is fed through a two stage, wet, mesophilic biological process. This process involves two stages, the hydrolysis or percolation stage and the anaerobic digestion stage. The hydrolysis or percolation stage is carried out under partial aerobic conditions. Process water is continually percolated through the mechanically agitated (horizontal stirring) device under slightly aerated conditions in a horizontal tunnel. Conducting the percolation process under slightly aerated conditions has the advantage of increasing the breakdown of the organic material thus reducing the retention time. The retention time in the percolation unit is 2 3 days. At the end of the percolation process the material is passed through a screw press which separates the liquid (which is fed into the digester) from the solids (which are composted or further processed). The liquid from the hydrolysis process is fed to an anaerobic plug flow filter filled with support material operating as an upflow anaerobic blanket sludge (UASB) reactor with a retention time of 4-5 days. The total process has a retention time of only seven days. Liquid from the digester is either recirculated within the digester or fed back into the percolator and reused as process water for the percolation process Feedstock Specifications The Biopercolat process is being used in one location, Kahlenberg, Germany to treat unsorted municipal solid waste (MSW), which includes organic waste (food and garden waste). To date, 4-19 April 2005

53 the technology has been used to process municipal solid waste only. Garden waste is a component of the MSW but not identified as a main component Energy Specifications At the Kahlenberg demonstration facility, which processes 20,000 tpy of MSW, the anaerobic process yielded about 2,500-2,800 ft 3 (70-80 m 3 ) of biogas per ton feedstock. The plant operation is self-sufficient in energy with more than one third of electricity available for sale. The digestion process uses about 50 kwh/ton leaving heat for sale up to 200 kwh/ton. The process reportedly generates a biogas containing about 70% methane Infrastructure Requirements As with the ISKA process, the Biopercolat process provides a complete mechanical-biological treatment process to handle municipal solid waste. Screening, shredding and separation processes are used at the front end to separate non-organic from organic waste fractions. At the back end of the process, the Percotrate material (digestate material) is stabilized before landfilling or it undergoes an aerobic drying process, patented by Wehrle-Werk called the Percotry process, which enables the dried material to be used as refuse derived fuel. The footprint of the Kahlenberg facility is unavailable Operations Elsewhere The first facility to open was a pilot plant located at the landfill site of Kahlenberg, Germany. From 2000 to 2002, the plant became a full scale demonstration facility processing 11,000 tpy of MSW (with a design capacity of 20,000 tpy throughput) from the community of Kahlenberg. The plant was owned by the customer and operated by Biopercolat. In the last four months, Biopercolat has entered into an agreement with Kahlenberg to construct a full scale plant to handle all of the community s MSW. As with the demonstration project, the full scale plant would be customer owned and operated by Biopercolat Company Standing Wehrle-Werk, Germany is a medium-sized company active in the field of waste water treatment, energy and environmental technologies and solutions. Wehrle-Werk has recently ventured into solid waste treatment with its first digestion facility at Kahlenberg, piloted in 1997 using the 'Biopercolat' process. The company has no supplier in North America and would want the customer to facilitate a suitable partnership or consortium with companies that could provide the mechanical installation and environmental qualification requirements April 2005

54 4.6 ISKA ISKA is a subsidiary of the German power and waste management conglomerate U-plus Umweltservice AG and is the exclusive license holder for the ISKA Percolation patents. Developed by U-plus Umweltservice AG, the ISKA technology is a relatively new technology that uses a mechanical-biological percolation process to treat municipal solid waste (MSW) Description of Technology As with the Biopercolat technology, the ISKA technology is designed to manage the entire municipal solid waste stream and not just source separate organic (SSO) component. The first stage of the process involves mechanical separation of the noncompostable components of the municipal solid waste stream from the organic or biodegradable components. Once separation is achieved, the organic fraction is put through a two stage, wet biological process. This process involves two stages, the hydrolysis or percolation stage and the anaerobic digestion stage. In the first stage, separated organic material is fed into the Percolator (horizontal, continuously operating, cylindrical reactor (plug flow), in which heated wash water from the anaerobic digester is sprayed over the organic material. The break down of the organic material occurs under aerobic conditions. The Percolator operates in a semi continuous fashion, accepting fresh material at the front end and removing unwanted solid waste material at the back end on a regular basis. Temperatures are maintained within a range of o F (40 to 45 o C). During this process contaminants such as stones, glass, grit and other non-organic debris are removed using a sand washing removal process. Other compostable solids are passed through a screw press to remove the solid component for composting and the liquid component for anaerobic digestion. The percolation process has a retention time of two (2) days. Liquids from the percolator (process water and liquid removed from the screw press) are fed into an anaerobic digester, featuring a solid and fluidized bed in which the liquid enters the fluidized bed through nozzles at the bottom and flow upward. Bacteria in the upper part of the digester are retained in a packed, solid bed. The solution is recirculated through the digester filter bed with fresh liquid feed from the Percolator. The digester appears to operate under 4-21 April 2005

55 o mesophilic conditions (30 C), although the literature remains very vague about the operating temperature conditions. The biogas is reported to typically contain 70% methane and 30% CO. The process wastewater is treated on-site to remove accumulated nitrogen, salts and fine suspended solids using a variety of techniques including ultrafiltration, injection of hot air and reverse osmosis. Once operational, the entire percolation process is water self-sufficient. The remaining solid fraction is composted and used as landfill cover in most countries. Buchen, Germany The Buchen facility is the first demonstration facility showcasing the ISKA technology and mechanical-biological treatment process. The mechanical separation system features a drum sieve with a mesh size of 3.5 to 6.0 at the front end to separate out the organic fraction of the municipal solid waste stream from plastics, paper, textiles and other contaminants. The mechanical separation process also employs a magnetic belt to remove metals. The organic fraction is then fed to the percolator, a horizontal, continuous feed (plug flow) cylindrical system made of steel. It features a central mixer and a hydraulically powered scraper. Heated water is fed from the top of the percolator and removed through screens at the bottom. Sand and small contaminants are removed using a sand washing system. The retention time in the percolator is two (2) days. The liquid from the percolator is directly fed into the digester along with the liquid produced by the screw press dewatering operation. The screw press dewaters digestate to 60% solids content. The digestate is then composted using an open windrow aerobic process for three weeks. The company claims that the overall process has a retention time of five days (2 days for the percolation process and 3 days for the digester) and produces a comparable amount of biogas as a dry, single-stage digestion system with a 20 day retention time Feedstock Specifications The system is designed to process unsorted municipal solid waste (MSW) but the company claims to have no feedstock restrictions and can process source separated food waste Processing plants will be designed and fitted to meet specific waste composition qualities in a given location and country in order to achieve the highest degree of commercial and operational efficiency, environmental soundness, and flexibility to respond to changing waste streams or management/disposal decisions over the lifespan of the facility. To date, however, the technology has been used to process municipal solid waste only. Garden waste is a component of the municipal solid waste but not identified as a main component of the feedstock Energy Specifications According to one source, the technology produces biogas at a rate of approximately 1,400-1,800 ft 3 /t (40-50 m 3 /t) of waste, equal to 300 kwh of primary energy. 26 In its literature, ISKA estimates that the facilities under construction will generate 1,800 ft 3 /t (50 m 3 /t) of biogas for MSW. Other sources claim 1,400-2,700 ft 3 /ton MSW. The lower biogas yield compared with other technologies is probably due to the shorter retention time MacViro, October April 2005

56 The Sydney facility in Australia is projected to generate 17,500 MWh of electricity annually with a feedstock of 175,000 tpy. The energy characteristics of other facilities is presented in Table Table 4.13 Energy Characteristics of ISKA Facilities Buchen, Germany - demonstration Buchen, Germany - expansion Facility Date of Operation Annual throughput tpy Energy generation ,000 Biogas 1,800 ft 3 /t (50 m 3 /t) 2005 (projected) Hellbronn, Germany 2005 (projected) Sydney, Australia 2005 (projected) 165,000 Biogas 291 million f 3 per year (8.25 million m 3 per year) Electricity gross 7.6GWh Electricity net 1.3 GWh 80, million f 3 per year (4million m 3 per year) (information provided 175,000 Projected electricity gross 17,500 MWh/yr The Buchen facility produces gross electricity of 7.6 GWh annually of which 1.3 GWh is available for sale. Energy is used internally to power the various processes including the percolation process, the digestion process and the incineration process. ISKA is a comprehensive integrated waste management system, and energy production is not its primary objective. Net energy production is low; therefore, the technology will not meet SMUD s primary objective of energy production and is likely not suitable for SMUD Infrastructure Requirements The ISKA technology provides a complete mechanical-biological treatment process to handle municipal solid waste. The anaerobic digestion system is one component of a larger MSW processing system, complete with front end garbage separation system (scalping trommel, magnets), the percolation process (first stage), the digestion process (second stage) and the aerobic composting system. Consequently, the land requirements are much greater than with a simple anaerobic digestion (one stage) system. The ISKA system points to its many advantages including high mass reduction, minimal space requirements, high level of automation, energy self-sufficiency and low emissions. ISKA modules are 30,000-40,000 tpy in size with plant size ranging from 75,000 to 200,000 tpy(minimum plant size 75,000 tpy and maximum plant size 200,000 tpy). The supplier states that multiple plants are possible. Land requirements for selected ISKA facilities are provided in Table April 2005

57 Facility Buchen, Germany - demonstration Buchan, Germany - expansion Table 4.14 Land Requirements for Selected ISKA AD Facilities Annual Throughput tpy Area 30,000 Area 1 acre (4,000 m 2 ) Building 0.3 acres (1,200 m 2 ) 165,000 Area 3.5 acres (14,000 m 2 ) Building 2.3 acres (9,500 m 2 ) Hellbronn, Germany 80,000 Area 2 acres (8,400 m 2 ) Building 1.3 acres (5,400 m 2 ) Sydney, Australia 175,000 Area 7.4 acres (30,000 m 2 ) Building not available Once operational the percolation process is water self-sufficient. The process is fed by wastewater from the dewatering process and re-condensation of moisture in the exhaust air Operations Elsewhere The technology is relatively new with the first demonstration plant opened in 2000 in Buchen, Germany. The Buchen facility is owned and operated by ISKA. Since 2000, the facility has processed 30,000 tpy of municipal solid waste. Success of the process at the Buchen facility has resulted in its expansion to handle municipal solid waste from the City of Ludwigsburg. The expanded facility will be able to handle 165,000 tons of waste per year and is expected to be operational in early Two new facilities are under construction in Heilbronn, Germany and Sydney, Australia. Both facilities will process municipal solid waste with the Sydney facility likely the largest facility of its kind in the southern hemisphere, with an annual MSW throughput of 175,000 tpy (with the ability to increase capacity to 260,000 tpy). The Heilbronn facility will process 80,000 tons per year. Both facilities are expected to commence operations in In addition, negotiations are underway with ISKA suppliers and two communities in the United Kingdom, one of which is Lancashire, to construct two new facilities to process municipal solid waste. Operational and planned ISKA AD facilities are identified in Table Table 4.15 ISKA Operational and Proposed AD Facilities Facility Feedstock Date of Operation Buchan, Germany - demonstration Buchan, Germany - expansion Annual throughput tpy MSW ,000 MSW 2005 (projected) Hellbronn, Germany MSW 2005 (projected) Sydney, Australia MSW 2005 (projected) Capital Costs 165,000 US $52 million ($40 million Euros) 80, ,000 US $55 million ($71 million Australia) 4-24 April 2005

58 ISKA has not constructed any AD facilities in North America that handle solid waste materials and does not appear to have any in the planning stages Company Standing ISKA GMbH is a subsidiary of U-plus Umweltservice AG which is one of the largest waste disposal companies in Germany. The patented ISKA technology has been commercially available since early 2000 and has been assigned commercial status in the UC Davis Conversion Technology database April 2005

59 4.7 Valorga The Valorga anaerobic digestion process is a patent of Valorga International SAS, which is one of the oldest companies involved in anaerobic digestion of residential organic waste Description of the Technology The Valorga process is a single stage, dry processing technology that was developed in France and has been used extensively throughout Europe over the past 25 years. The process is designed to treat organic solid waste but some plants (e.g. Amiens, France) handle mixed, unsorted residential waste (garbage). The Tilburg plant (Netherlands) handles separated at source food and garden waste and therefore will be used in this report to describe typical Valorga operating features. A Schematic of the Valorga System The Valorga process dilutes and pulps the organic fraction to about a 30% solids content. Transport and handling of the material is carried out with conveyor belts, screws and powerful pumps especially designed for highly viscous materials. This type of equipment is very robust, and consequently, the only pre-treatment necessary is removal of coarse impurities greater than about 1.73 inches (40 mm). A schematic of the Valorga system is provided below. The Valorga digestion process is a semi-continuous, high solid, one step, plug flow type process. The reactors are vertical cylinders and with no mechanical devices in the reactor. This allows the process to operate in high solid conditions without any hindrance to circulation or maintenance of mechanical devices. Mixing is accomplished via biogas injection at high pressure at the bottom of the reactor every 15 minutes. One drawback of this design is that the gas injection ports become clogged and maintenance is cumbersome. Retention time in the Tilburg plant is days at a mesophilic temperature of o F (35-40 o C). Average dry matter content in the Tilburg feedstock is approximately 25%-30%. The range of retention times for all Valorga plants is 18 to 25 days April 2005

60 The Valorga Process The treated material is removed and the digestate is dewatered by a screw press into a fiber and liquid fraction. The liquid is further treated: sand is removed by a hydrocyclone and suspended solids are later removed by a belt filter press. The Tilburg plant produces about 18,000 tons of compost yearly and testing shows that the compost is high quality. Although contaminant levels are low and the product is of high quality, the operators use it for landfill restoration. RIS staff visited the Valorga Amiens plant in 1992 and noted that digestate from the plant was land spread on nearby vineyards. We do not know if this practice is still in place in Feedstock Specifications The Tilburg Valorga digestion system is designed to handle 40,000 tons VGF (vegetable and garden fraction) and 6,000 t paper and cardboard, or 52,000 tpy VGF alone. The VGF consists of 38% kitchen waste and 62% garden waste. Quantities handled vary between 400 and 1,100 tons per week. This variation is due to the seasonal nature of the garden waste. To characterize the waste stream variation, the total solids (TS) and volatile solids (VS) vary between 37-55% and 32-65%, respectively. The high TS and low VS content correspond with the peak production of garden waste Energy Specifications Biogas production varies (especially with the ratio of cardboard to VGF material). Average values are about 2,900 ft 3 /t (82m 3 /t), though these can be as high as 3,700 ft 3 /t (106 m 3 /t) of waste. Expressed in terms of volatile solids feed to the digester, average biogas production is 14,000 ft 3 /t (400 m 3 /t) of VS but can be as high as 19,000 ft 3 /t (550 m 3 /t) of VS (volatile solids) in winter when there is less woody material. Methane production is in the order of 7,000-8,800 ft 3 /t ( m 3 /t) of VS (56%); the remaining 45% is CO 2. The biogas is converted or upgraded in the upgrading plant to natural gas quality. If the gas is used to produce electricity or steam, there is no need to remove CO 2. If it is to be used as compressed natural gas, CO 2 must be removed. Some of the gas is used for process heat at the plant itself and the rest is sold to a gas distributor and is transferred to the gas distribution network. Typical average gas yields for different waste input composition for Valorga facilities are provided in Table April 2005

61 Table 4.16 Typical Average Gas Yields for Different Feedstock Input Digestion Nm 3 CH 4 /raw ton Biogas (m 3 /t) Biogas (ft 3 /t) Biowaste + garden waste ,800-3,200 Biowaste + low level of cardboard ,700-4,000 Biowaste + cardboard + garden waste ,700-4,000 Biowaste + cardboard ,000-4,800 MSW ,000-5,100 The operation section provides information about the biogas yield for individual facilities Infrastructure Requirements A reported 30% of produced electricity is used within the plant; the remaining 70% is available for export. The volume of wastewater discharged is several fold less for a dry plant than for a wet plant, but no specific numbers are provided. Valorga report a space requirement of 3,200-4,300 f 2 ( m 2 ) of area for each 1,000 tpy capacity. On this basis, a 50,000t/y plant would need a site of 4-5 acres. Larger plants would need comparatively less space, as common areas such as receiving areas, etc. experience considerable economies of scale as a plant gets larger, and therefore proportionally less space is required for larger plants. However, using the Valorga rule of thumb, a site of 8-10 acres would be needed for a 100,000t/y plant. The land requirements for selected Valorga facilities is presented in Table Operations Location Tilburg, Netherlands Table 4.17 Land Requirements for Selected Valorga Facilities Capacity (tpy) Total Area 52,000 4 acres (16,000 m 2 ) Amiens, France 93, acres (33,600 m 2 ) Barcelona, Spain 240, acres (70,000 m 2 ) The Valorga AD system was first piloted in 1982 in a small facility located in Montpellier, France using municipal solid waste processed in a 180 ft 3 (5 m 3 ) digester. The Valorga process reached an industrial scale in the mid 1980s with plants built in La Buisse and Amies, France. The first industrial scale Valorga operating plant was implemented in 1984 in La Buisse, processing 8,000 tons of food waste annually. The average capacity of all plants in place in 4-28 April 2005

62 2003 was 60,000 tpy, with a total capacity of 884,400 tpy now in place world-wide (an increase of 45% between 2002 and 2003). Valorga AD plants produced nearly 2,800 million ft 3 (80 million m 3 ) of biogas in At present, Valorga operates 11 facilities in Europe, with three under construction as shown in Table Location Feedstock Capacity (tpy) Geneva, Switzerland Bassano Del Grappa, Italy SSO (+ green waste) MSW (44,000 tpy) & biowaste (8,000 tpy), sludge (3,000 tpy) Mons, Belgium MSW (58,000) and biowaste (37,000) Table 4.18 Valorga AD Facilities Start-up Operations 13, mesophilic - retention time days - biogas productivity is 3,900-4,200 ft 3 /t ( m 3 /t) - capital cost US $5,million - gross biogas 286,000 m3 - gross electricity 435,000 kwh - electricity sold 160,000 kwh 55, retention time 33 days - biogas productivity is 4,500 ft 3 /t (129 m 3 /t) 95, retention time 25 days minimum - biogas productivity is 3,900-4,200 ft 3 /t ( m 3 /t) - output is electricity and heat Amiens, France MSW 93, retention time days - biogas productivity is 5,300 ft 3 /t - (150 m 3 /t) - 95% steam (5,500 kw) is sold to nearby industry (5% used internally) Varennes- Jarcy, France MSW 110, output is electricity - retention time 25 days minimum - biogas productivity is 5,500 ft 3 /t - (154 m 3 /t) - capital cost US $38.9 million (30million Euros) (including existing equipment) Cadiz, Spain MSW 126, output is electricity and heat - retention time days minimum - biogas productivity is 4,600-5,300 ft 3 /t ( m 3 /t) La Coruna, Spain MSW 156, retention time 25 days minimum - biogas productivity is 5,200 ft 3 /t (145 m 3 /t) - output is electricity and heat Engelskirchen SSO/biowaste 35, retention time 25 days minimum - biogas productivity is 3,500-3,900 ft 3 /t ( m 3 /t) - output is electricity and heat (4,820 tons biogas annually) - capital cost US $7.9 million (6.1 million Euros) 4-29 April 2005

63 Frieburg, Germany Location Feedstock Capacity (tpy) Start-up Operations SSO/biowaste 36, output is electricity and heat - retention time 25 days minimum - biogas productivity is 3,900-4,200 ft 3 /t ( m 3 /t) Tilburg, Netherlands SSO/biowaste (+ garden) Calais, France SSO/biowaste 27,000 tpy Fats/oils 1,000 tpy Barcelona, Spain MSW 240, ,000 Hanover, Germany 52, retention time days - biogas 2,900 ft 3 /t (82 m 3 /t) - biogas 106 million ft 3/ yr (3 million m 3 /yr) - 18 GWh energy of which 3.3 GWh used internally and 14.7 GWh sold to gas distributor - capital cost US $15.6 million (12 million Euros) 28,000 Expected on line end of 2004 Under construction MSW 100,000 Under construction - expect to sell 6,500 MWh per yr electricity and produce 4,900 MWh hot water and 3,000 MWh steam per year for use internally - capital cost US $22.1 million (17million Euros) - output will be electricity - capital cost 52million Euros - retention time 25 days - output will be electricity and heat 4,100 ft 3 /t (114 m 3 /t) Company Standing The French company Valorga International SAS was formed in 2002 by Steinmuller Valorga Sarl. Valorga was initially founded in 1981 as a MSW (municipal solid waste, i.e. garbage) treatment company. The first Valorga process pilot plant was built in 1982 in the company s home of Montpelier, France. In 1988, the company started the first facility in the world to treat household waste by continuous anaerobic digestion with a high solid content in Amiens, France. Valorga currently runs 13 plants to treat mixed MSW, SSO and grey waste. The company has US agents April 2005

64 4.8 Wright Environmental Management Inc Wright Environmental Management Inc was listed as one of the AD technologies to evaluate in this project. Wright Environmental Management Inc. produces an aerobic composting technology, which does not produce the biogas of interest to the SMUD proposal, and therefore could not be considered a primary energy producing technology for this assessment. It could however be considered for the add-on composting stage April 2005

65 5.0 Technical Information on AD Technologies - WET 5.1 Methodology The approach to collecting information for the technical description component of the study was as follows: The list of 15 AD vendors in the Request for Proposal was used as the starting base for the study research; RIS in-house files from other AD projects were reviewed; A literature search was carried out at the outset of this study. Reports and articles were ordered and reviewed; A list of 36 AD suppliers in Biocycle magazine was used as a secondary data source. All 36 suppliers on this list were contacted to identify which technologies they represented; More detailed information was requested directly from AD suppliers. The available written information was summarized and follow-up contact was made with vendors of AD technologies to clarify the written information and to ask the following questions: - Type of technology (wet, dry, thermophilic, mesophilic one stage, two stage, etc.); - Number of facilities in operation; - Ability of the technology to process pure garden refuse; - Identification of facilities which process garden refuse and % of feedstock which garden refuse represents; - Requirement for additional feedstock in order to process garden refuse; - Extent to which additional feedstock enhances performance; - Identify all existing plants in operation, which process municipal solid waste (MSW), source separated municipal waste (SSO) or municipal waste in combination with other feedstocks (location, annual capacity, feedstocks, energy production); - Expected energy output per ton of waste (scfm biogas and MWhrs of electricity); - Amount and availability of heat or electricity required for operation (parasitic loads); - Infrastructure requirements (power, wastewater treatment); - Land requirements (footprint plus buffer); - Company track record (years in operation); - Warranties; - Parts and service support; and - Lead time required to fabricate equipment. For all technology descriptions, the information is presented in imperial units used in the United States as well as metric units used in Canada, Europe and Asia, which will enable comparison to other studies and literature, if required. Dry AD technologies were described in Section 4.0. Wet AD technologies are described in this section. 5-1 April 2005

66 5.2 Onsite Power Systems Inc. Onsite Power Systems, Inc., (OPS), a privately held corporation, acquired the exclusive licensing rights to an anaerobic digester process recently patented by the University of California. This is a two stage, wet, thermophilic process suitable for a wide range of infeed materials. The anaerobic phased solids (APS) technology was created to process high solids waste streams. Recent laboratory and engineering design improvements allow system flexibility for processing high liquids, high solids or a combination of both organic wastes Technology Description The APS digester system combines the features of both batch and continuous operations into one biological system. Solids to be digested are handled in batches, while the biogas production is continuous. This allows the solids to be loaded and unloaded without disrupting the anaerobic environment for the bacteria. The OPS design utilizes a hydraulic mixing system in the tanks with no moving or mechanical systems inside the digester tanks (reportedly resulting in a much lower maintenance cost and higher system dependability). A few of the other technologies described in this report (Dranco, Valorga, etc.) also use the same approach. APS Phased Solids - Circulation Process Flow Water Gravity Fed to Buffer Tank Buffer Tank Biogasification Reactor Biogas Tank Drainage System Hydrolysis 1 Hydrolysis 2 Hydrolysis 3 Hydrolysis 4 Solids Separator Water Recirculation from Gasification Tank Nutrient Enriched Water Soil Amendment Residue Material & Reclaimed Process Water A typical APS system consists of a number of hydrolysis tanks (typically four) coupled in a closed-loop configuration with one biogasification reactor tank. The hydrolysis tank(s) processes the organic waste in batches or semi-batches. Each hydrolysis tank is designed to hold a designated quantity of the identified feedstock based on site-specific requirements and 5-2 April 2005

67 feedstock characteristics. When the specific tank is loaded, it is then filled with water and sealed. Once filled, the tank remains in a sealed condition for a selected number of days, operating at an optimum process design temperature. This procedure enables the first phase of digestion to begin with the hydrolytic bacteria decomposing the feedstock materials and the acetogenic bacteria beginning to generate organic acids that become suspended in the digester liquid. The hydrolysis reactors are operated on different batch schedules so that the biogasification reactor is fed at a constant organic loading rate and therefore is constantly producing biogas. The biogasification reactor is specifically designed to maintain a high density of bacteria in the reactor to achieve efficient bioconversion. Liquid that carries soluble compounds is collected through filters installed in the reactor at three locations. This liquid is circulated intermittently between the hydrolysis tank and the biogasification tank to feed organic acids to the methanogenic bacteria. The collected liquid is transferred and distributed over the top of the hydrolysis reactor every 4 hours. The solids being digested are housed in the hydrolysis reactors, while most of the bacteria, especially methanogens, are housed in the biogasification reactor. The bacteria produce a mixture of 55 to 65 percent CH 4 (methane) and 35 to 45 percent CO 2 (carbon dioxide) resulting in a medium grade methane biogas. Biogas is collected from all the reactors and piped into an engine-generator for co-generation of electricity and heat. The APS digester operates at a thermophilic temperature of 135 F to achieve a high-rate of solids conversion. The solids retention time in the hydrolysis reactor ranges from 3 to 14 days, depending on the degradation rate of the solids. Food waste normally degrades very quickly, requiring a 3 to 5 day retention time. Crop residues such as rice straw are relatively slow to degrade and require a longer retention time of up to 14 days. The digested solid residue from the hydrolysis reactor can be dewatered and further processed into high-quality soil amendment and other agricultural products. When feedstock in the hydrolysis tank has reached the designed retention time, the tank is emptied. The remaining incompletely digested material or residue is in a solid form (digestate) or is dissolved in the liquid effluent. The company states that both of these products have value as landscaping fertilizer and other local agricultural applications, however, to date, other companies have not been successful at marketing the liquid fraction. The solid fraction is typically composted and becomes part of the compost marketplace. The company states that the APS digester system overcomes the fundamental obstacle of existing single-phase anaerobic digesters in that it separates the two distinct acids and methane phases into separate tanks or reactors, allowing each group of bacteria to thrive in their optimum environment. Separating the two phases provides the best environment, in terms of temperature and ph for each group of bacteria. However, a number of technologies described in this section also optimize digestion through two stage systems (e.g. Linde). Recent experience has shown that the additional cost of separating the AD process into two separate stages is not justified through the additional gas yielded, therefore some systems are tending towards a one-stage design. 5-3 April 2005

68 5.2.2 Feedstock Specifications The Onsite Systems APS design reportedly enables the processing of various sources of feedstock. The system efficiently digests organic waste streams ranging from process wastewater to high solids materials including green waste, bedding materials and food residues. On-Site Systems state that the only limitation in converting the system from a feedstock of 100% garden waste to 100% food waste is the time taken for the bacteria to adjust to the change in their food supply (the incoming waste stream). However, as shown elsewhere in this document, food waste yields higher amounts of gas, because of the different volatile solids and moisture content when compared to green waste. Incoming green waste is typically screened through a trommel (2-4 ) to remove large items like branches, etc Energy Specifications During the digestion process, methane is generated primarily in the gasification tank, however, some methane is generated in each of the hydrolysis tanks. The APS system operates at a gas pressure level of less than 1 PSI, and this biogas requires compression prior to its delivery to the power plant. Once the biogas arrives at the gas processing system, it is sent through a gas booster-compressor system and is raised to the required delivery pressure of the power generating plant Infrastructure Requirements A 400 tpd (100,000 tpy) facility would require about 2.5 acres (including plant, administration facilities, site, but not any pretreatment screening for yard waste). No other operating data are available Operations OPS s first project was the installation of a 400 kw, dual fuel cell power plant, at the Las Virgenes Municipal Wastewater Treatment Plant completed in November, This was the first large anaerobic digester fuel project undertaken by OPS, producing electricity from two fuel cells and providing steam heat to the digesters. UC Davis Onsite Power Pilot Digester - In July 2004, OPS received a contract from UC Davis to construct a small scale commercial demonstration digester system to be located on the UC Davis campus at the current pilot digester site. The digester is capable of processing 3 tpd (1,400 tpy) of green waste and food waste. The pre-screened feedstock is augured to the top of a tank with gravity forcing the solids down into a door at the bottom of the tank. The mix water is heated to 180 o F first, and is circulated through the tanks using a pump/mixer. In this process, approximately 70% of the volatile solids are digested, and about 65% - 70% of green waste is converted to energy. There are 4 hydrolysis tanks and one biogasification tank. Waste has a 10-day retention time. The hydrolysis tanks are filled to the top and after the ten days a new batch is put through. Digester contents are dewatered using a screw press. The solid digestate is sent to a composting facility to blend with other compost. Only the liquid carrying soluble compounds (organic acids) is transferred into the biogasification tank, and the level of the liquid in this tank is maintained at 5 feet. The hydrolysis and the biogasification tanks are filled with biomedia, 5-4 April 2005

69 plastic pieces with a high surface area that keeps the inoculants intact and distributes the methanogenic organisms evenly. This avoids stratification of the organisms and results in better gas production. The biogasification water circulates hydraulically and since there are no moving parts in the tanks, there can be no mechanical apparatus failure. Electricity is generated and a heat exchanger is connected to water jackets around the hydrolysis tanks. Excess waste heat is available for other energy recovery and use. In addition to the foregoing facilities, Onsite Power has described a number of other business opportunities currently under development: Grand Central Recycling & Transfer Station, Inc. (GCR), City of Industry, CA GCR has issued a conditional letter of intent to construct and install a 25 to 50 tpd (6,500 to 13,000 tpy) digester system utilizing green and food waste materials, subject to the verification of the digester performance in the UC Davis project. The system will include a complete digester system, gas storage system (designed to store biogas produced during 14 hours per day of non-operation of the recycling facility) and a 350 kw generator system. Construction could begin in July 2005 and is scheduled for nine months. California Energy Commission (CEC) will provide a sole source contract to fund the US $4 million project. CEC will spend US $995,000 over 3 years to test, validate and demonstrate the system. Onsite Power will provide US $500,000 and City of Industry will provide US $2,500,000 towards the project. California State University at Channel Islands (CSU CI) OPS has proposed a green-waste digester system on the campus at the California State University at Channel Islands (CSUCI) in Camarillo California. The plant will process 250 tpd (65,000 tpy) of municipal green waste diverted from Ventura County landfills, and the company states that it will generate enough biogas energy to yield over 3MW. The company states that the project will produce sufficient biogas to provide an energy source to power the existing campus electrical requirements. The project has reportedly gained extensive support from CSU CI, California State University Regents, California Integrated Waste Management Board, and Ventura county agencies. All of the necessary presentations and required permitting issues have been addressed and permits are ready to be issued. A third party review of the financial risks and technical issues was carried out and the report is currently under review. Gill s Onions, Oxnard, CA The first project for the food processing industry will most likely be established at an onion processing facility in Ventura County. Gill s Onions has funded laboratory testing of their onion product at UC Davis over the past twelve months. Longer term testing (6-12 months) is required to look at digestion stability of a single source of digester feedstock. This system will use the basic two-stage OPS digester technology. West Coast Rendering Co., Vernon CA West Coast Rendering (WCR) currently processes 80 tpd (20,000 tpy) of problematic animals (veterinary, zoo animals, slaughter, etc.). WCR s goal is to make a major paradigm shift in current operations and to use this large material source as feedstock for renewable energy 5-5 April 2005

70 production. The proposed project will also allow WCR to process BSE or Mad Cow suspect materials. WCR has issued a Letter of Interest to pursue this project, are securing project financing and are in the first stages of permitting this project. City of Vancouver, Washington The Solid Waste Division of Clark County Washington and the City of Vancouver Washington has presented a letter to OPS offering the opportunity to own and operate a 30 to 50 tpd (8,000 to 13,000 tpy) digester system. Vancouver and Clark County Washington have provided a commitment to provide the feedstock materials. The Solid Waste Division of Clark County is ready to begin the permitting process Company Standing Incorporated as Energy 2000, Inc. in April of 1996, a certificate of name change to Onsite Power Systems, Inc. was issued in October of In 1998, OPS acquired the exclusive licensing rights to a new anaerobic digester process, patented by the University of California. OPS, along with various engineering and design companies provided engineering and design support for this improved digester process. The companies that participated in the design meetings realized the market potential of the APS technology and offered participation in the demonstration project by sponsoring engineering and design services, installation support, and 70 % of the system s material. This effort resulted in the construction of an OPS-sponsored pilot demonstration digester system on the UC Davis campus. 5-6 April 2005

71 5.3 Arrow Ecology Ltd. Arrow Ecology Ltd. is a large scale Israeli environmental engineering company that developed and markets an anaerobic digestion process under the name of ArrowBio. ArrowBio is promoted by an international group of companies and agents. This technology is a mesophilic, two-stage anaerobic digestion technology with front-end wet separation (flotation and settling tank) Technology Description Mixed waste can be processed directly as tipped from the collection vehicle into a large flotation tank that is filled with bio-process liquid. The waste is then processed in two distinct stages: (1) hydro-mechanical methodology for separating the non-biodegradable and biodegradable fractions from unsorted or partially sorted municipal solid wastes; and (2) biological processing of the biodegradable fraction through acetogenic and then methanogenic bioreactors for intensive conversion to methane-rich biogas, water, and organic soil amendment products. Stage 1: Hydro Mechanical Separation In this stage, mixed MSW containing biodegradable and non-biodegradable materials is separated through a unique, liquid-based technology, involving gravitational settling, screening, and hydro-mechanical shredding of the waste. Heavy components such as glass and metals settle to the bottom of the tank, are removed and conveyed to a trommel screen that opens any plastic bags. Plastics and other light materials float to the top, while organics remain in suspension. The small fractions are returned to the settling tank. The large fractions go through mechanical and manual separation steps for recyclables (magnet, eddy current separation, hand sorting). Residuals from this mechanical sorting line are then sent back to the settling tank. The light fractions are removed from the tank by a paddle wheel, shredded and run through an inclined trommel screen. The schematic diagram provides an overview of how the system works. Arrow Bio Schematic 5-7 April 2005

72 The biodegradable material that remains in the floatation tank then enters the filtration systems to pulverize the material into a watery organic solution. This energy-rich solution contains biodegradable material, organic matter, paper and other substances that can now be treated in the bioreactors. Typically two hydro-separation systems are constructed in parallel for each ArrowBio facility. The first reactor, with a retention time of several hours, is where complex molecules such as carbohydrates are broken down into simpler fatty acids and sugars. The second reactor is the methanogenic reactor, in which the organics are converted to methane and CO 2. The reported effective solids retention time in the reactor is 2-3 months. The actual time that material physically remains in this process element is a fraction of this time. Lime may be added in the process to correct the ph. Stage 2 Biological Treatment In the biological reactors section, the organic fluid undergoes another two processes. The first is an acid-forming stage, where separated and prepared organic-rich water enters the acetogenic bioreactors for several hours of preliminary treatment. There, biological hydrolysis splits certain molecules into their component, readily metabolized, parts (e.g. simple sugars and organic acids). This rich mixture of organic liquid is then transported to the methanogenic reactor (b), for gasification by means of natural fermentation and other biological reactions. This process uses an advanced variant of anaerobic digestion that, with respect to solid waste processing, is unique to the ArrowBio Process. Known as Upflow Anaerobic Sludge Blanket (UASB) digestion, it results in a much faster and thorough degradation of biological materials, producing finished soil amendment products and a methane-rich biogas. UASB digestion is a wellestablished wastewater treatment process, but its application to MSW digestion is new. Outputs of the Arrowbio process include biogas, recyclables, digestate, wastewater, and nonrecyclable residuals. Two distinct soil amendment products are created; excess culture growths and organic matter that is not easily metabolized. Experience to date suggests that about 20% of the dry biodegradable input weight exits the UASB bioreactor as organic soil amendment products. A 100,000 tpy plant of typical waste would, therefore, contain about 66,000 tpy of biodegradable material, 50% of which is estimated to be water. The plant is projected to produce 14,000 tpy of the two soil amendment products representing a significant reduction from input weight. The biogas is collected at the upper part of the methanogenic reactor by means of a specially designed compartment. The gas is re-circulated by a compressor and re-injected into the methanogenic reactor close to its bottom, thus assuring a permanent agitation without mechanical devices. During routine operation, the biogas is also routed out of the system directly to energy generating units such as steam boilers or electrical generators. The biogas can also be stored in separate gas storage tanks or in simple inflatable buffer tanks. The biological solids material (or sludge) formed in the reactors is drawn off as needed to maintain a pre-set blanket height. Two distinct products are produced; excess culture growths and organic matter that is not easily metabolized. The former is formed from the decaying organisms of the biological activity whereas the latter consists largely of the lignocellulose portions of food (e.g. orange rinds), woody fragments and the bulk filler in disposable diapers. 5-8 April 2005

73 Both products can be dewatered and used as soil amendment. The long solid retention time in the reactors ensure a fully stabilized product, free of pathogenic germs, bacteria, weed seeds, etc. Furthermore, the company claims it is odorless and requires no further processing. The bio-liquid used in the ArrowBio Process is constantly re-circulated in the system. However, incoming waste contains water so that there would typically be a net export of water from the process. Wastewater from the UASB bioreactor, upflow is transferred to a settling tank. A portion of the supernatant is transferred as makeup water to Stage 1 of the plant. The remaining portion is transferred to an aerobic tank for polishing, to the degree required for the best off-site use. Water may be stored or used immediately for irrigation or released to the municipal wastewater system Feedstock Specifications The ArrowBio Process eliminates any need for prior separation or classification of mixed waste streams. Residential waste is well suited to the processing capabilities of this technology. Variations in material composition can be managed by the technology because at various points it has the capacity to regulate the flows between components. Waste can be received in a compacted or loose form. According to the supplier, the following types of wastes can be treated as received in addition to MSW: Mixed waste from food courts and restaurants; Leachate from landfill; Sludge and/or biosolids from sewage and water treatment plants; Industrial organic waste from the paper and food processing industries; Off-spec and expired food wastes; Manures and agricultural residues; Industrial settling tank sludge; Yard waste, grass and other garden trash; Wastewater. The vendor states that brush and excessive wood would likely not break down quickly enough, but leaves, grass, and other organics would be acceptable Energy Specifications ArrowBio claims as demonstrated ability to produce about 15,500 ft 3 (440 m 3 ) of biogas from each dry ton of organic matter. The biogas is reportedly 75% methane for each kg of dry biodegradable matter. A typical 100,000 tpy plant would generate about 33,000 tpy of dry biodegradable matter, producing 530 million ft 3 (15 million m 3 ) of bio-gas, or about 388 million ft 3 (11 million m 3 ) of methane. It is estimated that about 20% of the energy produced by the process is required internally, resulting in an export of 80% of the energy produced. One cubic meter of methane is equivalent to 10 KWh in energy potential. Assuming an efficiency of conversion to electricity of 35%, the potential electrical yield would be about 38,500MWh. Dividing by 8,760 hours per year means the plant could provide about 4.5 MW of electrical power. 5-9 April 2005

74 Process Consumables The ArrowBio Process is substantially self-sufficient. Methane rich biogas can provide all the energy requirements for operating the plant. City water is not needed, as the process generates excess water derived from the moisture content of the waste. A 100,000tpy plant would produce 33,000tpy of water. Wastewater treatment would be necessary before discharging effluent to a sewer. The wastewater would be of high strength (COD 600 mg/l, BOD 200 mg/l). All input materials required by the process are typically found within the MSW that is tipped at the facility, with the possible exception of the rare requirement to correct an aberrant ph in UASB digestion by adding slaked lime or sodium hydroxide Operations Tel Aviv, Israel - ArrowBio has one full-scale operational facility in Tel Aviv, Israel on a 1.5 acre site. It has a capacity of 70,000 tpy of MSW and has been operating since January, 2003, although it does not appear to be operating at design capacity yet (accepts 200 tpd or 51,000 tpy of MSW). The capital expenditure has been cited at US $12-17 million. A demonstration facility of 10 tons per day operated without interruption from 1999 to 2002 in Hadera, Israel. It is no longer in operation Company Standing Arrow Ecology Ltd. (since 1991), originally Hydro Power Ltd. (1975) specializes in project management of environmental programs for: Bio-technological and physio-chemical treatment of wastewater and sludge; Hydro-mechanical systems; and Environmental consulting/planning/laboratory services. The Company has only one plant in operation although they are pursuing a number of potential business opportunities. The company website notes that the first industrial contract for treating solid waste was signed June, A 200 tpd plant was scheduled to start in 2002 to process the town of Kfar Saba s solid waste. There is no further information available as to the current status of that facility April 2005

75 5.4 BTA Technology Description BTA (Biotechnische Abfallverwertung GmbH & Co KG) is a multistage, wet anaerobic digestion process primarily designed for the treatment of the organic fraction of municipal solid waste. A single stage process is mainly used for comparatively small, decentralized waste management units. Multistage digestion is mainly used for plants with capacity of more than 50,000 tpy. The BTA process was initially developed in a pilot plant in Garching, Germany to gain experience testing a range of feedstocks and to fine-tune the technology. The process can be operated in mesophilic or thermophilic temperature ranges. The process consists of two major steps: mechanical wet pretreatment and biological conversion. Mechanical pretreatment of the incoming waste separates out contaminants that are not digestible (such as plastics, textiles, stones and metals) by means of a rake and a heavy fraction trap. Biodegradable matter is pulped into a homogeneous suspension with a TS BTA System concentration of about 10% using re-circulated process water. Blending is achieved by means of an impeller at the bottom of the pulper stirring the mixture. The suspension is withdrawn through a screen at the bottom of the pulper. The screen retains the coarse, non-digestible materials. These are eventually extracted by an automated, mechanized rake. The BTA technology has a unique ability to distinguish and separate digestible matter from nonbiodegradables. It is this unique feature that convinced the City of Toronto to construct a BTA facility at the Dufferin Transfer Station in Toronto, Ontario, Canada (described later in this section). One of the reasons for choosing the BTA technology was that the pre-treatment step could reportedly remove plastics from the in-coming waste stream. BTA estimates that 98% of the biodegradable matter is suspended and sent on for digestion in their process. The suspension can then be heated to o F (65-70 o C) for at least one hour, killing both 5-11 April 2005

76 pathogens and weeds. Alternatively, pathogen and seed kill can be achieved by aerobically composting the digestate. The BTA process then employs separate, subsequent bioreactors for the digestion of organic matter. Liquid and solids in the pulp are separated in a dewatering device. The liquid (containing all of the readily soluble organics) is immediately pumped into a methane reactor where the dissolved contents are turned into biogas. After 2-4 days, the hydrolyzed suspension is dewatered and the hydrolysis-liquid is also fed into the AD reactor for approximately 3 days. Approximately 60-70% of the organic substances (VS) are turned into biogas within only a few days. The digestion residue is dewatered and, in general, sent to aerobic after-treatment. The water demand of all process types is met by recirculating the process water, which is contained in the waste. Depending upon the waste composition and local requirements, excess water is sent to the sewage system, or will receive additional treatment on-site before it can be discharged. Energy can be recovered from the generated biogas for use in gas engines or coheat and power stations. Depending on the waste composition, the gas yield ranges between 2,800-4,200 ft 3 /t ( m 3 /t) of waste feedstock Feedstock Specifications The BTA process is designed to treat organic waste from domestic sources (kitchen scraps, garden waste, paper, diapers, etc), commercial sources (restaurants, hotels, etc.) and agriculture (manure). The system is geared to process MSW organics. Typically, large volumes of green waste delivered to a BTA plant are isolated and used as a bulking agent to assist in composting the digestate. Brown leaves are discouraged since the process thrives on green waste. In addition, woody waste (branches, etc.) cause problems in the pulper since there is no mechanical chipping or material size reduction Energy Specifications The BTA process produces between 3,900-4,600 ft 3 /t ( m 3 /t) of biogas from every ton of biowaste. This biogas contains 60-65% methane. A 20,000 tpy plant will yield million kwh annually, while consuming 1.7 million kwh electricity and 1.1 million kwh heat annually. BTA state that the biogas produced from biowaste or commercial waste is so clean that it can be used to drive gas engines or cogeneration units without further purification (treatment or upgrading). In the case of the AD facility in Ypres, Belgium, the 55,000 tpy facility generates 2,400 3,900 ft 3 of biogas per ton feedstock ( m 3 /t) Operations The BTA process was initially developed by Biotechnische Abfallverwertung GmbH & Co KG in 1986 to treat OFMSW (organic fraction of municipal solid waste) from households, agriculture and commercial plants. The first plant on an industrial scale was built in Elsinore (Denmark) in 1990 with an annual capacity of 20,000 tons. The Elsinore plant eventually closed because of 5-12 April 2005

77 high operating costs. Thirteen plants are reported in operation using the BTA technology with 4 more under construction. An additional 10 plants use BTA pre-treatment technology but do not digest the waste. Three companies hold site licenses for the BTA process, including Canada Composting, Inc. in Toronto (for all of North America), Hitachi Zosen Co. in Tokyo, and BIOTEC Sistemi S.r. in Italy. BTA CCI Facility in Newmarket, Ontario, Canada The first North American BTA facility was designed for 150,000 tons of waste per year and commenced operations in Newmarket, Ontario in The facility is situated on 5.4 acres of land and was designed to convert 150,000 tons of incoming waste into 50,000 tons of high quality compost and approximately 5.5 megawatts (MW) of electricity and heat. After plant use of MW of this energy, the remaining electricity was to be sold as green energy to the Ontario power grid. Actual energy production is significantly less than these figures. Initially, only the front end of a two stage BTA process was constructed. A washed, largely undigested pulp, was produced and sent off-site for aerobic composting. The liquid resulting from the pulp dewatering process was digested and did produce a limited amount of biogas. The original business plan called for the construction of a solids digester once the first phase of the facility was on a firm financial footing. In 2002, the facility went into receivership due to odor problems and inadequate tipping fees. The plant was sold in 2003 to Halton Recycling (2003) Inc. Numerous modifications have since taken place to the facility, including enlarging the tipping floor, improving the biofilter and adding a backend Vertical Composting Unit (VCU) aerobic system to treat the pulp. In the VCU system, composting takes place inside modular chambers, 25 cubic meters in capacity. Processing is continuous with washed organic pulp mixed with wood waste amendment being loaded into the top of the chamber and the stabilized product removed from the bottom every day. Aeration is provided by natural convection forces that are accelerated by a fan mounted on top of each chamber (Halton Recycling /International Paper Industries hold a joint marketing agreement with New Zealand-based VCU Technology Ltd to jointly market VCU s products and services in the Canadian market). The City of Toronto recently signed a contract with HRL to receive a portion of their SSO starting in the fall 2004 and SSO and yard waste from York Region (where the facility is located) is also being processed at the facility. HRL have purchased a 10 acre site near the Newmarket facility and plan to construct enclosed composting to cure the material produced by the BTA facility. The BTA site experienced odor problems in November, 2004, but these were reportedly related to the large volumes of garden waste arriving at the site, rather than related to a process upset. Odor problems have continued in December BTA Digester at City of Toronto, Dufferin Street Transfer Station Site CCI commissioned a 25,000 tonne per year single stage AD plant in Toronto (at the Dufferin St Transfer Station site). The city issued an RFP in 1997 for facilities to process MSW (municipal solid waste garbage) and SSO and following the selection of the BTA process and final contract negotiations, construction began in During construction, the general contractor, Stone & Webster, filed bankruptcy and due to subsequent delays to sort out contract issues and to secure a new contractor, the facility did not begin processing material until September, April 2005

78 The facility was originally designed to process 15,000 tpy of MSW or 25,000 tpy of SSO, or some combination of each. As a result of the City s 2010 Task Force Report, the decision was made to process only SSO generated from the City s curbside collection activities (mostly grocery waste from the City s new curbside food waste collection program) at the Dufferin St facility. Following a lengthy commissioning period to stabilize the biological process at full design capacity, the City assumed control of the plant in May, 2004 although Canada Composting continues to operate the facility under contract to the City. SSO is screened into three fractions by a trommel screen. The small size fraction is directly transferred to the wet pre-treatment section. From the mid size fraction ferrous metals and aluminum are extracted by magnet and eddy-current separation. The remaining part is transferred to the wet pre-treatment comprising the BTA waste pulper and grit removal system. The purified pulp is digested in a mesophilic reactor where it is mixed with infused biogas. The digested pulp is dewatered and the solids transferred to an aerobic composting site. The facility is now processing between tpd over a five day per week operating schedule (processing about 30% of the City s current generation of SSO). The digestate is sent to Alltreat Farms windrow composting facility in Arthur, Ontario (about 50 miles from the City) for further curing, and is blended with other feedstocks at the Alltreat site, which has a capacity of 170,000 tpy. Tipping fees paid by the City to Alltreat are not publicly available. A listing of BTA plants currently operating and under construction is presented in Table April 2005

79 Location Table 5.1 Operating and Planned BTA Facilities Capacity (tpy) Plants Operating With The BTA Process Opening Date Infeed Newmarket, Ontario 150, commercial organics Toronto Dufferin 25, SSO and commercial organics County of Munich Brunnthal, Germany 24, residential SSO Karlsruhe, Germany 12, residential SSO Dietrichsdorf, Germany 20, commercial and residential SSO Villacidro (Italy/Sardinia) 45, mixed waste incl sewage sludge Mertingen (Germany) 20, biowaste/commercial waste Erkheim (Germany) 11, biowaste Elsinore (Denmark) (unconfirmed report that facility closed due to high operating costs) 20, Closed due to high costs biowaste Ypres (Belgium) 55, SSO (+ green waste) capital cost US $27 million (Euro 20 million) Kaufbeuren (Germany) 2, biowaste Leper (Belgium) 50, biowaste Mülheim a.d. Ruhr (Germany) 22, biowaste Ko-Sung (Korea) 3, biowaste/commercial waste Plants Incorporating BTA Pre-Treatment Technology Parramatta/Sydney (Australia) 35, commercial waste and organic sludges Verona (Italy) 70, mixed waste Pulawy (Poland) 22, mixed waste Nara City (Japan) 1, food waste Kushima City (Japan) 1, commercial waste Münster 20, biowaste Wels (Austria) 15, biowaste Schwabach 12, biowaste Baden-Baden 5, biowaste Kaufbeuren 2, biowaste BTA Plants Under Construction Alghoba (Libya) 11,000 mixed waste Komoro (Japan) 7,000 food waste 5-15 April 2005

80 5.4.6 Company Standing The BTA parent company is located in Germany. A Canadian company, Canada Composting Inc. (CCI) secured the rights to the BTA Process throughout Canada and the United States April 2005

81 5.5 Waasa, WABIO and Citec Originating from Finland and Sweden, CITEC Environment has been developing the Waasa anaerobic digestion technology for the past couple of decades to treat sewage sludge and later MSW. WABIO is no longer marketed but is very similar to Waasa Description of Technology The Waasa technology is considered a single stage, wet system using a thermophilic or mesophilic process (although most Waasa facilities use the thermophilic process). As with other recently evolving technologies, the Waasa system has been designed to treat municipal solid waste in which one component of the overall treatment involves anaerobic digestion. The organic fraction of MSW undergoes pretreatment in a pulper which shreds, homogenizes, and dilutes the material to the desired concentration of total solids (10-15% TS). Recycled process water and some fresh make-up water is used in the dilution. The slurry is then digested in large complete mix (completely stirred) reactors. One of the features of the technology is the design of a pre-chamber within the reactor to act as a preliminary stage similar to a two stage system. The pre-chamber enables the feedstock from the pulper to undergo inoculation in order to reduce short-circuiting of the feed (i.e., passage of a portion of the feed through the reactor with a shorter retention time than that for the average bulk material). The pre-chamber uses a plug flow approach, requiring the new feed to move along the pre-chamber over the course of a day or two before reaching the main reactor. Mixing is carried out by injection of biogas at the base of the reactor. A process flow schematic is presented in the figure below. 27 Process Flow Schematic for the Waasa System 27 Vandevivere. P. et. Al Types of Anaerobic Digesters for Solid Wastes April 2005

82 One of the disadvantages of the system occurs during the pretreatment process (designed to produce appropriate slurry quality while removing contaminants). This pretreatment process is complex and results in a % loss of volatile solids, which never make it to digester in order to generate biogas 28. The Waasa process is often confused with the WABIO technology. The WABIO and the Waasa technology, while having fundamental technical differences during their early years of development, are so similar now that the WABIO technology has become obsolete. After the Waasa-process was modified to thermophilic condition, making the upstream sanitation step on the DBA-WABIO-process somewhat obsolete 29. Both technologies were used on the first MSW treatment facility of its kind in Vaasa, Finland in Feedstock Specifications To date, the technology has been used to process primarily municipal solid waste. Garden waste is a component of the municipal solid waste but is not identified as a main component of the feedstock for any of the plants identified Energy Specifications In general the reported biogas production from the Waasa technology is in the range 3,500-5,300 f 3 /t ( m 3 /t) which has a heat value of kwh/ft 3 (6-7 kwh/m 3 ) biogas. A typical facility processing MSW generates 1,500 ft 3 /t (42 m 3 /t) of waste. Table 5.2 provides energy information for selected Waasa facilities. The company reports 20-30% internal use of biogas with the remaining 70-80% available for external use. Vagron/Groningen, Netherlands Table 5.2 Energy Information for Selected Waasa Facilities Facility Feedstock Annual throughput tpy Estimated biogas generation MSW 230,000 Biogas 1,500 ft 3 /t (42 m 3 /t) Energy - 48,000 MWh/year (35% electricity, 55% heat) Pinerolo, Italy MSW and biosolids 30,000 Energy - 30,000 MWh/year (35% electricity, 55% heat) Vaasa, Finland MSW 15,000 Energy - 9,000 MWh/year (30% electricity, 60% heat) Friesland, Netherlands MSW 90,000 Energy - 50,000 MWh/year (35% electricity, 55% heat) Kil, Sweden MSW 3,000 Energy 2,000 MWh/year (100% electricity) 28 Farneti et al Seattle Public Utilities, September April 2005

83 5.5.4 Infrastructure Requirements The suppliers of the Waasa technology claim to accommodate a wide capacity range from 500 to 200,000 tons per year (tpy). Land requirements are not available. Land requirements are specified at 27,000 ft 2 per 10,000 tpy (2,500 m 2 per 10,000 tpy) feedstock processed Operations Elsewhere In 2003, Citec has 8 facilities (see Table 5.3), primarily in Europe, using the Waasa technology to treat municipal solid waste as well as other waste. The facilities had a total processing capacity of 288,500 tons per year. Countries using the Waasa technology include: Scandinavia, Spain, France, Italy, Switzerland, Japan and the Benelux countries of Belgium, the Netherlands, and Luxembourg although not all facilities located in these countries treat MSW. The facilities in Japan treat combined biowaste and biosolids (sewage sludge). Table 5.3 Waasa Facilities Location Feedstock (Substrate) Annual Throughput tpy Vagron/Groningen, Netherlands Year of operation Features MSW 230, thermophilic Pinerolo, Italy MSW and biosolids 30, thermophilic Vaasa, Finland MSW 15, thermophilic - mesophilic Friesland, Netherlands MSW 90, thermophilic Kil, Sweden MSW 3, thermophilic Jouestsu, Japan Biowaste and biosolids 12, thermophilic Ikoma, Japan Biowaste and biosolids 3, , status unknown Shimoina, Japan Biowaste and biosolids 3, , status unknown - thermophilic - thermophilic Pinerolo, Italy - The Waasa facility in Pinerolo, Italy, has a treatment capacity of 30,000 tons of household waste and produces an estimated 30,000 MWh per year, including 35% in the form of electricity. Vagron/Groningen, Netherlands -The Waasa technology has been used in one of the largest MSW digestion plants in the world, which started operations in May Located in Vagron/Groningen, Netherlands the facility processes 230,000 tons of MSW in combination with commercial waste per year using four AD reactors, each with a capacity of about 97,000 ft 3 (2,750 m 3 ). The retention time for the process is 18 days. Vaasa, Finland - The MSW facility at Vaasa uses both thermophilic and mesophilic processes, running in parallel. The thermophilic process has a retention time of 10 days; the mesophilic design has a retention time of 20 days April 2005

84 5.5.6 Company Standing Citec was founded in 1984 and is a group of companies, originating from Finland and Sweden, providing services in information, engineering and environment to international clients. The financial state of Citec is good with annual growth of 20-40% during the last five years and average net profits were 9% during the same period April 2005

85 5.6 Linde Wet Linde-KCA-Dresden GmbH based in Germany and Linde BRV Biowaste Technologies AG based in Switzerland are fully owned subsidiaries of Linde AG, Germany. The companies supply both anaerobic and aerobic organic waste treatment systems. Linde-KCA-Dresden GmbH has been supplying biological wastewater and sludge treatment systems since 1973 and opened its first manure processing AD facility in Linde BRV Biowaste Technologies AG was founded in 1981 (formally known as BRV) and introduced the first manure AD system in Europe. In 1999, BRV became a subsidiary of Linde Description of Technology Linde offers a range of different systems, including anaerobic digestion, aerobic systems and comprehensive mechanical-biological treatment systems (MBT) for MSW (municipal solid waste). There is an increasing interest in MBT systems in the last two to three years in the UK and Europe, as it avoids the need for households to source separate organic and recyclable materials from the waste stream. Linde offer a complete range of AD systems, including both wet and dry digestion systems. Linde AD systems operate as single or two stage (wet) systems or as single stage (dry) processes and use both thermophilic and mesophilic digestion processes. The design of the system depends on the feedstock conditions and other factors. Wet System A front-end automated separation using a pulper and drum screen removes contaminants in the one stage system. In the two stage system, the pulped and separated waste is sent to a buffer and hydrolysis tank and is then sent to the reactor/digester tank. A gas recirculation unit uses gas injection to recirculate the materials into a centrally located draught tube within the digester. Linde Wet System 5-21 April 2005

86 5.6.2 Feedstock Specifications Linde state that their wet AD technology is particularly well suited to handle organic waste, sewage sludge and manure. Linde wet systems have been used primarily to handle source separated organic waste in combination with manure or sewage sludge. Linde operates several wet AD design facilities throughout Europe for processing source separated organic (SSO) materials in combination with other feedstock, including those listed in Table 5.4. Table 5.4 Feedstock Used in Linde Wet Facilities Location Feedstock Start-up Operations Wels, Austria biowaste - 15,000 tpy Thermophilic Furstenwalde, Germany SSO, industrial waste, agricultural residues 85,000 tpy Sagard, Germany Commercial, SSO, manure 48,000 tpy Radeberg, Germany Dunkirchen, France SSO & industrial waste 15,000 tpy sewage sludge 41,000 tpy SSO, industrial waste, sewage sludge 24,000 tpy Single stage -Mesophilic -Co-digestion 2004 Barcelona, Spain MSW 325,000 tpy Mesophilic SSO source separated organic Energy Specifications Table 5.5 provides energy outputs from different Linde AD systems that have processed municipal organic waste. One source estimates that the Linde technology used to treat MSW yields biogas of 3,500 ft 3 /t (100 m 3 /t) feedstock 30. Table 5.5 Energy Outputs from Selected Linde Wet Facilities Location Wet System Wels, Austria (2-stage, thermophilic) Capacity tpy Energy output 15,000 Biogas = 3,100-4,400 ft 3 /t ( m 3 /t). Methane content 60-65% Radeberg, Germany 56,000 Biogas = 88 million ft 3 /yr (2.5 million m 3 /yr) Electricity production = 760 kw 30 Ostrem, Karena. May Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. Columbia University April 2005

87 5.6.4 Infrastructure Requirements Because the company offers a variety of AD technologies and waste treatment solutions, the infrastructure requirements vary by facility and plant location Operations Elsewhere Linde report that they have about 100 AD operational facilities in Europe that handle organic waste as well as sewage sludge and animal manures. Over the past two years, Linde has constructed 20 new biogas facilities in Europe. The company has been actively involved in mechanical-biological waste treatment facilities to process municipal solid waste, recently announcing several mechanical-biological treatment ventures. Existing and proposed facilities that deal with organic wastes (including green waste) separated or as part of the municipal solid waste stream are provided in Table 5.6. Table 5.6 Existing and Proposed Linde Wet AD Facilities Location Capacity tpy Feedstock Start-up Additional Information Wels, Austria 15,000 biowaste Wet, mesophilic Furstenwalde, Germany 85,000 Biowaste 15,000, commercial 13,000, agricultural 57,000 Sagard, Germany 48,000 Commercial, biowaste, manure Radeberg, Germany 56,000 Biowaste and industrial -15,000, biosolid 41,000 Dunkirk, France 24,000 biowaste, industrial, biosolid Wet Wet, thermophilic Wet, horizontal plug flow, mesophilic - Biogas productivity 1,400 ft 3 /t (40 m 3 /t) Wet Barcelona, Spain 150,000 MSW Wet, 2 stage, mesophilic - Total solid 10.5% - Retention time - ~22 days - Biogas productivity estimated at 460 Mft 3 /yr (13 Mm 3 /yr) - Gross electricity 36,000 MWh/yr - Consumption 18,000 MWh/yr - Net electricity 18,000 MWh/yr Pinto/Madrid, Spain 73,000 MSW Under construction Lisbon, Portugal 40,000 Biowaste, market waste, industry waste Camposampiero, Italy 49,000 Biowaste, biosolids, manure Under construction Under construction Salto del Negro, Spain 75,000 MSW Under construction Burgos, Spain 40,000 MSW Under construction - Wet - Wet - Wet - Wet - Wet 5-23 April 2005

88 Wels, Austria The Wels plant uses a two stage thermophilic wet process. A batch separation stage uses a pulper followed by a drum screen to remove contaminants and reduce the organic material in size. The pulped organic material is sent to the hydrolysis tank to break down the organic material prior to the digester phase. Hydrolysis, acidogenesis and acetagenesis reactions occur in the hydrolysis tank; methanogenesis occurs in the digester (second stage). The retention time in the digester is 16 days. Linde has not constructed any AD facilities in North America to handle solid wastes materials and do not appear to have any in the planning stages Company Standing Linde is a substantial German company with well established anaerobic digestion technologies and processes to treat source separated organic waste as well as municipal solid waste. The Linde Group supplies chemical and gas processing technology and design and installation services through a number of affiliates in the United States April 2005

89 5.7 BioConverter BioConverter is an anaerobic digestion technology patented in 2001 by James McElvaney of McElvaney Associates Corporation Description of Technology BioConverter is the only US designed AD technology available, and has recently been reintroduced into the US marketplace. Bioconverter uses a wet, one stage, mesophilic, batch digestion process. A hydropulper at the front end of the process mixes and pulps the feedstock with water to reach the right consistency and moisture content. The pulped material is processed through a contaminant removal device before being delivered to Bioconversion digester. The slurry contains 10 to 15% total solids. Digestion takes place in heated cylindrical, fiberglass vessel(s) (vertical or horizontal). The BioConverter unit features a growth immobilization matrix, a heating coil for temperature maintenance, and sparging tubes for mixing/gas transfer. The digester vessel is maintained at mesophilic temperatures of 98.6 o F (37 o C). The company claims that the technology is 30 to 50% more efficient than other anaerobic digestion facilities and generates a biogas which is 65% methane (compared to 55% to 60% methane content for other technologies) Feedstock Specifications The BioConverter technology is designed to process all types of organic wastes, including green waste, manure and other agricultural waste, as well as primary and secondary sewage sludge (biosolids) from municipal and industrial wastewater treatment systems. It also claims to process fats, oils and grease and industrial waste (i.e. pulp and fiber). In 1984, a US $10 million investment was made in a pilot Unisyn AD system in Waimanalo, Hawaii, which processed tons of cow and poultry manure as well as agricultural waste. Later the feedstock was changed to mainly food waste and FOG (fats, oil and grease) waste. The project went through 4 different ownerships but continued to be operated by Unisyn Biowaste Technologies until 1999, when the operation closed down. The reason cited in a Biocycle article (Lynn, November 1999) was an inability to meet capital upgrade costs resulting from new regulations. By the end of the 1999, the project had accumulated over US $20 million in costs April 2005

90 Location Feedstock Start-up Operations Waimanalo, Hawaii Kihei, Hawaii Food processing waste, food waste and fats, oil and grease tpd Food waste (50%), green waste (25%), paper waste (25%) 2 tpd 1984 Operations closed in Operated from 1995 to 1997 BioConverter has recently entered into a contract with the City of Los Angeles and is in negotiations with City of Lancaster, California to construct AD BioConverter facilities (privately funded) at both locations to process green waste and sell the electricity generated back to the Cities. The BioConverter AD facility at Los Angeles proposes to process 2,600 tons of green waste per day. BioConverter has entered into negotiations with the City of Lancaster to construct a facility (privately owned and operated) that would process 200 tons (52,000 tpy) of green waste per day, generating natural gas and other useful products (i.e. fertilizer) that would be sold back to the City. The proposal has not received City Council approval to date Energy Specifications The BioConverter technology claims to yield a biogas with 65% to 75% methane content during the digestion process. The early 1980 s project in Waimanalo Hawaii yielded 320,000 ft 3 /d of biogas, which was converted to 550 kw of electricity. The technology generated about 3,000 ft 3 of biogas per ton of wet food waste. The announcements for the proposed Los Angeles BioConverter facility claim that the facility will generate 40 megawatts (MW) of electricity annually that will be sold back to Los Angeles at US $48 per MW. The City has committed to paying US $16 million per year for energy from the proposed facility over a period of 20 years. The company anticipates that about 20% of the energy produced will be used by the facility with the remaining 80% available for sale. The company, however, is permitted to use up to 25% of the energy produced for its operational use. The price will increase annually on a basis of 25% of the Los Angeles Consumer Price Index. The calculated 20 year levelized cost is about US $50/MW hour. The project will help Los Angeles displace about US $12 million of natural gas annually according to the LADWP (Los Angeles Department of Water and Power) Board Letter for Approval submission (November 18, 2003). The duration of the agreement is 25 years Infrastructure Requirements With the Los Angeles agreement, BioConverter will assume responsibility for developing and constructing the anaerobic digestion facility, including obtaining all necessary permits and required environmental approvals, as well as reimbursing the Los Angeles Board of Water and Power Commission for constructing a substation and transmission lines to connect the plant to the city's power system. Bioconverter also will operate the facility. A location has not been identified for the Los Angeles Bioconverter project. A relatively large footprint is required for the facility. The required environmental assessment study has not been 5-26 April 2005

91 started to date. The facility is expected to be in operation approximately five years from now (2010). The preliminary engineering project capital cost has been estimated at US $174 million. The Lancaster facility is expected to cost US $44 million and is to be located on 18 acres of land Operations Elsewhere Both operations in Hawaii were shut down. The Waimanalo facility was closed due to an inability to meet capital upgrade costs resulting from new regulations. It is not known why the Kihei facility closed Company Standing McElvaney Associates Corporation (MAC) is a solid waste consulting and technology development company, based in the United States, claiming over 36 years combined experience in BioConverter Technology development, management and operations. Although the Bioconverter technology has been patented only since 2001, it is based on previous experience with the two commercial BioConversion systems in Hawaii. The Conversion Technology database, developed by the California Integrated Waste Management Board and the Dept. of Biological and Agricultural Engineering at the University of California, Davis, classifies the BioConverter technology as pre-commercial. According to the LADWP Board Letter of Approval, Termination of the Agreement occurs upon any of the following events: (a) if BioConverter Los Angeles, LLC fails to deliver the required electricity from the Project within 60 months after the Agreement s effective date, (b) if a Notice to Proceed (certifying completion of environmental assessment, selection of project location and design work) is not issued by LADWP within 30 months from the Agreement s effective date, (c) if the Project is not operational within 30 months from LADWP s issuance of a Notice to Proceed, (d) 300 months from the Agreement s effective date, or (e) by mutual agreement of the Parties. Termination may also occur due to contract default by either party April 2005

92 5.8 Entec Entec (Environment Technology GmbH) is an Austrian based company that established its first biogas (anaerobic digestion) plant in Since then, Entec has constructed over 100 facilities in over 16 countries throughout Europe and Asia. Entec offers six different digestion technologies to handle an assortment of feedstocks, ranging from biowastes, sewage sludge, animal waste, and industrial food wastes Description of Technology Entec specializes in handling municipal solid waste that has not been source separated. The municipal solid waste received at the facilities undergoes a series of pretreatment processes to remove the non-organic portion of the waste stream. Pretreatment employs bag shredders and waste shredders and includes removal of unwanted material during the hydro pulping process. The hydropulper is fully automatic and removes plastic, glass, metal and sand from the waste stream, leaving behind the organic fraction in the form of a slurry. The system achieves a 90-95% contaminant removal rate. Entec designed the BIMA (Biogas Induced Mixing Arrangement) system to handle the slurry or sludge containing high solid concentration. This technology features a single stage, wet system approach using either a thermophilic or mesophilic digestion process. The design of the system depends on the feedstock conditions and other factors. The BIMA technology is more commonly used for MSW or biowastes April 2005