Feasibility of Generating Green Power through Anaerobic Digestion

164 Pages·2005·3.48 MB·English

by  Maria Kelleher

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Final Report
April 2005

Report to
SMUD
Advanced Renewable and Distributed Generation Program

Prepared By

In Association with
MacViro Consultants Inc.
Table of Contents
Page
Executive Summary i
Glossary of Terms vi

1.0 Introduction 1-1

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

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

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

5.0 Technical Information on AD Technologies - WET 5-1
5.1 Methodology 5-1
5.2 Onsite Power Systems 5-2
5.3 Arrow Ecology Ltd 5-7
5.4 BTA 5-11
5.5 Waasa, WABIO and Citec 5-17
5.6 Linde - WET 5-21
5.7 BioConverter 5-25
5.8 Entec 5-28
Page
6.0 Screening and Analysis of Available AD Technologies 6-1
6.1 Overview 6-1
6.2 Technical Screening Criteria 6-2
6.3 Summary of Technical Data for AD Technologies 6-4
6.4 Technical Analysis of AD Technologies By Design Parameters 6-7
6.5 Gas Production and Net Energy Available From Different AD Technologies 6-9
6.6 Technical Screening of AD Technologies 6-11
6.7 Evaluation of Broader Concept Using SMUD Criteria 6-13
6.8 Evaluation Using Sacramento Waste Authority Criteria 6-14

7 Economic Analysis of Anaerobic Digestion of Garden Waste 7-1
7.1 Overview 7-1
7.2 Description of Facility Components 7-2
7.3 Plant Energy Balance 7-5
7.4 Costs and Financial Analysis for 100,000 ton/year Garden Waste AD Facility 7-6
(Dry, Thermophilic) at a Greenfield Site – Option 1
7.5 Costs and Financial Analysis for 200,000 ton/year Garden Waste AD Facility 7-10
(Dry, Thermophilic) at a Greenfield Site – Option 2
7.6 Costs and Financial Analysis for 100,000 ton/year Garden Waste AD Facility 7-10
(Dry, Thermophilic) at a Co-located Site – Options 3 & 4
7.7 Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food 7-12
Waste AD Facility (Wet, Mesophilic) at a Greenfield Site – Option 5
7.8 Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food 7-13
Waste AD Facility (Wet, Mesophilic) at a Co-located Site – Option 6
7.9 Costs and Financial Analysis for 100,000 ton/year Garden Waste with Food 7-13
Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Option 7
7.10 Costs and Financial Analysis for 50,000 ton/year Garden Waste with Food 7-14
Waste AD Facility (Dry, Thermophilic) at a Co-located Site – Option 8
7.11 Discussion of Costs For Greenfield Site 7-14
7.12 Economic Conditions Which Make AD Viable 7-16
7.13 Next Steps in Research 7-17

8.0 Conclusions and Recommendations 8-1
8.1 Conclusions 8-1
8.2 Recommendations 8-2

Appendices
Appendix A 100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site
Appendix B 200,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Greenfield Site
Appendix C 100,000 ton/yr Garden Waste AD Facility (Dry, Thermophilic) at a Co-located Site
Appendix D 100,000 ton/yr Garden Waste and Food Waste AD Facility (Wet, Mesophilic) at a
Greenfield Site
Appendix E 100,000 ton/yr Garden Waste and Food Waste AD Facility (Wet, Mesophilic) at a
Co-located Site
Appendix F 100,000 ton/yr Garden Waste and Food Waste AD Facility (Dry, Thermophilic) at
a Co-located Site
Appendix G 50,000 ton/yr Garden Waste and Food Waste AD Facility (Dry, Thermophilic) at a
Co-located Site

Tables Page
Table 3.1 Key Firms Generating Biogas from MSW Feedstock in Europe in 2003 3-2

Table 3.2 Communities in the United States Investigating Anaerobic Digestion for MSW 3-3

Table 3.3 Biogas Yield from MSW Materials 3-11

Table 3.4 Biogas Yield 3-12

Table 3.5 Biogas Composition 3-12

Table 3.6 Biogas Production 3-12

Table 4.1 Anaerobic Digestion Technologies Profiled 4-2

Table 4.2 Reported Energy Production, Internal Energy Use and Energy Available for 4-4
Export at Selected Kompogas Facilities
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 4-10
Export at Selected DRANCO Facilities
Table 4.6 DRANCO Demonstration Plants 4-11

Table 4.7 Full Scale DRANCO Plants 4-12

Table 4.8 Planned DRANCO Plants 4-12

Table 4.9 Feedstocks of Linde Dry Digestion Facilities 4-16

Table 4.10 Energy Production for Selected Linde Dry AD Facilities 4-17

Table 4.11 Existing and proposed Linde Dry AD Facilities 4-17

Table 4.12 Linde Mechanical-Biological Treatment Facilities featuring Aerobic Treatment 4-18

Table 4.13 Energy Characteristics of ISKA Facilities 4-23
Tables Page
Table 4.14 Land Requirements of Selected ISKA AD Facilities 4-24

Table 4.15 ISKA Operational and Proposed AD Facilities 4-24

Table 4.16 Typical Average Gas Yields for Different Feedstock 4-28

Table 4.17 Land Requirements for Selected Valorga Facilities 4-28

Table 4.18 Valorga AD Facilities 4-29

Table 5.1 Operating and Planned BTA Facilities 5-15

Table 5.2 Energy Information for Selected Waasa Facilities 5-18

Table 5.3 Waasa Facilities 5-19

Table 5.4 Feedstock Used in Linde Wet Facilities 5-22

Table 5.5 Energy Outputs from Selected Linde Wet Facilities 5-22

Table 5.6 Existing and Proposed Linde Wet AD Facilities 5-23

Table 5.7 Energy Information for Entec Facilities 5-30

Table 5.8 Entec Operations 5-30
Table 6.1 Summary of Key Technical Data For Thirteen Anaerobic Digestion 6-5
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 6-8

Table 6.4 Characteristics of Mesophilic Vs Thermophilic Designs 6-8

Table 6.5 Available Information on Reported Gas Production and Net Energy Available 6-10
for Export For Dry Anaerobic Digestion Technologies
Table 6.6 Available Reported Information on Gas Production and Net Energy Available 6-10
for Export For Wet Anaerobic Digestion Technologies
Table 6.7 Screening of Anaerobic Digestion Technologies 6-12
Table 7.1 Plant Capital Cost Estimate – 100,000 ton/yr Garden Waste (Dry, 7-7
Thermophilic AD Plant, Greenfield Site)
Table 7.2 Plant Operating and Maintenance Cost Estimate – 100,000 ton/yr Garden 7-7
Waste (Dry, Thermophilic AD Plant, Greenfield Site)
Table 7.3 Financial Analysis: Input Assumptions and Data –100,000 ton/yr Garden 7-8
Waste (Dry, Thermophilic AD Plant, Greenfield Site)
Table 7.4 Tipping Fee and Power Price Calculation – 100,000 ton/yr Garden Waste 7-9
(Dry, Thermophilic AD Plant, Greenfield Site)
Tables Page
Table 7.5 Summary of Costs for Options 1-4 7-12
Table 7.6 Summary of Costs for Greenfield Sites 7-16
Table 7.7 Summary of Costs for Co-located Sites 7-17
Table 7.8 Financial Analysis Summary 7-19

Figures Page
Figure 2.1 Garden Refuse Collected In the City of Sacramento By Month, 2002 2-1
and 2003
Figure 3.1 Flow Diagram for Anaerobic Digestion 3-4

Figure 3.2 Possible AD System Processes 3-5

Figure 3.3 AD Technologies Supplied By Different Vendors 3-10

Figure 7-1 On-Site Cogeneration Schematic with Annual Energy Flows 7-6
100,000 Ton per Year Garden Waste Facility
Green Waste To Energy Economic Feasibility Study – Final Report

Executive Summary

Anaerobic Digestion
Anaerobic digestion is a naturally occurring biological process that uses microbes to break down
organic material in the absence of oxygen. In engineered anaerobic digesters, the digestion of
organic waste takes place in a special reactor, or enclosed chamber, where critical
environmental conditions such as moisture content, temperature and pH levels can be
controlled to maximize microbe generation, gas generation and waste decomposition rates.
Anaerobic digestion has been in use for several decades to treat sewage sludge, animal wastes
and industrial wastewater. Only in the past decade, has the technology become a recognized
method for processing solid organic waste from residential and commercial sources. The
benefit of an AD process is that it is a net generator of energy which can be sold off-site in the
form of heat, steam or electricity.

Background To Study
The Advanced Renewable and Distributed Generation Technologies (AR&DGT) group of SMUD
engaged the services of IEC, with RIS International Ltd as sub-contractor, to explore the
feasibility of generating green power through the anaerobic digestion of garden refuse from the
Sacramento, Citrus Heights and Sacramento County areas. About 260,000 tons of garden
refuse are potentially available as a feedstock for a processing facility. Sacramento Waste
Authority (SWA) is currently searching for a local site for aerobic composting of garden refuse,
in order to reduce transportation outside the county.

SMUD’s Renewable Portfolio Standard (RPS) requires 20% of SMUD’s energy needs to be met
with non-large hydro renewable energy by 2011. The RPS requirement can be met by
conventional renewables such as wind and geothermal, as well as emerging renewable energy
sources such as solar and biomass.

Biomass based sources of renewable energy are seen as desirable because they use a locally
generated and sustainable feedstock material (such as agricultural and municipal waste
streams), and create local economic and environmental benefits.

The purpose of this study was to collect and evaluate data on anaerobic digestion technologies,
and assess the viability and costs of digesting garden wastes generated in the Sacramento
area, and how this technology could be used to generate green energy from garden wastes.

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Green Waste To Energy Economic Feasibility Study – Final Report

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.

Distr ibution of 74 Existing AD Facilities Processing the Distribution of 33 Planned AD Facilities Processing the
Organic Fraction of MSW Organic Fraction of MSW

(cid:131) 28 in Germany (cid:131) 8 Kompogas
(cid:131) 12 in Switzerland (cid:131) 6 Dranco
(cid:131) 7 in Spain (cid:131) 3 ISKA
(cid:131) 5 each in Austria and Italy (cid:131) 3 APS (UC Davis, Industry, Vancouver
(cid:131) 4 each in Japan and France Washington)

(cid:131) 3 each in Belgium and Netherlands (cid:131) 1 Bioconverter (Los Angeles)
(cid:131) 2 in Canada (cid:131) 3 Valorga
(cid:131) 1 each in Finland, Sweden and Denmark (this (cid:131) 2 BTA
may be closed), Libya, Korea and Portugal (cid:131) 6 Linde
(cid:131) 1 Biopercolat

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

(cid:131) Gas production for the same materials is similar for most of the AD technologies;
(cid:131) Gas production for all technologies is lower for garden waste and higher for food waste,
paper waste and MSW;
(cid:131) 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;
(cid:131) 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
(cid:131) Dry technologies, therefore, are preferred where energy production is a key evaluation
criterion.

Europe has experienced some success handling garden waste in AD systems. Several AD
facilities located throughout Europe process a feedstock consisting primarily of garden waste.

Screening of AD Technologies
Anaerobic digestion systems are broadly defined as wet or dry technologies. Wet AD
technologies are suitable for situations where significant removal of contaminants such as
plastic bags is desirable at the front end of the process. Dry AD technologies are more suited to
relatively clean feedstocks which do not require significant contaminant removal. Dry AD
technologies were considered more suitable for the application under consideration.

Thirteen (13) commercially viable AD technologies were identified during the course of this
study. Six dry AD technologies were researched and evaluated:

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Green Waste To Energy Economic Feasibility Study – Final Report

(cid:131) Kompogas (Kompogas, Switzerland)
(cid:131) Dranco (Organic Waste Systems, Belgium)
(cid:131) Linde (Linde-KCA-Dresden GmbH, Germany)
(cid:131) Biopercolat (Wehrle-Werk, Germany)
(cid:131) ISKA (U-plus Umweltservice AG, Germany)
(cid:131) Valorga (Valorga, France)

Seven wet AD technologies were evaluated:

(cid:131) APS (Onsite Power Systems, United States)
(cid:131) ArrowBio (Arrow Ecology Ltd, Israel)
(cid:131) BTA (Biotechnische Abfallverwer-tund GmbH, Germany)
(cid:131) Waasa (Citec Environmental, Finland)
(cid:131) Linde (Linde-KCA-Dresden GmbH, Germany)
(cid:131) BioConverter (Bioconverter, United States)
(cid:131) 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:

(cid:131) Proven Technology (has facilities in operation)
(cid:131) Flexible Technology (can handle a range of feedstocks, including garden waste)
(cid:131) Company Track Record (has a good operating record in established AD facilities)
(cid:131) 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:

(cid:131) Three facility sizes (50,000, 100,000 and 200,000 tons/year capacity);
(cid:131) Two AD system designs (wet and dry),
(cid:131) Two types of feedstocks (garden waste only and garden waste with food waste) and
(cid:131) Two site situations (Greenfield site and co-located with other waste management
facilities)

iii April 2005
Green Waste To Energy Economic Feasibility Study – Final Report

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
Garden and Garden and Garden and Garden and
Feedstock Garden Waste Garden Waste Garden Waste Garden Waste Food Waste Food Waste Food Waste Food Waste
AD Technology Dry Dry Dry Dry Wet Wet Dry Dry
Size (TPY) 100,000 200,000 100,000 100,000 100,000 100,000 100,000 50,000
Location Greenfields Greenfields Co-Located Co-Located Greenfields Co-Located Co-Located Co-Located
Capital Grants ($) 0 0 0 16,760,000 0 0 0 0
Capital Cost ($) 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 ($) 1,650,000 3,300,000 0 0 1,775,000 0 0 0
Amortized Capital Per Ton ($/Ton) 32.72 29.04 29.24 11.53 36.35 32.85 29.24 26.29
Annual O&M Per Ton ($/Ton) 24.60 19.79 19.05 19.05 28.36 22.81 19.05 26.82
Annual Digestate Composting and Residue
Disposal Cost Per Ton ($/Ton) 16.50 16.50 0.00 0.00 17.75 0.00 0.00 0.00
Total Annual Cost Per Ton ($/Ton) 73.82 65.33 48.29 30.58 82.46 55.66 48.29 53.11
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) 68.23 59.75 42.71 25.00 75.08 48.29 40.70 45.52
Cost per kWh Input (If Input Tipping Fee is
set at $25/ton) 0.568 0.470 0.271 0.065 0.506 0.270 0.199 0.241

The analysis showed that capital costs are highest for a greenfield site, and that co-located AD
facilities result in considerable capital and operating cost savings. On this basis, a greenfield
AD site was eliminated from further consideration, and the analysis focused on co-located site
options. Phase 2 should explore co-located AD site options in further detail.

The analysis shows that the addition of some food waste to the AD facility feedstock improves
the financial performance of the facility by increasing energy revenues. Energy revenues could
increase considerably from those shown in the table if the AD facility could be located close to a
heat or steam customer, so that all of the energy and heat generated by the AD biogas can be
sold. The cost analysis did not evaluate this option, as a specific location was not evaluated.

The cost analysis shows that the highest cost component per ton of input is the amortization of
capital costs, therefore efforts should be made to identify potential capital grants for construction
of the AD facility. The California Energy Commission (CEC) and the California Integrated
Waste Management Board (CIWMB) are both interested in supporting biomass based
conversion technologies such as anaerobic digestion.

Greenfield Site vs. Co-Location
It was concluded that establishing an AD facility on a greenfield site (constructing an AD facility
on a new, undeveloped site) was not viable economically, because of the high costs of
constructing various components such as a scale house, admin building, engine generator set,
wastewater treatment, tipping floor and conveyors which would already be established at other
waste management facilities. Co-locating the AD facility at an existing waste management

iv April 2005