Practical Information about Anaerobic Digesters

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Practical Information about Anaerobic Digesters

• Presentation to the Ohio Public Utilities
  Commission
• Joseph M. Kramer
• Energy Center of Wisconsin
• March 9, 2006

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Energy Center of Wisconsin

• Non-profit energy efficiency and renewable energy
  research organization
• Energy and the Environment linking energy,
  environment and economy
• Industrial Best Practices increasing energy
  efficiency for industry
• Building Performance residential, commercial
• Energy Literacy education and outreach

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Primary Sources Cited

• Agricultural Biogas Casebook 2004 Update
• Great Lakes Biomass State and Regional
  Partnership
• AgSTAR Handbook
• US EPA AgSTAR Program

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Biogas Systems - Background

• Components
• Manure collection
• Anaerobic digester
• Solids separation (optional)
• Effluent storage
• Gas handling
• Gas use

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Conditions for Installing AD

• Farm characteristics (per AgSTAR)
• Manure collection equivalent to 500 cows or 2000
  swine
• Stable manure production and frequent collection
• Manure collected as liquid, slurry, or semi-solid
• Single point collection
• Minimal bedding and other materials

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Digestion Benefits to Farm

• Odor reduction
• On-farm energy source
• Improved fertilizer quality of manure
• Reduced surface and groundwater contamination
• Pathogen reduction
• Other products offset costs

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Systems as of July 2004
AD Systems as of July 2004 Farms 21 Digesters
29 FB Grants (2003-4) New AD 37 Change
system 3
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Farm Types

• 21 farms 29 digesters
• 19 dairies (gt30,000 head)
• 1 swine finishing (8,300 head)
• 1 duck (500,000 head)
• Farm Bill Grants (new systems)
• 36 dairies (including 3 ethanol/dairy/beef)
• 1 poultry
• Not included in this group are 3 awards from
  2003 that were withdrawn and awarded again in
  2004, 3 grant awards for modifications to or
  replacement of existing systems covered in the
  casebook.

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Herd Sizes for Dairies
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Digester Types

• Covered Lagoon Emerald Dairy (1999)
• psychrophilic

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Digester Types (continued)

• Complete Mix Lagoon Apex Pork (1998)
• mesophilic

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Digester Types (continued)

• Complete Mix Tank (German Design)Vir Clair
  Farms (2004)
• mesophilic

Photo Biogas Direct
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Digester Types (continued)

• Complete Mix Tank Five Star Dairy (2004)
• thermophilic

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Digester Types (continued)

• Plug-Flow Haubenschild Farms (1999)
• mesophilic

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Digester Types (continued)

• Mixed Plug-Flow Loop
• Gordondale Farms (2001)
• mesophilic

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Digester Types (continued)

• Vertical Plug-Flow Tank (x4)
• Fair Oaks Dairy (2004)
• mesophilic

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Digester Performance

• Once stabilized, systems generally functioned as
  intended
• For some, biogas applications were problematic
• Engine generator set electricity/heat
• Microturbine electricity/heat
• Boiler - heat

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Issues with Electricity Generation

• Low rates for electricity sales
• High cost of energy generation equipment
• Increased maintenance demand
• Costs of interconnection and line upgrades WI
  has rules for interconnecting DG facilities PSC
  119.02
• Alternative Biogas Use
• Gas cleanup and sales - Emerald Dairy, Intrepid
  Technology and Resources, Microgy

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Herd Size and Generation Capacity
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Costs of Dairy Digester Systems

• Dairy plug-flow and mixed plug-flow(includes
  energy generation)
• 417-763 per cow (design capacity)
• Other dairy systems cost information not
  available

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Benefits Reported by Owners (Annual)

• Electricity Sales 23,000 to 66,000
  (32-78/head)
• Bedding Cost Offsets 29,000 to 75,000
  (32/head)
• Com. Fertilizer Rpl 30,000 to 50,000
  (41-60/head)
• Odor Control quality of life, avoided lawsuits
  and complaints, continuing operation or ability
  to site new, increased operational flexibility
• Others reduced herbicide use, reduced pest
  control need, propane replacement, reduced lime
  for fields, systems and practices

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Business Models

• Farm Owns All most common
• Utility Owns Generation less risk for farm,
  less income potential from electricity sales and
  less farm control over generation
• No Farm Outlay (Microgy/Dairyland model) farm
  owns digester but non-recourse financing, utility
  owns generation, gas purchase agreement

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Business Models (cont.)

• Shared Facilities
• Centralized digester manure trucked or piped in
• Centralized gas processing plant gas piped in
• Shared Expertise multiple farms and digesters
  shared support crew, contract administration,
  financing support, possibly marketing of solids
• Combined with Ethanol Production use process
  heat and other products

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AD in Summary

• AD systems solve many (not nutrient management)
  issues
• Provide income streams, cost offsets,
  non-monetized benefits
• Commercial technology with many operating systems
  in the field

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Wisconsin Biobased Industry Development
Initiative 2005

• What is needed to increase use?
• Reduce up-front costs or improve payback
• Provide technology information to public
• Internalize externalities market mechanisms
• Explore non-electrical biogas uses
• Explore options for smaller farms
• Clarify funding of line upgrades

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More Information

• Agricultural Biogas Casebook
• http//www.cglg.org/biomass/pub/AgriculturalBiogas
  Casebook.pdf
• AgSTAR Handbook and Software
• www.epa.gov/agstar/
• Wisconsin Biobased Industry Development
  Initiative
• http//bioeconomy.wi.gov/

Joe Kramer Energy Center of Wisconsin Madison,
Wisconsin 608-238-8276 jkramer_at_ecw.org