Small Digester Feasibility in the Upper Midwest

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1 Amanda Bilek Energy Program Associate The MN Project , x5

2 The Minnesota Project is Non Profit Formed in 1979 Mission: Connecting people with policy to build strong local economies, vibrant communities and a healthy environment Areas of focus: Renewable Energy/Agriculture & Water/ Local Food

3 Overview Why we are interested in studying digesters Economic and environmental benefits Overview of digesters installed in the Haubenschild dairy, Princeton, MN Top Deck Holstein Inc., Westgate, IA Vir Clar dairy, Fond de Lac, Wisc Common misconceptions about digesters Overview of MN and WI dairy industry MN Project s small digester project Project progress Current farm sites under condsideration Current engineering proposals Initial economic evaluation

4 How does a digester work? Manure is collected, put in covered tank Bacteria break down manure Heated digesters are more efficient Biogas is produced and captured 60% methane, 40% CO 2, other trace gases Biogas is routed to be burned for electricity production or another use Digestate is produced Volume is slightly reduced (3-7%) Nutrient levels remain the same during before and after digestion

5 GAS UTILIZATION (electric generation or another use) SOLID SEPARATION SALE OF SEPARATED SOLIDS LAND APPLICATION BARN-collect manure HOLDING TANK DIGESTER DIGESTATE STORAGE

6 A Solid Separator

7 Why do we study digesters? Environmental Benefits Economic Benefits

8 Environmental Benefits Improved air quality Odor reduction Reduction of biological oxygen demand Distributed generation of electricity Reduced greenhouse gas emissions

9 Economic Benefits Sale of electricity-depending on agreement with utility Sale of dried bedding fibers Captured reused heat from engine generator No nutrients are lost during digestion-manure retains all fertilizer benefits

10 Claimed Economic Benefits-harder to measure Odor reduction Weed reduction/herbicide savings Pathogen reduction Fly population is reduced Reused bedding from separated solids, replacing sawdust or sand

11 Overview of s Installed in Haubenschild Dairy Top Deck Holstein, Inc. Vir Clar Dairy

12 Haubenschild Dairy 850 head dairy farm located in Princeton, MN Plug-flow digester Fuel cell that runs off cleaned biogas Benefits: Sold carbon credits to the Chicago Climate Exchange Low maintenance Can be used in many climates Drawbacks: er reactor volume investment = $336,000

13 Top Deck Holstein, Inc. 700 head dairy farm located in Westgate, Iowa Plug-flow digester Benefits: Farm has a solids separator Low maintenance Can be used in many climates Drawbacks: Sand and excess water should be avoided er reactor volume investment = $500,000

14 VirClarDairy 1300 head dairy located near Fond du Lac, WI Complete mix digester Benefits: High rate of biogas production Manure solids used for bedding Drawbacks: High level of mechanical wear Comparatively expensive investment = $1,000,000

15 Common Misconceptions about s s require a lot of water to function You must scrub the biogas before putting it through an engine The digester failures in the 70 s prove that digesters aren t feasible s aren t appropriate for community scale models s are only for farms with 500 head or more

16 Applications in India and China digesters are very common It is common for many small digesters to be hooked up in a system Biogas is often used for cooking and heating

17 pictures from China

18 Current status of Minnesota and Wisconsin dairy industry Minnesota: # of Dairy Farms: 5,800 Average Herd Size: About 100 Head Number of farms with more than 500 head = 60 Wisconsin: # of Dairy Farms: 15, 300 Average Herd Size: About 100 Head Number of farms with more than 500

19 Pilot Project Goal: Establish a pilot scale digester on a MN dairy farm with less than 300 cows Project Funded by the Natural Resources Trust Fund, as recommended by the Legislative Commission on Minnesota Resources Partners: The Minnesota Project University of Minnesota Applied Economics Department and Biosystems and Ag Engineering Department Minnesota Department of Agriculture Minnesota Milk Producers Association Natural Resources Conservation Service Stearns Soil and Water Conservation District

20 Beginning Project Steps-selecting a pilot farm site Project started by open solicitation statewide for interested farmers Narrowed to 5 farms in Stearns County Chose 2 farms from 5 as possible sites

21 Criteria for Choosing Farms Farmers have shown interest in the project (done background research on digesters) Leaders in dairy industry Highest electricity and heat costscreating greatest opportunity for payback return High level of farm management Existing parlor and barn set-up

22 Site 1: Jerry and Linda Jennissen, Brooten, MN cows Currently spends $12,000/yr on electricity (including electric and heat) Has 3 day manure storage in place (nothing permanent) Sand bedding

23 Site 2: Art and Tim Kerfeld, Melrose, MN 130 cows Currently spend $6,000/yr on electricity Currently spend $3,000/yr on propane for heat Permanent manure storage Straw and sawdust bedding

24 System Design & Engineer Criteria Farmers determined they wanted electricity component to be a part of the project 40 kw engine generator set required (Minnesota net metering law) Some proven on ground experience maintenance agreement between farmer and engineer Commitment to project success

25 Engineering Firms Proposals: Open bid solicitation for pilot digester designs 5 different designs from 5 different engineers All proposals have an electricity generation component except one All firms have varying years of experience and familiarity working with farmers

26 Engineering Firms Proposals Continued: Each proposal has a solid separating component as a major benefit Narrowed down to 2 firms

27 Engineering Firm #1-system description Modular construction off farm site Size digester tank to current and future cow numbers-two tanks Scheduled maintenance provided by company Solids grinder for reused bedding 5-7 day retention time Remote site monitoring

28 Engineering Firm #1-pros and cons PROS Vast experience with modular design, pumping and piping Reliable business structure Close to installing demonstration project in Wisconsin CONS Lack of on the ground technology Lack of experience working with farms

29 Engineering Firm #1-costs and payback Costs - system (heat exchangers) = $156,000 -Solids separation = $50,000 -Electrical generation = $100,000 Payback (annual basis) -Electricity =$15,000 -Heat = $8,000 -Solids for bedding and sale = $25,000 Initial payback period = 7 years

30 Engineer Firm #2-system description On-site construction with raw materials One digester tank Scheduled maintenance done by farmer with some engineering oversight Solids grinder for reused bedding 20 day retention time Complete mix for better temperature distribution

31 Engineering Firm #2-pros and cons PROS Vast practical digester experience Worked with different systems-already done a lot of troubleshooting of design flaws Good electrical generation experience A lot of experience working with farms CONS No one the ground technology No existing business/company structure

32 Engineering Firm #2-costs and payback Costs - system (heat exchangers) = $170,000 -Solid separation = $40,000 -Electrical generation = $70,000 Payback (annual basis) -Electricity = $22,000 -Heat = $3,000 -Solids for bedding and sale = $28,000 Initial payback period = 6 years

33 Other factors to consider Sale of carbon credits Major equipment repairs-unknown how long equipment will last Change in milk production from switching to current bedding to separated solids Reduced hauling costs

34 Next Steps Extend project for additional yeardigester installation Spring 07 Re-bid for system designs Winter 06 Give existing engineers some time to get system up and running at other sites Search for systems with even lower capital costs Project analysis Summer 07 Detailed project economics System performance

35 Thank You Contact Info: Amanda Bilek Energy Program Associate The MN Project , x5