Small-Scale Anaerobic Digestion and Manure Management

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1 Small-Scale Anaerobic Digestion and Manure Management Stephanie Lansing Environmental Science and Technology University of Maryland Curt Gooch Dairy Environmental Systems and Sustainability Engineering Cornell PRO-DAIRY Program Cornell University

2 ANAEROBIC DIGESTION BASICS Biogas Food Waste CH 4 (Methane) H2 H 2 O CO CO 2 H 2 S Biogas Generator Manure, Crops, Wastewater Sludge Food Waste ANY ORGANICS Anaerobic Environment (1) Hydrolysis fatty acids, sugars (2) Acidogenesis alcohols CO 2, H 2 (3) Acetogensis acetic acid, CO 2, H 2 (4) Methanogenesis CH 4 and CO 2 Liquid Fertilizer with 25-80% Less Solids and 50% More Dissolved Nutrients Manure

3 Anaerobic Digesters in the World The majority of US digesters are at wastewater treatment plants, with only 265 on-farm digesters

4 Anaerobic Digestion Scale Waste Sludge Digester in Boston (top) Thermal Hydrolysis Digester in DC (bottom) Dairy Manure Digester Guapiles, Costa Rica

5 Challenge #1: Small-Scale Digestion in MD The US does not have many digesters, with the overwhelming majority located at large dairies due to increased revenue with economy-of-scale

6 Majority of the ag-based digesters treat dairy manure on large-scale farms, with a growing number co-digesting with food waste

7 Agricultural Digestion Opportunities Livestock operations have consistent biomass collected in one spot. Without digestion, manure is a source of GHG emissions (10% of US GHG emissions). Digesters produce non-intermittent, renewable energy, with a small land footprint In Germany (>9,000 digesters), the majority co-digest with food waste and tipping fees (more $$ to farmers), which increases energy production, assuming the nutrients from the food waste can be incorporated into nutrient management plans. The USEPA has identified more than 11,000 viable agricultural AD systems using current technology (power 3 million homes, reduce methane emissions by 54 million metric tons of CO 2(eq) 11 million passenger vehicles), YET, we still have only 365 systems in operation.

8 US Agricultural Digesters Market Penetration is slow Average cost of US digesters is $1.5 million, average farm size with digesters is dairy cows. Of the 260 farm-based US digestion systems only FOUR dairy digesters are on farms with 200 cows or less, which accounts for 87% of dairy farms. Dairy Cows US Dairy Farm Size Dairy Farms Percent of Total ,800 32% ,700 17% ,500 25% ,900 14% ,800 7% ,300 6%

9 Digesters with food waste-only or food waste co-digestion, with the majority being co-digestion facilities with manurebased digesters (50)

10 Co Digestion Potential

11 Food Waste Co-digestion at Kilby Farm Covered lagoon dairy manure digester currently unheated in Colora, MD Food processing waste from cranberry, ice cream, chicken and meatballs and the manure from 450 cows. Food waste was 500% more productive in producing biogas Lisboa and Lansing, 2013 in Waste Management Digester input consists of 96.8% (by volume) dairy manure and the remaining is the food waste.

12 Watershed Implications of Digestion: Nutrient Management Regulatory oversight of AD is based on how digestion fits into a farm s nutrient management plan. The digester effluent has most of the nutrients from the manure conserved. Nutrients in a dissolved form for land application. Food waste that is co-digested will also have nutrients that will be applied. Can separate manure solids post-digestion for compost or reuse as bedding, which decreases on-farm expenses and might reduce phosphorus additions due to recycling the bedding material.

13 Challenge #2: Small-Scale Digestion in MD In the US, electricity pricing, cost-sharing, and incentives for renewables varies by state. In Germany, smaller-scale digester systems get a higher price for their electricity to encourage smaller sustainable farming practices.

14 Annual net costs per cow as a function of farm herd size. Economic Analysis of all US Small-scale Digesters A: Calculated without cost sharing (top) B: Calculated using 50% cost sharing (bottom) Solids Circles: Existing Digestion System. Open Circles: Proposed Digestion Systems * Systems with Gen-sets Conclusions: To make small-scale digesters profitable, it is recommended to have > 50% cost-sharing, co-digest with food waste and receive tipping fees, and separate the solids after digestion and re-use as solids as bedding to reduce costs. Klavon, Lansing et al., 2013

15 Digesters in Europe

16 Slide Courtesy of Harm Grobrugge, Vice-President European Biogas Association

17 Slide Courtesy of Harm Grobrugge, Vice-President European Biogas Association

18 Slide Courtesy of Harm Grobrugge, Vice-President European Biogas Association

19 Challenge #3: Small-Scale Digestion in MD In developing countries located in tropical climates, small-scale systems do not need outside heating, eliminating the need for costly combined heat and power (CHP) systems.

20 Small-Scale Manure Digesters Tubular Polyethylene Plastic Bag No Mechanical Parts Simple to build and operate Low-cost ($500 - $2000)

21 Two digester system: 160 m 3 Antananarivo, Madagascar with WSUP Design for pumped latrine waste from 2000 people Secondary aerobic and subsurface planted gravel beds Gas used directly in a broiler for cleaning pumping equipment and worker showers

22 Haiti Hospital Sanitation Digesters with Post-Treatment Wetlands

23 UMD Small-Scale Digesters Six flexible biogas bags digesters situated in insulated, heated culverts Influent can be pre-heated and radiant piping used for in-vessel heating Automatic loading and temperature control at 30ºC

24 UMD Small-Scale Plug Flow Digesters Produced 3x the energy needed to counteract digester heat loss Cost: ($16,800) higher than tropical systems ($500-$1500) due to heating and insulation. Lansing et al., 2014: Transactions of ASABE

25 Field-Scale Temperature Study Methane production at 28ºC was 13% less than 35ºC, and operating at 22ºC was 30% less than 35ºC. Arikan, Mulbry and Lansing, 2015

26 Digestion Challenges ($ $ $ $) Understanding dairy industry pressures (low milk prices) and lower economic return from manure-only waste digestion, but there is little food waste separation and recovery compared to other countries, difficulty in codigesting poultry litter and other feedstocks due to regional specialization. Importance of scrubbing H 2 S from biogas, especially for CHP systems and understanding frequency of generator malfunction (current NE SARE Grant). Dependent on electricity price for large-scale systems and year-round demand for direct use of biogas for small-scale systems for economic return. Most treatment systems do not have an economic return Difficulties and time to obtain financing, cost-sharing, and to operate. Klavon, Lansing et al., 2013 in Biomass & Bionenergy

27 Conclusions: There is no Silver Bullet. We know the benefits. There is an industry ready to build you a digestion system, but current electric prices and cost to build in the US does not make them necessarily economical. It can be done, especially with food waste digestion. Money and policy efforts are needed to specifically include the small-scale farmer in this industry, especially in a state like Maryland..

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