Anaerobic Digestion Presented To: Waste to Energy Workshop for Farm, Food Processing, & Wood Industries By: Rick Sievertsen SEBESTA BLOMBERG & ASSOCIATES, INC www.sebesta.com December 11, 2006
Biomass Sources Animal Manure Wood Waste Sawdust Wood chips Slash C&D debris Food Processing Waste Landfill Gas Distillers Grains Corn Stalks Dedicated Energy Crops
Biomass Technologies Anaerobic Digestion Combustion Gasification
Anaerobic Digestion Oxygen-free, microbial breakdown of manure or other waste into biogas and an odor-reduced, nutrient-rich effluent.
Farm Use CAPTURED WASTE HEAT Farm heat $ offsets Farm refrigeration $ offsets Waste-to-Energy System Characteristics BIOGAS Methane captured carbon credits Engine / Generator Set ELECTRICITY Peak production Long-term contract Green Tag premium CAPTURING ADDED VALUE Waste Manure Anaerobic Digester DIGESTED MANURE NPK mineralized Odor reduced Pathogens, weed seeds controlled De- Watering De- Filtrate Slightly reduced N P 40-60% Useable for on-farm fertilizer Solids Bedding (on-farm) - or - Compost / Organic Fertilizer
Biogas Uses Use directly in boilers Use to produce electricity Upgrade to pipeline-quality gas
Benefits Reduces odor Produces Medium-Btu (500-600 BTU) gas (50-60% methane) Reduces manure volume Digester effluent can be used as fertilizer 100% fertilizer value available first year Can be applied to growing crops Digested solids can be used as fertilizer or separated and reused as bedding material (dairy)
Limitations Requires high-moisture fuel (8-10 % solids) Requires steady-state operating conditions Does not reduce nutrient content May have large footprint 15-20 day hydraulic detention times Swine manure alone does not produce much gas 29 cf/day (biogas) swine (growing-finishing) vs. 44 cf/day (dairy)
Research Evaluation of increasing methane production by blending hog manure and various biomass sources corn stalks, switchgrass and sugar beet pulp Bench-scale batch testing in a 5 to 10 gallon digester equipped with mixing and temperature control.
Research Preliminary results Switchgrass and sugar beet pulp not promising Corn stover has good gas production potential 50 to 75% of the heating value of the stover recovered as methane Final results expected first quarter 2007
Research Next Steps Investigate pretreatment for switchgrass, wood, crop residues Scale up corn stover/hog manure blends (1000 5000 hogs) Investigate the effect of mesophilic and thermophilic conditions on enhancing methane production
Economics Fertilizer value of manure typically less than the energy content value Biogas production costs range from $4 to $6 per million Btu recoverable Includes debt service on capital costs Highly sensitive to transportation costs, labor costs and potential gas production
Economics May be eligible for additional credits $3 4/ton of CO2 for carbon credits Methane generally has a multiplier of 21 Green power credits (demand/value highly sensitive to location)
Manure/Feedstock Characterization Technology Evaluation Effluent Evaluation Gas Use Evaluation Feasibility Study Components Site Configurations and Permitting Requirements Funding & Investor Opportunities Greenhouse Gas Benefits Determination
Next Steps Initial Feasibility Study Business Plan Development Preliminary Engineering Construction Document Preparation Construction Services Post Construction - Startup
Summary Biogas is a technically feasible substitute for natural gas. Economic returns are attractive today and expected to become more so over time.
Summary For farmers supplying stover or dedicated energy crops, there would be significant economic gain. Can retain the fertilizer value of manure while capturing methane and capitalizing energy content.
For More Information, contact: Rick Sievertsen RSievertsen@sebesta.com 319/294-5580 Offices Worldwide www.sebesta.com