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Oregon’s Methane Project - Experience and Potential

Oregon’s Methane Project - Experience and Potential. Mike Gamroth Oregon State University Dept. of Animal Sciences. The process. Anaerobic digestion – like the rumen Longer retention Methane collection Methane use Heat, hot water Combustion engine electricity. “Methane digester”.

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Oregon’s Methane Project - Experience and Potential

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  1. Oregon’s Methane Project -Experience and Potential Mike Gamroth Oregon State University Dept. of Animal Sciences

  2. The process • Anaerobic digestion – like the rumen • Longer retention • Methane collection • Methane use • Heat, hot water • Combustion engine electricity “Methane digester”

  3. Basic concepts • Decomposition of organic material • Oxygen-free environment • Numerous strains of microorganisms • Biogas • Methane 50-80% • CO2 20-50% • Other gases

  4. Ambient temperature • Covered lagoon • Lowest output • Mesophilic • Around 100º F • More forgiving • Thermophilic • Highest output, lower retention time

  5. Digester types • Plug flow • Suited to scraped manure • Most common on dairies • Long rectangular tanks • Heat added, in-ground or insulated • Retention time (RT) 15 to 20 days

  6. Digester types • Complete mix • Typically upright round tanks • Benefits from regular feeding • Can handle “wetter” manure • When co-digesting, mixing important

  7. Digester types • Covered lagoon • Lowest cost, simplest to operate • Best suited to warm climates, wet manure • Lowest gas output • Often will be “seasonal”

  8. Digester types • Biofilm • Can augment any digester • A place for bacterial activity • Reduces retention time

  9. Economics 101 • A thrifty digester system can payback in 7 to 10 years • Initial cost • Operation costs • Value of energy, tax credits • Other benefits – odor control, solids sales

  10. Benefits of digestion • Generate energy from biomass • Odor reduction • More readily available nitrogen • Pathogen reduction $65 $68 $80 $83

  11. Why there aren’t more… • Poor design • Lack of skills, time • Excessive maintenance, operation time • Diminishing returns over time • Lack of interest • Out of business EPA and Meyer, et al

  12. Keys to success • Know your manure quality • Match the digester technology with the manure • Select a tested design and keep it simple • Take advantage of incentives • Monitor the system daily • Line up operation and maintenance backup

  13. Resources • http://www.epa.gov/agstar/index.html • Our project: • Energy Trust of Oregon • Oregon Beef Council • Oregon Dairy Farmers Association • Amanda Green (360) 751-4190

  14. A partnership of Cal-gon Farms and Portland General Electric

  15. The system • Scraped manure • Piston pump to feed digester • Digester effluent through a screw-press screen • Liquids stored in lagoon • Solids in covered bunker

  16. Uses • Lagoon liquids mixed with water and irrigated onto field corn • Solids are sold off the farm and used as bedding • Recycling lagoon liquids through separator when not used for digester

  17. Research project • Questions about the farm’s nutrient balance • Questions about the start-up and stabilization of the digester • Received money from a grant program to sample the digester during start-up and for a two month period during operation • Evaluate solids as a soil amendment

  18. Ending Svc Date kWh # Days Avg kWh/day 5/30/2002 8527 31 275 7/30/2002 12301 32 384 8/29/2002 14817 30 494 9/28/2002 17886 30 596 10/29/2002 23115 31 746 11/27/2002 19614 29 676 8/3/2003 271677 336 660 Electrical Output Cal-Gon Farms Biogas Project Generation Record (based on PGE bills)

  19. Basic results

  20. Exporting solids to reduce nutrient loading 1 Average of 51 separators, Willamette Valley, 1995

  21. Solids plots

  22. DAF separation 90%+ P removal

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