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Potential for Anaerobic Digestion of Crop Residues

Potential for Anaerobic Digestion of Crop Residues. Ron Fleming & Malcolm MacAlpine (Ridgetown Campus of University of Guelph), Jim Todd (OMAFRA). CSBE09-706. Funding. OMAFRA – Alternative Renewable Fuels Plus program U of Guelph/OMAFRA Agreement. Objectives.

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Potential for Anaerobic Digestion of Crop Residues

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  1. Potential for Anaerobic Digestion of Crop Residues Ron Fleming & Malcolm MacAlpine (Ridgetown Campus of University of Guelph), Jim Todd (OMAFRA) CSBE09-706

  2. Funding • OMAFRA – Alternative Renewable Fuels Plus program • U of Guelph/OMAFRA Agreement

  3. Objectives • Suitability of various agricultural by-products, mainly related to vegetable production and processing, as feedstocks for AD • Feedstock handling, processing and storage requirements • Optimum conditions to maximize methane production • Economic potential of using vegetable wastes as energy feedstocks • Nutrient quality of digestate

  4. Overview • 3 year project – 2008 to 2010 • Use a pilot scale anaerobic digester • Potential in Ontario to use organic “waste” materials common in agriculture to produce energy through the use of an anaerobic digester • Consider livestock manure as an input • Look at crop residuals from various field crops

  5. Top 10 Vegetable Crops for Marketed Production in Ontario

  6. Example: Tomato Waste • Available for 8 weeks – August/September • Waste represents 3 to 13% of total harvested • 3 types of processing wastes: • Pomace (mostly skins) – 800 t in 2008 • Lye sludge (+/- 94% water) and Screenings (stems, seeds, etc) – 16,000 to 19,000 t

  7. Baking wastes Waste grease Canola cake, 15 % fat Waste bread Molasses Skimmed grease Food waste Corn silage, waxy stage, high-grain Grass silage, first cut Corn silage, dough stage, high-grain Green maize, dough stage Brewer`s grain silage Grass Fodder beets Silage from sugar beet leafs Potato peelings Whey Potato mash, fresh Liquid swine manure Liquid cattle manure Potential Biogas Yields 657 600 552 486 469 400 220 202 195 171 155 291 103 93 90 68 39 35 36 25 100 200 300 400 600 (m3 biogas/tonne)

  8. Description of AD System • 152 cm diameter, 130 cm depth, flexible domed top, total volume = 2.7 m3; liquid volume = approx. 1.8 m3 • Complete-mixed mesophilic system

  9. Mobile Anaerobic Digester

  10. Feeding Hopper and Auger

  11. Auger Tube Outlet

  12. Mixing Paddle and Heating Coils

  13. Electric and Heating Systems

  14. Gas Analyzer and Flow Meter

  15. Flare and Pressure Relief Tube

  16. Test Method • Various materials/mixtures tested • Approx. 4 weeks for each recipe • Daily Monday to Friday: • Gas samples analyzed • Gas volume recorded • Gas flared • Mixer started • Material added

  17. Loading rate • Ranged from 0.5 to 1.2 kg VS/m3 digester capacity • Average hydraulic retention time ranged from 21 to 40 days

  18. Input #1 Sugar beets + swine manure www.extension.umn.edu/.../DC7715.html

  19. Adding mixture of sugar beets and manure to feed hopper

  20. Input #2Liquid swine manure • Had been stored for several months • Represents an input that is plentiful

  21. Input #3Sweet potatoes • Chopped fine • Added to digestate, mixed and added to digester as a slurry • No new liquids added

  22. Input #4Sweet potatoes + (fresh) swine manure • Digestate removed • Sweet potatoes mixed with fresh swine manure

  23. Input #5Swine manure • Freshly produced manure

  24. Input #6Dried tobacco • Nicotine-free tobacco leaves (dry) • Mixed with digestate before adding to digester as a slurry

  25. Sample Analysis • Biogas: • Methane (CH4), Carbon Dioxide (CO2) • Inputs and outputs: • N, P, K, pH, NH4-N, C, ash • Calculated C:N ratio • Calculated Volatile Solids

  26. Results for 2008

  27. Example of Daily Inputs and Methane Production – Sweet Potatoes & Swine manure

  28. Example of Cumulative Gas Production and VS Inputs – Sweet Potatoes & Swine manure

  29. Sugar beets & swine manure – poor gas production – but – first test for the unit & problems with temperature control • Fresh swine manure yielded twice as much methane as older swine manure • Dried tobacco was the most difficult to mix • Digestion led to a decrease in DM and an increase in NH4-N

  30. Advantages of this test setup • Can change recipe fairly easily • Don’t need huge quantities of inputs • Is a good demonstration unit – technology transfer

  31. Limitations • Currently only able to add inputs 5 days per week • A few design problems – e.g. input auger not sufficient for many materials – some re-design needed • Initial difficulty keeping temperature constant – has been resolved • Assumes gas production stabilized within 4 weeks

  32. This year • Continue testing – vegetable wastes + other farm organic materials • Document logistical considerations for various materials • Document economic considerations

  33. Questions?

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