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Anaerobic Co-digestion of Biomass for Methane Production : Recent Research Achievements

Anaerobic Co-digestion of Biomass for Methane Production : Recent Research Achievements . Wei Wu CE 521 . Introduction . Anaerobic Digestion . Anaerobic digestion (AD) Organic Matter + H 2 O + Bacteria CH 4 + CO 2 + NH 3 + H 2 S Traditionally

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Anaerobic Co-digestion of Biomass for Methane Production : Recent Research Achievements

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  1. Anaerobic Co-digestion of Biomass for Methane Production : Recent Research Achievements Wei Wu CE 521

  2. Introduction

  3. Anaerobic Digestion • Anaerobic digestion (AD) Organic Matter + H2O + Bacteria CH4 + CO2 + NH3 + H2S • Traditionally • Single substrate and single purpose • Manure was digested to produce energy • Sewage sludge should be stabilized • Industrial waste water should be pre-treated • Recently • Co-digestion of two or more substrate and multi-purpose

  4. Co-digestion • Co-digestion • Two or more substrates • Major amount of a main basic substrates (e.g. manure or sewage sludge) + Minor amount of a singe, or a variety of additional substrates • Multi-purpose process serving at the same time • Waste upgrading • Energy production • Improvement of fertilizer quality

  5. Co-digestion—Cont. • Factors impact the production of biogas • The type of waste being digested • Its concentration • Its temperature • The presence of toxic materials • The pH and alkalinity • The hydraulic retention time • The solids retention time • The ration of food to microorganism • The rate of digester loading • The rate at which toxic end products of digestion are removed

  6. Improve the C/N ratio, buffering capacity and more biodegradable substrate Benefits of Co-digestion • Improved nutrient balance and digestion performance • A nutrient ratio of TOC:N:P = 300:5:1 to achieve optimal digestion performance Manure Low C/N ratio– high ammonia High alkalinity Rich in macro/micro nutrient Crop or Crop residues High C/N ratio– high carbon content Low alkalinity Lack of macro/micro nutrient

  7. Benefits of Co-digestion • Effective utilization of digester volumes • Help to utilize the availability of free capacities • Co- digestion of energy crops and manure resulted in the doubling of the plant capacity from 500 kW to 1000 kW retaining the digester volume (Lindorfer et al., 2007) • The wide distribution of sewage treatment plants minimizes transportation costs • Equalization of particulate, floating, settling, acidifying etc. wastes, through dilution by manure

  8. Types of digester Mesophilic AD Approximately 30-35° C Retention time of 15 – 30 d Continuously stirred tank reactors (CSTRS) under mesophilic conditions Co-digestion • Thermophilic AD • Exceed 55 ° C • Retention time of 12-14 d

  9. Co-digestion • Source of organic waste streams can be co-digested with manure • Food Industry • Waste from potato, sugar beet, meat, and dairy processing • Grain Industry • Damaged grain • Paper Industry • Newspaper and recycled paper • Domestic Wastes • Livestock Wastes • Crop Residues • Corn stover and switchgrass

  10. Increased by 65 % Cow manure alone Cow manure alone Cow manure alone Manure + 30% sugar beet tops Manure + 30% grass Manure + 30% oat straw Increased by 58 % Increased by 16 % Case 1 Lehtomaki et al., 2007

  11. Case 2 • Whey co-digestion with diluted poultry manure • For an hydraulic retention time of 18 days at 35 ° C and organic loading rate of 4.9 g COD/L • Biogas production increased by 40% Gelegenis et al., 2007

  12. Case 3 • Co-digestion of solid slaughter house waste, fruit-vegetable wastes, and manure • Possibility to treat combined waste of • Manure (cattle and swine) • Solid slaughterhouse wastes (rumen, paunch content, and blood from cattle and swine) • Fruit-vegetable wastes Alvarez et al., 2007

  13. Drawbacks of Co-digestion • Increased digester effluent chemical oxygen demand (COD) • Additional pretreatment requirements • Increased mixing requirements • Wastewater treatment requirements • High utilization degree required

  14. Conclusion • Co-digestion offers several possible ecological, technological, and economical advantages • There is very limited research, specifically in the U.S., that characterizes the digestibility of a number of the waste streams • The potential economic impact of fully utilizing alternative waste streams with AD of manure seems to be great, but economic analysis must be done to quantify this information

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