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Biomass & Biofuels Anareobic Digestion

Biomass & Biofuels Anareobic Digestion. San Jose State University FX Rongère March 2009. Biochemical Conversion. Thermochemical Conversion. Extraction. Anaerobic Digestion. Fermentation. Direct Combustion. Gasification. Pyrolysis Liquefaction. Steam. Gas. Oil. Charcoal. Biogas.

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Biomass & Biofuels Anareobic Digestion

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  1. Biomass & BiofuelsAnareobic Digestion San Jose State University FX Rongère March 2009

  2. Biochemical Conversion Thermochemical Conversion Extraction Anaerobic Digestion Fermentation Direct Combustion Gasification Pyrolysis Liquefaction Steam Gas Oil Charcoal Biogas Ethanol Bio-diesel Heat Electricity Transportation Biofuels • Biofuels cover a broad range of technologies and applications: Source: From Boyle, Renewable Energy, 2nd edition, 2004

  3. Anaerobic Digestion • Breakdown of biodegradable material by micro-organisms (bacteria) in absence of gaseous oxygen • It applies to 3 different waste treatments: • Landfill • Animal waste – Manure • Waste water treatment • It generates a biogas composed of:

  4. Anaerobic Digestion • The process includes 4 major biological or chemical stages:

  5. Carbohydrates • Polymer base on Glucose molecule C6H12O6 α-D-glucopyranose Mono-mere Cellulose Poly-mere

  6. Carbohydrates • Proteins: R’ O O H — N — C — C — C— C R O — H H H NH2 Carboxyl Group Example of a protein structure: Myoglobin Amino Group peptide bond

  7. O O O R R R C C O O H — CH — CH — CH — H Carbohydrates • Fats: • Polymers of fatty acids and alcohols Fatty acids C O Alcohols

  8. O R— C O — H H O N—C— C H O — H R Hydrolysis  • Converts Complex organic matters (Carbohydrates, Proteins and fats) in Soluble organic molecules (Sugar, Amino-acids, Fatty acids) Fatty Acids Sugar - Glucose Amino Acids

  9. O CH3— C butanonic acid (butyric acid) O — H O O CH3— CH2— CH2— C CH3— CH2— C O — H Fermentation - Acidogenesis  • Decomposition in volatile Fatty Acids (C3 and C4), acetic acid and H2 ethanoic acid (acetic acid / vinegar) propionic acid O — H

  10.  Acetogenesis • Conversion of the volatile fatty acids in acetic acid and H2 • Bacteria syntrophic (mutually beneficial) with the methanogens Acetic Acid

  11. Methanogenesis • Acetotrophic methanogens 2 CH3COOH  2 CO2 + H2 CH3COOH  CO + CH3OH • Methylotrophic methanogens 4 CH3OH + 6 H2 3 CH4 + 2 H2O • Hydrogenotrophic methanogens CO2 + 4 H2 CH4 + 2 H2O Resulting Biogas

  12. Anaerobic digestion drawbacks • Bacterias are sensitive to: • Oxygen • Temperature (35o optimal - Mesophilic) • pH (stability and slightly acidic) • Toxic component (H2S, NH3, metals) • Optimization and control of an anaerobic bio-digestor are complex • Takes time (several days to several years)

  13. Municipal Solid Waste • MSW production in the USA Europe Japan • Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: • Facts and Figures for 2005

  14. Municipal Solid Waste • Domestic waste sources in the USA • Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: • Facts and Figures for 2005

  15. Landfill • MSW treatment in the USA • Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: • Facts and Figures for 2005

  16. Landfill/Recovery/Combustion in the USA • Source: EPA Municipal Solid Waste Generation, Recycling, and Disposal in the United States: • Facts and Figures for 2005

  17. Landfill • MSW treatment in the world 1995 Source: Kai Sipilä, VTT Processes, Finland MUNICIPAL AND COMMERCIAL SOLID WASTE FOR PYROLYSIS (OILS ) AND GASIFICATION MARKETS 2002

  18. Landfill • Structure of a modern landfill

  19. Landfill • Biogas is used to generate electricity or is sold to utilities • Major issues: • Pollutants: Siloxanes, SO2, Solanes, Aliphatics components, explosive cycloalcnes • CH4 content variation

  20. Internal Combustion Engine • Diesel cycle Pressure P2 P1 Volume V1 V2

  21. Methane • CH4 • Energy Content: 802 kJ/mol=50,125 kj/kg • Methane Combustion: CH4+2 O2 -> CO2 + 2 H2O • Stoichiometry: 17.4 • Auto-ignition temperature: 537°C • Adiabatic Flame Temperature: 1,950°C • Explosive limits: 5–15%

  22. Perfect compressor Diesel Cycle • Adiabatic Compression Air is close to an ideal gas:

  23. Compression ratio • Compression ratio • Is determined by the methane auto-ignition temperature: 537oC

  24. Perfect transfer Constant pressure Combustion • Max temperature is limited by the materials typically 1,200oC VF is the volume at the end of the combustion A part of the power is generated during the combustion phase

  25. Diesel Cycle • Adiabatic Expansion (similar to the compression) Venting pressure is not equal to P1. It is defined by the expansion to V2 Conversion rate of a Diesel cycle is about 40%. Venting temperature of 400oC allows cogeneration

  26. Advantages/Disadvantages

  27. Other Engines • Stirling Engines

  28. Other Engines • Gas turbines 50 30 kW Capstone microturbines convert flare gas at Lopez Canyon Landfill in Sylmar, CA for 1.5 MW 20 30 kW Capstone microturbines convert flare gas at in La Ciotat, France

  29. Liquefied Natural Gas Generation • Prometheus generates Liquefied Natural Gas from landfill biogas.

  30. California MSW • 70 MM tons per year of MSW generation leading to 11 lb/day/capita (more than 2 times the USA average) • 43 MM tons are sent to landfills (61% of total MSW), thermal conversion is about 20% of total MSW • There are three MSW mass-burn for 67 MWe and 46 landfill gas to energy facilities (LFGTE) for 280 MW Potential: .15 to .45 m3 of biogas/kg Biogas = 60% methane 1,800 MM Therm/y 21 TWh/y Electricity 2.8 GW Spittelau incineration plant in Vienna.

  31. MSW Component and properties * Ash: proportion of non burning residues † HHV: Higher Heating Value, energy content for combustion in absence of water Source: CEC-500-2006-095 Direct Combustion potential: 4,000 MMTherm/y, 30 TWh/y, 4.1 GW

  32. Manure bio gas

  33. Potential in California • California is the first state of the USA for dairies

  34. California • Dairies • 1.7 Millions cows • 2,153 dairies (2002) • 5 leading counties • Tulare • Merced • Stanislaus • San Bernadino • King Potential is: 2.4kWh/day/cow (assuming 20% used for digester heating, conversion rate:30%) 170 MM Therms/y, 1,500 GWh/y, 200 MW

  35. Process Digestion duration: 15-20 days Temperature: 36oC

  36. Energy in Dairies • Wide variation: • 300 – 1,500 kWh/cow/y1 • Narrower interval: • 700 – 900 kWh/cow/y2,5 • Total California: • 1,190 GWh/y3 Using digesters, California dairies may be energy neutral SCE guide - 2004 1: SCE guide – 2004 2: Audit PG&E 3: A Consumer’s Look at California’s Dairy Industry - 2002 4: PG&E electricity bills – 2004 (Livestock) 5: Scott Sanford University of Wisconsin (Wisconsin data)

  37. Examples • Biogas by-products can be used by microturbines for on-site energy use, such as at this Wisconsin wastewater treatment plant • Digesting tanks at Microgy, Inc.'s biogas plant process manure from about 10,000 cows into methane and compost. Credit: Microgy, Inc.

  38. Types of Anaerobic Digesters • There are many different types of digesters: • Covered lagoons • Complete mix digesters • Complete Stirred Tank Reactors (CSTR) • Completely Mixed Flow Reactors (CMF) • Continuous Flow Stirred Tank (CFST) • Plug flow digesters • Anaerobic Sequencing Batch Reactor • Fixed film digesters

  39. Covered Lagoons • Advantages • Low cost (relative) • Low tech / easy to construct • Disadvantages • Cover maintenance / life • Large footprint • Solids / nutrient accumulation

  40. Complete Mix Digesters • Advantages • High level of experience • Works over wide range of influent Total Solids (TS) • Can be used with scrape or flush systems and swine or dairy systems • Disadvantages • Poor biomass immobilization • Mechanical mixing requirement

  41. Plug Flow Digesters • Advantages • Good track record with Dairy manure • Works well with scrape systems • Disadvantages • Requires high solids manure (11 - 14 %) • Not compatible with sand bedding

  42. Haubenschild Farm • 750 cow dairy in Minnesota • 59,500 pounds of milk per day • Plug-flow manure digester: • 130'LX30'WX14'D • 1/2 million gallons • 20,000 gallons each day • constant 100F degrees • 72,500 cf of biogas per day • Biogas is 60% methane & 35% CO2 • Electric generator: • 150kW diesel cycle generator • Waste heat recovery for digester operation and building heat

  43. Haubenschild Farm

  44. Cost Analysis Source: C. Nelson, J. Lamb Final Report: Haubenschild Farms Anaerobic Digester The Minnesota Project Aug. 2002

  45. Revenues Simple Payback: Internal Rate of return: Horizon: 20 years IRR=23%

  46. Other animals • California farm animal population

  47. Companies to follow • Capstone www.capstone.com • STM-bio • Prometheus-Energy www.prometheus-energy.com • RealEnergy www.realenergy.com • Cummins www.cummins.com • Solar www.mysolar.cat.com • Microgy www.environmentalpower.com/companies/microgy/

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