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Anaerobic Digestion: Biomass to Bioenergy. Douglas W. Hamilton, Ph.D., P.E. Associate Professor, Biosystems and Agricultural Engineering Waste Management Specialist, Oklahoma Cooperative Extension Service. Anaerobic Digestion of Manure. Understanding Basic Processes. Digestion Process.
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Anaerobic Digestion:Biomass to Bioenergy Douglas W. Hamilton, Ph.D., P.E. Associate Professor, Biosystems and Agricultural Engineering Waste Management Specialist, Oklahoma Cooperative Extension Service
Anaerobic Digestion of Manure • Understanding Basic Processes
Digestion Process Biogas CH4 CO2 H2 NH3 H2S +
Liquifiers Acid Formers Methane Formers
Hydrolizers Acid Formers Methanogens
Community Needs • Food • Proper pH • Sufficient Temperature • Sufficient Time to Reproduce • Absence of Inhibitory Substances
Community Needs Proper pH : ~ 6.5 to 7.5
Community Needs Sufficient Temperature Psychrophilic (15-25o C) Mesophilic (30-38o C) Thermophilic (50-60o C)
Community Needs Sufficient time to reproduce
Anaerobic Digestion of Manure • Understanding Basic Processes • Types of Reactors
Low Rate Reactor SRT = HRT
High Rate Reactor SRT > HRT
Anaerobic Digestion of Manure • Understanding Basic Processes • Types of Reactors • Organic Matter of Wastewater and Manure • Methane Production Potential • Toxic and Inhibitory Materials
Codigestion Mixing a highly digestible material with a source of microorganisms (manure) to produce a large volume of biogas.
Methane Potential • Volatile Solids Content
Combustion OM + O2→ CO2 + H2O + Ash + Heat
Combustion TS FS OM + O2→ CO2 + H2O + Ash + Heat
Combustion TS VS FS OM + O2→ CO2 + H2O + Ash + Heat
Aerobic Catabolism OM + O2→ CO2 + H2O + Cells + Heat
Aerobic Catabolism OM + O2→ CO2 + H2O + Cells + Heat Oxygen Demand
Aerobic Catabolism OM + O2→ CO2 + H2O + Cells + Heat Oxygen Demand COD BODu
Methane Potential • Volatile Solids Content • COD
Anaerobic Catabolism OM + Heat → CH4 + CO2 + H2O + Cells
Anaerobic Catabolism OM + Heat → CH4 + CO2 + H2O + Cells Biogas
Combustion OM + Heat → CH4 + CO2 + H2O + Cells CH4 + 2O2→ CO2 + H2O + Heat
Combustion OM + Heat → CH4 + CO2 + H2O + Cells CH4 + 2O2→ CO2 + H2O + Heat Oxygen Demand
Combustion CH4 +2O2→ CO2 + H2O + Heat Two moles O2 per mole CH4
Combustion CH4 +2O2→ CO2 + H2O + Heat 2nOD = nCH4
Combustion CH4 +2O2→ CO2 + H2O + Heat PV = nRT
Combustion CH4 +2O2→ CO2 + H2O + Heat VCH4 = 2nODRT/P
Ultimate Gas Yield CH4 +2O2→ CO2 + H2O + Heat 0.38 L CH4 produced per kg OD removed @ 20oC and 1 atm
Methane Potential • Volatile Solids Content • COD • BMP
BMP Biochemical Methane Potential www.bioprocess.com
D.P. Chynoweth www.agen.ufl.edu
Specific Methane Yield (L CH4 g-1 VS) D.P. Chynoweth www.agen.ufl.edu
Community Needs • Food • Proper pH • Sufficient Temperature • Sufficient Time to Reproduce • Absence of Inhibitory Substances
Methane Potential • Volatile Solids Content • COD • BMP • ATA
Inhibition (%) I = (1 - Pt/Pc) X 100 Where: Pc = gas produced 0% inclusion Pt = gas produced at test inclusion
Methane Potential • Volatile Solids Content • COD • BMP • ATA • Pilot Testing