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 CH 4 CO 2 H 2 NH 3 H 2 S + Biogas

Acid Formers Methane Formers Liquifiers

Acid Formers Methanogens Hydrolizers

Community Needs 1.Food 2.Proper pH 3.Sufficient Temperature 4.Sufficient Time to Reproduce 5.Absence of Inhibitory Substances

Community Needs Proper pH : ~ 6.5 to 7.5

Community Needs Sufficient Temperature Psychrophilic (15-25 o C) Mesophilic (30-38 o C) Thermophilic (50-60 o C)

Community Needs Sufficient time to reproduce

HRT = Volume of Reactor/Flow out

SRT = Solids in Reactor/Solids Leaving

Anaerobic Digestion of Manure  Understanding Basic Processes  Types of Reactors

Low Rate Reactor SRT = HRT

High Rate Reactor SRT > HRT

How much energy?

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 + O 2 → CO 2 + H 2 O + Ash + Heat

Combustion OM + O 2 → CO 2 + H 2 O + Ash + Heat TS FS

Combustion OM + O 2 → CO 2 + H 2 O + Ash + Heat TS FS VS

VS db % Beef Manure82 Dairy Manure84 Wood Shavings99 Alfalfa Silage95 Grease99

Aerobic Catabolism OM + O 2 → CO 2 + H 2 O + Cells + Heat

Aerobic Catabolism OM + O 2 → CO 2 + H 2 O + Cells + Heat Oxygen Demand

Aerobic Catabolism OM + O 2 → CO 2 + H 2 O + Cells + Heat Oxygen Demand COD BOD u

Methane Potential  Volatile Solids Content  COD

Anaerobic Catabolism OM + Heat → CH 4 + CO 2 + H 2 O + Cells

Anaerobic Catabolism OM + Heat → CH 4 + CO 2 + H 2 O + Cells Biogas

Combustion OM + Heat → CH 4 + CO 2 + H 2 O + Cells CH 4 + 2O 2 → CO 2 + H 2 O + Heat

Combustion OM + Heat → CH 4 + CO 2 + H 2 O + Cells CH 4 + 2O 2 → CO 2 + H 2 O + Heat Oxygen Demand

Combustion CH 4 +2O 2 → CO 2 + H 2 O + Heat Two moles O 2 per mole CH 4

Combustion CH 4 +2O 2 → CO 2 + H 2 O + Heat 2n OD = n CH4

Combustion CH 4 +2O 2 → CO 2 + H 2 O + Heat PV = nRT

Combustion CH 4 +2O 2 → CO 2 + H 2 O + Heat V CH4 = 2n OD RT/P

Ultimate Gas Yield CH 4 +2O 2 → CO 2 + H 2 O + Heat 0.38 L CH 4 produced per kg OD 20 o C and 1 atm

VS db % COD:VS Beef Manure821.2 Dairy Manure841.2 Wood Shavings Alfalfa Silage Grease

Methane Potential  Volatile Solids Content  COD  BMP

BMP Biochemical Methane Potential

D.P. Chynoweth

VS db % COD:VS COD converted to CH 4 % Beef Manure Dairy Manure Wood Shavings Alfalfa Silage Grease

D.P. Chynoweth Specific Methane Yield (L CH 4 g -1 VS)

VS db % COD:VS COD converted to CH 4 % Specific Methane Yield L CH 4 g -1 VS Beef Manure Dairy Manure Wood Shavings Alfalfa Silage Grease

Community Needs 1.Food 2.Proper pH 3.Sufficient Temperature 4.Sufficient Time to Reproduce 5.Absence of Inhibitory Substances

Methane Potential  Volatile Solids Content  COD  BMP  ATA

ATA Anaerobic Toxicity Assay

Inhibition (%) I = (1 - Pt/Pc) X 100 Where: Pc = gas produced 0% inclusion Pt = gas produced at test inclusion

ATA Anaerobic Toxicity Assay

Methane Potential  Volatile Solids Content  COD  BMP  ATA  Pilot Testing

Pilot Scale Testing

B o S o θ v 1 - K µ m θ s – 1 + K VRE = Chen, Y.R. and A.G. Hashimoto Substrate utilization kinetic model for biological treatment processes. Biotech &. Bioeng. 22:

Any Questions?