anaerobic digestion: biomass to bioenergy douglas w. hamilton, ph.d., p.e. associate professor,...
TRANSCRIPT
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
CH4
CO2
H2
NH3
H2S
+
Biogas
Acid Formers
Methane Formers
Liquifiers
Acid Formers
Methanogens
Hydrolizers
Community Needs1. 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 (15-25o C)Mesophilic (30-38o C)Thermophilic (50-60o 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 + O2 → CO2 + H2O + Ash + Heat
Combustion
OM + O2 → CO2 + H2O + Ash + Heat
TS FS
Combustion
OM + O2 → CO2 + H2O + Ash + Heat
TS FSVS
VS db%
Beef Manure 82
Dairy Manure 84
Wood Shavings 99
Alfalfa Silage 95
Grease 99
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 DemandCODBODu
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
VS db%
COD:VS
Beef Manure 82 1.2
Dairy Manure 84 1.2
Wood Shavings 99 0.19
Alfalfa Silage 95 0.70
Grease 99 0.40
Methane Potential Volatile Solids Content COD BMP
BMP Biochemical Methane Potential
www.bioprocess.com
D.P. Chynowethwww.agen.ufl.edu
VS db%
COD:VSCOD
converted to CH4
%
Beef Manure 82 1.2 17
Dairy Manure 84 1.2 55
Wood Shavings 99 0.19 33
Alfalfa Silage 95 0.70 110
Grease 99 0.40 52
D.P. Chynowethwww.agen.ufl.edu
Sp
ecif
ic M
eth
ane
Yie
ld (
L C
H4 g
-1 V
S)
VS db%
COD:VSCOD
converted to CH4
%
Specific Methane
YieldL CH4 g-1 VS
Beef Manure 82 1.2 17 0.084
Dairy Manure 84 1.2 55 0.24
Wood Shavings 99 0.19 33 0.067
Alfalfa Silage 95 0.70 110 0.30
Grease 99 0.40 52 0.81
Community Needs1. 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% inclusionPt = gas produced at test inclusion
ATA Anaerobic Toxicity Assay
Methane Potential Volatile Solids Content COD BMP ATA Pilot Testing
Pilot Scale Testing
Pilot Scale Testing
BoSo θv
1 - K µmθs – 1 + K
VRE =
Chen, Y.R. and A.G. Hashimoto. 1980. Substrate utilization kinetic model for biological treatment processes. Biotech &. Bioeng. 22:2081-2095
Any Questions?