BIOCHEMISTRY OF BIOGAS PRODUCTION · sugars, amino-acids, fatty acids Volatile fatty acids...
Transcript of BIOCHEMISTRY OF BIOGAS PRODUCTION · sugars, amino-acids, fatty acids Volatile fatty acids...
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BIOCHEMISTRY OF BIOGAS
PRODUCTION
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What is biogas?
Biogas is a mixture of CO2 and CH4
CH4+2 O2
Only CH4, is suitable, biogas should contain at least 50%
Biogas is produced of organic products using anaerobic
conditions and several microorganisms
CO2 + 2 H2O +Energy
C6H12O6 → 3 CH4 + 3 CO2
C OO
C
H
HH
H
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From what is biogas produced?
• In nature:
Wetlands
Rice fields
Intestines of animals
Manures
• Biogas can also be produced of organic products like:
Waste from agro-industrial units
Energy crops (corn, sorghum)
Effluent from wastewater treatment
Decomposition of organic waste fraction
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The production contains 4 steps:
1. Hydrolysis Hydrolases
2. Acidogenesis Acidogenic bacteria
3. Acetogenesis Acetogenic bacteria
4. Methanogenesis Methanoic Archaea
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Archaea
Constructed like procaryotes, but aren‘t bacteria!!!
Anerobic
Occur in extreme conditions e.g. geyser
Methanic archaea
Swamps
Sludge facilities
Animal digestive organs
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Step 1: Hydrolysis
Macromolecules (carbohydrates, fat, proteins) are
decomposed by enzymes, which are hydrolases.
C O
C
CC
C
H
HH
H
OH
H OH
CH2
OH
C O
C
CC
C
H
HH
H
ROH
H OH
CH2
OH
O O
C O
C
CC
C
H
HH
H
OH
H OH
R
CH2
OH
C O
C
CC
C
H
HH
H
OH
H OH
CH2
OH
O
C O
C
CC
C
H
HH
H
OH
OH
H OH
OH
CH2
OH
C O
C
CC
C
H
HH
H
OH
OH
H OH
OH
CH2
OH
C O
C
CC
C
H
HH
H
OH
OH
H OH
OH
CH2
OH
C O
C
CC
C
H
HH
H
OH
OH
H OH
OH
CH2
OH
Hydrolyse
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Step 2: Acidogenesis
Small organic
molecules to
carbonic acids
Oligomers
(Soluble organic
molecules)
sugars, amino-acids, fatty
acids
Volatile fatty acids
(Carbonic acids:
formic, acetic, propionic
butyric, valeric)
+ alcohol
Acidogenic bacteria
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Step 3: Acetogenesis
conversion to
acetate and CO2
Carbonic acids
formic, acetic, propionic,
butyric, valeric
+ alcohol
H2 and
CO2
CH3COO-
Acetogenic bacteria
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Step 4: Methanogenesis
final conversion
to CH4
70% 30%
CH4 +
CO2
CH4 + H
2O
Acetate +
alcoholCO
2, H
2
Methanoic Archaea
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Methanogenesis:
1) methane is made of formate (HCOO-) or CO2 :
CO2 + 4H2 CH4 + 2H2O
2) methane is made of acetate(CH3COO-) witch is the salt of
acetic acid:
2CH3 CH2OH + CO2 2CH3COOH + CH4
2CH3COOH + CH4 CH4 + CO2
3) methane is made of alcohols like methanol:
CH3OH + H2 CH4 + H2O
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Complex organic
molecules
carbohydrates, proteins, fats
Carbonic acids
formic, acetic,
propionic, butyric, valeric,
+ alcohol
H2 and
CO2
Acetate +
alcohol
CH4
+ CO2
CH4 + H
2O
2
3 3
4 4
1 1
Summary
of the
steps
Soluble organic
molecules
sugars, amino-acids, fatty
acids
BIOGAS
HYDROLYSIS
ACETOGENESIS
ACIDOGENESIS
METHANOGENESIS
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