anaerobic digestion - anaerobic digestion peat bog permafrost ruminants • anaerobic = without...
Post on 30-Jul-2020
1 views
Embed Size (px)
TRANSCRIPT
www.nq-biogas.com
Dr. agr. Melanie Hecht NQ-Anlagentechnik GmbH
Anaerobic Digestion
www.nq-biogas.com 2
NQ-Anlagentechnik GmbH
• since 1993 a full-line supplier of biogas plants and components
• approval planning - construction - start-up & services/maintenance
• by now constructed ~ 250 biogas plants in Germany, Switzerland, Austria and Croatia
• biological service: lab analyses consulting (feeding/stirring, crop rotation and more) on-site visits dimensioning
NQ-concrete digester NQ-bp 620kWel.NQ-150 agitator
www.nq-biogas.com 3
Veterinarska stanica Dvor
• start-up 04/2009
• 2x16/6 digesters (2x1205 m3)
• 135 kW el.
(MAN, gas engine, 6 cyl.)
• chicken/bull manure, cattle slurry
www.nq-biogas.com 4
Anaerobic digestion
NQ-Anlage 380kW
www.nq-biogas.com
Anaerobic digestion
peat bog
permafrost
ruminants
• anaerobic = without oxygen (O 2 )
• digestion = mechanical and chemical breakdown of organic
material into smaller compounds (macro to micro)
• renewable energy source replaces fossil fuels (oil, gas)
� methane (CH 4 ) = combustible
23 times the climate warming potential of CO 2
� digestate = fertilizer
www.nq-biogas.com
Substrates for Anaerobic Digestion
www.nq-biogas.com
Substrates for Anaerobic Digestion
• organic materials:
• agricultural: manure, slurry, good availability (€) methanogenic bacteria solvent (4-8 % DM) trace elements/nutrients
energy crops (corn, grass, sunflowers) by-products
• organic wastes: MSW, catering-/biowaste
agro/food industry often requires separation techology
www.nq-biogas.com
Substrates for Anaerobic Digestion
• non-degradable: lignin (wood) • hard to degrade: cellulose, hemicellulose
• continuity: keep a calm hand
Types of digestion: • dry digestion: > 35 % dry matter (DM) • wet digestion: < 20% DM
referring to DM in main digester
www.nq-biogas.com
Substrates for Anaerobic Digestion
• Contaminants: heavy metals disinfectants antibiotics pesticides, fungicides
sand, stones bones, feathers plastic, plastic bands, glass hair wire, metal parts
www.nq-biogas.com
Substrates for Anaerobic Digestion
www.nq-biogas.com
Fundamentals of Anaerobic Digestion
www.nq-biogas.com 12
micro: CH4 (methane) CO2 (carbon dioxide)
macro: starch proteins fat ?
The anaerobic digestion process
www.nq-biogas.com 13
4 steps of microbial degradation
parallel in space and time
acidogenesis
hydrolysishydrolysis
acetogenesis
methanogenesis
The anaerobic digestion process
macro: starch proteins fat
www.nq-biogas.com 14
hydrolysis
acetogenesis
methanogenesis
acidogenesis
complex polymers
biogas (CH4 + CO2) + residue
The anaerobic digestion process
www.nq-biogas.com 15
complex polymers
monomers
hydrolysis
carbohydrates, fat and proteins are broken down into mono/di- saccharides, fatty acids and amino acids by exo-enzymes
biogas (CH4 + CO2) + residue
The anaerobic digestion process
www.nq-biogas.com 16
complex polymers
monomers
H2 + CO2 propionic / butyric acid
acetic acid
acidogenesis
monomers are taken up by bacteria and converted to H2, CO2, volatile fatty acids (VFA) and alcohols by fermentation
The anaerobic digestion process
biogas (CH4 + CO2) + residue
hydrolysis
carbohydrates, fat and proteins are broken down into mono/di- saccharides, fatty acids and amino acids by exo-enzymes
www.nq-biogas.com 17
complex polymers
monomers
H2 + CO2
H2 + CO2
propionic / butyric acid
acetic acid
The anaerobic digestion process
biogas (CH4 + CO2) + residue
acetogenesis VFA, H2 and CO2 are partly metabolized into acetic acid
acidogenesis
monomers are taken up by bacteria and converted to H2, CO2, volatile fatty acids (VFA) and alcohols by fermentation
hydrolysis
carbohydrates, fat and proteins are broken down into mono/di- saccharides, fatty acids and amino acids by exo-enzymes
www.nq-biogas.com 18
H2 + CO2
H2 + CO2
propionic / butyric acid
acetic acid
complex polymers
monomers
The anaerobic digestion process
biogas (CH4 + CO2) + residue
acetogenesis VFA, H2 and CO2 are partly metabolized into acetic acid
acidogenesis
monomers are taken up by bacteria and converted to H2, CO2, volatile fatty acids (VFA) and alcohols by fermentation
hydrolysis
carbohydrates, fat and proteins are broken down into mono/di- saccharides, fatty acids and amino acids by exo-enzymes
methanogenesis acetic acid, H2 and CO2 are converted into CH4 and CO2
30%70%
very sensitive to environmental changes, e.g. T, pH, VFA rate-limiting reaction in anaerobic digestion!
www.nq-biogas.com 19
Archaea
peat bogblack smoker
archaea
www.nq-biogas.com
Environmental Parameters
www.nq-biogas.com 21
Louis Pasteur (1822 □ 1895) founder of the germ theory of disease
„The germ itself is nothing, the terrain is everything.“
Bacteria need...
...certain environmental conditions.
www.nq-biogas.com 22
Environmental parameters
alcalinity / buffer
capacity
VFA
pH nutrients
ammonium NH4
electric conductivity
temperature
bacterial growth / process control
www.nq-biogas.com 23
alcalinity / buffer
capacity
VFA
pH nutrients
ammonium NH4
electric conductivity
temperature
bacterial growth / process control
Environmental parameters
www.nq-biogas.com 24
volatile fatty acids (VFA):
C5 valeric acid CH3 - CH2 - CH2 - CH2 - COOH
C4 butyric acid CH3 - CH2 - CH2 - COOH
C3 propionic acid CH3 - CH2 - COOH
C2 acetic acid CH3 - COOH
Complex polymers
biogas (CH4 + CO2) + residue
Monomers
H2 + CO2
H2 + CO2
propionic / butyric acid
acetic acid
acid = H+ (protons) = pH
Environmental parameters
pH (alcalinity/acidity)
www.nq-biogas.com 25
C2 acetic acid CH3 - COOH
Effect on pH by acids:
Environmental parameters
www.nq-biogas.com 26
C2 acetic acid CH3 - COOH
Effect on pH by acids:
Environmental parameters
www.nq-biogas.com 27
C2 acetic acid CH3 – COO - + H+
H+
pH
14
1
7
pH
alkaline
acidic
Environmental parameters
Effect on pH by acids:
www.nq-biogas.com 28
C2 acetic acid CH3 - COOH
H+
pH
14
1
7
pH
alkaline
acidic
Environmental parameters
Effect on pH by acids:
www.nq-biogas.com 29
C2 acetic acid CH3 – COO - + H+
H+
pH
14
1
7
pH
alkaline
acidic
Environmental parameters
Effect on pH by acids:
www.nq-biogas.com 30
C2 acetic acid CH3 – COO - + H+
H+
pH
14
1
7
pH
alkaline
acidic
Environmental parameters
Effect on pH by acids:
www.nq-biogas.com 31
Effect of alkalinity on pH:
hydrogen carbonate HCO3 -
H+
pH
14
1
7
pH
alkaline
acidic
Environmental parameters
www.nq-biogas.com 32
H+
pH
14
1
7
pH
hydrogen carbonate HCO3 -
alkaline
acidic
Environmental parameters
Effect of alkalinity on pH:
www.nq-biogas.com 33
CH3–COOH CH3–COO - + H+ HCO3
- H2CO3
acetic acid acetate hydrogen hydrogen water carbon carbonate bicarbonate dioxide
Environmental parameters
Effect of alkalinity on pH:
www.nq-biogas.com 34
• alkalinity (= hydrogen carbonate / HCO3 -)
neutralizes (= buffers) acids (H+)
stabilizes pH
keeps environmental conditions in digesters stable
CH3–COOH CH3–COO - + H+ HCO3
- H2CO3
acetic acid acetate hydrogen hydrogen carbonate bicarbonate
Environmental parameters
Effect of alkalinity on pH:
www.nq-biogas.com 35
• alkalinity (= hydrogen carbonate / HCO3 -)
neutralizes (= buffers) acids (H+)
stabilizes pH
keeps environmental conditions in d
Recommended