anaerobic digestion - anaerobic digestion peat bog permafrost ruminants • anaerobic = without...

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  • 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

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    Anaerobic digestion

    NQ-Anlage 380kW

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    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

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    Substrates for Anaerobic Digestion

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    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

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    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

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    Substrates for Anaerobic Digestion

    • Contaminants: heavy metals disinfectants antibiotics pesticides, fungicides

    sand, stones bones, feathers plastic, plastic bands, glass hair wire, metal parts

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    Substrates for Anaerobic Digestion

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    Fundamentals of Anaerobic Digestion

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    micro: CH4 (methane) CO2 (carbon dioxide)

    macro: starch proteins fat ?

    The anaerobic digestion process

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    4 steps of microbial degradation

    parallel in space and time

    acidogenesis

    hydrolysishydrolysis

    acetogenesis

    methanogenesis

    The anaerobic digestion process

    macro: starch proteins fat

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    hydrolysis

    acetogenesis

    methanogenesis

    acidogenesis

    complex polymers

    biogas (CH4 + CO2) + residue

    The anaerobic digestion process

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    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

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    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

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    Environmental Parameters

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    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.

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    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)

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    C2 acetic acid CH3 - COOH

    Effect on pH by acids:

    Environmental parameters

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    C2 acetic acid CH3 - COOH

    Effect on pH by acids:

    Environmental parameters

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    C2 acetic acid CH3 – COO - + H+

    H+

    pH

    14

    1

    7

    pH

    alkaline

    acidic

    Environmental parameters

    Effect on pH by acids:

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    C2 acetic acid CH3 - COOH

    H+

    pH

    14

    1

    7

    pH

    alkaline

    acidic

    Environmental parameters

    Effect on pH by acids:

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    C2 acetic acid CH3 – COO - + H+

    H+

    pH

    14

    1

    7

    pH

    alkaline

    acidic

    Environmental parameters

    Effect on pH by acids:

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    C2 acetic acid CH3 – COO - + H+

    H+

    pH

    14

    1

    7

    pH

    alkaline

    acidic

    Environmental parameters

    Effect on pH by acids:

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    Effect of alkalinity on pH:

    hydrogen carbonate HCO3 -

    H+

    pH

    14

    1

    7

    pH

    alkaline

    acidic

    Environmental parameters

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    H+

    pH

    14

    1

    7

    pH

    hydrogen carbonate HCO3 -

    alkaline

    acidic

    Environmental parameters

    Effect of alkalinity on pH:

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    CH3–COOH CH3–COO - + H+ HCO3

    - H2CO3

    acetic acid acetate hydrogen hydrogen water carbon carbonate bicarbonate dioxide

    Environmental parameters

    Effect of alkalinity on pH:

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    • 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:

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    • alkalinity (= hydrogen carbonate / HCO3 -)

    neutralizes (= buffers) acids (H+)

    stabilizes pH

    keeps environmental conditions in d

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