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Biogas production Biomas in Biomas out (Digestate) Gas out.

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Presentation on theme: "Biogas production Biomas in Biomas out (Digestate) Gas out."— Presentation transcript:

1 Biogas production Biomas in Biomas out (Digestate) Gas out

2 Where are we? Why do we want? How do we manage? What do we need? From where should we start? What do we want to know?

3 Biogas knowledge piramide Optimizing operational condition& designing biogas system Methane productivity& potential, reaction, inhibition operational condition, digetibility Identification of biogas field in general Obtaining technical ability to obtain data to support project

4 Biogas plant concept Pig slurry FeBiomas out (Digestate)  Additional income for the farmers  Clean energy (kitchen)  Digestate is an excellent fertilizer  Less odour  Sanitaion

5 The microbiology process Biomasse: Animal manure Organic waste Hydrolysis Dissolved substrate Acidogenesis H 2 +CO 2 Acetognesis VFA>C2 CH 4 +H 2 O+ CO 2 CH 3 -COOH Methanogenesis

6 Methane produktion Biomasse: Animal manure Organic waste Hydrolysis Dissolved substrate Acidogenesis H 2 +CO 2 Acetognesis VFA>C2 CH 4 +H 2 O+ CO 2 CH 3 -COOH Methanogenesis Hydrolysis is process rate controlling VFA transformation reduced due to: High NH3 Sudden changes in environment High H 2 concentration Feedback: High VFA conc. reduces hydrolysis

7 Physical process COMPOSITE MATERIAL MACROMOLECULES Physical process: Disintegration Lysis Non enzymatic decay Phase separation Physical breakdown (shearing)

8 Biological and chemical process MACROMOLECULES SIMPLE SUBSTRATES Hydrolysis (chemical) A→B 1 +B 2 (H 2 O is used) Hydrolytic enzymes (biological/chemical) Made by micro-organisms – same outcome

9 SIMPLE SUBSTRATES VOLATILE FATTY ACIDS ACETATE & HYDROGEN Acidogenesis: (biological) Volatile fatty acids are generated from monosaccarides, fat and aminoacids. (sugar-degraders & aminoacid-degraders) Acetogenesis: (biological) Acetate is generated from LCFAs. (lcfa- degraders) and from sugar (sugar-degraders)

10 ACETATE & HYDROGEN BIOGAS Methanogenesis (biogas production) Acetoclastic methanogenesis CH 3 COOH → CH 4 + CO 2 Hydrogenotrophic methanogenesis CO 2 + 4H 2 → CH 4 + 2H 2 O

11 Biogas knowledge pyramide Inhibition Optimizing operational condition& designing biogas system Methane productivity& potential, reaction, inhibition operational condition, digetibility Identification of biogas field in general Obtaining technical ability to obtain data to support project

12 H 2 inhibition VFA component Acetic acid

13 Ammonia inhibition Ammonia inhibition: 1,5 – 2,5 g N/L, after adaptation inhibition at 4 g N/L (Angelidaki og Ahring 1998)

14 Ammonia chemistry pH= -log(H + ) Thus if the concentration of [H + ] is Neutral: mol then pH = –log(10 -7 )=7 Acid: mol then pH = –log(10 -2 )=2 Basic: mol then pH = –log( )=10

15 Ammonia-ammonium equilibrium

16 Ammonia inhibition In literature ammonia inhibition has been assessed relating biogas production to Reactive ammonium (NH 3 ) Total Nitrogen Ammonium How is NH 3 related to NH 4 + How would you recommend that the inhibition is expressed (reactive ammonium, total nitrogen or ammonium

17 Inhibition at high and low pH SH 2 NH 3

18 VFA inhibition Inhibition at a ratio of propionic acid to acetic acid at 1.4:1 Inhibition at 2 g VFA Ltr -1

19 Temperature Bacteria adaptation Batstone et al. 2002

20 SIMPLE SUBSTRATES VOLATILE FATTY ACIDS ACETATE & HYDROGEN Acidogenesis: (biological) Volatile fatty acids are generated from monosaccarides and aminoacids. (sugar-degraders & aminoacid-degraders) Acetogenesis: (biological) Acetate is generated from LCFAs. (lcfa- degraders) and from sugar (sugar-degraders) What happens if the temperature suddenly drops?

21 Metane production as affected by NH 4 + koncentration interacting with temperature 20 days retention time in CSTR digester

22 Biogas knowledge piramide Digestibilty Optimizing operational condition& designing biogas system Methane productivity& potential, reaction, inhibition operational condition, digestibility Identification of biogas field in general Obtaining technical ability to obtain data to support project

23 Definitioner VS (Volatile solids): – The fraction of dry matter (DM) in slurry that is transformed to gas at high temperature/incineration (550 o C) for one hour – How would you measure VS? Methane productivity: – CH 4 production pr. unit VS – CH 4 production pr. unit COD

24 Source of energy in animal slurry

25 Energy production CH 4 - source Biogas, CH 4 +CO 2

26 Characterisation of biogas potential In the biological process the maximum biogas production BMP (liter CH 4 kg(VS) -1 ) – Volume of methane produced when residence time is in principle very long Inoculum Biomas BMP is estimated in batch fermentation at 35 o C Fermentation time days

27 Anaerobic Digestibility  The theoretical biogas production can be calculated from knowing the chemical composition of the biomass:TBMP  In the biological process the maximum biogas production: BMP  Anaerobic digestibility =BMP/TBMP Question - BMP/TBMP ↑ digestibility?? - BMP/TBMP ↓ digestibility ??

28 Biodegradability (BMP/TBMP) examples

29  Low digestibility  lignin : Non degradable in anaerobic environments  hydrolysis of cellulose blocked by lignin.  Lignin  glue to hold lignocellulosic matrix  protective coat  used to assess digestibility of feed in animal science Lignocellulose

30 Lignocellulose in VS (volatile solid)

31 Fermentation result - animal manure

32 Digestability of the biomass CH 4 L kg(VS) -1

33 Energy potential of biomass Dry matterVolatile solids in pct of dry matter (DM) Total energy content Energy production in biogas plant %MJ/ kg DM Pig slurry68016,39,8 Cattle slurry ,37,6 Clover grass ,314,6 Straw90 19,19,6 Why is biogas energy production of straw so low

34 Methane produkcion crops and organic waste

35 Biogas production estimates With the Hashimoto equation one can assess production of biogas as affected by: temperature, hydraulic retention time, micro-organism activity biomass composition

36 Hashimoto equation HRT or θHydraulic retention time SRTSolid retention time ΓIs the specific gas yield B0B0 The ultimate or specific methane yield, measured with batch fermentation at more than 60 days and at 35 o C. µ maximal specific growth rate of the micro organisms, µ m a function of temperature and residues feed to the reactor K is a kinetic parameter depending of the rate of feed, feed composition and bacterial consortium, S0S0 Concentration of organic components in feed to the reactor Nm 3 The volume CH 4 produced, calculated at 0 o C (273 o K)

37 Hashimoto model predictions’

38 Summarising Biogas is efficient in producing energy from biomasses with a high water content Biogas transform the biomas reducing VS and thus reduced GHG emission potential of the slurry Biogas transform biomas organic N into ammonium that is an efficient fertilizer


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