Gas out Biomas in Biomas out (Digestate) Biogas production

Where are we. Why do we want. How do we manage. What do we need 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?

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

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

The microbiology process Biomasse: Animal manure Organic waste Hydrolysis Dissolved substrate Acidogenesis H2+CO2 Acetognesis VFA>C2 CH4+H2O+ CO2 CH3-COOH Methanogenesis

Methane produktion Hydrolysis is process rate controlling Biomasse: Animal manure Organic waste Hydrolysis Dissolved substrate Acidogenesis H2+CO2 Acetognesis VFA>C2 CH4+H2O+ CO2 CH3-COOH Methanogenesis Hydrolysis is process rate controlling VFA transformation reduced due to: High NH3 Sudden changes in environment High H2 concentration Feedback: High VFA conc. reduces hydrolysis Cellulose består af glucose (C6 kulstof) Hemicellulose består af xylose og andre kulhydrater mannose, arabnose etc. Hydrolyse ved glycosidase, xylanase Lipaser Proteaser

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

Biological and chemical process MACROMOLECULES SIMPLE SUBSTRATES Hydrolysis (chemical) A→B1+B2 (H2O is used) Hydrolytic enzymes (biological/chemical) Made by micro-organisms – same outcome

Acidogenesis: (biological) 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)

Methanogenesis (biogas production) Acetoclastic methanogenesis ACETATE & HYDROGEN BIOGAS Methanogenesis (biogas production) Acetoclastic methanogenesis CH3COOH → CH4 + CO2 Hydrogenotrophic methanogenesis CO2 + 4H2 → CH4 + 2H2O

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

H2inhibition Acetic acid VFA component

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

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

Ammonia-ammonium equilibrium

Ammonia inhibition In literature ammonia inhibition has been assessed relating biogas production to Reactive ammonium (NH3) Total Nitrogen Ammonium How is NH3 related to NH4+ How would you recommend that the inhibition is expressed (reactive ammonium, total nitrogen or ammonium

Inhibition at high and low pH SH2 NH3

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

Temperature Bacteria adaptation Batstone et al. 2002

Acidogenesis: (biological) 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?

Metane production as affected by NH4+ koncentration interacting with temperature Bemærk ammoniak inhibering øges ved stigende temperatur 20 days retention time in CSTR digester

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

Definitioner VS (Volatile solids): Methane productivity: The fraction of dry matter (DM) in slurry that is transformed to gas at high temperature/incineration (550oC) for one hour How would you measure VS? Methane productivity: CH4 production pr. unit VS CH4 production pr. unit COD 35.9 MJ energy can be produced pr. m3 CH4 or 45 MJ kg CH4. En kubikmeter gylle fra kvæg og svin er 350-500 MJ energi (hvilket omtrent svarer til energien i 10-15 liter benzin)

Source of energy in animal slurry Mentioned to make clear that this presentation is about animal manure management and about the two green house gases methane and nitroux oxide. The slide is also presenting the content of the presentation.

Energy production Biogas, CH4 +CO2 CH4 - source

Characterisation of biogas potential In the biological process the maximum biogas production BMP (liter CH4 kg(VS)-1) Volume of methane produced when residence time is in principle very long Biomas Batchudrådning af gylle Bemærk hældning af kurven de første 10 dage den samlede metan produktion (Bo ultimativ biogas produktion) Inoculum BMP is estimated in batch fermentation at 35oC Fermentation time 70-100 days

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 ??

Biodegradability (BMP/TBMP) examples Here we presented BMP, TBMP and BMP per TBMP which we call biodegradability. First BMP were around 200 to 400 and TBMP were around 450 to 530 liter per kg vs ). Here you can see the biodegradability as percentage, For som animal manure and crops, the biodegradability were quite high which were around 80 to 90 percentage, but we also can see that some animal manure have quite low digestibility.

Lignocellulose 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 in VS (volatile solid) The figure shows the lignocellulose fractions in VS. For most animal manure samples, the lignocellulose content were around 40-80 % of VS except piglet which has quite low lignocellulose, that seems because piglet has milk as daily diet. It is interesting to see the lignocelluloses in Calf manure which are quite high because calf manure contains large amount of straw as bedding materials. That’s why the characteristics of calf manure were close to energy crop rather than animal manure. For the energy crop lignocellulose were around 60 to 80 percentage.

Fermentation result - animal manure The figure shows fermentation results to determine BMP. As you can see it, for the first two weeks the great majority of methane gas were produced. And thereafter only small amounts were released. We can also clearly see that there is some relation between lignin concentration and cumulative methane yield which is BMP. From this figure, we could also realized that BMP test require such a large amount of work in long period.

Digestability of the biomass CH4 L kg(VS)-1

Energy potential of biomass Dry matter Volatile solids in pct of dry matter (DM) Total energy content Energy production in biogas plant % MJ/ kg DM MJ/kg DM Pig slurry 6 80 16,3 9,8 Cattle slurry 10 15,3 7,6 Clover grass 20 90 18,3 14,6 Straw 19,1 9,6 Why is biogas energy production of straw so low

Methane produkcion crops and organic waste Whey = valle Bleaching clay -

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

Hashimoto equation HRT or θ Hydraulic retention time SRT Solid retention time Γ Is the specific gas yield B0 The ultimate or specific methane yield, measured with batch fermentation at more than 60 days and at 35oC. µ maximal specific growth rate of the micro organisms, µm 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, S0 Concentration of organic components in feed to the reactor Nm3 The volume CH4 produced, calculated at 0oC (273oK)

Hashimoto model predictions’

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