Biogas production. Kjetill Østgaard, Workshop Seaweed for Biofuel

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1 Biogas production Kjetill Østgaard, Workshop Seaweed for Biofuel

2 Contents: Basics of bio-energy & -gas 1. Intro; bioenergy? politics? ecomomy? 2. Biogas basics 3. Once upon a time 4. Process operation Case seaweeds 5. Seaweeds? 6. The HRAD concept 7. Biogas for transport; LBG & CBG 8. Concluding remarks

3 1a Intro: Bioenergy? In the beginning was the redox reaction Primary production: CO 2 + energy biomass Bioenergy (def.): Biomass CO 2 + energy

4 COD? 1: Def.: COD is the amount of oxygen needed to oxidize some organic compound completely to CO 2. 2: Measure: Oxidize with potassium dichromate, yellow In the colour beginning due to Cr was 6+. the redox reaction 3: Calculate: Balance reaction eq. to find moles O 2 needed. 4: Estimate: Use average composition; ex. biomass C 5 H 7 O 2 N. Primary production: CO 2 + energy biomass 5: COD balance: COD substr. +COD oxygen = COD biomass +COD prod. (with by def. COD oxygen / Weight oxygen = - 1) Bioenergy (def.): Biomass CO 2 + energy

5 Some conclusions: Energy yield? Combustion! At high temperature when necessary. Water content? Wet oxidation: By microbes Energy storage & transport? Transformation: Biomass biofuel (+byproducts & losses) liquids (biodiesel, bioethanol) / biogas

6 1b Intro: Politics? The Swedish lessons There is no energy source without negative environmental impact. 2. The major energy source of the future will be: Stop wasting. Corresponding strategy: Diversify! 3. The key to successful economic developent is disconneting growth from energy demand.

7 1c Intro: Economy? The economy is in the totality, stupid. ecopro, Verdal

8 2. Total process Hydrolysis Acidogenesis VFA Acetogenesis VFA H 2 +CO 2 Methanogenesis H 2 +CO 2 CH 4 /CO 2 50%/50%

9 Volatile fatty acids VFA: H-COOH formic acid CH 3 -COOH acetic CH 3 -CH 2 -COOH propionic CH 3 -CH 2 -CH 2 -COOH butyric CH 3 -CH 2 -CH 2 -CH 2 -COOH valeric CH 3 -CH 2 -CH 2 -CH 2 -CH 2 -COOH kaproic etc CH 3 -CHOH-COOH lactic acid CH 3 -OH metanol H 3 -CH 2 -OH ethanol a.o. -

10 2. Total process Hydrolysis Acidogenesis VFA Acetogenesis VFA H 2 +CO 2 Methanogenesis H 2 +CO 2 CH 4 /CO 2 50%/50%

11 VFA acetogenesis: Case ethanol: 1. S-organism: 2 C 2 H 5 OH + 2 H 2 O 2 CH 3 COOH + 4 H 2 ΔG 0 =+9.7kJ ΔG <0 at P H2 <10-4 atm 2. Methanobacterium bryantii: 4 H 2 + CO 2 CH H 2 O ΔG 0 =-131kJ ΔG <0 at P H2 >10-6 atm

12 Morale: H 2 flux depends on gradient: Stay close! Acetogens + Methanogens = True

13 Interspecies hydrogen transfer Stay close: = Syntrophic consortia! Clustering will also promote granule formation, c.f. UASB.

14 Granule structure by FISH domain level probes lower level probes Red methanogens Green uncultured bacteria - Sekiguchi et al. (1999).

15 4. Process operation Process rate limiting at 1 Hydrolysis recalcitrant materials 2 Acidogenesis - never - 3 Acetogenesis overload; surgjæring low ph 4 Methanogenesis short sludge age; low μ max Conclusion: Stabilize at steady state! Local cases: Go see Ladehammeren or Høvringen ww treatment plants, or Heggstadmoen landfill

16 Biogas resources of Norway Waste: Price << 0 Potential 6 TWh Cultivation?? Price??

17 5. Seaweeds? Red Green Brown Jan Rueness 2012

18 5. Seaweeds? Red Green Brown Jan Rueness 2012

19 Brown seaweeds Physical structure Chemical composition Alginate Laminaran Mannitol Others: Fucoidan Protein Cellulose Polyphenols («tannins»)

20 Brown seaweeds Physical structure Particle size by grinding / milling Gel matrix dissociation by osmotic shock & Na + / Ca ++ competition EGTA treatment Acid hydrolysis etc.; ORD

21 Brown seaweeds Fermentation of Ascophyllum nodosum : Polyphenol content limited alginate lyase activity manniton consumption methane production Degradation stimulated by fixation of polyphenols by formaldehyde etc.

22 Brown seaweeds Fermentation of Laminaria hyperborea stipe: Polyphenols of peripheral tissu gave extended lag phase due to polyphenols compared to core Crosslinking by polyphenols or Ca-guluronate residues apparently limited yield in batch systems

23 Brown seaweeds Fermentation of Laminaria hyperborea fronds: Easily degradable; acetate + some propionate as dominant VFAs Diauxic pattern in batch («dessert first») Successful methane production in continuous reactor systems

24 Brown seaweeds Fermentation of Laminaria digitata: Easily degradable; low in polyphenols, low in high G alginate Fermentation of Saccharina latissima? VDM Verlag Dr. Müller 2009

25 6. The HRAD concept High Rate Anaerobic Digestion Compact: In need of retention to keep biocatalyst stuck at high throughput flow = low HRT C.f. BIONA project

26 UASB Developed by Lettinga, Wageningen. Note sludge separation zone on top. Biopaq Granules

27 Hydrolysis in recycled pretreatment: - washout of VFAs to avoid product inhibition Retention?????????????

28 7. Biogas for transport Biofuels: Biodiesel ~ C 8 H 6 O 2 ~ vegetable oils and lipids < B20 in standard diesel engines Bioethanol C 2 H 5 OH by fermentation & destillation E20 USA, E85 Sweden up to E98 Brazil Biogas CH 4 (+ CO 2 ) by fermentation. Purified, compressed CLG or liquified LBG (-163 o C) standard combustion / 80 % in dual diesel

29 LBG -163 C Lidköping Biogas - opened summer GWh corresponding to: cars doing km /year ton CO 2 reduction / year

30 European route E14

31 8. Concluding remarks 1. Any industry generating organic waste has to consider local biogas production as a part of waste management. 2. This is also true for any seaweed based industry producing alginate, fertilizer, bioethanol or other products. 3. Thus; biogas will in any case be a major or minor product in any significant uilization of brown seaweed biomass. 4. Any cultivation for bioenergy has to compete with wastes priced at << 0 as raw materials. This is absolutely possible. 5. LBG is rapidly becoming a significant liquid fuel for the transport sector. Accordingly, LNG will follow. 6. A more direct price competition will thus be established between LBG/LNG and conventional liquid fuels.

32 8. Concluding remarks c.t.d. 7. It is difficult to imagine a significant market for seaweed biomass until full scale downstream processing adapted to the particularities of this raw material has been fully developed to the level of becoming competitively cost effective. 8. If started in time (preferably yesterday), this is a realistic goal for biogas production from brown seaweeds.

O 2. What is anaerobic digestion?

O 2. What is anaerobic digestion? What is anaerobic digestion? Microbial degradation of organic material under anaerobic conditions Ubiquitous, naturally-occurring process Occurs in swamps, hydric soils, landfills, digestive tracks of