Microbiology in Anaerobic Digesters Examples for Process Inhibition and Control. Heike Sträuber, Dept. Environmental Microbiology

Transcription

1 Microbiology in Anaerobic Digesters Examples for Process Inhibition and Control Heike Sträuber, Dept. Environmental Microbiology Workshop Large Scale Bioenergy Lab 2, Flensburg/Oeversee, 29 th January 2018

2 Helmholtz Centre for Environmental Research UFZ PAGE 2

3 Helmholtz Centre for Environmental Research UFZ PAGE 3

4 Group Microbiology of Anaerobic Systems (MicAS) Anaerobic digestion of lignocellulosic and nitrogen-rich waste Bioaugmentation of anaerobic bioreactors Trace elements in anaerobic digestion Process monitoring based on biogas isotopic signature Biotechnological application of anaerobic fermentations (carboxylate platform, syngas platform and combinations thereof) Biomethanation of hydrogen from excess electricity (Power-to-Gas) Carbon and energy flow and syntrophic interactions in anaerobic consortia Metagenome-based analysis of metabolic networks in anaerobic consortia Microbial ecology of hydrocarbon-contaminated aquifers PAGE 4

5 Energy crops used for biogas production are TE-deficient TE limitation is a specific problem for agricultural biogas plants Co-digestion with manure or commercial TE additives Hinken et al. (2008), Water Sci Technol 58: PAGE 5

6 TE limitations affect microbial functions on all AD stages Fe deficiency: Clostridia (high Fe demand) vs. LAB Less efficient hydrolysis of plant fibers (cellulose) as LAB can only hydrolyze starch Fe deficiency: Clostridia (high Fe demand) vs. LAB Lactate fermentation is favoured over butyrate fermentation Schnürer (2009) Microbiological Handbook for Biogas Plants PAGE 6 Syntrophic VFA oxidizers depend on Fe, Ni, Se, W, Mo acidification due to VFA accumulation Methanogens require Fe, Ni, Co, Mo, W, Zn, Se Cytochrome-containing methanogens need more Ni (Methanosarcinaceae) Methylotrophic and acetoclastic pathways need more Co

7 Effects of TE limitation on the microbial community level? Diversity Functional redundancy Methanogenesis and syntrophic VFA oxidation are most vulnerable steps Overall process stability Schnürer (2009) Microbiological Handbook for Biogas Plants PAGE 7

8 Lab-scale experiment to study the effect of TE deprivation on the AD microbiome CSTR, 10 L working vol Feedstock: Distillers grains + TE mix (Ni, Co, Mo, W) + FerroSorp DG OLR: 5 g VS L -1 d -1 HRT: 25 days Mesophilic (37 C) R1 R2 Two identical reactors R1 and R2 operated in parallel for 72 weeks Start of TE deprivation in week 72: TE supply omitted, FerroSorp DG reduced to one third in R2 Wintsche et al. (2016), Frontiers Microbiol 7: 2034 PAGE 8

9 Decline of trace elements in reactor R2 Wintsche et al. (2016), Frontiers Microbiol 7: 2034 PAGE 9

10 Wintsche et al. (2016), Frontiers Microbiol 7: 2034 PAGE 10

11 Methanogenic community dynamics and activity shifts (T-RFLP fingerprinting of mcra) RNA (mcra transcripts) DNA (mcra genes) NMDS based on Bray-Curtis dissimilarity Activity shift (transcript level) more pronounced than community shift (DNA level) Methanoculleus could better cope with TE deprivation than Methanosarcina (Ni, Co, Mo, W, Mn) Wintsche et al. (2016), Frontiers Microbiol 7: 2034 PAGE 11

12 Summary: Effects of TE deprivation on the microbial communities in lab-scale digesters Slowly increasing TE deficits (Ni, Co, Mo, W) did not affect process efficiency (methane yield), yet acetate and TAN levels increased Community and activity shifts of methanogens from Methanosarcina to Methanoculleus Bacterial community less affected TE supply is critical to sustain the activity of the heavy-duty methanogen Methanosarcina* Methanoculleus can substitute Methanosarcina and keep AD running under TE limitation PAGE 12 Wintsche et al. (2016), Frontiers Microbiol 7: 2034 * De Vrieze et al. (2012) Bioresource Technol 112:1-9

13 Alternative energy crops: intertillages and biomass from marginal plains Example: sweet clover (Melilotus spp.) Pioneer plant, intertillage Adapted to dry and sandy soils Rye Maize Dicoumarol Sweet clover Coumarin (up to 5% TS ) PAGE 13

14 Biogas production from coumarin-rich plants: Effects on the microbiome? Experimental setup: Two parallel CSTR (38 C) Co-digestion of grass silage and cow manure OLR = 3 g VS L -1 d -1 HRT = 21 d Coumarin (5% TS grass silage) added daily to reactor 1 from day 21 Reactor 2 as coumarin-free control Monitoring of process parameters and microbial communities Popp et al. (2015) FEMS Microbiol Ecol 91: fiv103 PAGE 14

15 PAGE 15

16 Reactor 1 with coumarin Coumarinfree control reactor 2 PAGE 16

17 Shift of the bacterial community upon coumarin adaptation No effect of coumarin on the methanogenic community Methanoculleus Methanosarcina Reactor 1 Reactor 2 mcra genes, MwoI Bacterial 16S rrna genes, HaeIII, Bray-Curtis Popp et al. (2015) FEMS Microbiol Ecol 91: fiv103 PAGE 17

18 Details of coumarin inhibition: Batch tests Non-adapted inoculum Coumarin-adapted inoculum Relative gas production (%) Control Inhibition of VFA degradation No inhibition with adapted inoculum Popp et al. (2017) Appl Environ Microbiol, 83:e PAGE 18

19 Summary: Effect of coumarin on AD Coumarin-rich plants not suited as fodder plants can be used as feedstock for biogas production when an acclimatised reactor microbiome is used Coumarin inhibits AD in non-acclimatised reactors but can be degraded by acclimatised microbiomes Inhibition affects mainly the VFA degradation, either by direct inhibition of syntrophic VFA-oxidising bacteria (e.g., propionate degradation by Syntrophobacter fumaroxidans) or by inhibiting the interspecies electron transfers in syntrophic consortia of VFA degraders and hydrogenotrophic methanogens (e.g., butyrate degradation by Syntrophomonas wolfei) Propionate degradation is the most vulnerable step as syntrophic propionate degraders are directly inhibited and lack functional redundancy PAGE 19

20 From biogas plants to biorefineries Biomass Anaerobic digestion Fertilizer Methane Run-out of 20 year feed-in tariff new business areas required for older plants PAGE 20

21 Anaerobic fermentation Anaerobic digestion process Organic matter (lignocellulose, proteins, fats) Monomers (sugars, amino acids, long-chain fatty acids) Organic acids, alcohols, CO 2, H 2 Acetate, C1-bodies, CO 2, H 2 Biogas (CH 4 + CO 2 ) Hydrolysis Fermenting bacteria Acidogenesis Fermenting bacteria Acetogenesis Syntrophic bacteria Methanogenesis Methanogenic archaea PAGE 21

22 Carboxylate platform Products Main products: short-chain fatty acids (SCFA or VFA) (acetic acid, propionic acid, n-butyric acid) Secondary products: medium-chain fatty acids (MCFA) carboxylates with a chain length C5-C10 O O caproic acid (C6) OH caprylic acid (C8) OH PAGE 22

23 Application Fuels Esterification Bio-plastics Food additives Lubricants Cosmetics industry Surfactants MCFA Animal feed Pharmaceutical industry PAGE 23

24 The CAPRAFERM process Production of MCFA (mainly caproate (C6) and caprylate (C8)) from biomass by anaerobic fermentation with a microbiome Solid substrates containing lactate (dedicated crop silages, biowaste) Inhibition of the methane production by intelligent process control (no chemicals) Exploitation of microbial chain elongation with ethanol and lactate Integrated process PAGE 24

25 Bio-Electro-Refinery for the production of alkanes and esters from biomass Partners: Junior Research Group Microbial Bioelectrocatalysis and Bioelectrotechnology (Falk Harnisch) Patent applications: DE A1, WO A1 Urban et al. 2017, Energy & Environmental Science, 10:2231 PAGE 25

26 Concept for refitting German biogas plants (CapAcidy project) From biogas plants to biorefineries PAGE 26

27 Microbial chain elongation Primary fermentation products in acidogenesis Secondary fermentation products of chain elongating processes Example: Clostridium kluyveri Source: Hollister et al. (2012) - modified PAGE 27

28 Microbial chain elongation Primary fermentation products in acidogenesis Secondary fermentation products of chain elongating processes Lactate Example: Megasphaera elsdenii Source: Hollister et al. (2012) - modified PAGE 28

29 Leach-bed reactor (batch) Gas Sträuber et al. (2012) Energy, Sustain & Soc 2:13 PAGE 29

30 Summary: Carboxylate platform Reactor microbiomes vs. pure cultures In two-phase biogas plants, organic acids can be stored to produce biogas on demand (flexibility bonus) or to produce platform chemicals Advantages: Non-sterile substrates can be used easy and affordable process management Complex and varying substrates can be used Continuous production possible Existing biogas technology and infrastructure can be adapted Challenges: Product yields many side reactions No pure products - Advanced downstream processing necessary Microbial resource management steering of the microbiome towards the desired reactions PAGE 30

31 Acknowledgements Dep. Biorefineries Maria Braune Arne Gröngröft Babett Wintsche Denny Popp Sabine Kleinsteuber Ute Lohse Nicole Thiemich Dep. Biochemical Conversion Jan Liebetrau Jürgen Pröter Jaqueline Daniel-Gromke Biogas lab PAGE 31

32 Thank you for your attention