Making and harvesting VFA using high nitrogen substrates Yue Zhang - PowerPoint PPT Presentation

Making and harvesting VFA using high nitrogen substrates Yue Zhang ADNet Research Colloquium 11-12 September 2017, Southampton 1

Content • Context  VFA/carboxylate platform  Previous laboratory experience ADNet PoC 2014016: production and extraction of C3 and • C4 aliphatic carboxylic acids from the anaerobic digestion of waste blood as a model substrate  Results  Reflection The next step • 2

VFA/carboxylate platform • Volatile fatty acids (VFA) serve as platform molecules for the production of chemicals and polymers from organic waste streams • Recalcitrant materials: gasification & syngas fermentation  Independent of CO:CO 2 :H 2 ratios  Tolerant to gasification by-products, e.g. NH 3 , NO x , H 2 S Putrescible materials: direct fermentation •  Microorganisms for VFA fermentation are naturally abundant 3

VFA/carboxylate platform • Alcohol production via VFA platform vs direct production  VFA production does not require sterile conditions  No external enzymes are required to carry out the hydrolysis step  All biodegradable organic wastes can be used for VFA production 4

Previous studies 16000 Acetic Propionic Iso-Butyric n-Butyric 14000 Iso-Valeric n-Valeric 12000 FW 1 VFA profile (mg l -1 ) Hexanoic Heptanoic 10000 8000 6000 4000 2000 0 0 50 100 150 200 250 300 Time (days) • The high nitrogen content of substrates results in a high digester total ammonia nitrogen and this can lead to raised concentrations of VFA, and in particular of propionic acid. 5

High nitrogen substrates • High ammonia content  Methanogen inhibitor  High buffering capacity, no need to add base solution for pH control • Rich in nutrients  Again, minimal input of chemicals Waste blood chosen as a model substrate •  Readily available  No need for particle size reduction 6

Experiments • Open culture fermentation  Operational modes: batch, fed-batch, semi-continuous  Methanogen inhibitor  Enzymatic pretreatment • Recovery  Esterification  Membrane based solvent extraction 7

Results – VFA production Semi-continuous test Fed-batch test • Due to high ammonia concentration in fermentation broth, a range of high VFA concentration up to 100 g L -1 was achieved with a blood VS of 13.5%, without addition of external methanogen inhibitor. • In general, acetic, n-butyric and iso-valeric acids were the dominant species, although different operational conditions affected the VFA concentration, profile, production rate and yield. • 70-90% of the population was from the Clostridiales order with a large participation from the Sporanaerobacter genus. 8

Results – Esterification Waste blood H 2 SO 4 Methanol Mixed culture Biomass water VFA-methyl Acidification Esterification fermentation removal removal esters Biomass water (NH 4 ) 2 SO 4 9

Results – Membrane based extraction Waste blood Octanol-TOA/VFA Mixed culture Biomass Membrane based VFA VFA fermentation removal solvent extraction recovery Octanol Biomass -TOA Water/VFA 10

Amino acid contents of blood Reference: Kramer S.L., Waibel P.E., Behrends B.R. and El Kandelgy S.M. (1978) Amino acids in commercially produced blood meals. J. Agric. Food Chem. 26, 979-981. 11

Amino acid fermentation References: 12 Ramsay I.R. and Pullammanappallil P.C. (2001) Protein degradation during anaerobic wastewater treatment: derivation of stoichiometry. Biodegradation 12: 247-256. Schönheit P., Buckel W. and Martin W.F. (2016) On the origin of heterotrophy. Trends in microbiology 24: 12-25.

Previous studies - revisit 16000 Acetic Propionic Iso-Butyric n-Butyric 14000 Iso-Valeric n-Valeric 12000 FW 1 VFA profile (mg l -1 ) Hexanoic Heptanoic 10000 Selective propionic acid 8000 production, but: 6000 • 100 mg HPr L -1 day -1 4000 • ~5% of VS 2000 0 0 50 100 150 200 250 300 Time (days) • Other VFA was degraded to biogas; propionic acid has the slowest degradation rate 13

VFA/carboxylate platform • Alcohol production via VFA platform vs direct production  VFA production does not require sterile conditions  All biodegradable organic wastes can be used for VFA production  No external enzymes are required to carry out the hydrolysis step Challenges •  Selectivity  Solids in the effluent 14

Follow up Solids Liquor High nitrogen Leach-bed Selective VFA Anaerobic Biogas substrates fermenter extraction digestion VFA, Digestate Other chemicals An additional unit? • Chain elongation • BES 15

Acknowledgements Thanks to Anaerobic Digestion Network PoC 2014016 Dr Jersson Plácido … and to Newton Fund Institutional Links and AD Network for continuing support to take this work forward Miss Victoria Outram Mrs Jing Lu 16