Making and harvesting VFA using high nitrogen substrates

Transcription

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

2 Content Context VFA/carboxylate platform Previous laboratory experience ADNet PoC : 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

3 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

4 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

5 Previous studies Acetic Propionic Iso-Butyric n-butyric FW 1 VFA profile (mg l -1 ) Iso-Valeric Hexanoic n-valeric Heptanoic 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

6 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

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

8 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 % of the population was from the Clostridiales order with a large participation from the Sporanaerobacter genus. 8

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

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

11 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,

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

13 Previous studies - revisit Acetic Propionic Iso-Butyric n-butyric FW 1 VFA profile (mg l -1 ) Iso-Valeric Hexanoic n-valeric Heptanoic Selective propionic acid production, but: 100 mg HPr L -1 day -1 ~5% of VS Time (days) Other VFA was degraded to biogas; propionic acid has the slowest degradation rate 13

14 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

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

16 Acknowledgements Thanks to Anaerobic Digestion Network PoC 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