AUTHOR=Jourdin Ludovic , Raes Sanne M. T. , Buisman Cees J. N. , Strik David P. B. T. B. 

TITLE=Critical Biofilm Growth throughout Unmodified Carbon Felts Allows Continuous Bioelectrochemical Chain Elongation from CO2 up to Caproate at High Current Density

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 6 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2018.00007

DOI=10.3389/fenrg.2018.00007

ISSN=2296-598X

ABSTRACT=Current challenges for microbial electrosynthesis include the production of higher value chemicals than acetate, at high rates, using cheap electrode materials. We demonstrate here the continuous, biofilm-driven production of acetate (C2), n butyrate (nC4), and n-caproate (nC6) from sole CO2 on unmodified carbon felt electrodes. No other organics were detected. This is the first quantified continuous demonstration of n-caproate production from CO2 using an electrode as sole electron donor. During continuous nutrients supply mode a thick biofilm was developed covering the whole thickness of the felt (1.2 cm deep), which coincided with high current densities and organics production rates. Current density reached up to -14 kA m-3electrode  (-175 A m-2). Maximum sustained production rates of 9.8 ± 0.65 g L-1 day-1 C2, 3.2 ± 0.1 g L-1 day-1 nC4, and 0.95 ± 0.05 g L-1 day-1 nC6 were achieved (averaged between duplicates), at electron recoveries of 60-100%. Scanning electron micrographs revealed a morphologically highly diverse biofilm with long filamentous microorganism assemblies (~400 µm). n-Caproate is a valuable chemical for various industrial application, e.g. it can be used as feed additives or serve as precursor for liquid biofuels production.