Towards a hybrid anaerobic digester-microbial fuel cell integrated energy recovery system: An overview of the development of an electrogenic biofilm

•We develop an electrogenic biofilm using the effluent of an anaerobic digester as both substrate and bacterial source.•We correlate the development of the electrogenic biofilm with improved current density.•We visualize the direct bacterial nanowire interaction with the carbon nanotube electrode using SEM.•We show selectivity of the poised potential electrode for electrogenic bacteria.

An electrogenic biofilm was developed on a macroporous chitosan-carbon nanotube (CHIT-CNT) electrode under constant poised potential (−0.25 V versus Ag/AgCl reference electrode) and flow through conditions utilizing the effluent of an anaerobic digester as both the inoculant and substrate for the electrogenic biofilm. After 125 days of inoculation the bioelectrode demonstrated an open circuit potential of −0.62 V and a current density of 9.43 μA cm−3 (at −0.25 V). Scanning electron microscopy images indicate thorough surface coverage of the biofilm with a high density of bacterial nanowires physically connecting bacteria to bacteria and bacteria to carbon nanotube (electrode surface) suggesting the nanowires are electrically conductive. DGGE was used to identify the major bacterial and archaeal populations.