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

An electrogenic biofilm was developed on a macroporous chitosan-carbon nanotube (CHIT-CNT) electrode under constant poised potential (-0.25V 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 -0.62V and a current density of 9.43µAcm(-3) (at -0.25V). 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.

Fabrication of macroporous chitosan scaffolds doped with carbon nanotubes and their characterization in microbial fuel cell operation.

Chitosan (CHIT) scaffolds doped with multi-walled carbon nanotubes (CNT) were fabricated and evaluated for their utility as a microbial fuel cell (MFC) anodic material. High resolution microscopy verified the ability of Shewanella oneidensis MR-1 to directly colonize CHIT-CNT scaffolds. Cross-linking agents 1-ethyl-3-[3-dimethylaminopropyl] carbodimide hydrochloride (EDC), glutaraldehyde and glyoxal were independently studied for their ability to strengthen the CHIT-CNT matrix without disrupting the final pore structure. 2.5 vol% glyoxal was found to be the optimal cross-linker in terms of porosity (BET surface area=30.2 m(2) g(-1)) and structural stability. Glyoxyl and EDC cross-linked CHIT-CNT scaffolds were then studied for their ability to transfer electrons to underlying glassy carbon. Results showed an open circuit cell voltage of 600 mV and a maximum power density of 4.75 W/m(3) at a current density of 16 A/m(3) was achieved in non stirred batch mode, which compares well with published data using carbon felt electrodes where a power density of 3.5 W/m(3) at a current density of 7 A/m(3) have been reported. Additionally, CHIT-CNT scaffolds were impregnated into carbon felt electrodes and these results suggest that CHIT-CNT scaffolds can be successfully integrated with multiple support materials to create hybrid electrode materials. Further, preliminary tests indicate that the integrated scaffolds offer a robust macroporous electrode material that can be used in flow-through configurations.