Power generation and anode bacterial community compositions of sediment fuel cells differing in anode materials and carbon sources

For monitoring environmental conditions of remote places, sustainable power generators are necessary to power telemetry sensor systems. A sediment microbial fuel cell (SMFC) is a device that produces electricity biologically from organic matters in sediment. Because a SMFC utilizes sediment organic materials and microbial catalysts in river or oceanic sediment, a SMFC can be a feasible solution for sustainable power generation in remote places. However, oligotrophic sediment conditions often limit energy source supply, resulting in insufficient power output for operating electronic devices. The objective of this study is to investigate power generation and anode bacterial communities of SMFCs with different anode materials and carbon sources for enhancement of power output and longevity of SMFCs. Four kinds of anode electrodes were tested in SMFCs; a magnesium electrode (M), a magnesium electrode supplied with chitin particles (M+C), a graphite electrode (G), and a graphite electrode supplied with chitin particles (G+C). Average maximum power density was highest in Mg+C (1878 ± 982 mW m^-2), followed by M (848 ± 348 mW m^-2), G+C (1.9 ± 0.6 mW m^-2) and G (0.7 ± 0.6 mW m^-2). Maximum power densities of the magnesium electrodes were ̃1,000 times larger than those of the graphite electrodes. The chitin supplement increased maximum power densities by 121% in the magnesium anodes and 164% in the graphite anodes on average. A magnesium electrode in M+C degraded more slowly than that of M. Anode bacterial communities of the magnesium anodes were diverse than the graphite anodes, and the supplemented chitin greatly influenced anode bacterial community compositions. Although magnesium corrosion was a main process of power production in the magnesium-anode SMFCs, species-level anode bacterial communities were very different between M and M+C. Anode bacterial communities of the chitin-absent anodes had larger richness estimates and diversity estimates than those of the chitin-supplemented anodes, suggesting that the saturated carbon source greatly simplified anode bacterial communities.