Bioelectrochemical production of methane by a hydrogenophilic methanogenic culture

In this research, we investigated the bioelectrochemical production of methane gas from carbon dioxide reduction by using a microbial biocathode, based on a hydrogenophilic methanogenic culture, not previously acclimated in bioelectrochemical systems. Methane production was found to proceed on plain carbon cathodes, polarized at potentials more negative than -650 mV (vs. SHE), both via direct extracellular electron transfer and via abiotically produced hydrogen gas (i.e., via hydrogenophilic methanogenesis). The relative contribution of these routes to methane production was highly dependent on the cathode potential. The use of redox mediators (i.e.: Neutral Red, E°'= -325 mV vs. SHE) allowed to carry out the reaction at less reducing potentials (-450 mV vs. SHE), even thought methane production rates were remarkable lower than in the mediator-less systems. However, methane production could be increased through the formation of a biofilm on high specific surface electrodes.