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Cathode and catholyte are usually optimized to improve microbial electrosynthesis process, whereas the anodic counter reaction was not systematically investigated and optimized for these applications yet. Nevertheless, the anolyte and especially the anode material can limit the cathodic bioelectrochemical process. This paper compares for the first time the performance of different anode materials as counter electrodes for a cathodic bioelectrochemical process, the bioelectromethanogenesis. It was observed that depending on the anode material the cathodic methane production varies from 0.96 µmol/d with a carbon fabric anode to 25.44 µmol/d with a carbon felt anode of the same geometrical surface area. The used anolyte also affected the methane production rate at the cathode. Especially, the pH of the anolyte showed an impact on the system; an anolyte with pH 5 produced up to 2.0 times more methane compared to one with pH 8.5. The proton availability is discussed as one reason for this effect. Although some of the measured effects cannot be explained completely so far this study advises researchers to strongly consider the anode impact during process development and optimization of a cathodic bioelectrochemical synthesis process.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Bioelectromethanogenesis, a technology to convert electrical energy into CH 4 , is on the transition from lab-scale to industrial application. But the question arises if it is really a sustainable technology or just another scientific artifact. Especially the energy efficiency is a crucial aspect to allow conclusions about the applicability. In this paper, the basics of energy calculations are applied to literature data to model the energy efficiency. Different scenarios were calculated, showing that further research has to be conducted to turn bioelectromethanogenesis into a feasible technology.