Electrochemically assisted methane production in a biofilm reactor

Microbial electrolysis is a new technology for the production of value-added products, such as gaseous biofuels, from waste organic substrates. This study describes the performance of a methane-producing microbial electrolysis cell (MEC) operated at ambient temperature with a Geobacter sulfurreducens microbial bioanode and a methanogenic microbial biocathode. The cell was initially operated at a controlled cathode potential of −850 mV (vs. standard hydrogen electrode, SHE) in order to develop a methanogenic biofilm capable of reducing carbon dioxide to methane gas using abiotically produced hydrogen gas or directly the polarized electrode as electron donors. Subsequently, G. sulfurreducens was inoculated at the anode and the MEC was operated at a controlled anode potential of +500 mV, with acetate serving as electron donor. The rate of methane production at the cathode was found to be primarily limited by the acetate oxidation kinetics and in turn by G. sulfurreducens concentration at the anode of the MEC. Temperature had also a main impact on acetate oxidation kinetics, with an apparent activation energy of 58.1 kJ mol−1.

Graphical abstractMicrobial electrolysis cells employing biological anodes and cathodes are a novel and sustainable approach for the production of gaseous fuels, such as methane, from waste organic substrates.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A two-chamber MEC was developed that generates methane gas from acetate at ambient temperature. ► The MEC employed a methanogenic biocathode coupled to a Geobacter sulfurreducens bioanode. ► The MEC performance was markedly limited by the concentration of microorganisms in each chamber.