LAUSR

Abstract Microbial electrolysis cells (MECs) have been proposed as a method for storing surplus renewable energy as biofuels, with methane being of particular interest given the existing natural gas infrastructure. However, the effect of the relative size of electrodes and the organic load of the wastewater on the overall performance of MECs designed for methane production remains poorly understood. Here we have explored the use of two MECs containing different relative cathodic and anodic surface areas and compared their methane production from wastewater containing lw (200 ppm) or high (4000 ppm) organic loads. The MEC containing a relatively larger cathode could increase energy storage efficiency by a factor of 1.2 and 3 under high and low organic loads respectively. These results highlight that the relative surface area of the electrodes should be designed according to the rate limiting process. Larger anodes offer more suitable conditions for the attachment of fermentative bacteria, whereas larger cathodes appear to provide more appropriate conditions for methanogens.