Combined energy storage and methane bioelectrosynthesis from carbon dioxide in a microbial electrosynthesis system

Abstract

This study demonstrates a novel approach for combined energy carrier production and energy storage in a Microbial Electrosynthesis System (MES). Continuous production of high purity methane (CH4) from carbon dioxide (CO2) was achieved in a 0.65 L carbon felt - filled cathode compartment of a membraneless MES. CH4 production reached 0.72 L d−1 at an energy consumption of 26 Wh LCH4−1. Owing to the membraneless design of the MES, pH control of the electrode compartments was not required, with the cathode compartment pH remaining below 8.5. Electrochemical characterization showed a progressive increase of the MES internal capacitance from 2.1 F to 3.2 F. Bioelectrochemical conversion of CO2 to CH4 can be used for long-term energy storage (power-to-gas conversion) combined with CO2 sequestration, while the internal capacitance of electroactive biofilms can be exploited to develop bioelectrochemical supercapacitors for fast energy return to the electrical grid.