Abstract
We present a study on a microbial electrolysis cell with methanogenic microorganisms adapted to reduce CO2 to CH4 with the direct injection of electrons and without the artificial addition of H2 or an additional carbon source except gaseous CO2. This is a new approach in comparison to previous work in which both bicarbonate and gaseous CO2 served as the carbon source. The methanogens used are known to perform well in anaerobic reactors and metabolize H2 and CO2 to CH4 and water. This study shows the biofilm formation of those microorganisms on a carbon felt electrode and the long‐term performance for CO2 reduction to CH4 using direct electrochemical reduction. CO2 reduction is performed simply by electron uptake with gaseous CO2 as the sole carbon source in a defined medium. This “electrometabolism” in such microbial electrolysis cells depends strongly on the potential applied as well as on the environmental conditions. We investigated the performance using different adaption mechanisms and a constant potential of −700 mV vs. Ag/AgCl for CH4 generation at 30–35 °C. The experiments were performed by using two‐compartment electrochemical cells. Production rates with Faradaic efficiencies of around 22 % were observed.
Highlights
CO2 reduction has gained high interest in the last decade because of research in the field of carbon capture and utilization (CCU), which is a viable strategy for cyclic carbon use
The negative potential applied was necessary for the growth of a biofilm as the utilized microorganisms are exoelectrogenic and can immobilize on the carbon-based electrode because of their ability to take up electrons
The reduction potential was set at À700 mV vs. Ag/AgCl according to the theoretical reduction potential of CO2 to CH4 [Eqs. (1)–(6)]
Summary
Bio-Electrocatalytic Application of Microorganisms for Carbon Dioxide Reduction to Methane. We present a study on a microbial electrolysis cell with methanogenic microorganisms adapted to reduce CO2 to CH4 with the direct injection of electrons and without the artificial addition of H2 or an additional carbon source except gaseous CO2. This is a new approach in comparison to previous work in which both bicarbonate and gaseous CO2 served as the carbon source. CO2 reduction is performed by electron uptake with gaseous CO2 as the sole carbon source in a defined medium This “electrometabolism” in such microbial electrolysis cells depends strongly on the potential applied as well as on the environmental conditions. Production rates with Faradaic efficiencies of around 22 % were observed
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