Engineering electrochemical CO2 reduction to formate under bioprocess-compatible conditions to bioreactor scale

Abstract

The coupling of electrochemical CO2 reduction to formate with the microbial biosynthesis of valuable products is promising for exploiting CO2 as well as to store excess renewable electricity. Here, electrochemical CO2 reduction to formate at bioprocess-compatible conditions was transferred from the scale of 50 mL electrochemical cells to 1 L electrobioreactors. In the 1 L electrobioreactor, a reproducible coulombic efficiency of 74.9±5.5 % and formate production rate of 0.038±0.005 mmol h−1 cm−2 could be achieved. Autoclaving by standard steam sterilization was shown to negatively affect the reliability of the process performance and, therefore, needs further investigation. However, mass transfer is not limiting for the process performance. Thus, the coupling of electrochemical CO2 reduction to formate with microbial biosynthesis in sterile conditions at technical scale can be targeted in the future.