Making quantitative sense of electromicrobial production

The integration of electrochemical and microbial processes offers a unique opportunity to displace fossil carbon with CO2 and renewable energy as the primary feedstocks for carbon-based chemicals. Yet, it is unclear which strategy for CO2 activation and electron transfer to microbes has the capacity to transform the chemical industry. Here, we systematically survey experimental data for microbial growth on compounds that can be produced electrochemically, either directly or indirectly. We show that only a few strategies can support efficient electromicrobial production, where formate and methanol seem the best electron mediators in terms of energetic efficiency of feedstock bioconversion under both anaerobic and aerobic conditions. We further show that direct attachment of microbes to the cathode is highly constrained due to an inherent discrepancy between the rates of the electrochemical and biological processes. Our quantitative perspective provides a data-driven roadmap towards an economically and environmentally viable realization of electromicrobial production.