Constraints on the Efficiency of Electromicrobial Production

Abstract

AbstractElectromicrobial production technologies (EMP) aim to combine renewable electricity and microbial metabolism. We have constructed molecular to reactor scale models of EMP systems using H2-oxidation and extracellular electron transfer (EET). We predict the electrical-to-biofuel conversion efficiency could rise to ≥ 52% with in vivo CO2-fixation. H2 and EET-mediated EMP both need reactors with high surface areas. H2-diffusion at ambient pressure requires areas 20 to 2,000 times that of the solar photovoltaic (PV) supplying the system. Agitation can reduce this to less than the PV area, and the power needed becomes negligible when storing ≥ 1.1 megawatts. EET-mediated systems can be built that are ≤ 10 times the PV area and have minimal resistive energy losses if a conductive extracellular matrix (ECM) with a resistivity and height seen in natural conductive biofilms is used. The system area can be reduced to less than the PV area if the ECM conductivity and height are increased to those of conductive artificial polymers. Schemes that use electrochemical CO2-fixation could achieve electrical-to-fuel efficiencies of almost 50% with no complications of O2-sensitivity.