Improved reactor design enables productivity of microbial electrosynthesis on par with classical biotechnology

Abstract

Microbial electrosynthesis (MES) converts (renewable) electrical energy into CO₂-derived chemicals including fuels. To achieve commercial viability of this process, improvements in production rate, energy efficiency, and product titer are imperative. Employing a compact plate reactor with zero gap anode configuration and NiMo-plated reticulated vitreous carbon cathodes substantially improved electrosynthesis rates of methane and acetic acid. Electromethanogenesis rates exceeded 10 L L^-1_catholyte d^-1 using an undefined mixed culture. Continuous thermophilic MES by Thermoanaerobacter kivui produced acetic acid at a rate of up to 3.5 g L^-1_catholyte h^-1 at a titer of 14 g/L, surpassing continuous gas fermentation without biomass retention and on par with glucose fermentation by T. kivui in chemostats. Coulombic efficiencies reached 80 %-90 % and energy efficiencies up to 30 % for acetate and methane production. The performance of this plate reactor demonstrates that MES can deliver production rates that are competitive with those of established biotechnologies.

Keywords: Acetate production rate; Acetogen; Bioelectrochemistry; Electromethanogenesis; MES; Methanococcus maripaludis; Thermoanaerobacter kivui.