Microbial electrosynthesis from CO₂: forever a promise?

Microbial electrosynthesis (MES) is an electrochemical process used to drive microbial metabolism for bio-production, such as the reduction of CO₂ into industrially relevant organic products as an alternative to current fossil-fuel-derived commodities. After a decade of research on MES from CO₂, figures of merit have increased significantly but are plateauing yet far from those expected to allow competitiveness for synthesis of commodity chemicals. Here we discuss the substantial technological shortcomings still associated with MES and evoke possible ways to mitigate them. It appears particularly challenging to obtain both relevant production rates (driven by high current densities) and energy conversion efficiency (i.e. low cell voltage) in microbial-compatible electrolytes. More competitive processes could arise by decoupling effective abiotic electroreductions (e.g. CO₂ to CO or ethanol; H₂ evolution) with subsequent fermentation processes.