Upper limit efficiency estimates for electromicrobial production of drop-in jet fuels.

Microbes which participate in extracellular electron uptake (EEU) or H oxidation have the ability to manufacture organic compounds using electricity as the primary source of metabolic energy. So-called electromicrobial production could be valuable to efficiently synthesize drop-in jet fuels using renewable energy. Here, we calculate the upper limit electrical-to-fuel conversion efficiency for a model jet fuel blend containing 85% straight-chain alkanes and 15% terpenoids. When using the Calvin cycle for carbon-fixation, the energy conversion efficiency is 37.8% when using EEU for electron delivery and 40.1% when using H oxidation. The production efficiency can be raised to 44.2% when using the Formolase formate-assimilation pathway, and to 49.2% with the Wood-Ljungdahl pathway. This efficiency can be further raised by swapping the well-known Aldehyde Deformolating Oxygenase (ADO) termination pathway with the recently discovered Fatty Acid Photodecarboxylase (FAP) pathway. If these systems were supplied with electricity from a maximally-efficient silicon solar photovoltaic, even the least efficient pathway exceeds the maximum solar-to-fuel efficiency of all known forms of photosynthesis.