Techno-Economic Assessment of Electromicrobial Production of n -Butanol from Air-Captured CO 2 .

Electromicrobial production (EMP), where electrochemically generated substrates (e.g., H 2 ) are used as energy sources for microbial processes, has garnered significant interest as a method of producing fuels and other value-added chemicals from CO 2 . Combining these processes with direct air capture (DAC) has the potential to enable a truly circular carbon economy. Here, we analyze the economics of a hypothetical system that combines adsorbent-based DAC with EMP to produce n -butanol, a potential replacement for fossil fuels. First-principles-based modeling is used to predict the performance of the DAC and bioprocess components. A process model is then developed to map material and energy flows, and a techno-economic assessment is performed to determine the minimum fuel selling price. Beyond assessing a specific set of conditions, this analytical framework provides a tool to reveal potential pathways toward the economic viability of this process. We show that an EMP system utilizing an engineered knallgas bacterium can achieve butanol production costs of <$6/gal ($1.58/L) if a set of optimistic assumptions can be realized.