Efficiency estimates for electromicrobial production of branched-chain hydrocarbons

Timothy J Sheppard; David A Specht; Buz Barstow

doi:10.1016/j.isci.2023.108773

Efficiency estimates for electromicrobial production of branched-chain hydrocarbons

iScience. 2023 Dec 21;27(1):108773. doi: 10.1016/j.isci.2023.108773. eCollection 2024 Jan 19.

Authors

Timothy J Sheppard¹, David A Specht¹, Buz Barstow¹

Affiliation

¹ Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA.

Abstract

In electromicrobial production (EMP), electricity is used as microbial energy to produce complex molecules starting from simple compounds like CO₂. The aviation industry requires sustainable fuel alternatives that can meet demands for high-altitude performance and modern emissions standards. EMP of jet fuel components provides a unique opportunity to generate fuel blends compatible with modern engines producing net-neutral emissions. Branched-chain hydrocarbons modulate the boiling and freezing points of liquid fuels at high altitudes. In this study, we analyze the pathways necessary to generate branched-chain hydrocarbons in vivo utilizing extracellular electron uptake (EEU) and H₂-oxidation for electron delivery, the Calvin cycle for CO₂-fixation and the aldehyde deformolating oxygenase decarboxylation pathway. We find the maximum electrical-to-fuel energy conversion efficiencies to be ${40.0}_{- 4.4}^{+ 0.6} %$ and ${39.8}_{- 4.5}^{+ 0.7} %$ . For a model blend containing straight-chain, branched-chain, and terpenoid components, increasing the fraction of branched-chain alkanes from zero to 47% only lowers the electrical energy conversion efficiency from ${40.1}_{- 4.5}^{+ 0.7} %$ to ${39.5}_{- 4.6}^{+ 0.7} %$ .

Keywords: Chemistry; Electrochemical materials science; Electrochemistry; Interfacial electrochemistry.