# Efficiency estimates for electromicrobial production of branched-chain hydrocarbons

## TL;DR

This paper explores using electromicrobial production to create branched-chain hydrocarbons for sustainable aviation fuels with high efficiency.

## Contribution

The study provides new efficiency estimates for producing branched-chain hydrocarbons via electromicrobial processes.

## Key findings

- Maximum electrical-to-fuel energy conversion efficiencies reach up to 40.0−4.4+0.6%.
- Branched-chain hydrocarbons can be produced at efficiencies comparable to straight-chain alkanes.

## 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%.

•Electromicrobial production could support the aviation sector’s need for biofuels•A relevant fuel blend could be produced at efficiencies higher than convention•A combination of differentially structured hydrocarbons can achieve drop-in fuels•Branched-chain hydrocarbons can be made at efficiencies similar to straight-chains

Electromicrobial production could support the aviation sector’s need for biofuels

A relevant fuel blend could be produced at efficiencies higher than convention

A combination of differentially structured hydrocarbons can achieve drop-in fuels

Branched-chain hydrocarbons can be made at efficiencies similar to straight-chains

Chemistry; Electrochemistry; Electrochemical materials science; Interfacial electrochemistry