How sustainable is CO2 conversion to ethanol? – A life cycle assessment of a new electrocatalytic carbon utilisation process

Abstract

Although bioethanol production is considered to be sustainable from a global warming perspective, its dependence on agricultural systems, land management, and geographical limitations has sparked concern. The electrocatalytic CO₂ reduction reaction (CO₂RR) is a promising alternative pathway to produce fuels, such as ethanol, through captured CO₂ and electricity. The CO₂RR has been studied exhaustively in the literature, but the potential environmental impacts of producing ethanol in a practical process on a large scale are unknown. In this paper, we perform a life cycle assessment to quantify the potential environmental benefits of ethanol production via a proposed electrocatalytic captured CO₂ reduction (ECCR) system coupled with an innovative product separation design at a commercially relevant scale. The production of bioethanol via grain fermentation was used as the reference in the comparison of nine environmental impact categories. Results indicate that ethanol via ECCR has a lower or comparable associated impact in all examined environmental categories, depending on the nature of the energy supplied to the system. Specifically for global warming, the ECCR becomes competitive against the reference when the electricity supplied has a carbon intensity lower than 63 gCO₂eq per kW h. Overall, the proposed ECCR system is a modular and versatile alternative that presents a clear advantage on land use and water consumption. This early-stage technology has the capability of producing ethanol sustainably whilst offering the associated benefits of a carbon capture and utilisation pathway.