Ex-ante Life Cycle Assessment of industrial-scale electrochemical CO2 reduction to Formic Acid

Abstract

Transitioning industries away from fossil fuels is imperative due to both climate change and geopolitical considerations. Electrochemistry presents an op- portunity to convert captured CO2 into a de-fossilized carbon feedstock for the chemical industry. In this Thesis an industrial scale electrochemical formic acid production plant was simulated based on a pilot electrolyser. The obtained mass and energy balances, evaluated under three operational scenarios and utilizing four alternative downstream methods, were subject to an ex-ante life cycle assessment, with a scope of present and 2050 Germany. Additionally, scenarios for the real- ization and environmental implications of electrolyzer operation based on excess renewable electricity were explored. Compared to conventional formic acid production, electrolytic production has a substantially higher energy demand, which contributes most impacts in the assessed categories. Scenarios minimizing energy use demonstrated reduced envi- ronmental impacts. The change in the environmental impacts of energy towards 2050 (reduced climate impacts and non-renewable energy use, and increased re- newable energy use, abiotic depletion potential of materials, and water scarcity) is reflected in the production impacts of formic acid. At present, energy use (non-renewable and renewable) and climate impacts of electrolytic formic acid production are higher than of conventional production. In 2050, the comparison between production methods becomes less clear-cut; while electrolytic production reduces fossil fuel dependence, its climate advantages hinge on the efficiency of the electrolyzer. Notwithstanding, electrolytic formic acid production demonstrates a reduction in water scarcity impacts compared to conventional methods across both temporal scopes. Electrolyzer materials have a minor contribution to the overall impacts. Con- sequently, intermittent electrolyzer operation, enabled by increasing the cell size to process more CO2 during periods of excess renewable energy supply, could achieve impacts reductions in all environmental categories, specifically, ranging from -41% of water scarcity to an impressive -81% of climate impacts. In electrolyzer devel- opment, priority should be given to minimizing electricity consumption, even if it entails enlarging the cell area. Additionally, the ability to operate intermittently stands out as a crucial feature for maximizing environmental merits. To facili- tate industrial realization, the development of a viable and efficient technology for purifying the CO2 recycle stream is required.