Carbon footprint assessment of ethylene oxide production via CO2 electrolysis

Abstract

Electrochemical CO₂ reduction to value-added chemicals is a promising carbon capture and utilization pathway for decarbonizing the chemicals sector. Recent advances demonstrate production of ethylene oxide—a major commodity chemical—from CO₂ via a tandem electrocatalysis approach with ethylene as an intermediate. This study evaluates for the first time, the carbon footprint of ethylene oxide produced by this emerging technology under various conditions. We estimate the cradle-to-gate carbon footprint to range from −2.6 to 10.2 tonnes CO₂-eq. per tonne ethylene oxide depending on the electricity supply (from zero-carbon to the 2022 Canadian average grid mix of 0.128 kg CO₂-eq. per kW h), compared to 2.32 tonnes CO₂-eq. per tonne for conventional fossil-based ethylene oxide. Negative values indicate the process emits less CO₂-eq. than captured from the CO₂ feedstock source, without implying net atmospheric CO₂ removal. Scenario analysis shows large-scale deployment could achieve emissions savings over conventional production if the process performance improves by at least 50% and is powered by low carbon electricity (<0.06 kg CO₂-eq. per kW h). We determine via sensitivity analyses that, in order of priority, technology improvements should focus on (i) increasing the CO₂ to ethylene faradaic efficiency, (ii) reducing the energy demand for ethylene electrosynthesis and (iii) enhancing the CO₂ single pass conversion efficiency. An examination of safety considerations highlights that the emerging pathway could enable ethylene oxide production with higher yields and safer operating conditions than the conventional pathway. This work provides valuable insights into the carbon reduction potential and development priorities for CO₂ electrolysis-based ethylene oxide, supporting efforts to decarbonize the chemicals sector.