Comparative Life Cycle Assessment of Electrochemical Upgrading of CO2 to Fuels and Feedstocks
Development of electrochemical pathways to convert CO2 into fuels and feedstock is rapidly progressing over the past decade. Here we present a comparative cradle-to-gate life cycle assessment (LCA) of one and two-step electrochemical conversion of CO2 to eight major value-added products; wherein we consider CO2 capture, conversion and product separation in our process model. We measure the carbon intensity (i.e., global warming impact) of one and two-step electrochemical routes with its counterparts – thermochemical CO2 utilization and fossil-fuel based conventional synthesis routes for those same products. Despite inevitable carbonate formation in one-step CO2 electrolysis, this analysis reveals one-step electrosynthesis would be equally compelling (through the lens of climate benefits) as compared to two-step route. This analysis further reveals that the carbon intensity of electrosynthesis products is due to significant energy requirement for the conversion (70-80% for gas products) and product separation (40-85% for liquid products) phases. Electrochemical route is highly sensitive to the electricity emission factor and is compelling only when coupled with electricity with low emission intensity (<0.25 kg CO2e/kWh). As the technology advances, we identify the near-term products that would provide climate benefits over fossil-based routes, including syngas, ethylene and n-propanol. We further identify technological goals required for electrochemical route to be competitive, notably achieving liquid product concentration >20 wt%. It is our hope that this analysis will guide the CO2 electrosynthesis community to target achieving these technological goals, such that when coupled with low-carbon electricity, electrochemical route would bring climate benefits in near future.