Comparative Life Cycle Assessment of Electrochemical Upgrading of CO2 to Fuels and Feedstocks
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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.