Towards fossil-free ethylene: ex-ante techno-economic comparison of three alternative processes at low technology readiness levels

Ethylene production processes using alternative carbon sources like biomass or CO 2 could have great potential for the olefins industry. Comparing the benefits and pitfalls of different process routes is challenging due to the vastly different feedstocks and key conversion technologies involved. Here, we performed an ex-ante techno-economic and environmental assessment to explore potential trade-offs of three low technology readiness level ethylene production processes. The three routes were: 1) biobased syngas fermentation to ethanol followed by ethanol dehydration, 2) direct electrochemical conversion of CO 2 , and 3) indirect CO 2 and H 2 O electrolysis to form syngas followed by a Fischer-Tropsch step. This study found three main takeaways. Firstly, the biobased route significantly outperforms the direct and indirect routes in terms of techno-economic and carbon footprint performance. Secondly, the electrolyzer unit is the main factor limiting the techno-economic performance of the direct and indirect cases, reemphasizing the need for continued technological advancements and cost reductions by researchers in this domain. Finally, the indirect plant design, incorporating two electrolyzers and a Fischer-Tropsch step, is not techno-economically feasible for ethylene production, underscoring the need for further research on Fischer-Tropsch plant designs to advance the replacement of traditional fossil-based refineries. • Bio-syngas fermentation with ethanol dehydration to ethylene outperforms electrochemical routes. • Electrolyzer cost and efficiency are the main barriers for direct and indirect CO 2 -to-ethylene routes. • Indirect route is better suited to alternative plant designs.