Biochar Enhances Fischer-Tropsch Electrofuels from CO2 and Renewable Energy.

Electrofuels have emerged as a promising category of alternative fuels for decarbonizing long-distance modes of transport where electrification opportunities might be limited. Despite the favorable environmental performance, their high cost, driven mostly by the expensive electrolytic hydrogen (H2), still poses a challenge to their widespread adoption. Here, we propose a novel approach based on carbon dioxide (CO2) gasification of biochar via the reverse Boudouard reaction to decrease the H2 demand in Fischer-Tropsch (FT) electrofuel synthesis. We adopt a system expansion approach and assess the life-cycle environmental impacts and techno-economic feasibility of this route considering the replacement of different end-uses of biochar. The comparison to the standard reverse water-gas shift (RWGS) configuration showcases that shifting to the Boudouard route could lead to a reduction in cost, carbon footprint, and impact on human health and ecosystems quality. Nevertheless, collateral damage toward resource depletion could take place depending on the choice of the expanded system for the analysis. In our best case scenario, we improve the global warming impact by 11% and lower the cost by 10% while achieving damage reductions in the range of 10-17% to human health, ecosystem quality, and resource scarcity. Overall, this work sheds light on the potential economic and environmental benefits of a more efficient material integration among processes. Moreover, our results hint at the importance of defining proper system expansion scenarios in assessing alternative technologies, as varying system boundaries could yield different assessment outcomes.