Technical evaluation and life-cycle assessment of solid oxide co-electrolysis integration in biomass-to-liquid processes for sustainable aviation fuel production

Building upon prior research, this paper integrates solid oxide electrolysis (SOEL) into a Biomass-to-Liquid (BtL) process, facilitating the production of sustainable aviation fuel (SAF) through gasification, co-electrolysis, and Fischer-Tropsch synthesis. Two different integration concepts are developed: An in-line integration resulting in a directly electrified-Biomass-to-Liquid (eBtL) process and a parallel integration for a Power-and-Biomass-to-Liquid (PBtL) process. To maximize process efficiency, the SOEL is operated under endothermic conditions with heat supply from syngas cooling after gasification. The developed processes allow for an increase in carbon efficiency up to about 61% to 94%. The electrolysis power required corresponds to electrification ratios of 0.32 to 0.83 MW_el/MW_th. Compared to the conventional H₂ addition in PBtL processes, electricity demand can be reduced by 13% to 29% when using co-electrolysis instead of steam electrolysis. The resulting increase in energy yield and energy efficiency is because up to 17% of the SOEL's energy demand can be substituted with heat in the electrified BtL processes. A life cycle analysis shows the absolute requirement to operate the process with renewable electricity to reduce indirect greenhouse gas emissions. A critical evaluation of the technological feasibility indicates further development requirements for the SOEL and the gasification heat recovery technology to enable the integration approach.