Life cycle assessment of sustainable aviation fuel production in the European context

Abstract

Sustainable aviation fuels (SAF) play a key role in reducing greenhouse gas emissions, particularly for long distance flights lacking viable alternatives. Within three EU-project, different SAF production routes and process configurations have been analyzed to turn biomass waste streams into fuel. In order to comparably assess the environmental impacts of the variety in production routes, a semi-automated tool was developed that utilizes thorough validated process simulation data as input, enabling the user to link simulation results to background data from life cycle assessment (LCA) databases. Finally, the life cycle impact assessment is performed automatically utilizing the open source framework Brightway2. The assessed processes were: A) Straw/bark gasification, autothermal/allothermal reforming, optional CO2 separation, Fischer Tropsch (COMSYN process) B) Woody residues gasification, hydrogen addition from electrolysis, Fischer Tropsch (FLEXCHX process) C) Lignin liquefaction, hydropyrolysis, hydrodeoxygenation (ABC-Salt process) By selecting different process configurations in dependence of the biomass type and plant location environmental impacts can be minimised. Additionally, SAF production volumes can be increased by adding hydrogen to the process. However, this creates a trade-off with the SAF's climate change (CC) impact, especially when the underlying CC impact of electricity for electrolysis is high. Energetic integration with other processes like the lignin providing pulp mill in process C can reduce environmental impacts of SAF production significantly. Overall, the use of fossil fuels in the supply chain, e.g., biomass harvesting, electricity generation or transport, hinders the production of true net-zero SAF but great CC reductions of 75-90% can already be achieved.