Sustainable aviation fuel (SAF) production through power-to-liquid (PtL): A combined techno-economic and life cycle assessment

The current research critically evaluates the technical, economic, and environmental performance of a Power-to-Liquid (PtL) system for the production of sustainable aviation fuel (SAF). This SAF production system comprises a direct air capture (DAC) unit, an off-shore wind farm, an alkaline electrolyser and a refinery plant (reverse water gas shift coupled with a Fischer-Tropsch reactor). The calculated carbon conversion efficiency, hydrogen conversion efficiency, and Power-to-liquids efficiency are 88 %, 39.16 % and 25.6 %, respectively. The heat integration between the refinery and the DAC unit enhances the system's energy performance, while water integration between the DAC and refinery units and the electrolyser reduces the demand for fresh water. The economic assessment estimates a minimum jet fuel selling price (MJSP) of 5.16 £/kg. The process is OPEX intensive due to the electricity requirements, while the CAPEX is dominated by the DAC unit. A Well-to-Wake (WtWa) life cycle assessment (LCA) shows that the global warming potential (GWP) equals 21.43 gCO2eq/MJSAF, and is highly dependent on the upstream emissions of the off-shore wind electricity. Within a 95 % confidence interval, a stochastic Monte Carlo LCA reveals that the GWP of the SAF falls below the UK aviation mandate treshold of 50 % emissions reduction compared to fossil jet fuel. Moreover, the resulting WtWa water footprint is 0.480 l/MJSAF, with the refinery's cooling water requirements and the electricity's water footprint to pose as the main contributors. The study concludes with estimating the required monetary value of SAF certificates for different scenarios under the UK SAF mandate guidelines.