Recent advancements in sustainable aviation fuels

Sustainable alternative fuels, or SAFs, are recognized to have lower carbon footprints and emit fewer greenhouse emissions. As a carbon-neutral alternative and intended drop-in fuels, SAFs would be an appropriate path forward for sustainable aviation. Current approved drop-in fuels enable 50% blending of SAFs, which decreases CO₂ emissions up to 40%. However, CO₂ emissions can be reduced much further by using 100% SAFs or hydrogen. Comprehensive analysis of SAFs in terms of their operational performance, impact on gaseous and particulate emissions, seal swell, engine and fuel systems compatibility, blow-off limits, ignition and relight, vibrations, and noise is essential to move towards 100% SAFs. Furthermore, SAF has been demonstrated to reduce other emissions like NOx, particulate and CO₂ emissions subjective to the fuel production pathways. Therefore, engineering novel fuels and innovative production pathways may lower emissions and reduce the costs of aircraft system design and operation, resulting in cheaper air travel. This study thoroughly examined and discussed all the aspects mentioned above. Hydrogen, a potential competitor for SAFs, has also been analyzed in this study in terms of future production capability to meet aviation needs and the impact of hydrogen combustion on design changes, emissions, and fuel systems. Furthermore, to reduce experimental costs related to SAFs, this study explored approaches for modeling and predicting novel fuel performance in the preliminary stages of fuel assessment.