Comparative life cycle evaluation of alternative fuels for a futuristic subsonic long-range aircraft

Liquid hydrogen (LH2) and 100% synthetic paraffinic kerosene (SPK), or sustainable aviation fuel, are promising substitutes for traditional Jet-A fuel in long-haul aviation, as long as they are produced through processes that result in net-zero well-to-wake (WTWa) emissions. This research assesses the WTWa environmental performance, including non-CO2 effects, of a blended wing body aircraft (with a capacity of 300 passengers and a range of 13,890 km) operating on either LH2 or 100% SPK. The study uses the GREET model to evaluate both fuel production and in-flight emissions. Reviewing over 100 different fuel production methods, the analysis finds that LH2 can reach net-zero or even negative WTWa CO2-equivalent emissions if generated from biomass or via fermentation methods paired with carbon capture. Non-CO2 emissions are shown to play a substantial role in overall climate impact. When miscanthus is used as the biomass feedstock, 100% SPK can cut WTWa CO2-equivalent emissions by 70–85% compared to Jet-A. A broader supply analysis suggests that by 2050, hydrogen and SAF production could be sufficient to meet the energy needs of long-haul aviation, assuming a 4% yearly growth in air traffic and complete transition to these alternative fuels. These results offer important direction for future research, cost assessments, and policy-making aimed at decarbonizing long-haul aviation.