Comparing alternative fuels for a futuristic subsonic long-range aircraft on a life cycle basis

Abstract

Liquid hydrogen (LH2) and 100% synthetic paraffinic kerosene (SPK), or sustainable aviation fuel (SAF), represent viable alternatives to conventional Jet-A for long-haul aviation, provided they are produced via pathways enabling net-zero well-to-wake (WTWa) emissions. This study evaluates the WTWa performance, including non-CO2 emissions, of a blended wing body aircraft (300 passengers, 13,890 km range) powered by either LH2 or 100% SPK. Use-phase emissions are quantified, and fuel production impacts are assessed using the GREET model. Analysis of over 100 production pathways reveals that LH2 can achieve net-zero or negative WTWa CO2-equivalent emissions when produced from biomass or integrated fermentation with carbon sequestration. Non-CO2 emissions are shown to contribute significantly to WTWa impacts. When miscanthus is used as a feedstock, 100% SPK reduces WTWa CO2-equivalent emissions by 70–85% compared to Jet-A. A high-level supply analysis indicates that SAF and hydrogen production in 2050 could meet the energy demands of long-haul aviation, assuming a 4% annual traffic growth rate and full adoption of these fuels. These findings provide critical insights to guide R&D investments, fuel cost analyses, and aviation policy development for sustainable long-haul aviation.