Well-to-wake climate performance of e-fuels in aviation based on life cycle assessment

Aviation causes about 3.5% of effective anthropogenic radiative forcing. About two-thirds of this comes from non-CO 2 short-lived climate forcers (SLCFs), which current aviation policy does not yet regulate. This study compares the well-to-wake climate impact of e-kerosene, liquid hydrogen and ammonia, each made with wind or solar electricity, with that of conventional jet fuel (CJF). Contrail cirrus, NO x , water vapour, hydrogen and ammonia slip and N 2 O are included and assessed with four metrics: ATR 20 , ATR 100 , GWP 20 and GWP 100 . SLCFs cause 83% of the tank-to-wake impact of CJF under ATR 20 and 96–100% of that of the alternative fuels. Liquid hydrogen made with wind electricity has the lowest impact under all four metrics. It is 181.3 gCO 2 -eq·MJ −1 under ATR 20 (60% below CJF) and 58.0 gCO 2 -eq·MJ −1 under GWP 100 (66% below CJF). Per passenger-km, a long-range hydrogen aircraft that uses 42% more energy is still 46–59% below CJF if contrail cirrus is counted per kilometre. E-kerosene made with wind electricity is 26–53% below CJF. Ammonia made with wind electricity is only 7% (ATR 20 ) to 36% (GWP 100 ) below CJF at a NO x emission of 10 g·kg −1 , and above CJF under ATR 20 at more than 11.1 g·kg −1 . Under GWP 100 , the e-fuels are below CJF only with electricity below 126 (ammonia), 143 (e-kerosene) or 233 (liquid hydrogen) gCO 2 -eq·kWh −1 . At the 2025 EU grid average of 209 gCO 2 -eq·kWh −1 , e-kerosene and ammonia would therefore be worse than CJF. Fuel policy should include SLCFs and require additional renewable electricity.