Measurements of particle emissions of an A350-941 burning 100 % sustainable aviation fuels in cruise

Abstract. In order to reduce aviation’s CO₂ emissions and comply with current climate targets, the European Union plans a mandatory quota of 2 % sustainable aviation fuel (SAF) by 2025, rising up to ≥ 70 % SAF by 2050. In addition to a reduction of life cycle CO₂-emissions the use of SAF can also have a positive impact on particle emissions and contrail properties. In this study we present observations from the ECLIF3 (Emission and CLimate Impact of alternative Fuels) aircraft campaign, which investigated exhaust and contrail characteristics of an Airbus A350-941 equipped with Rolls-Royce Trent XWB-84 engines. For the first time, non-volatile and total particle emissions of 100 % HEFA-SPK (Hydro-processed Esters and Fatty Acids – Synthetic Paraffinic Kerosene) SAF, a blended fuel and a reference Jet A-1 were measured in flight. A maximum reduction in non-volatile particle number emissions of ∼41 % compared to the reference Jet A-1 fuel was measured at low cruise engine power settings when using 100 % HEFA-SPK. The reduction decreases to ∼29 % for typical cruise engine settings and to ∼22 % at high cruise engine power settings. The size of non-volatile particles was slightly smaller for HEFA-SPK compared to Jet A-1. We show a comprehensive analysis of the hydrogen content of globally available fuels. Our results demonstrate the impact of the fuel composition in terms of its aromatic, hydrogen and sulfur content as well as of the effect of engine power settings on particle emissions. We demonstrate that the use of HEFA-SPK can significantly reduce particle emissions and thus contrail ice particles, and therefore can provide an aviation climate benefit.