Tests conducted in spring 2023 by the Swiss Air Force and the Federal Office of Civil Aviation (FOCA) have confirmed that sustainable aviation fuel (SAF) significantly reduces both fossil CO₂ emissions and particulate pollution. The measurements took place on the military airfield in Payerne using a Cessna 560 XL Citation Excel business jet operated by the Swiss Air Force. The aircraft remained on the ground for controlled engine testing.
The joint study, carried out by experts from the Zurich University of Applied Sciences (ZHAW), the Paul Scherrer Institute (PSI), FOCA and the Air Force, focused on the formation of ultrafine soot particles and volatile compounds during the combustion of SAF. The findings were clear: fossil CO₂ emissions decrease in direct proportion to the SAF blend used. A 35% SAF blend led to a 35% reduction in fossil CO₂.
More striking was the reduction in soot emissions: depending on engine settings, the number of soot particles dropped by up to 35%. The most significant improvement was observed at idle thrust levels—such as when aircraft taxi on the ground—where emissions are usually highest. SAF generally contain no soot-forming aromatic hydrocarbons and are sulfur-free. As a result, even partial blends reduce not only soot, but also gaseous pollutants, contributing to lower particulate matter concentrations and better air quality around airports.
The SAF used in the study was produced from organic waste materials such as used cooking oil and animal fats from slaughterhouse waste. It met all technical standards of conventional kerosene and required no modifications to the aircraft or refueling infrastructure. In fact, one tank was filled with standard Jet A-1, the other with the SAF blend, allowing for real-time comparisons during testing.
While similar effects had previously been documented for large commercial engines, this study provides valuable data for smaller engines used in business jets, showing that SAF benefits extend across aircraft categories.
Overall, the results underscore the dual benefit of SAF: lower climate impact and better air quality. When factoring in full life cycle emissions, SAF can reduce CO₂ by up to 80% compared to fossil jet fuel. These outcomes support ongoing SAF strategies in Switzerland and internationally as part of a broader shift toward cleaner aviation.
Source:
Federal Office of Civil Aviation (FOCA) – Nachhaltiger Flugtreibstoff im Test zeigt: weniger fossiles CO₂, weniger Feinstaub