Sustainable aviation fuel means less fossil CO2, less particulate matter

Two years ago, the Swiss Air Force and the Federal Office of Civil Aviation (FOCA) carried out test measurements with sustainable aviation fuel (SAF) at the Payerne military airfield. The results confirm this: SAF reduces emissions of soot particles and fossil CO2.

During the test measurements in spring 2023, a working group of environmental experts from the Zurich University of Applied Sciences (ZHAW), the Paul Scherrer Institute PSI, the Swiss Air Force and the FOCA wanted to find out what happens to ultrafine soot emissions and volatile particles when SAF is burned. The Air Force provided a Cessna 560 XL Citation Excel for the tests, which were carried out exclusively on the ground.

Proportional values

The data collected has now been analyzed. A clear picture emerged: fossil CO2 emissions are falling in the same proportion as the proportion of SAF used in fuel. In other words, 35 percent SAF in the fuel means 35 percent less CO2.

Significant decrease in soot emissions

Depending on the engine configuration, these are up to 35 percent lower. The reduction is particularly significant when the aircraft is idling - for example, when it is on the ground with the engine running. The reason: SAFs generally contain no soot-forming aromatic hydrocarbons and are therefore cleaner than pure fossil kerosene. They are also sulphur-free. This means that even with a low admixture, not only are fewer soot particles produced, but also fewer gaseous aromatic and sulphurous substances, which contribute to an overall reduction in particulate matter pollution and an improvement in air quality.

Better for the climate and air

Sustainable aviation fuels are a promising approach to reducing fossil CO2 emissions in aviation. Compared to fossil fuels, SAF makes it possible to avoid up to 80 percent of CO2 emissions without modifying today's engines, including all production and transportation costs. The use of SAF is a win-win situation, as it also has a positive effect on the air quality at and around an airport. While similar results were already available for large engines, the measurements in Payerne on a business jet engine show that further pollutant emissions can also be reduced with SAF on small engines.

The results of the test measurements are summarized in a scientific publication published.

Picture: Nadine Schröder/Swiss Air Force