NASA and DLR study shows SAF produces up to 70% fewer ice crystal contrails

In Washington, cleaner-burning jet fuels made from sustainable sources can produce 50%-70% fewer ice crystal contrails at cruising altitude, reducing aviation’s impact on the environment, according to research conducted by NASA and the German Aerospace Center (DLR).

Ice crystal contrail formations can linger in the upper atmosphere for hours and affect the way Earth is heated and cooled. They produce localized increases in temperature – which over time impacts climate change.

By using alternative fuel, jet engines release fewer soot particles, resulting in fewer ice crystal formations. The crystals that do form are larger, but that does not create a problem because they fall more quickly and melt in the warmer air below.

Known as Emission and Climate Impact of Alternative Fuel experiment by DLR and ND-MAX (“N” for NASA, “D” for DLR, and MAX for maximum research opportunity) by NASA, the campaign was staged from Ramstein Air Base southwest of Frankfurt, Germany. 

The international collaboration saw the DLR’s Advanced Technology Research Aircraft A320 airliner burning alternative biofuels while NASA’s DC-8 “Flying Laboratory” trailed a safe distance behind, sampling and analyzing gases and particles in the German aircraft’s wake.

The experiment was the latest step in a series of research campaigns, some in the United States and some in Germany, that used different aircraft, flight conditions, and sampling techniques to build a knowledge base about alternative fuels. 

NASA led previous research flight programs over California called Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS I and II) in 2013 and 2014. During these campaigns, NASA’s DC-8 burned the alternate fuels, while smaller, business-class jets, such as the NASA Falcon HU-25 and DLR Falcon 20, flew behind to gather data.

Those flights showed that using a blend of half biofuel and half regular fuel reduced soot emissions by as much as 50%-70%. Researchers had intended to study contrail research as part of the ACCESS campaigns, but atmospheric conditions prevented contrail formation. The more recent tests over Germany allowed researchers to gather the data they needed.