DLR: Switching to SAF reduces climate impact by 25%

German Aerospace Centre (DLR), via its KuuL (Climate-friendly ultra-efficient long-haul flight) study, reported (20-Sep-2023) long haul flights account for around 10% of passengers annually but generate approximately 40% of the air transport's carbon dioxide emissions, due to the long distances and flight times involved. DLR found small changes in flight altitude and airspeed, together with the choice of energy source, can significantly reduce their climate impact. In addition, aircraft specially designed for flight at different altitudes will also make a "decisive contribution to climate compatibility on long haul routes". Highlights include:

• Switching from kerosene to sustainable aviation fuels (SAFs) reduces the climate impact by approximately 25%, without the need for new aircraft, while the actual climate impact of carbon dioxide emissions can be reduced by 100% if the SAFs are produced using a carbon-dioxide-neutral process;
• Use of SAFs can also reduce the impact of non-carbon dioxide effects, with condensation trails and the resulting contrail cirrus the most significant factors;
• If in addition to a change of fuel, the maximum flight altitude is reduced by 2000 metres, a reduction in the climate impact of up to 70% can be achieved. However, at this altitude, the aircraft design must also be modified due to the higher air density, and, in particular, the sweep angle of the wings must be reduced. The flight speed would also have to be reduced by up to 15% to remain energy efficient;
• Hydrogen powered long haul aircraft could be a long term prospect alongside SAFs.

DLR institute of aerodynamics and flow technology project leader Martin Hepperle commented: "In the long term, a compromise must be found here between energy demand, cost effectiveness and climate impact". [more - original PR]