Sustainable aviation fuel

Today’s commercial aircraft have a service life of over 25 years, during which they will continue to run on liquid fuels. Even if the much-vaunted electric, hybrid and hydrogen-powered aircraft projects come to fruition as planned, the requisite rollover of present aircraft fleets will extend well beyond 2050. At current development levels, the new power technologies are also only suitable for short- and medium-haul aircraft: long-haul flights will remain reliant on kerosene power for the foreseeable future. And some 80% of all of aviation’s carbon dioxide emissions are generated by flights of more than 1,500 kilometres.

The key to achieving the carbon dioxide reduction targets that the air transport sector has set itself is the use of sustainable aviation fuels or SAF. In the longer term, switching from fossil kerosene to (SAF) should make aviation almost carbon-neutral. At present, however, sustainable aviation fuels are only available in limited volumes, and are considerably more expensive than conventional kerosene. This is why SWISS is working actively, through targeted measures and collaborations, to drive the development and expand the availability of SAF together with the Lufthansa Group, its partners and its customers.

Sustainable aviation fuel (SAF) is a collective term for all fuels that are manufactured without using fossil energy sources. A number of production methods are used that draw on a range of source materials, such as biomass-to-liquid, HEFA, power-to-liquid and sun-to-liquid. All these procedures pursue the same goal: to re-use the carbon that is present in existing sustainable biomass or gases and turn it into propulsion fuel.

The present generation of sustainable aviation fuels are largely manufactured from biogenic waste such as used cooking oil or fat. When such fuels are combusted, the process only generates as much carbon dioxide as was previously extracted from the atmosphere elsewhere – by plants, for example. So it is only the production and the transport of these sustainable aviation fuels that create new carbon emissions. Compared to fossil fuels, today’s SAF generates some 80% fewer carbon dioxide emissions. The SAF presently used by SWISS and the Lufthansa Group is made solely from biogenic waste, meets the highest sustainability criteria (RSB EU RED II Fuel Certification) and is certificated to ISCC or RSB standards, which ensure that its manufacture does not compete with food production.

In future it will be possible to manufacture SAF using power-to-liquid and sun-to-liquid procedures. As the energy (electricity or heat) needed to do so will be generated from renewable sources and the carbon required will be drawn from the atmosphere, a ‘closed carbon cycle’ can be created in which the fuels manufactured are almost entirely carbon-neutral.

In purely chemical terms, SAF is comparable to conventional kerosene: it is just not based on fossil raw materials. SAF is a so-called ‘drop-in fuel’ which is added to fossil fuels to produce certificated Jet A-1 kerosene that is delivered to the aircraft via the existing fuel supply channels. SAF can thus be used to power existing aircraft and their engines, and can be handled using existing fuelling facilities. SAF also produces fewer fine dust particles when combusted. This results in less cloud formation, which also reduces aviation’s non-CO₂ effects and its overall impact on the climate.

In view of the limited availability of biofuels, SWISS is promoting the development of solar fuels, and established a strategic collaboration to this end with Synhelion, a pioneer in the sustainable solar fuel field, at the beginning of 2022. The aim of the partnership is to accelerate the market launch of this forward-looking technology, to bring pilot production projects in Europe to fruition and to scale up global manufacturing capacities. In June 2024, Synhelion opened the world's first demonstration plant for the production of solar fuel, supported by SWISS and the Lufthansa Group as partners. SWISS will be the first airline to fly with solar kerosene.