An illustration shows a person standing on a step ladder, pouring a green liquid from a bottle into the fuel tank of an airplaneVirtually no human activity is as difficult to decarbonise as flying. Relatively light, energy-dense aviation fuel — or Jet A-1, as the most common type is known — packs vast amounts of energy into a tiny amount of space and weight. Finding an equally efficient alternative is a daunting prospect.
The production of power-to-liquids fuels, meanwhile, could require vast amounts of renewable electricity that could otherwise be used as a clean energy source elsewhere. SAFs do not entirely eliminate carbon emissions. To be used in many aircraft, they still have to be mixed with some proportion of conventional jet fuel. There are also carbon emissions related to their production and transport.