Is SAF the most efficient path to economy-wide decarbonisation?

18th July, 2025

The UK’s SAF mandate came into operation in early 2025. It supports the use of primarily waste-based feedstocks to create jet fuel, creating a “closed loop” of carbon emissions that, over time, will increasingly displace the use of kerosene produced from fossil fuels, while reducing net emissions on a lifecycle basis. 

The theory behind displacing fossil fuels is sound, but AEF believes that one question that has been repeatedly overlooked in evaluating SAF’s decarbonisation potential is whether these feedstocks are best used in creating jet fuel. As the aviation industry clamours to access scarce supplies of used cooking oil, black bin bag waste and even sewage, alternative uses of these waste resources in other economic sectors are often overlooked.

In many cases, these waste feedstocks are already being used in other sectors. The best example is biodiesel, which is made from used cooking oil. If all this oil was suddenly diverted to aviation fuel, what would this mean for decarbonisation in the road-haulage sector? Another example is renewable energy, which can be combined with green hydrogen to make e-fuels. However, this is a very energy-intensive process, and what consideration has been given to how much of this scarce renewable energy should be diverted to e-fuels, or should it go to electrifying the road fleet, or powering homes more cheaply?

In our new report, The Best Use of Scarce Materials: Is SAF the most efficient path to economy-wide decarbonisation?, we explore these complex economy-wide questions. While the answer to these questions will change as other industries decarbonise faster and no longer need access to waste materials, or additional renewable energy capacity means that electricity prices in the UK fall to more competitive levels, our analysis shows that there is not a single feedstock for which the answer today is an unambiguous yes.

A short summary of the report is also available here