Sustainable Aviation Fuels: hope or hype?

16th November, 2023

‘Sustainable Aviation Fuel’ is a term coined by the aviation industry to refer to liquid hydrocarbon fuels made from alternative sources, such as biofuels, waste-to-liquid fuels and synthetic fuels. These are often presented as the answer to the decarbonisation challenge by politicians, the aviation industry and even the UN. AEF’s new report: ‘Sustainable Aviation Fuels: hope or hype?’ takes a look at the sustainability claims and common misconceptions about SAF. The report finds:

• The term ‘SAF’ to describe all non-kerosene liquid fuels for aviation is unhelpful. The sustainability of alternative fuels needs to be assessed, not assumed.
• We need a better-quality conversation about how alternative fuels work as a tool of climate mitigation, based on the understanding that they deliver no CO2 reduction at the tailpipe. At the moment there is a risk of greenwash in public discussion, and of goal-setting at a political level that isn’t based on the right information.
• While the discipline of lifecycle analysis (LCA) is deeply entrenched as an approach for appraising fuel sustainability, the LCA score of a fuel can vary hugely depending on the assumptions made, including location, and in some cases can lead to perverse outcomes whereby a fuel is purported to reduce emissions by greater than 100%, even in the absence of any carbon capture component to the fuel’s production.
• AEF’s view is that the ‘additional carbon’ framing has particular merit in appraising which alternative fuels actually deliver additional atmospheric CO2 reduction in their production and use, rather than those that simply make opportunistic use of waste carbon that would otherwise have other uses or degrade much more slowly. 
• There is a need for greater transparency about how different systems of carbon accounting align to ensure that no emissions are lost and that no savings are double-counted.
• There is some evidence that alternative fuels may generate lower non-CO2 impacts than kerosene, but until specific targets are in place for tackling non-CO2 we should not be creating policy incentives for alternative fuels based on theoretical non-CO2 benefits.
• If restricted to options that result in additional carbon removal from the atmosphere, the role of alternative hydrocarbons (‘SAFs’) in aviation decarbonisation appears starkly limited.

Want to learn more about SAF?
Take a look at our press briefing on the topic, which includes key questions that need to be answered, as well as recommended reading.

AEF’s report was based on a recently commissioned report by from alternative fuel experts, Cerulogy: ‘Scrutinising the future role of alternative fuels in delivering aviation decarbonisation’.