The Government’s SAF mandate aims to boost the use of alternative fuels, but making jet fuel from waste won’t solve the aviation emissions problem

The UK Government has announced the details of its ‘Sustainable Aviation Fuel’ (SAF) mandate, which requires increasing amounts of alternative fuels to be blended with kerosene from the 1st January 2025. 

‘Sustainable Aviation Fuels’ (sometimes called ‘alternative aviation fuels’) are liquid fuels that work like kerosene but are made from a source other than fossil fuel. They release as much CO₂ as kerosene once burned in an aircraft, but are intended to deliver net emissions reductions as a result of the way the feedstock or energy for the fuel has been derived. 

There are several different types of SAF, all with different challenges to scale and all with varying degrees of sustainability. These include using used cooking and other waste oils (categorised as HEFA – hydrogenated esters and fatty acids), municipal wastes, and synthetic fuel (e-fuel) made from hydrogen and captured carbon. HEFA is the cheapest type of SAF, but is limited in supply and is already in demand from other sectors such as road transport. 

The mandate will require 2% of the total fuel supplied to aviation in the UK in 2025 to be SAF. This will rise to 10% by 2030 and 22% by 2040. Despite Jet Zero’s 2050 forecast for alternative fuels, the mandate only sets targets out to 2040, acknowledging the uncertainty of what may be possible after this date. 

The Government has decided to not limit the supply of HEFA for the first two years of the mandate, but then to curb its production to no more than 71% of the total SAF target in 2030 (equivalent to 7.1% of total aviation fuel use in 2030) and 33% of the 2040 SAF target.  

The allowable level of HEFA is much higher than we, and many others, were expecting, and appears to be the result of airline pressure, with the chief executive of industry group AirlinesUK, Tim Alderslade, describing it as a win. HEFA will form the bulk of SAF production out to 2030, while the sub-mandate for power-to-liquid (or e-fuel), widely regarded as the most sustainable alternative liquid fuel for aviation if produced using  green hydrogen and carbon captured from the air (DAC), is low and generally lags behind the EU’s ambition.

Responding to the Government’s UK SAF mandate, AEF Policy Director Cait Hewitt said:

“Both Ministers and the aviation industry like to make out that alternative fuels will be the big solution for tackling aviation emissions. But the truth is that these fuels will be in limited supply and most of them will be produced using wastes. That doesn’t even reduce CO₂; it just takes carbon, like plastic bottles, that’s laying in a rubbish dump and puts it back in the atmosphere. So it’s actually not even sustainable. 

If this mandate means the Government finally acknowledging the aviation emissions problem can’t be solved without some policy action, then perhaps it’s a step in the right direction. But what we really need is a reduction in aviation emissions. A percentage mandate for alternative fuel in an industry hungry for growth can’t guarantee that. So for the time being, it remains the case that the best way to cut emissions from flying is to fly less.“

We welcome the fact that there’s no mention of ‘guilt free flying’ an idea which accompanied earlier ‘Jet Zero’ announcements, but the Government’s statement nevertheless makes some misleading claims. SAF does not “produce up to 70% less carbon emissions” when used in an aircraft, as the Transport Secretary Mark Harper claims. As noted above, it produces as much CO₂ as kerosene when combusted. The only difference is that SAF is made from carbon sources other than fossil fuel, allowing producers to claim lower ‘net’ emissions. And making aviation fuel out of waste is not, in our view, either sustainable or efficient, especially when the waste derives from unsustainable products such as plastics. As the UK has committed to cutting the amount of waste produced, this isn’t a ‘feedstock’ that can be sustainably scaled up. 

Price support

Even with the mandate set, the policy discussions will still continue. Alongside the mandate announcement, an eight week consultation has been published on a ‘revenue certainty mechanism,’ to provide assurances to investors in relation to the potential production of alternative fuels in the UK. NGOs are united in arguing that while revenue certainty may help secure investment, any mechanism should be funded by the industry and not the taxpayer.

Cait Hewitt said:

“On the revenue certainty mechanism, whatever form this takes, the important thing is that it’s airlines, not the public, who pay for any fuels or technologies designed to help cut emissions. With no tax on aircraft fuel and no effective emissions charges for flights outside Europe, it’s about time we made the polluters pay.”

For more on AEF’s views on SAF, see here.

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