British Prime Minister Rachel Reeves describes what is called sustainable aviation fuel (SAF) as a “game changer.” She said fuel “can reduce carbon emissions by 70%” as she announced government support for a series of airport expansions.
This number is misleading. Optimistic estimates suggest that replacing sustainable alternatives by completely replacing fossil jet fuel could lead to around 70% of total savings. However, it is difficult to generate enough SAFs to bring about change on such a scale. Even if the UK achieves its ambitious goals, a 7% saving annually by 2030 would be more reasonable.
SAFs are synthetic liquid fuels derived from things other than fossil fuels. These inputs must be processed into a safe, burnable liquid, as it is important to minimize weight. This is why long-range battery-powered planes are unlikely to take off anytime soon.
The UK categorizes three main routes for creating sustainable aviation fuels. It can be derived from oils and fats such as used cooking oils and tallows. It can come from other types of materials, such as urban solid waste, agricultural residues, and sewage. Alternatively, it can be made from hydrogen and trapped carbon using renewable power.
SAFs can also be produced from products such as bioenergy crops and palm oil. However, the UK does not qualify it as sustainable due to concerns about land use and wildlife impacts.
Emissions that would have been generated anyway
Burning SAF actually releases the same amount of CO2 into fossil jet fuel. Instead, most savings arise from the way in which the waste and renewable energy is described to produce it.
Jenya Smyk/Shutterstock
SAFs essentially rely on the assumption that if waste or energy crops were not used to make this fuel, they would incinerate, deteriorate, or release carbon embodied in some way. For fuels derived from renewable energy and captured carbon, we assume that carbon was born from the atmosphere in the first place. This allows these emissions to be deducted from the total impact of SAF, reducing emissions over traditional aviation fuels.
Is sustainable aviation fuel sustainable?
Estimates of greenhouse gas SAF reductions vary widely due to the different ways in which they can be produced and the complexity that accounts for the entire lifecycle emissions, from waste to fuel production to planar engines. A 2023 review by the Royal Society shows this well. SAFs have been found to be capable of generating negative emissions effectively at best (111% reduction), but at worst, they are more carbon-intensive than fossil kerosene jet fuel (69% increase). It may be.
Policy incentives are likely to drive increased production, but there remains serious concerns that SAFs need to address before they become serious competitors for traditional jet fuels. For example, there are strict restrictions on the amount of used cooking oil, and the use of other ingredients is still in its early stages.
Meanwhile, renewable energy used to make fuel must compete with increasing demand from electric vehicles, AI data centers and more. And it goes without saying that the industry is not profitable enough to simply attract early capital investments and will take on established rivals.
UK SAF Production
The UK SAF Mandate, which came into effect in January, aims to gradually increase the proportion of sustainable fuels to UK aviation fuel suppliers, from 2% of total jet fuel in 2025 to 22% in 2040. It has legal obligations.
This is one of the ever-growing commitments around the world, such as Refuelu and the US SAF Grand Challenge, seeking to increase demand and encourage more investment in production.
As of 2023, 97% of UK supply is derived from used cooking oil, while the rest comes from food waste. Only 8% of this edible oil is sourced from the UK, with most imported from China and Malaysia. The UK is made up of 16% of the global SAF market, despite representing only 1% of total passengers.
APS (UK) / Aramie
Currently, SAF’s only commercial producer in the UK is the Phillips 66 Humber refinery, which processes used cooking oil. Previous government allocated £135 million in funding to nine projects with the aim of installing five factories under construction by 2025.
In an industry with razor profit margins, SAFs remain significantly more expensive than traditional aviation fuels. The market appears rocky with a company that involves potential producers filing for bankruptcy and drawing out shells due to profitability concerns.
A 7% saving is plausible
Let’s assume that if fossil jet fuel is completely replaced by SAF, Rachel Reeves’ 70% savings are the deliverable. While this is optimistic in itself, it does not go beyond the realm of possibilities.
However, while it is not so reasonable to retain that many sustainable fuels, the total demand for jet fuel in the UK is more than 10 times the current global production of SAFs. But let’s assume that the Rocky Global market can offer the UK’s ambitious demand of 10% SAF use by 2030.
Reeves’ figures are an optimistic value of 7% savings across the UK industry. Those savings could disappear if you revise the expected growth in passenger numbers, assuming an airport expansion plan.
SAF has a role to play in decarbonisation, but growth is clearly opposed to its impact and potential. If the UK wants to meet its climate targets, it should instead seek alternatives to flying where possible.
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