There isn’t enough ‘sustainable’ aviation fuel to make a dent in our emissions, and there won’t be for years

The UK chancellor, Rachel Reeves, has described so-called sustainable aviation gas (SAF) as a “game changer.” As she introduced authorities help for a collection of airport expansions, she mentioned that the gas “can reduce carbon emissions from flying by 70%.”

This quantity is deceptive. Optimistic estimates do recommend that absolutely changing fossil jet gas with its sustainable different may result in complete financial savings of round 70%. However it will likely be arduous to provide sufficient SAF to make a distinction on that form of scale. Even when the UK meets its formidable targets, an annual saving of seven% by 2030 is extra believable.

SAF is an artificial liquid gas derived from one thing aside from fossil fuels. These inputs need to be processed right into a liquid that may be burned safely whereas additionally storing a whole lot of power for its weight, since minimizing weight is essential. Because of this long-haul electrical battery-powered planes are unlikely to take off any time soon.

The UK classifies three major pathways for creating sustainable aviation gas. It may be derived from oils or fat, together with used cooking oil or tallow. It may come from different types of fabric, resembling municipal solid wasteagricultural residues, or sewage. Or it may be comprised of hydrogen and captured carbon utilizing renewable electricity.

SAF can be produced from bioenergy crops, and merchandise resembling palm oil. Nonetheless, the UK will not certify it as sustainablebecause of issues about land use and impacts on wildlife.

Emissions that may have occurred anyway

Burning SAF really emits a similar amount of CO₂ to fossil jet gas. As an alternative, most financial savings come from how we account for the waste and renewable power that’s used to provide it.

SAF basically depends on assumptions that if waste or power crops weren’t used to make this gas, they’d be incinerated, would degrade, or would in a roundabout way launch their embodied carbon anyway. Within the case of gas derived from renewable power and captured carbon, it assumes that carbon got here from the ambiance within the first place. This enables these emissions to be deducted from the entire influence of SAF, resulting in decrease emissions than standard aviation gas.

Is sustainable aviation gas even sustainable?

Estimates of how a lot greenhouse gasoline SAF may lower range tremendously because of the many alternative methods it may be produced, and the complexities of accounting for emissions throughout your entire life cycle from waste, to gas manufacturing, to airplane engine. A 2023 review by the Royal Society illustrates this properly. It discovered SAF may at finest produce successfully unfavourable emissions (a 111% discount), whereas at worst it might be extra carbon intensive than fossil kerosene jet gas (a 69% improve).

Whereas coverage incentives are prone to encourage elevated manufacturing, there stay critical issues that can have to be addressed earlier than SAF can develop into a critical competitor for standard jet gas. There are arduous limits to the quantity of used cooking oil obtainable, as an example, and using different feedstocks is still in its infancy.

In the meantime, any renewable energy used to make the gas must compete with rising demand from electrical automobiles, AI information facilities and extra. And there are massive worries the business merely will not be worthwhile sufficient to draw preliminary capital funding, not to mention tackle its well-established rival.

UK SAF manufacturing

Coming into impact in January, the UK’s SAF mandate units authorized obligations for aviation gas suppliers within the UK to progressively improve proportions of sustainable gas, from 2% of complete jet gas in 2025 to 10% in 2030, and 22% in 2040.

That is one in every of a growing number of commitments globallytogether with RefuelEUand the US SAF grand challengewhich search to extend demand and encourage extra funding in manufacturing.

As of 2023, 97% of the UK’s provide is derived from used cooking oil, with the remainder from meals waste. Solely 8% of this cooking oil is sourced from the UK, with most being imported from China and Malaysia. The UK additionally contains 16% of the worldwide SAF market, regardless of representing only 1% of total passengers.

Currentlythe one business producer of SAF within the UK is the Phillips 66 Humber Refinery which processes used cooking oil. The earlier authorities allocated £135 million of funding to 9 tasks, aiming to have five plants under construction by 2025. Regardless of a number of tasks deciding on websites, on the time of writing none seem like underneath building.

In an business with razor-thin profit marginsSAF stays considerably more expensive than standard aviation gas. With potential producers filing for bankruptcy and firms together with Shell pulling out because of profitability issues, the market is looking rocky.

A 7% saving is extra believable

Allow us to assume that Rachel Reeves’ 70% saving is deliverable if fossil jet gas was absolutely changed with SAF. That is optimistic in itself, however not past the realms of chance.

Getting maintain of that a lot sustainable gas is much less believable, nonetheless—the entire demand for jet gas within the UK is greater than ten occasions the present world manufacturing of SAF. However let’s assume that the rocky world market can ship the UK’s formidable demand of 10% SAF use by 2030.

Reeves’ determine then turns into an optimistic worth of seven% financial savings throughout the UK business. If we then right for anticipated progress of passenger numbers, assuming plans for airport expansionthese financial savings are prone to vanish.

Whereas SAF has a task to play in decarbonization, progress sits in clear opposition to its impacts and potential. If the UK has any hope of assembly its local weather targets, it ought to as an alternative be looking for options to flying the place attainable.

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