What is Sustainable Aviation Fuel (SAF)?

2 Feb 2022 by Tom Otley
Neste Sustainable-Aviation-Fuel--truck-at-airport

Sustainable Aviation Fuel (SAF) is an aviation fuel made from sustainable and renewable sources which can act as a substitute for fossil jet fuel.

SAF is perhaps best understood as a collective term for many different types of fuel. It is the feedstock – what goes into the mix to create the SAF – as well as the process by which it is made that determines just how “sustainable” the fuel is.

Most existing forms of SAF might also be termed biofuels, which, as the name suggests, means a fuel produced from biological resources (plant or animal material) but which also includes used cooking oil, and municipal and household waste. It is also possible to create synthetic fuels from hydrogen and carbon dioxide – these are often referred to as e-kerosene, power-to-liquid and e-fuels. As an added complication, some NGOs, such as clean transport campaign group Transport and Environment, use the term SAF to refer to “sustainable advanced fuels”. These are the same as sustainable aviation fuels but don’t carry the implication that the fuels have to be used for aviation.

How sustainable is it?

It depends on how it is made. To use the term “sustainable’’ validly, the fuel must meet criteria such as lifecycle carbon emissions reduction, limited freshwater requirements, no competition with needed food production (such as first-generation biofuels) and no deforestation count.

There are some processes that seem to have obvious benefits – using household waste, for instance, or used cooking oil. But even then, it is important to certify that the oil is, in fact, waste. A recent study showed that more than half of the waste cooking oil for SAF in the EU came from abroad. China supplies more than a third (34 per cent) while almost a fifth (19 per cent) of waste oil comes from the major palm oil producers Malaysia and Indonesia combined. The increasing reliance on imports means that the price of used cooking oil can sometimes rise above virgin oils, such as palm oil. This could potentially lead to virgin oils being reclassified as waste to meet demand, so driving deforestation.

Finnish-based company Neste is currently the world’s largest supplier of SAF but it includes in its feedstock palm fatty acid distillate (PFAD). Transport and Environment says: “PFAD is a byproduct of the palm oil industry that is used in other industries. Thus, its promotion for biofuel use, beyond directly creating an incentive for more palm oil cultivation, leaves a gap in these other industries as they would need other feedstocks – such as virgin palm oil.”

Neste defends its use of PFAD, saying that it is just one of several feedstocks it uses: “Proportions of individual raw materials in Neste’s refining vary from year to year, depending on their availability, price and specific market requirements, for example.”

It argues that this provides flexibility and allows it to “respond to the needs of different markets and customers… We are constantly looking into diversifying our portfolio with new raw materials. Replacing fossil oil with renewable and recycled raw materials helps to reduce crude oil dependency [and] greenhouse gas emissions, and combat climate change.”

Other companies, such as Velocys, use municipal and wood waste. Lanzajet, launched by biotech company Lanzatech, uses ethanol, which, depending on the market, might come from corn (in the US), sugarcane (in Brazil) and wood waste (in Europe), but also steel mill waste gases from its planned plant in South Wales. The proposed facility will yield about 100 million litres per annum.

Can existing aircraft use SAF?

Yes. The chemical and physical characteristics of SAF are almost identical to those of conventional jet fuel. This means they can be safely mixed with the latter to varying degrees, can use the same supply infrastructure and do not require any adaptation of either aircraft or engines. It means that SAF is often referred to as a “drop-in fuel” – that is, fuel that can be automatically incorporated into existing airport fuelling systems.

All fuels (and SAF) must be certified to be used in commercial flights, and there are several bio-based aviation fuel production pathways that have been certified, with others in the approval process.

How much does it cost?

Here lies the problem. As Henrik Wareborn, chief executive of Velocys says: “The spot market for SAF is currently at US$2,500 per tonne. That’s what airlines pay for the small volumes available today. The similar price for fossil jet fuel is US$500 per tonne, meaning SAF is five or six times the price. It is eye-wateringly expensive and hard to procure.”

Production must rise and prices must fall before its widespread use. As put by IATA: “Insufficient supply and high prices have limited airline uptake to 120 million litres in 2021– a small fraction of the 350 billion litres that airlines would consume in a normal year.”

There is no single solution to reducing the high cost of SAF in the long term. Producing it in volume will obviously make the price drop, but for that to happen, governments will have to play a role in carbon pricing, either through emissions trading systems or a carbon tax. This would mean that an airline would have to either pay for SAF, or pay a similar price for the carbon they will emit from their flights up to whatever the percentage mandate is. So if the mandate for SAF is 5 per cent, they would have to pay a penalty equivalent to the carbon emitted for 5 per cent of their flights. This would encourage them to purchase SAF, which would drive demand and so help to bring down the cost. Campaigners point out that all other transport fuels – apart from kerosene –are taxed, and so removing this exemption would raise revenue and help to close the gap, while also affecting some demand management (by raising the cost of flying and so reducing demand).

As part of the ReFuelEU Aviation initiative, there are proposals to introduce such a tax on the 27 countries in the EU on a gradual scale over the next ten years – still, as you can imagine, airlines are not keen on this.

“Making jet fuel more expensive through taxation scores an ‘own goal’ on competitiveness that does little to accelerate the commercialisation of SAF,” says IATA director general Willie Walsh.

IATA argues that taxes “siphon money from the industry that could support emissions-reducing investments in fleet renewal and clean technologies”. In other words, by reducing the potential profits of the airline industry, it leaves less money to invest in technologies such as SAF.

To read more about SAF and our coverage, use this link

Sustainable Aviation Fuels

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