What is Sustainable Aviation Fuel (SAF)?

What you need to know about SAF

The world’s appetite for flying keeps on growing, fuelling concerns about how to shrink the carbon footprint of air travel – today the cause of about 2.5% of all energy-related emissions.

While that’s a relatively small share of global emissions, it looks set to increase in the decades to come as other sectors, such as road transport, cut their emissions by switching to electric – still a distant technological prospect for commercial aircraft. Increasing demand for air travel will also play a role.

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For the airline industry and many governments across the world, the solution is so-called sustainable aviation fuel (SAF), which can cut emissions by between 50% and nearly 100%, depending on how it is made, without requiring aircraft modifications.

How is SAF made?

SAF can be made from a variety of raw materials, or feedstocks, using different techniques, but today virtually all of it is made using the Hydroprocessed Esters and Fatty Acids (HEFA) process. This refining technique involves stripping oxygen from the fat molecules of natural oils and fats and replacing it with hydrogen. HEFA fuel has various uses, including in aviation.

Used cooking oil (UCO) is currently the most common feedstock for SAF, especially in Europe where policies promote its use as a recycled waste product that does not compete for land with food production or carry a high risk for deforestation, in contrast to virgin oils derived from soybeans or palm.

Other countries are prioritising feedstocks that can be easily sourced locally, such as soy in the United States or palm oil in Brazil. The two agricultural powerhouses are also expected to produce large quantities of SAF by converting ethanol made from corn or sugarcane – another kind of drop-in fuel known as alcohol-to-jet.

SAF can also be made without crops or organic waste. Synthetic fuels – known as e-SAF or power-to-liquid SAF – are made from two gases: green hydrogen, generated from renewable electricity, and carbon dioxide captured from the atmosphere or industrial processes. E-SAF can reduce emissions by up to 90% compared to fossil fuel-based jet fuels, but it remains prohibitively expensive to manufacture.

How much SAF are airlines using?

SAF accounted for just 0.3% of global jet fuel production in 2024, according to the International Air Transport Association (IATA), which has called the take-up rate “disappointing”. The industry body estimates SAF will reach 0.7% in 2025.

Cost is the main reason for the slow rollout. Currently, SAF is between two and seven times more expensive than traditional jet fuel. That’s primarily down to the limited availability of feedstocks like UCO and challenges in making production more cost-efficient by scaling it up. Meanwhile, the price of fossil fuel-based jet fuel is kept artificially low due to wide-ranging tax exemptions.

Some countries are trying to expand the market for cleaner aviation fuels by offering financial incentives and making SAF use compulsory.

The European Union and the UK introduced the world’s first SAF mandates in January 2025, requiring fuel suppliers to blend at least 2% SAF with conventional kerosene. The blending requirement will gradually increase to reach 32% in the EU and 22% in the UK by 2040.

SAF mandates are also coming into force over the next few years in Singapore and Brazil, and other major aviation hubs such as Japan and China plan to introduce targets.

The US has opted for direct subsidies and tax credits – rather than mandates – to stimulate SAF production.

Will SAF lead to net-zero air travel?

Existing and advanced-stage SAF projects will meet just 2%-4% of jet fuel demand by 2030, according to the International Energy Agency (IEA), far short of what is needed to put the sector on track to meet its goal of reaching net zero by 2050.

Airlines have been sounding the alarm about scant supplies and demanding policies to incentivise production. In March, the CEOs of Ryanair, International Airline Group (IAG), Lufthansa and Air France-KLM said the EU’s 6% SAF requirement for 2030 would be impossible to meet because of the high cost and scarcity of the fuel.

Luis Gallego, CEO of IAG, the parent company of British Airways and Iberia, called for an urgent EU aviation strategy “to have SAF at competitive prices”, Reuters reported. Without that, he said, “the only realistic solution is to move the 2030 SAF mandate to the right”.

The EU responded at the time by saying its SAF targets were “realistic and feasible”.

Airlines and fuel producers have also been pressing for more government financial support to expand the production of e-SAF and lower the cost.

Is SAF really a sustainable and climate-friendly solution?

Governments and the International Civil Aviation Organization require certification to prove the sustainability of any given batch of SAF, and the raw materials used to make it.

The world’s leading certification system is the industry-led ISCC (International Sustainability and Carbon Certification), which issues certificates used by EU regulators to prove the origin and sustainability of SAF produced and used in the bloc.

Approved third-party auditors inspect SAF producers and traders of raw materials around the world, and – if standards are met on feedstock origins and carbon savings – they receive the ISCC’s stamp of approval.

But guaranteeing the sustainability of feedstocks throughout complex supply chains is challenging.

In the case of UCO, suppliers at the point of origin such as restaurants and individuals are required to fill out a self-declaration form. The system relies on their honest declaration that their product is actually waste oil, used repeatedly and no longer suitable for cooking.

The ISCC verification system has been criticised by European industry members and national regulators for failing to catch cases of fraud in biodiesel supplies. In 2024, the ISCC conducted 79 “integrity assessments” – around two-thirds targeting Asia-based suppliers – which independently monitored the work of auditors. A third of the analysed cases showed violations of certification requirements, leading to the withdrawal of 11 certificates.  

Is SAF making air travel more expensive?

With airlines currently paying a significant premium to add SAF to their airport fuel supplies, some have started to pass the extra cost onto passengers.

Air France-KLM and Lufthansa have added mandatory SAF levies to tickets, with the German flag carrier charging up to 72 euros ($82) per flight depending on the route and fare.

In Singapore, which wants to become a regional SAF hub, travellers flying out of the country will pay a SAF levy from 2026, when all departing flights will be required to carry 1% SAF. Preliminary estimates from the Civil Aviation Authority of Singapore suggest that economy-class passengers may incur an extra S$3 ($2.30) levy for short-haul flights and S$16 ($12.40) for long-haul flights.

A growing number of airlines also offer customers the option to pay a voluntary SAF charge to help offset the carbon footprint of their journey. British Airways, for example, encourages members of its loyalty programme to make voluntary contributions, enabling them to pay with and earn points.

Low-cost Spanish airline Vueling, also owned by IAG, offers passengers the chance to make a contribution equivalent to the cost of 2% of the total fuel needed to reach their destination to be provided in the form of SAF – a contribution it matches.

This article was developed with the support of Journalismfund Europe.