What you need to know about sustainable aviation fuel

The world’s insatiable appetite for flying is fuelling concerns about how to shrink the carbon footprint of air travel, today the source of about 2.5 per cent of humanity’s planet-warming emissions related to energy.

While that is a relatively small share of total global emissions, it looks set to increase in the decades to come, as significantly cutting emissions is still a distant technological prospect for commercial aircraft, even as other sectors, such as road transport, are doing so by going electric. 

For airlines and governments across the world, the solution is sustainable aviation fuel (SAF), which backers say

can cut emissions by more than 80 per cent,

without requiring aircraft modifications.

SAF is designed to be a drop-in fuel for planes, needing no new additional infrastructure at airports. Current technology allows up to 50 per cent of SAF to be blended with fossil fuel-based jet fuel. 

Here are some key things to know about SAF:

How is sustainable aviation fuel (SAF) made?

The fuel can be made from a variety of raw materials, or feedstocks, using different techniques, but today virtually all of it is made from hydroprocessed esters and fatty acids (Hefa). The Hefa production process 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 of deforestation, in contrast to virgin oils derived from soya beans or palm.

Other regions are prioritising feedstocks that can be easily sourced locally, such as soya in the US and 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 using hydrogen, generated from renewable electricity, and carbon dioxide captured from the atmosphere or industrial processes.

How much SAF are airlines using?

A tiny amount. SAF accounted for just 0.3 per cent of global jet fuel production in 2024, according to the International Air Transport Association, which has called the take-up rate “disappointing”.

Cost is the main reason for the slow roll-out. Currently, SAF is between two and seven times more expensive than traditional jet fuel, depending on how it is produced. That is primarily down to the limited availability of feedstocks like UCO, which is hard to collect from restaurants and households. The price of fossil fuel-based jet fuel is also kept artificially low because of wide-ranging tax exemptions.

Around the world, a number of governments are trying to expand the market for cleaner aviation fuels by offering financial incentives and making the use of SAF in planes 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 per cent SAF with conventional kerosene. The blending requirement will gradually increase to reach 32 per cent in the EU and 22 per cent 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 for its use.

Singapore has been very active in trying to grow regional demand for such fuel. In May, the World Economic Forum and Singapore’s GenZero, a Temasek-owned investment platform, launched the Green Fuel Forward initiative to scale up production of SAF. The initiative draws in airlines, refiners, logistics companies, banks and others to invest in greater SAF usage.

Will SAF lead to net-zero air travel?

That remains to be seen. Existing and planned SAF projects in advanced stages will meet between 2 per cent and 4 per cent of jet fuel demand by 2030, according to the International Energy Agency, 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 to lower costs. In March, the chief executive officers of Ryanair, the International Airline Group (IAG), Lufthansa and Air France-KLM warned that the EU’s 6 per cent SAF requirement for 2030 would be impossible to meet because of the high cost and scarcity of the greener fuel.

Asked to comment, the EU said the current SAF targets are “realistic and feasible”.

Who guarantees that SAF is a climate-friendly solution?

Governments and the International Civil Aviation Organisation require specific certification to prove the sustainability of a batch of SAF and the raw materials needed for its production.

The world’s leading certification scheme is the International Sustainability and Carbon Certification (ISCC), an industry-led initiative that aims to support “sustainable, fully traceable, deforestation-free and climate-friendly supply chains”. EU regulators use ISCC certificates as proof of origin and sustainability of SAF produced and used in the bloc.

Approved third-party auditors are in charge of inspecting SAF plants and their suppliers along the global supply chain, which are then approved by the ISCC following EU standards. 

Throughout the different stages of the SAF supply chain, the ISCC requires operators to pass certified information on the origin of raw materials and their carbon savings from one operator to another. But for some feedstocks, tracing their origin can be tricky.

In the case of UCO – the main raw material used in the EU today – 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 claim that their product is actually waste oil. So there is some room for fraud, and efforts from airlines and regulators to close any loopholes are key.

Are air ticket prices higher because of SAF?

Some airlines have started passing on the extra costs of SAF to passengers, but for now this remains a small amount. However, IAG warned in 2024 that airfares would need to rise to fund the shift to cleaner fuels.

Air France-KLM and Lufthansa have added mandatory SAF levies to tickets, with the German flag carrier charging up to €72 (S$110) per flight depending on the route and fare, to cover the cost of complying with Europe’s new SAF mandates.

While stopping short of applying a surcharge, British Airways encourages members of its loyalty programme to make voluntary contributions for SAF, enabling them to pay with and earn points.

In Singapore, travellers flying out of the country will pay an SAF levy from 2026, when all departing flights will be required to carry fuel with 1 per cent SAF. Preliminary estimates from the Civil Aviation Authority of Singapore suggest that economy-class passengers may incur an additional $3 levy for short-haul flights, $6 for medium-haul and $16 for long-haul flights.

A growing number of airlines also offer customers the option to pay a voluntary SAF charge as a way to help offset the carbon footprint of their journey.