What Is Sustainable Aviation Fuel, and Is It Truly a Greener Alternative for Flying?

The aviation industry is making significant investments in sustainable aviation fuel, or SAF—an alternative fuel derived from renewable biomass and waste materials. Numerous airlines worldwide are testing its viability; notable news emerged in November when the first fully SAF-powered transatlantic flight took place on a commercial airline (British carrier Virgin Atlantic). While the emissions-heavy airline sector is touting SAF as a key solution for its decarbonization ambitions, experts warn that various environmental challenges and obstacles remain.

What exactly is sustainable aviation fuel, and why is it gaining traction?

SAF is a liquid, energy-rich fuel obtained from non-petroleum sources, known as feedstocks, which include renewable materials like used cooking oil, municipal waste, and algae. It is estimated to reduce the carbon emissions of traditional kerosene-based jet fuel by up to 80 percent. Additionally, SAF is appealing because of its 'drop-in' compatibility with existing aircraft technology, allowing it to be safely blended with conventional jet fuel and used in current airplane engines and supply systems.

Presently, SAF is viewed as the leading solution for the aviation sector to achieve urgent climate objectives set by the U.N. and new government mandates that require airlines to utilize SAF to operate in certain jurisdictions (now established in regions such as the European Union, United Kingdom, and Singapore). The International Air Transport Association (IATA), representing around 300 airlines globally, has pledged to achieve net-zero emissions by 2050, with SAF playing a crucial role in 65 percent of its strategy to reach this target.

What are the obstacles and challenges facing the adoption of SAF?

Currently, only 0.2 percent of the aviation fuel used globally each year is SAF. According to fuel expert Nikita Pavlenko from the nonprofit International Council on Clean Transportation (ICCT), "SAF use is a drop in the bucket."

What’s causing this situation? SAF is not only up to five times more expensive than conventional jet fuel, but it is also in short supply: While about 158 million gallons were produced in 2023, the International Air Transport Association (IATA) estimates that 119 billion gallons of SAF will be required annually to achieve net-zero emissions by 2050.

The challenges of cost and funding significantly hinder scalability. The ICCT reports that the current supply of SAF falls short because the investments airlines are making today are inadequate for scaling up production and creating viable markets. Many organizations argue that airlines are unlikely to absorb the higher fuel costs, as it would increase their operating expenses, raise ticket prices, and potentially reduce demand by making flights less affordable for customers. To address this, these groups recommend that government mandates and economic incentives, such as subsidies and tax credits (like those introduced in the U.S. through the Inflation Reduction Act for SAF producers), are essential to increase supply.

Moreover, advocates for SAF emphasize the need for greater access to capital to support emerging fuel producers. Some airlines are taking proactive measures to invest in this area: for example, United Airlines launched a $200 million venture capital fund last year to invest in SAF technology.

Airlines like Lufthansa and SAS are passing some of the costs onto passengers by offering 'green fares,' which are typically priced higher and include the use of SAF along with other carbon reduction measures like offsets in the ticket price. Other carriers, such as Air France, British Airways, and JetBlue, allow passengers to contribute a supplementary fee to support SAF usage and development. Meanwhile, Singapore is taking a more definitive approach: starting in 2026, all passengers flying from Singapore will be required to pay a mandatory SAF fare levy. The Civil Aviation Authority of Singapore has indicated that these fees will vary based on factors like distance and fare class, with sample increases for economy-class tickets on direct flights from Singapore to Bangkok ($2.20), Tokyo ($4.40), and London ($11.75).

Currently, there remains a significant gap between the available funding for SAF and the production levels required.

So, is sustainable aviation fuel truly sustainable?

Some critics argue that the term 'sustainable aviation fuel' is inherently contradictory.

While SAF is considered a lower-carbon fuel alternative, it is not without carbon emissions. In fact, when burned, SAF emits amounts of carbon dioxide comparable to that of traditional jet fuel; however, it has lower overall life-cycle emissions, primarily due to its feedstocks, such as biomass, which absorb similar quantities of carbon from the atmosphere during their growth. The life-cycle CO2 emissions of each SAF product vary and are influenced by other environmental factors (like deforestation and competition for food crops) based on the feedstock types and production methods used. Furthermore, current IATA regulations restrict SAF to comprise only 10 to 50 percent of the fuel blend for aircraft, necessitating that the remainder be conventional jet fuel, which has higher carbon emissions.

Most importantly, the supply of SAF is extremely limited, raising increasing concerns about whether the significant amount needed can be produced quickly enough to meet the aviation industry's deadlines and targets.

In the end, prominent environmentalists and analysts warn that allowing unchecked growth in the aviation sector while relying on SAF as a catch-all solution for decarbonization challenges will prevent airlines from achieving their climate objectives. Currently, as Pavlenko points out, the most effective way to reduce airline emissions is straightforward: "The least polluting flight is one that doesn’t happen."