The Race to Invent a Greener Jet Fuel

Sustainable aviation fuels are approaching a breakthrough moment. Made mostly from agricultural, food and industrial waste or crops, SAFs are produced chemically or through microbial fermentation, as in a brewery, from non-fossil-fuel materials. Such materials range from used beef fat to trash to waste carbon from the atmosphere or factories. Used in a blend with traditional jet fuel, SAFs promise to cut carbon emissions from jets by as much as 80%.

SAFs comprise just 0.1% of jet fuel in use today and are beset by challenges like high cost and uneven supply chains. But with some airlines aiming to reach net zero carbon emissions by 2050, aviation biofuel manufacturing is poised to grow. American companies such as LanzaTech, LanzaJet, Fulcrum BioEnergy and World Energy, Finnish oil giant Neste, the Netherlands’ SkyNRG and others are already selling directly to airlines including United, American, Delta and JetBlue, or indirectly in partnership with oil companies like Exxon and Shell.

The idea of alternatives to oil-based fuels isn’t new. The first diesel engine, invented by Rudolf Diesel in Germany in 1892, was adapted to run on peanut oil. During World War II, national air forces sought to develop substitutes for kerosene, while the rapid rise in oil prices in the 2000s led to a wave of interest in algae-based jet fuel. None of these experiments proved to be commercially viable, but the technology has continued to improve. In 2008, a Virgin Atlantic 747 flew from London to Amsterdam using a combination of traditional fuel and biofuel made from coconut and other plant oils. From 2011 to 2015, 22 airlines around the world flew about 2,500 commercial flights with biofuel blends.

The most popular commercial SAFs today are made from used vegetable oil and animal fat refined in a process called HEFA, which removes oxygen and adds hydrogen. Neste, which patented its first vegetable oil-based fuel in 1997, is the market leader. The company projects that by early next year it will be capable of producing 1.5 million tons of fuel at plants in Finland and the Netherlands and at Singapore’s Changi Airport. Similar technology is used by the biggest American SAF producer, World Energy, which currently supplies Los Angeles International Airport with sustainable aviation fuel from its Paramount, Calif., plant by truck, and plans to open a pipeline early next year.

Several other SAF technologies have in recent years emerged from dozens of new companies. Illinois-based LanzaTech uses bacteria found in rabbit droppings to metabolize carbon waste from steel factories. The company has two plants in China, one near Beijing and the other close to the Mongolian border, and others under construction in India, the U.K., Canada and Belgium. A plant in Soperton, Ga., built by a LanzaTech spinoff called LanzaJet, is almost complete. Gevo, based in Colorado, makes crop-based fuel using low-grade corn. The process takes place in giant fermenters that look “like they’re making moonshine,” says CEO Pat Gruber.

One producer with a new technology is Colorado-based Alder Fuels, which has received grants from the Departments of Energy and Defense. Alder uses agricultural and forestry waste to produce crude oil that can be processed into finished jet fuel, taking advantage of existing oil industry infrastructure. The company has a contract to help produce some 1.5 billion gallons of SAF for United Airlines.

Many questions confront the new SAF industry, including how well the fuels will perform at higher concentrations. All current SAFs must be used in blends with petroleum-based jet kerosene. Only a few as-yet-untested technologies aim to make up 100% of a jet’s fuel.
Securing a consistent supply of raw materials is also a concern. SAF supporters claim that many of their technologies use trash or waste carbon as their raw material, and that crops and agricultural waste can be obtained from land that is too low-quality for growing food. But critics have long complained that the automobile-gas ethanol industry diverts farmers from growing crops for people, and there is simply not enough used vegetable oil and animal fat available to meet the demand for SAFs.

The biggest issue for SAFs is whether they can be produced cost-effectively at scale. Currently, SAFs cost from two to four times more per ton than fossil fuel-based aviation fuel. The industry is benefiting, however, from new government backing. At the Paris Air Show in June, French President Emmanuel Macron announced a 200 million euro public-private partnership to increase production, with a new SAF plant under construction in the town of Lacq. In the U.S., support for SAFs might even be bipartisan: “I don’t get thrown out of Republican offices anymore,” says Gevo’s Gruber, whose company invested $800 million to build its South Dakota plant.

Government mandates are also helping to promote the industry. The European Union and the U.K. have a provisional agreement to begin requiring all flights to include SAFs in their fuel mix, rising from 2% in 2025 to 70% by 2050. Other countries are considering similar measures, including Brazil, Singapore, New Zealand and Japan. The U.S. offers SAF manufacturers a tax credit of $1.25 per gallon if they reduce greenhouse gas emissions by 50%, increasing to $1.75 a gallon for greater reductions.

In the long term, the potential market for low-emission aviation fuels is enormous. The U.S. consumed about 23 billion gallons of aviation fuel in 2019, including military and civilian use, while global commercial consumption reached 95 billion gallons in the same year. With a decarbonized supply chain, SAFs can achieve emissions reductions of up to 80% over fossil fuels, estimates the European Union Aviation Safety Agency.

Dozens of airlines worldwide, including American, United, Delta and others in the U.S., have committed to increasing alternative fuel usage. So have Amazon Air Freight and corporate airline customers like Boston Consulting Group, Bank of America and American Express Global Travel. As of mid-2023, according to the Centre for Aviation, some 499,000 commercial flights had been flown worldwide on some blend of sustainable aviation fuel.

Ted Anton is a professor of English at DePaul University. This essay is adapted from his new book, “Programmable Planet: The Synthetic Biology Revolution,” published this month by Columbia University Press.