Off to a flying start

Sustainable aviation fuel (SAF) demand currently exceeds supply, with demand growing in response to increasing domestic and international legislation requiring or incentivizing its use.

After the White House issued a SAF Grand Challenge in 2021, SAF demand increased, explains Matt Murdock, CEO of Raven SR, a Pinedale, Wyoming-based sustainable fuel company. The challenge calls for companies to supply 3 billion gallons of SAF by 2030, aiming to reduce aviation emissions by 20 percent and to produce 35 billion gallons to supply 100 percent of expected domestic commercial jet fuel use by 2050.

A SAF production process called HEFA, which involves the conversion of hydrotreated esters and fatty acids, has been an early frontrunner in the ongoing search for the largest and best production process for SAF. However, alcohol to jet (AtJ) is a biofuel technology to watch, says Tad Hepner, vice president of strategy and innovation for the Renewable Fuels Association, Ellisville, Missouri.

“HEFA can get us a ways down the road, but if we’re looking at 35 billion gallons, we have to look at something else that’s already produced at scale,” Hepner says, adding AtJ has a “massive head start” on the renewable carbon intensity score.

Deerfield, Illinois-based LanzaTech and its spinoff company LanzaJet have introduced AtJ to the market. AtJ enables the use of ethanol—including waste-derived ethanol—in aviation fuel production, with up to 90 percent conversion to SAF, says Tom Dower, LanzaTech vice president of public policy.

“These cleaner-burning, lower-carbon-intensity fuels can drive down aviation sector emissions, reduce contrails and clean the air around airports when used at scale, benefiting local communities,” Dower says.

Certified platforms

Netherlands-based SkyNRG—which sources, blends and distributes SAF to airlines worldwide—notes six technology platforms certified to produce SAF for use in commercial aviation:

• Fischer-Tropsch—breaks up material containing carbon into individual building blocks in a gas form.
• Hydrotreated esters and fatty acids (HEFA)—refines vegetable oils, waste oils or fats through a process that employs hydrogen.
• Synthesized iso-paraffins—a biological platform where microbes convert C6 sugars into farnesene, which, after treatment with hydrogen, can be used as SAF.
• Alcohol to jet (AtJ)—converts alcohols into SAF by removing the oxygen and linking the molecules together to get the desired carbon chain length. Two feedstocks approved for use in the AtJ technology are ethanol and iso-butanol.
• Catalytic hydrothermolysis—converts fatty acid esters and free fatty acids into SAF via catalytic hydrothermolysis followed by any combination of hydrotreatment, hydrocracking or hydroisomerization and fractionation.
• Hydroprocessed hydrocarbons, esters and fatty acids (HC-HEFA)—upgrades bio-derived hydrocarbons, free fatty acids and fatty acid esters in that they are hydroprocessed to saturate the hydrocarbon molecules and remove all oxygen. A recognized bio source is the Botryococcus braunii algae species.

Murdock points out that many of these SAF technologies have been established for a while but have become better and more efficient as businesses rise up around their production.

Raven SR’s technology involves a noncombustion thermal chemical reductive process, converting organic waste and landfill gas to hydrogen and synthetic fuels. According to Raven SR, global SAF supply comprises only 0.03 percent of total jet fuel consumption given the limited feedstock supply.

Raven SR recently signed a memorandum of understanding to supply SAF to Japan-based All Nippon Airways (ANA) for major global routes starting in 2025. As part of the agreement, 50,000 tons of SAF will be supplied in the first year, with annual incremental increases to 200,000 tons after 10 years.

The company will produce the supply at its facilities using local green waste and municipal solid waste. It plans to begin commercial SAF production by 2025 in California, expanding production by 200,000 tons per year until 2034 in the U.S. and Europe.

In its infancy

Hepner says the sustainable aviation fuel market is in its infancy.

Some 16 million to 20 million gallons of SAF are produced in the U.S; globally, the number is under 2 billion, he says.

In an effort to meet the federal government’s SAF Grand Challenge, “a lot of the industry is focused on these first 3 billion gallons, and a lot of the SAF produced now is by the HEFA pathway,” Hepner says. The airline industry uses 17 billion to 20 billion gallons of fuel annually, he says. Southwest and American Airlines are two companies signing agreements to purchase SAF when it is produced, with tax credits being one driving factor.

SAF and alternative transportation fuel markets are growing rapidly, says Michael McAdams, president of the Advanced Biofuels Association, Washington. He cites a January reportfrom France-based International Energy Agency predicting global biofuel demand will rise by 38 billion liters between 2023 and 2028. Demand for renewable diesel and SAF are expected to grow the most in advanced economies such as the U.S.

The fuels are poised to play a huge role in powering heavy industrial vehicles that are difficult or impossible to electrify, McAdams adds.

While alternative transportation fuel markets are well-established around the world and heavily geared toward ground transport, SAF markets are in the earliest stages of development, Dower says.

“Aviation, often identified as a ‘hard-to-abate’ sector, is responsible for approximately 2 percent of global GHG [greenhouse gas] emissions today but is expected to rise over the coming decades as air travel becomes affordable for more people in countries around the world,” he adds.

Dower concurs AtJ can play a significant role in meeting growing SAF demand as HEFA becomes less popular.

“In Europe, they’re beginning to realize that half of [what’s needed to produce HEFA] comes from vegetable crops, food crops, animal crops and is also not a green solution, going into competition with food security and issues like that,” he says.

Incentivizing SAF

Government policies have been a key driver for renewable and sustainable fuel production, expanding into SAF, Dower explains.

Examples include renewable fuel standard mandates, federal tax credits, government grants, loans and loan guarantees.

The European Parliament established a timeline obliging EU airports and fuel suppliers to ensure at least 2 percent of aviation fuels will be green in 2025, increasing each year to 70 percent in 2050.

“Europeans have put a stick down—if you don’t fly with the actual molecule, there will be penalties on the airlines,” Murdock says. “On the American side, they are actually providing carrots. If you do, there are credits available.”

Following the SAF Grand Challenge, Congress created a new SAF tax credit within the Inflation Reduction Act, providing a carbon intensity-based incentive for SAF that is at least 50 percent cleaner than petroleum-based jet fuel. Congress also provided more than $244 million in SAF-related grants through the U.S. Department of Transportation’s Federal Aviation Administration.

Hepner says while other countries are putting their own SAF programs into place, it remains to be seen how they will work together. He says one key statutory program governing SAF is the Renewable Fuel Standard (RFS), updated by the Environmental Protection Agency last June for 2023 to 2025. The RFS establishes requirements for volumes of biofuels—including advanced biofuels—to be blended into the U.S. transportation fuel supply.

McAdams says another piece of legislation to watch is the upcoming Farm Bill, passed every five years to authorize programs at the U.S. Department of Agriculture (USDA).

He expects to see provisions under consideration supporting the SAF sector, including increasing eligibility for SAF in existing USDA programs, developing more feedstock resources for SAF production and standardizing further adoption of the Argonne National Lab’s Greenhouse Gases, Regulated Emissions and Energy Use in the Technologies (GREET) model used by many federal agencies to quantify emissions reductions.

“I’m a big believer that waste-to-fuels is going to probably be one of the best solutions out there because waste is everywhere, whether it be biomass or other organic wastes,” Murdock says. “It really provides a very close-to-home solution. …When you get rid of waste and create clean fuels at the same time, you are solving two problems at once.

“The waste management companies of the world can be a player in this and can say ‘We’re going to help contribute to cleaning up the environment’ at the same time,” he adds.

The author is a freelance journalist based in Venice, Florida, who wrote this article on behalf of Waste Today. She can be reached at brzozowski.carol@gmail.com.