As the topic of sustainability looms larger in the psyche of the aviation industry, the question is no longer whether, but when.
Fifteen years ago this month, the General Aviation Manufacturers Association (GAMA) and the International Business Aviation Council (IBAC) announced their Business Aviation Commitment on Climate Change (BACCC), establishing aggressive industry targets to improve fuel efficiency and reduce carbon dioxide emissions. In 2021, it was updated to include the business aviation industry pledge for net-zero carbon neutrality by 2050.
To get there, the document laid out a four-legged plan of attack, consisting of technological advances in airframes and engines, improvements in air traffic control, market-based measures such as the purchase of carbon offsets, and lastly, the use of low-carbon alternative fuels.
Technologies such as electric propulsion, hybrid-electric, and even hydrogen-powered aircraft remain tantalizing visions of aviation’s future. However, still consigned to feasibility studies and test programs, such future advances at a viable commercial level remain on the distant horizon, as they each face yet-unsolved hurdles.
“With aviation, the idea of an electric or hydrogen-powered plane is just a long way off. It's anticipated that by 2050, because of the lack of viable commercial technology that’s going to become available and proven—even once it becomes approved, it’s going to take about 30 years to change the commercial aviation fleet over. So, there’s quite a long runway in that space,” said Scott Lewis, president of sustainable aviation fuel (SAF) producer World Energy’s net-zero services. He noted that without the use of SAF, aviation’s share of carbon emissions will rise from its current 2% to 25% by 2050.
Nearest Solution
SAF has long been recognized as the most immediate and effective solution for the industry in its quest to reach net-zero emissions. According to the BACCC, business aviation anticipates a CO2 life cycle reduction of 40% in absolute terms from biofuels by 2050.
Sustainable aviation fuel is produced from an ever-growing array of feedstocks, with eight approved production pathways and 10 more under consideration. However, it is still in its infancy, especially compared to jet fuel production, which has a 75-year head start.
“SAF is the only thing available today that can fit with today’s aircraft and today’s airports with today’s infrastructure,” said Annie Petsonk, assistant secretary for aviation and international affairs with the U.S. Department of Transportation (DOT). “That is super important because today’s aircraft are still going to be flying tomorrow, 10 years from now, and potentially 20, 30, or 40 years from now. So, there will be a durable market for SAF going forward.”
Earlier this year, the International Air Transport Association (IATA) announced that its prediction of a tripling of worldwide sustainable aviation fuel production in 2024 was on track, with global production of unblended SAF expected to reach nearly 1.5 million tonnes. While an impressive-sounding amount, that equates to just half a percent of the total jet fuel the industry needs.
“SAF will provide about 65% of the mitigation needed for airlines to achieve net-zero carbon emissions by 2050,” explained IATA director general Willie Walsh, adding that he is encouraged about the expected tripling of SAF output from 2023. “We still have a long way to go, but the direction of exponential increases is starting to come into focus.”
Three years ago, the Biden administration issued its SAF Grand Challenge to the U.S. fuel industry to reach a goal of 3 billion gallons of neat sustainable aviation fuel production a year by 2030, with longer-range goals of the complete replacement of petroleum-based jet fuel by SAF by 2050. In the intervening years, the industry has picked up the gauntlet.
“When we initially set it, there were a lot of discussions about whether that was too ambitious," said Alejandro Moreno, an official with the Department of Energy’s Office of Energy Efficiency who was speaking during the North American SAF Conference and Expo in September. “We are now on track at the low end to meet it and even exceed it.”
In 2021 when the challenge was released, the U.S. produced 5 million gallons of SAF. In the first six months of 2024 alone, that number has jumped to 52 million gallons as production facilities continue to come online.
IATA noted that more than 140 renewable fuel projects with the capacity to produce SAF are expected to be operational by 2030. If they reach their expected output rates, worldwide renewable fuel capacity could reach nearly 40 billion gallons by that date, and possibly more as demand will dictate the amount of investment in renewable fuel refineries and technology. With a three- to five-year time lag from planning and funding to operation of a new refinery, those expectations could even skew upwards in that time horizon.
“The interest in SAF is growing, and there is plenty of potential,” added Walsh, “but the concrete plans that we have seen so far are far from sufficient. Governments have to set clear expectations for aviation to achieve a 5% CO2 emissions reduction through SAF 2030 and to be net-zero carbon emissions by 2050.”
SAF’s environmental benefits do not come from how it is burned in engines; the emissions that are emitted from the tailpipe are the same as those from jet-A. When producers or distributors highlight its benefits over conventional jet fuel, it is the life cycle carbon emissions of sustainable aviation fuel that they are referring to. Rather than taking more carbon from the ground in the form of petroleum and releasing it into the atmosphere during combustion, SAF production uses renewable feedstocks such as waste fats, oils, and greases in the most common first-generation fuels available today.
More Feedstocks
With 80% of all SAF produced over the next half-decade expected to come via the HEFA production pathway using feedstocks such as used cooking oil, animal fats, and waste greases, IATA notes that accelerating the use of other pathways using feedstocks such as agricultural and forestry residue is crucial to expanding the potential for sustainable aviation fuel production.
Existing petroleum refineries can be used to co-process up to 5% of approved renewable feedstocks alongside the conventional crude oil content. IATA believes this solution can be implemented quickly, but it would require government policies to ensure consistent life cycle carbon reduction assessments.
Indeed, the SAF Grand Challenge noted that synthetic fuels must deliver at least a 50% reduction in life cycle greenhouse gas emissions compared to standard jet-A. The feedstocks contribute heavily toward this reduction with a focus on waste materials that would otherwise go unused.
At the World Energy plant near Los Angeles, for example, long strings of railroad cars filled with beef tallow constantly stream into the refinery, where they are steam heated, causing the fats they contain to liquefy for easy extraction, on their way to be converted into renewable fuels.
Other processes look to use municipal solid waste, forestry and agricultural residues, algae, oil seed crops grown on fallow or otherwise unusable agricultural land, alcohols, and even hydrogen and carbon derived from the air itself, with the molecules broken apart with electricity and recombined into usable hydrocarbons.
Included among them is corn-based ethanol, which could become an abundant feedstock. “One of our regional conservation partnership projects funded by the Inflation Reduction Act is working with a dozen ethanol plants to create a climate-smart supply of corn that will reduce the carbon intensity score of the feedstock and improve the ethanol quality for use in SAF,” said U.S. Agriculture Secretary Tom Vilsack, who addressed the September SAF conference via video.
At the conference, other less common potential feedstocks were highlighted, including biomass derived from industrial hemp, extraordinarily large sweet potatoes (dubbed "energy tubers"), and even milk waste products.
Everything Counts
It is no longer enough to simply produce SAF. The fuel’s carbon intensity is now a crucial consideration, with every step of the production process taken into account in the final environmental benefit calculation.
All agree the energy used in its production should be renewably sourced so as not to drag the carbon score down, and the further the SAF is transported from its production site, the more impact there is on its life cycle carbon reduction. “Every gram of carbon emitted gets counted,” said World Energy’s Lewis. “Any time we can take a gram of carbon out of the total footprint, we’re going to be looking to do it.”
SAF is presently approved to blend up to 50% with conventional jet fuel. The most common blend ratio on the market is 30%, which yields approximately 24% in life cycle emissions savings compared to conventional jet fuel.
Neat, 100% SAF is currently not approved for use due to the absence of aromatic compounds found in petroleum-based fuels. Those compounds interact with the gaskets in fuel systems, causing them to swell and seal the systems. One airframer learned firsthand what that means when the fuel truck it acquired to handle neat SAF in its testing program developed leaks due to the absence of aromatics in the fuel. Modern aircraft and engines are being designed to handle neat SAF without the risk of fuel system leakage, and Gulfstream demonstrated this a year ago staging the first transatlantic flight on 100% SAF, followed a few days later by the first commercial 100% SAF flight.
New commercial jets are expected to remain in service for 30 years, and according to industry data provider JetNet, half the fleet of delivered business jets and turboprops are still in service more than four decades from initial factory delivery, so any fuel supply must be suitable for legacy aircraft as well. Though SAF producers are by no means capable of supplying pure SAF in significant quantities today, researchers are planning for the eventuality of it becoming a larger and larger fraction of the fuel component.
To restore those missing aromatics, a company has developed a plant-based fuel additive. “That is crucially important because that is what enables this industry to move from the current requirement of only allowing 50% SAF in the engine to 100% SAF and relying on sustainable ingredients,” said the DOT's Petsonk. “It’s a new market potentially for U.S. agriculture and also requires the fuel providers to work basically hand-in-hand with the aircraft manufacturers and the engine manufacturers.”
In the meantime, SAF is only available for business aviation at a relative handful of airports worldwide. In the U.S., they are clustered on the West Coast due mainly to the tax incentives afforded to producers from the low-carbon fuel standards enacted by states such as California, Oregon, and Washington. Earlier this year, Signature Aviation—which offers SAF at all of its locations in California and has pumped more than 40 million gallons of blended SAF since 2020—made the change to remove conventional jet fuel entirely from its FBOs at Los Angeles International and San Francisco International airports, going entirely with SAF blends.
New Mexico passed legislation to establish a fuel standard of its own earlier this year, and similar measures are under deliberation in Minnesota, Michigan, Illinois, New York, Massachusetts, New Jersey, Pennsylvania, Vermont, and Hawaii.
William Hohenstein, a director in the U.S. Department of Agriculture’s office of energy and environmental policy, views this increased focus on carbon intensity as a major change in the industry over the past several years. “There’s clear linking of the production of the fuel and the carbon intensity, and that is embedded deeply in policy, whether that be what California does for the California Fuel Standard, or what we are doing at the federal level through tax credits. That’s really profound because it creates the potential to take every element of the life cycle assessment of the fuel and look at that as an opportunity to mitigate.” The goal is the greater the carbon reduction, the higher the reward for the producers.
Those measures and their possible accompanying incentives will be critical to advancing the adoption of SAF as the industry expands its reach. In 2022, the first blended SAF was transported from Texas to the Northeast via the Colonial pipeline in a two-week, 1,500-mile journey that ended at New York’s LaGuardia Airport. In the words of SAF producer Neste U.S., “What we’re doing here is showing that just around the corner is a future where passengers at Atlanta Hartsfield-Jackson up to LaGuardia, JFK, and EWR can board a plane flying on SAF.”
Expanding Reach
The reach of SAF has expanded even further since then. Last month, World Fuel Services announced a two-year agreement with DHL Express for the delivery of blended SAF to Miami International Airport (KMIA). Over that period, World Fuel will deliver approximately 60 million gallons of blended SAF, of which 18 million gallons will be neat SAF provided by Valero. It will be delivered into the KMIA fuel supplies and represents the largest commitment to SAF use thus far in the Sunshine State, as well as the first continuous deliveries there.
In July, Neste announced that it would supply 1 million gallons of blended SAF via pipeline to United Airlines at Chicago O’Hare International Airport through the end of 2024, representing the first major delivery in the Midwest. That move came in response to Illinois rolling out a new SAF purchase tax credit with every gallon of SAF purchased by air common carriers in the state, earning a sustainable aviation fuel purchase credit of $1.50.
"While the market for SAF is still in its infancy, there is a huge opportunity today for airlines and policymakers to work together to support its continued growth,” said United president Brett Hart. “SAF at O’Hare was made possible thanks to Governor Pritzker and the Illinois Legislature passing tax incentives.”
Those incentives are proving crucial to the development and adoption of SAF. At the end of this year, the Inflation Reduction Act's (IRA) SAF blender’s tax credit will expire and be replaced with the Clean Fuel Production Credit (CFPC). It will offer the same credit amounts for SAF: $1.25 for each gallon of SAF in a qualified mixture. According to the U.S. Internal Revenue Service, to qualify for the credit, the SAF must have a minimum reduction of 50% in life cycle greenhouse gas emissions compared to conventional jet-A, with an additional one cent for each percent that the reduction exceeds 50% up to a total of $1.75 per gallon. When stacked with state incentives, they make a powerful incentive for SAF producers, yet the CFPC is due to sunset in 2027 unless it is renewed under the next administration.
“There is uncertainty about how the policies will be extended, whether they will be extended or not, and that provides market uncertainty,” said Zia Haq, senior analyst at the U.S. Department of Energy’s bioenergy technologies office, adding that these incentives are critical to the industry in terms of closing the gap between cost of production and cost of selling the fuel, a delta which is generally considered one of the major stumbling blocks in the widespread acceptance of SAF.
With investors and potential SAF producers looking to enter a successful, profitable industry, that can mean the difference between attracting project funding or not. "The inflation reduction act and the tax credits have a limited timeline association with them and these investments in the biorefineries are big ticket timeline items that need longer certainty,” Haq said.
To further enhance the development of the SAF industry, the FAA in August handed out $291 million in grants under the Fueling Aviation’s Sustainable Transition (FAST) program, which was also established as part of the IRA in 2022. The SAF portion of the program accounted for $244.5 million in funding to support the build-out of infrastructure projects related to SAF production, transportation, blending, and storage.
The eventual key to SAF is regional production, with the finished fuel produced in the vicinity of urban areas where it can be quickly and easily transported to airports.
The Minnesota SAF Hub—a coalition of more than 300 businesses, universities, cities, counties, and philanthropic organizations in the Minneapolis-St. Paul area—aims to establish the first large-scale sustainable aviation fuel value chain in the U.S.
The group celebrated a major milestone in September with a commercial flight from Minneapolis-Saint Paul International Airport (KMSP) powered by SAF produced by Montana Renewables, from winter camelina, a locally-grown oilseed crop.
But until the paradigm of locally grown and produced SAF becomes a reality, the industry can rely upon book-and-claim processes, which separate the actual fuel from its benefits. Customers can purchase SAF (in reality, its environmental benefits) at airports far from available fuel deliveries. In keeping with the need to preserve the fuel’s carbon intensity scores by minimizing its transport, the actual SAF would then be pumped into a different aircraft at an airport perhaps thousands of miles away.
“At some point, the scale would tip to where SAF is available at more airports,” said Madison Carroll, executive director for the Council on Sustainable Fuels Accountability. “That is the goal: that SAF really becomes ubiquitous and accessible everywhere. Eventually, there would not be a need for book-and-claim because SAF would be the majority of the fuel available.”
Of the 23 billion gallons of jet fuel produced in the U.S. and supplied to the aviation sector, business aviation accounts for just 3% of that amount, yet according to Keith Sawyer, Avfuel’s manager of alternative fuels, the sector last year used more than 10% of the SAF produced. “Business aviation is sending a pretty significant demand signal to manufacturers and producers,” he said. “Now it’s a small portion versus an airline, but it is a reliable, predictable demand signal [to SAF investors] from these corporations and fixed-base operators.”