Considering the onslaught of sustainable aviation fuel (SAF) project and offtake agreement announcements, companies highlighting their unique conversion technologies, and varying assessments of where the industry is and must be to reach incremental goals, it can be difficult to assess what stage of development the industry has actually reached. To address this, researchers with the International Energy Agency’s (IEA) Task 39 released a report on the state of SAF production and availability in Q1 of 2024.

Jack Saddler, professor emeritus at the University of British Columbia, and Susan van Dyk, research associate with the University of British Columbia, shared the report’s findings during an October webinar. 

Saddler discussed Canadian—and specifically, British Columbian—efforts to address climate change through programs such as the BC-Sustainable Marine, Aviation, Rail and Trucking Fuels Consortium (BC-SMART), while van Dyk explained the pros and cons of different SAF production pathways, various technologies’ commercialization statuses, policy’s role in the industry’s buildout, and progress made thus far in displacing fossil-based jet fuel. 

SAF has a key role to play in reducing aviation emissions, constituting 65% of the total emissions reductions needed to reach net zero by 2050, van Dyk explained. A volume of 400 billion liters (approx. 105.6 billion gallons) must be produced annually to reach net zero, but current production levels are still below 1% of the volume needed by 2050, she said.

It may seem that SAF is moving forward by leaps and bounds. As according to the International Civil Air Organization, there are 337 SAF production facilities that are announced, under construction or operational, and a total of 127 airports have distributed SAF and signed offtake agreements for 53 billion liters (approx. 14 billion gallons) of fuel. However, van Dyk cautioned against an overly optimistic view of these numbers, because many of the facilities may not be completed, and offtake agreements are essentially a memorandum of understanding with the purpose of helping SAF production facilities obtain funding. Though hundreds of projects have been announced, data indicates that it is likely many of the projects will fail, with the success percentages ranging from 25% to 50%. “Not all these companies will succeed, that’s just the reality,” van Dyk said.

Understanding Timelines 
A total of 11 technology pathways are approved for SAF production, including the hydrotreated esters and fatty acids process (HEFA), alcohol-to-jet process, Fischer-Tropsch and others. “I think what people forget sometimes is that ASTM approval does not mean that the technology is commercial or that the fuel produced will be sustainable—ASTM is only concerned with the safety aspect,” van Dyk said.

These pathways do not all offer the same degree of sustainability benefits or possess the same level of commercial viability. “When we [anticipate] how fast technologies are going to become commercial, and how quickly we will see production and expansion, HEFA is still the only fully commercial technology,” she said. “And it’s generally agreed that by 2030, the majority of SAF will come from HEFA.” 

However, the limited volume of waste fats and oils requires other technologies to fill in the gap, and many of these technologies are not going to be able to scale up in time, according to van Dyk.  She explained that people overestimate how quickly these technologies will move through technology readiness levels (TRL) and reach fully commercial stage. Moving through each of the nine TRL stages takes two to three years. “[If] a company is only at pilot scale, that should tell you that, realistically, it’s going to be years before they reach commercial scale—regardless of what they try to tell you, it will take time,” she said. For example, even after permitting, financing and construction are complete, it may take a company an entire year of commissioning before the plant runs at full capacity. Average construction times for SAF facilities using complex technologies like gasification stand at around five years.  

Many investors are wary of new SAF technologies because they remain a high-cost, high-risk investment. At conferences, investors have communicated that they are waiting for the first project to prove itself and succeed before they jump onboard, van Dyk explained.

Overly optimistic scaling is another issue. Companies with novel SAF technologies may announce plans to jump from pilot plant up to a 200- to 400-liter facility, but that speed of scaling may be problematic. Van Dyk provided the example of Fulcrum BioEnergy, a plant that turned municipal solid waste into ethanol and then SAF, explaining that some within the industry believed that the 40-million-liter plant scaled up too soon. When looking at the data, it appears unlikely that the U.S. and European Union will be able to achieve 2030 goals. “We have to be realistic,” she said. “Things are going to [be] slower than we think. And the reality is that the targets are so ambitious that meeting these SAF targets will be extremely challenging.”

Sourcing Challenges 
Supply chains for forest and agricultural residues are nonexistent, which is a problem, van Dyk explained. It is easy for feedstocks and supply chains to be a “forgotten critical issue” when understanding a technology’s potential. Many of the lowest-carbon-intensity feedstocks also have the lowest energy density and are the most spread out geographically, making an efficient, cost-effective supply chain crucial. Agricultural supply chains exist, but they are not designed for transporting low-energy feedstocks such as crop residues, which also are not economical to transport over long distances, van Dyk explained. Because of this, the feedstock must be located near the biorefinery, which may cause difficulties when trying to position the fuel source near a large airport.

SAF Percentages 
When hearing about a new SAF project, those interested in the progress of the SAF industry must keep in mind that 95% of  technologies actually produce varying ratios of SAF alongside other fuels, including renewable diesel and light ends such as naphtha (which can be converted into gasoline). “Some companies say that they’re going to produce SAF because this is sort of the buzzword,” van Dyk said. In reality, she explained, these facilities determine how much of which fuel they would like to produce depending on the economic advantage it provides. Choosing to produce a higher ratio of jet fuel requires them to add more processing equipment, making the process more expensive, thus lowering a plant’s incentive to produce SAF. 

Misconceptions about the total capacity of a SAF plant can lead to an overestimation of the total volume of SAF being produced, van Dyk said. Several factors make HEFA a more attractive process for producing renewable diesel rather than SAF. A HEFA refinery initially produces 15% SAF, but that could be increased to 50% or more with extra investment. However, increasing a facility’s ratio of SAF to over 50% of total volume reduces overall yields of liquid fuels by 10% and requires the addition of second hydrocracker, van Dyk said. “Not only do you have a bigger investment and it’s more expensive, but you also have a lower yield of valuable liquid hydrocarbon products,” she said. “SAF production from HEFA biorefineries is not favorable economically unless there are additional policy drivers.” Currently, U.S. policy offers higher tax credits for renewable diesel, which may disincentivize SAF production. However, there are other pathways attracting attention from project developers, policymakers and investors.

Ethanol: Crop or Cellulosic? 
The alcohol-to-jet (ATJ) pathway, frequently discussed with ethanol as the feedstock, is another production method that has garnered attention due to projects such as LanzaJet’s Freedom Pines facility in Soperton, Georgia. Usage of sugarcane ethanol as a feedstock for the ATJ process constitutes a “low-hanging fruit,” explains van Dyk. The United Kingdom and EU do not recognize crop-based ethanol’s potential, requiring ATJ SAF to be derived from cellulosic sources. “If you look at technoeconomic analyses for SAF from cellulosic ethanol, the minimum selling price is more than double that of corn ethanol-to-jet,” van Dyk said. Price is not the only problem; cellulosic ethanol has not attained widespread commercial production. Van Dyk explained that since the first cellulosic ethanol project started in 2013, most projects have failed or only attained limited success due to a variety of factors.

One of the challenges is the large-scale storage required for the massive amounts of residue required to operate throughout the year. Van Dyk referenced a technoeconomic analysis that stated a 200-million-liter facility would need a total of 2 million bales stored. When stored for long periods of time, crop residue tends to degrade, impacting process yields. She highlighted the efforts of Idaho National Laboratory in seeking solutions for the degradation problem, explaining that their research is “substantial” in eliminating the challenges preventing widespread commercialization.  
Crop-based ethanol does not face these feedstock problems and is already being widely produced. “With alcohol-to-jet, we have the potential opportunity to use crop-based ethanol to prove all these different technologies,” she said. “And the other benefit with ethanol is that because it’s a high-density intermediate ... it can be transported over long distances, which is already happening.”

Fischer-Tropsch Complications 
The Fischer-Tropsch process begins with gasification of biomass into syngas, which then goes through Fischer-Tropsch synthesis, followed by hydrotreating/hydrocracking. The closure of the first commercial Fischer-Tropsch refinery, Fulcrum BioEnergy, will have a negative impact on commercializing this technology because it highlights the challenges faced by this process, van Dyk explained. Feedstock complexity was the major problem for the defunct facility, with some reports citing buildup of a “cement-like substance meters deep in the gasifier” and formation of corrosive nitric acid, she said.

Feedstock challenges are a significant barrier to commercializing Fischer-Tropsch SAF. “You get the tar formation and contaminants, the syngas cleanup is expensive because of the oxygen in the biomass, and you get a very low hydrogen-to-carbon ratio,” van Dyk said. “You have very low feedstock density, so transportation costs are expensive, and you have to build the facility closer to the feedstock. There are all these project challenges because these feedstocks haven’t previously been used.”

The syngas conversion portion of the process is commercialized, but for biomass-based Fischer-Tropsch SAF projects, the challenge lies in the feedstock. Van Dyk explains that the process is proven commercially when natural gas is used as the feedstock, but biomass and waste sources present a challenge due to ash content and processing.

Power-to-Liquids 
The power-to-liquids process utilizes carbon dioxide—collected through direct air capture or point source capture—and employs the water-gas shift reaction to make carbon monoxide (CO). After that CO is combined with hydrogen produced via electrolysis using water and renewable electricity, a syngas is created. The syngas can be upgraded to SAF through a Fischer-Tropsch synthesis or methanol synthesis. This pathway is a favorite in the EU, which has a current mandate requiring 600 million liters of eSAF by 2030, but meeting this goal is unlikely, according to van Dyk. “While there’s been a lot of announcements of power-to-liquids companies, most are not at final investment decision stage and, ... if you look at that seven-year timeframe, it’s going to be very, very difficult to get that,” she said. Although elements of the process such as electrolysis and Fischer-Tropsch are commercial, CO2 capture is not widely proven and the water-gas shift reaction is still at a lower TRL.

Renewable electricity is in high demand, and supplies are strained as electricity usage for EV charging, heating, decarbonizing the grid and other applications increases. Van Dyk referenced a McKinsey study that found 36 megawatts per hour are needed to make one ton of efuel; that number increases to roughly 1.1 terawatts of electricity per 50,000 tons of efuels when direct air capture (an energy-intensive technology) is used to collect the CO2 needed. 

The draw of this technology is its “theoretically unlimited potential,” according to van Dyk, and it could be a good solution if the price of renewable electricity drops significantly.

Flying Forward 
With the current goals set by governments and organizations around the world, there is still a tremendous amount of work to be done before these goals will be achievable. Overcoming the cost differential is vital, according to van Dyk. Currently, HEFA-produced SAF costs over $2,000 per ton, while conventional jet fuel costs about $700 per ton. That significant gap must be addressed via long-term policies to push these production technologies toward commercialization by derisking investment.

“We’re going to see a higher cost of producing SAF for a long, long, time,” she said. “We have limited availability of feedstocks and there’s limited investment. I think companies will tell you there’s a lot of funding out there, but the problem is that it is still very high risk because these technologies have not been proven yet.”

Stable policy will help derisk investment to improve commercialization, but moving a technology from pilot to full commercialization will take time. “A country might say, ‘Okay, we want 10% by 2030,’” van Dyk said. “But that is just an ambition until there are policies put in place to actually achieve that.”

Author: Katie Schroeder 
Associate Editor, Biomass Magazine 
Katie.schroeder@bbiinternational.com