J. NAVA, BBA Consultants, Toronto, Ontario, Canada
Commercial aviation accounts for roughly 2% of global anthropogenic carbon dioxide (CO2) emissions and approximately 12% of transport‑sector emissions.1 Without intervention, international aviation emissions are forecast to triple by 2050.2 Electric or hydrogen (H2) propulsion remains impractical for long‑range flights, so sustainable aviation fuel (SAF) has become the primary near‑term decarbonization option. SAFs are drop‑in fuels produced from non‑petroleum feedstocks that can reduce lifecycle greenhouse gas (GHG) emissions by up to 94%.3 Multiple SAF production pathways exist, but only a few have commercial approval and scale.
This article analyzes future trends for major pathways—hydroprocessed esters and fatty acids (HEFA), Fischer–Tropsch (FT) and gasification‑FT (GFT), alcohol-to-jet (ATJ), and fast pyrolysis (FP)—and asserts that the FT pathway may become dominant. Technical, commercial, logistics and environmental, social and governance (ESG) aspects are discussed, as well.
Overview of current SAF pathways. The major ASTM International-approved pathways for SAF production are summarized in TABLE 1. HEFA uses triglyceride feedstocks (waste fats, used cooking oil and vegetable oils) that are hydroprocessed into synthetic paraffinic kerosene (SPK). The FT pathway gasifies biomass, municipal solid waste (MSW) or energy crops into syngas, which is upgraded via the FT reaction and hydroprocessing into jet fuel.3 ATJ dehydrates and oligomerizes ethanol or isobutanol (from cellulosic biomass or sugar crops) before hydrogenation to jet fuel.3 FP rapidly heats biomass to produce a bio‑oil intermediate that is then hydrotreated. Each pathway’s technology readiness level (TRL), blending limit, typical lifecycle GHG reduction and key challenges are summarized in TABLE 1.
Commercial trends and production outlook.
HEFA: Maturing but limited by feedstock supply. The hydroprocessing of lipids dominates SAF production. Pan American Finance estimates that HEFA accounts for > 90% of production and announced capacity through 2030.4 Mature refinery hydroprocessing units can be repurposed for HEFA, and the pathway is already approved for 50% blending.3 However, the availability of waste fats and oils is limited. The International Energy Agency (IEA) estimates global waste fats and oils at 34 MMt–42 MMt, sufficient for only ~10 % of expected SAF demand.5 Competition with renewable diesel and contradictory data in used cooking oil imports highlight governance challenges.5 Many HEFA projects rely on first‑generation oilseed crops such as soybean or palm oil, raising indirect land‑use change concerns, as well.
FT/GFT: Potential for scale and dominant future pathway. The FT process can use abundant feedstocks (forestry residues, agricultural waste, MSW, energy crops) and benefits from decades of coal‑to‑liquids operations. Gasification and FT individually are commercial, but their integration with biomass feedstocks is nascent. The U.S. SAF Grand Challenge aims for 3 Bgpy of SAF production by 2030, increasing to 35 Bgpy by 2050—the National Renewable Energy Labratory (NREL) details that HEFA will supply most volumes to 2030, while FT and ATJ contribute smaller amounts.8 However, demonstration plants must be built soon for FT to contribute to the overall production pool by 2030.8 FT research focuses on improving catalyst selectivity because traditional cobalt or iron catalysts follow the Anderson–Schulz–Flory distribution (kerosene fraction of ~40 %). New bimetallic catalysts, the addition of water vapor and microchannel reactors can increase jet fuel selectivity and conversion efficiency.5 The coprocessing of FT liquids, up to 5%, in refineries was initiated in 2020. At the time of this publication, the possibility of raising the limit to 30% was under review.
Recent commercial developments illustrate both promises and challenges. Fulcrum BioEnergy’s Nevada (U.S.) plant processed 175,000 tpy of MSW to produce ~11 MMgpy of SAF and diesel but required > $500 MM in capital—the facility ceased operations in 2024.4 Red Rock Biofuels’ woody biomass project closed before completion, whereas Velocys plans to convert 100,000 tpy of wood waste into 20 MMgpy of SAF.5 High capital intensity, syngas clean‑up requirements, feedstock aggregation and project finance remain barriers to this production pathway. Nevertheless, the ability to tap diverse residues and MSW, the potential integration with carbon capture and power‑to‑liquids (PtL) technologies, and high GHG reduction (> 86 %)6 position FT/GFT as a dominant long‑term pathway.
ATJ: Moderate growth potential. ATJ leverages existing ethanol/isobutanol production infrastructure. ATJ technology benefits from mature components (dehydration, oligomerization and hydrotreating) and flexible feedstock options.2 LanzaJet’s Freedom Pines Fuels plant aims to produce 9 MMgpy of SAF using ethanol, and several companies are exploring methanol-to-jet pathways. However, ATJ remains energy‑intensive, and ethanol‑derived jet is currently limited to 30% blending.3
FP: Emergent pathway for forest residues. FP or catalytic FP rapidly heats biomass to 500°C–600°C (932°F–1,112°F), creating a liquid bio‑oil that can be stabilized via catalytic upgrading and then hydrotreated into jet fuel. NREL’s catalytic FP program notes that this approach yields a stabilized oil with reduced oxygen content, derisking transportation and storage.7 Forest residues and woody wastes offer large resource potential—133 MM dry tons could supply roughly 8 Bgpy of hydrocarbon fuels.7 Catalytic FP can use low‑cost zeolite catalysts without co-fed H2, but lacks integrated scale-up data.7 While the pathway may complement FT and HEFA by tapping underutilized lignocellulosic resources, it remains at pilot scale, with no ASTM International annex yet. Lifecycle analyses indicate a 36%–67% GHG reduction, but hydrotreating requires significant H2, affecting cost and carbon intensity.
Logistics and supply chain considerations. SAF must meet stringent quality and blending requirements. After a synthetic kerosene component passes ASTM D7566, blending with Jet A must occur upstream of use; the final blend is redesignated under the conventional Jet A standard (ASTM D1655), enabling transport in existing pipelines.1 Each batch generates a certificate of quality, and retesting at supply chain hand‑offs ensures traceability.1 The mode of transport depends on production location and volume: Jet A primarily moves by pipeline, while neat biofuels from standalone plants typically travel by rail, barge or truck.1 Co-processed SAF from a petroleum refinery can be shipped by pipeline alongside Jet A. The NREL recommends blending SAF at terminals rather than airports because terminals already have blending equipment; whereas, blending at airports would require expensive equipment, insurance and increased truck traffic. Neat SAFs from different ASTM annexes cannot be commingled before blending.1
The supply chain also hinges on feedstock logistics. HEFA feedstocks are dispersed and face competing demands from food and fuel markets, raising traceability and fraud concerns. FT and FP pathways require large volumes of biomass or waste, necessitating regional aggregation, densification and long‑distance transport, which increases costs and emissions. Municipal waste and forestry residues are often wet or bulky; densification technologies and contractual agreements with waste management entities are crucial. ATJ and direct sugars to hydrocarbons (DSHC) rely on fermentable sugars or alcohol; thus, the logistics mirror existing biofuel supply chains but may compete with food or feed uses. Overall, building reliable feedstock supply chains and blending infrastructure are as important as conversion technology.
ESG considerations. The following are ESG items to consider:
Environmental: All SAF pathways offer significant GHG reductions compared with fossil jet fuel.6 FT/GFT pathways can even achieve net‑negative emissions when paired with carbon capture and storage, while HEFA and ATJ reductions depend strongly on feedstock type and H2 source. HEFA production raises indirect land‑use change and biodiversity concerns when vegetable oils are sourced from primary crops. FT and pyrolysis rely on waste and residue streams, minimizing land‑use impacts but potentially emitting particulates during biomass collection and gasification. ATJ and DSHC require sustainable sugar or alcohol supplies; large‑scale sugar production may drive deforestation or fertilizer runoff.
Social: SAF deployment can generate rural jobs in feedstock production and biorefinery operations. However, community acceptance depends on responsible feedstock sourcing. HEFA projects have faced complaints of overusing low‑wage labor in used‑oil collection, whereas municipal‑waste‑to‑jet projects may reduce landfill burdens and create local employment.4 Transparent certification and fair contract arrangements are necessary to ensure equitable benefits.
Governance: Governments influence SAF deployment through mandates, incentives and sustainability criteria. As previously mentioned, the U.S. SAF Grand Challenge targets 3 Bgpy of SAF production by 2030, increasing to 35 Bgpy by 2050.8 The EU’s ReFuelEU Aviation initiative requires airlines to use 2% SAF by 2025, increasing to 70% by 2050.2 Sustainability frameworks such as CORSIA and the Renewable Fuel Standard specify eligible feedstocks and lifecycle accounting rules, but enforcement varies. Clear governance on feedstock traceability and certification will be essential for public acceptance.
Why FT may become the dominant pathway for SAF production. Several trends point toward FT/GFT becoming the dominant SAF pathway beyond the mid‑2030s:
Feedstock flexibility and scale: FT can convert a wide variety of non‑food feedstocks—including MSW, agricultural residues and dedicated energy crops—into high‑quality fuels.3 Such feedstocks are abundant—e.g., the U.S. has hundreds of millions of tons of forestry and agricultural residues. In contrast, HEFA feedstocks are limited to tens of millions of tons.5
Superior GHG performance: Lifecycle analysis shows FT pathways provide the highest GHG reductions (86%–104%) among current SAF options, especially when coupled with renewable H2 and carbon capture.6
Integration potential with refineries: Coprocessing FT synthetic liquids, up to 5%, in existing petroleum refineries is already proven. Coprocessing limits could increase to 30%, enabling rapid capacity growth without building entirely new infrastructure. This integration also simplifies logistics since co-processed SAF travels by existing pipelines.1
Technological improvements: Advances in gasifier design, microchannel FT reactors and catalysts are improving yields and reducing capital intensity.2 R&D is addressing syngas cleanup and catalyst selectivity issues.5
Policy momentum: Numerous countries have announced waste‑to‑fuel incentives, and other government programs (e.g., the U.S. Inflation Reduction Act) provide production credits for waste‑based SAF. These policies disproportionately favor FT/GFT projects using MSW and residues.
Nevertheless, significant hurdles remain. High capital costs, long project development timelines and challenges in financing first‑of‑a‑kind biorefineries have delayed many FT projects.4 Syngas cleanup and oxygen removal are technically demanding and require robust catalysts and gas separation systems.5 Achieving widespread adoption will require coordinated policy support, risk‑sharing mechanisms and sustained R&D.
FIG. 1 illustrates estimated lifecycle GHG reduction ranges for the major SAF pathways discussed in this article. While ranges vary by feedstock, process energy source and allocation method, FIG. 1 highlights the superior climate performance of FT/GFT relative to other pathways.
Baseline costs and learning rates for SAF production pathways are detailed in TABLE 2. Projected levelized costs of SAF production pathways from 2025–2050 are shown in FIG. 2.
Fossil jet fuel costs have historically ranged around $10/GJ–$20/GJ.12 Conversely, current SAF production costs are higher, with HEFA (most commercially mature) at roughly $30/GJ–$40/GJ in 2025.10,11 HEFA’s cost is dominated by feedstock prices, so reductions are limited.10
Emerging thermochemical pathways like FT and FP are estimated at $50/GJ–$60/GJ today9,12 but have greater potential reductions. GFT from MSW can be cheaper initially (~$45/GJ) due to waste credits.10 ATJ costs vary depending on feedstock: ~$40/GJ–$45/GJ for sugar/starch ethanol, and up to ~$78/GJ for cellulosic ethanol.9
Learning rates of 5%–20% per doubling of cumulative production are typical for advanced biofuels.11 This analysis uses 5% for HEFA (feedstock-limited); 15% for FT, GFT and FP (early-stage, high scaling potential); and 12% for ATJ (fermentation mature, upgrading new).11
Takeaways. HEFA currently dominates the SAF market due to technical maturity and existing refining infrastructure. However, limited lipid feedstocks and competition with renewable diesel constrains its long‑term scalability. ATJ is progressing but faces high costs and limited blending allowances. FP offers a promising route for utilizing abundant forest residues but is still at pilot scale. The FT pathway—particularly when integrated with the gasification of wastes and residues—stands out as the only option capable of scaling to tens of billions of gallons while delivering the largest GHG reductions. Continued R&D in catalysts and integration, supportive policies, robust supply chains and careful attention to ESG factors will determine whether FT becomes the dominant SAF pathway in the coming decades. HP
LITERATURE CITED
NREL, “Sustainable aviation fuel blending and logistics,” September 2024, online: https://docs.nrel.gov/docs/fy24osti/90979.pdf
Idrissov, C., “Sustainable aviation fuel: Key market drivers and production tech,” November 15, 2024, online: https://www.idtechex.com/en/research-article/sustainable-aviation-fuel-key-market-drivers-and-production-tech/32080
U.S. Department of Energy, “Sustainable aviation fuel,” Office of Critical Minerals and Energy Innovation, Alternative Fuels Data Center, online: https://afdc.energy.gov/fuels/sustainable-aviation-fuel
Pan American Finance, “Global sustainable aviation fuel report: Production pathways and feedstock,” 2025, online: https://panamericanfinance.com/insights/energy-transition/global-saf-report-2024/production-pathways-and-feedstock-saf24/
Van Dyk, S. and J. Saddler, “Progress in commercialization of biojet/sustainable aviation fuel (SAF): Technologies and policies,” IEA Bioenergy, January 2024, online: https://www.ieabioenergy.com/wp-content/uploads/2024/06/IEA-Bioenergy-Task-39-SAF-report.pdf
De Jong, S., et al., “Lifecycle analysis of greenhouse gas emissions from renewable jet fuel production,” Biotechnology for Biofuels and Bioproducts, March 14, 2017.
Griffin, M., “Production of sustainable aviation fuel from woody biomass via catalytic fast pyrolysis and hydrotreating,” NREL, 2024, online: https://www.gti.energy/wp-content/uploads/2024/09/31-tcbiomass2024-Presentation-Michael-Griffin-V2.pdf
Rosales, O., et al., “Sustainable aviation fuel (SAF) state-of-industry report: State of SAF production process,” NREL, July 2024, online: https://docs.nrel.gov/docs/fy24osti/87802.pdf
De Jong, S., et al., “Cost optimization of biofuel production—Harmonized techno-economic assessments,” Biotechnology for Biofuels, 2017.
Pavlenko, N., S. Searle and A. Christensen, “The cost of supporting alternative jet fuels in the European Union,” International Council on Clean Transportation (ICCT), March 20, 2019, online: https://theicct.org/publication/the-cost-of-supporting-alternative-jet-fuels-in-the-european-union/
IEA, “Advanced biofuels—Potential for cost reduction,” IEA Bioenergy, 2020, online: https://task39.ieabioenergy.com/wp-content/uploads/sites/37/2020/02/Advanced-Biofuels-Potential-for-Cost-Reduction-Final-Draft.pdf
Yang, F. and Y. Yao, “Sustainable aviation fuel pathways: Emissions, costs and uncertainty,” Resources, Conservation and Recycling, April 2025.
Joe Nava is a process design and project management expert with > 36 yrs of experience in EPC/EPCM, spanning oil, gas, petrochemicals and advanced low-carbon fuels. Nava is specialized in hydrogen, ammonia, methanol, SAF and decarbonization projects worldwide, integrating technical depth with financial modeling, strategy and execution excellence.