An Alternative Pathway to Sustainable Aviation Fuel

September 05, 2025

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by Alexei Beltyukov and Stephen Sims (Universal Fuel Technologies/SAF Magazine) ... FT processes remain more expensive than HEFA, primarily due to higher capital costs per unit of production capacity and more complex production processes.

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FT plants making SAF will produce up to 20% byproduct of renewable naphtha or liquid petroleum gas (LPG). While these materials can reduce carbon intensity in fossil fuels or as chemical feedstocks, their economic value falls short of SAF. Additionally, FT plants that process gasified waste are often located far from potential buyers of naphtha or LPG, further complicating their monetization.

Biofuel engineers are making notable progress in increasing the economic viability of FT by finding new opportunities for its low-value byproducts. Emerging technologies for renewable naphtha include using it for an integrated hydrogen unit that turns renewable feed sources into hydrogen with low greenhouse gas emissions. One add-on chemical process can upgrade renewable naphtha and LPG into aromatic SAF, a molecule type that FT does not make but is needed in jet fuel. Both the HEFA and FT pathways only produce paraffinic SAF. A way to produce this type of molecule from a low-value byproduct would unlock the economic viability of distributed FT and HEFA plants, enabling their widespread adoption.

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Even before the 100% SAF becomes a reality, a producer that can offer a fully fungible product like drop-in SAF with a molecular composition matching that of a fossil jet fuel would be able to use common carrier pipelines and fuel storage facilities, saving costs and making it easier for the airports and airlines to use their product.

A significant way to decrease the cost-per-unit of FT SAF and increase the technology's economic viability is to increase the value of the byproducts. With 20% of the plant's output transformed from low-value naphtha and LPG to high-value aromatic SAF, this technology increases the plants revenue by anywhere from 10% to 20%. Including this add-on technology would make the FT plant a better investment, produce more cost-competitive SAF with conventional fuels, and enable a fully synthetic, 100% drop-in-ready product that can be sold directly to airlines without blending, once ASTM-approved.

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SAF is a crucial element in aviation's mission to reduce carbon emissions, offering a scalable solution that works with existing infrastructure while addressing waste management challenges. Meeting the International Air Transport Association's net-zero emissions goal by 2050 will require substantial investments in SAF technologies and infrastructure, with estimates suggesting investments in the hundreds of billions of dollars across the supply chain.

The pathway to sustainable aviation involves multiple parallel approaches. While HEFA technology has paved the way for initial SAF adoption, the industry must diversify its production methods to meet future demand. FT pathways, despite challenges in initial capital costs and waste management integration, offer auspicious opportunities. By optimizing byproduct utilization and effectively processing solid waste, this technology addresses multiple environmental challenges simultaneously: reducing aviation emissions, managing municipal waste and decreasing reliance on fossil fuels.

As the industry continues to evolve, integrating waste-to-fuel technologies with existing infrastructure and developing new processing capabilities will be crucial. These advancements will not only support aviation's sustainability goals but also contribute to a broader circular economy, where waste materials become valuable resources. With continued investment in research, development and scaling of these technologies, the aviation industry can work toward a future where sustainable fuel is not just an alternative, but a new standard. READ MORE

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Expanding Beyond HEFA with Feedstock Diversity (GAFT/SAF Magazine)

Excerpt from GAFT/SAF Magazine: But as the industry begins to mature, a critical constraint is coming into focus: the tightening supply of waste-based lipid feedstocks such as used cooking oil (UCO) and tallow. These feedstocks, once seen as abundant and underutilized, are now facing unprecedented demand not only from SAF producers, but also the broader biofuels and oleochemical markets. The challenge is already affecting project development. Several large-scale SAF facilities have been delayed, scaled back or shelved due to concerns over long-term feedstock availability.

Compounding this issue is the growing scrutiny over the traceability and authenticity of the feedstocks that do make it to market.

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The EU’s ReFuelEU regulation excludes food- and feed-based oils from eligible SAF feedstocks and introduces submandates for synthetic aviation fuels starting in 2030. The U.K. SAF mandate includes a hard cap on HEFA use, limiting it to 71% of total SAF volumes by 2030. In the United States, trade tensions and proposed tax credit revisions could disincentivize the use of imported UCO, placing further pressure on domestic feedstock supply. With mandates rising and lipids running short, the SAF industry faces a fundamental question: How do we scale beyond HEFA without abandoning the infrastructure already in place?

New Feedstocks for a Proven Platform
This is where new technological approaches are beginning to gain attention. One promising pathway lies not in abandoning HEFA, but in rethinking its inputs. Dutch company GAFT is developing a system to produce SAF-compatible lipids from nonfossil, nonfood carbon sources. Their approach combines electrochemistry and fermentation: first converting CO2 and water into volatile carboxylic acids (VCAs) using renewable electricity, then feeding those acids into a microbial fermentation process that produces lipids and proteins.

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SkyNRG’s report estimates that by 2050, under a current-trends scenario, SAF demand will reach 196 mmt, roughly 13 times today’s supply. If the world is to meet this target without exhausting waste oil supply or triggering indirect land use change from crop-based feedstocks, a major diversification of inputs will be needed. Their modeling shows that while HEFA can continue to play a role, only about a quarter of 2050 SAF demand can be met from lipid-based sources. The remainder must come from advanced biofuels, e-fuels and other non-HEFA pathways. In the best-case scenario, in which sustainability rules, policy support and technology readiness align, the SAF sector could fully substitute fossil jet fuel by 2050, reducing aviation emissions by up to 1.1 billion mt of CO2 annually.

Getting there, however, will require more than incremental change.

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To scale sustainably, producers need feedstock strategies that are both diverse and regionally adaptable—producers must be able to work with what is locally available, whether that be CO2, industrial residues or biomass.

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If the past decade was about proving that SAF works, the next will be about making it work at scale, in every geography, under every constraint. That means unlocking new carbon streams, upgrading underutilized residues and integrating SAF production into broader energy and agricultural systems. The future of SAF is not just about refining, it is about reimagining the supply chain from the molecule up. READ MORE

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woody biomass waste management used cooking oil (UCO) syngas (synthesis gas) Sustainability supply chain precursors/biointermediates pathways naphtha/bionaphtha/renewable naphtha MSW (Municipal Solid Waste) Methanol/Biomethanol/Renewable Methanol liquid petroleum gas (LPG) Jetfuel (Sustainable Aviation Fuel (SAF)) Investing Hydrocarbon-Hydroprocesed Esters and Fatty Acids (HC-HEFA-SPK) history HEFA (Hydro-processed esters and fatty acids) forest residue/waste FOG (Fats/Oils/Grease) Fischer-Tropsch/FT Fischer-Tropsch Synthetic Paraffinic Kerosene with Aromatics (FT-SPK/A) Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK) Fischer-Tropsch Synthetic Kerosene with Aromatics (FT-SKA) fermentation ethanol/bioethanol drop-in biofuels/hydrocarbons co-products butanol/biobutanol BioChemicals/Renewable Chemicals Bio LPG (Bio Liquid Petroleum Gas) Aviation Fuel/Sustainable Aviation Fuel (SAF) ASTM aromatics Agricultural waste/residue Netherlands Carbon Dioxide (CO2) water Lipid glycerin European Union (EU) environmental policy Transportation Fuels Policy

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