Beyond the HEFA Tipping Point
To decarbonise aviation globally, sustainable aviation fuel (SAF) production must scale up. The HEFA pathway can provide a (relatively) low-cost route to SAF and involves the extraction of oils, followed by hydrotreatment, isomerisation, and hydrocracking processes similar to those in petroleum refining
However, the feedstocks for HEFA/HVO processes are finite, with the “HEFA tipping point” expected to occur beyond 2030, as global SAF demand will outpace the availability of HEFA SAF. IDTechEx has published a report titled “Sustainable Biofuels and E-Fuels Market 2026-2036: Technologies, Players, Forecasts,” which forecasts global SAF capacity over the next decade and analyses emerging alternative SAF technologies.
ATJ pathway for SAF
The alcohol-to-jet (ATJ) process upgrades ethanol or methanol into hydrocarbon fuels suitable for blending with petroleum jet fuel. Kerosene and byproducts such as renewable diesel and gasoline are produced by dehydration, followed by oligomerisation, hydrogenation, isomerisation, and distillation. This technology is currently more expensive than the HEFA pathway, but is expected to become more appealing as the HEFA tipping point approaches. Some players developing technologies for this pathway include ExxonMobil, Honeywell UOP, LanzaJet, and Axens.
Another consideration is that ethanol is a first-generation biofuel whose green credentials are often debated, particularly given its impact on land use. This will lead to an eventual phase-out of conventional bioethanol in key regions such as the EU. However, the ATJ pathway will still be viable for other routes. IDTechEx has reported that bioethanol can also be produced via low-carbon feedstocks such as captured carbon dioxide and cellulose.
Cellulosic ethanol production is a complex, expensive process in comparison to conventional ethanol production. As a result, there have been both project failures and success stories over the past 12 years. There are several facilities around the world that can produce cellulosic ethanol at ~10,000 tonnes per annum, from players such as Raízen and Versalis. The anticipated global increase in SAF demand could create more demand for cellulosic ethanol via the ATJ pathway.
Gasification
Gasification of biomass produces syngas, which can be used to produce bio-hydrogen, methanol, or longer-chain hydrocarbon fuels. Biomethanol markets have the most near-term potential, while biogas reforming has typically been the leading technology for biomethanol, it will soon be surpassed by new gasification projects, as biogas gasification offers lower upfront costs and a quicker payback time. Globally, demand for low-carbon methanol is driven by a need for clean marine fuels, decarbonisation of the chemical sector, and use as a feedstock for SAF.
There are fewer project developers targeting SAF via the gasification/Fischer-Tropsch route. IDTechEx has stated that key lessons must be learnt from past failures, such as the technical issues that caused the shutdown of Fulcrum BioEnergy’s plant in Nevada.
Alternative routes
Alternative biofuel pathways are being explored, but they are generally at lower technology readiness levels. Hydrothermal liquefaction and pyrolysis oil upgrading are promising, but only a small number of companies are active in this space. Additionally, third-generation algae biofuels hold significant potential, but it will likely take over a decade to achieve widespread commercial-scale production.
Outlook
For sustainable aviation fuels and renewable diesel, the HEFA/HVO pathway will continue to dominate production, but the long-term success of decarbonising global transportation requires alternative routes. These include second-generation biofuel pathways such as ATJ and gasification, as well as e-fuels and algae fuels. IDTechEx’s “Sustainable Biofuels and E-Fuels Markets 2026-2036: Technologies, Players, Forecasts” examines emerging e-fuel and biofuel technologies, identifying key players, drivers, and barriers for sustainable fuel market growth.
