Progress in Commercialization of Biojet/Sustainable Aviation Fuels (SAF): Technologies and policies

IEA Bioenergy Task 39 has already published several SAF related reports, with the latest dedicated report in 2021 (on biojet/SAF commercialization). The current report has a dominant focus on technologies, key developments in commercialization and recent research-and-development trends.

Download the full report: “Progress in Commercialization of Biojet/Sustainable Aviation Fuels (SAF): Technologies and policies”

In the past few years, the production and use of SAF have grown substantially. IATA estimated SAF production reached 300-450 million liters in 2022, a significant increase from the 2021 production of 100 million liters. In addition to the increasing availability of SAF, the number of new facilities that have been announced and are under construction should result in an exponential increase in SAF production by 2030. This has been partially driven by SAF-specific policies in jurisdictions such as the EU (the ReFuelEU Aviation mandate) and the USA (the Inflation Reduction Act (IRA) and state-specific SAF tax credits).

There has been significant progress in the commercialization of technologies accompanied by considerable investment in research and development. As there are specific challenges associated with various pathways, the lipid-derived HEFA-pathway – currently the only fully commercial pathway – will continue to supply the majority of SAF volumes up to 2030. However, alternative technologies, such as gasification with Fischer-Tropsch and alcohol-to-jet, are nearing commercial status. Although several companies are pursuing the power-to-liquids technology for efuels SAF production, this pathway is at a lower technology readiness level, with components of this technology, such as the reverse water gas shift reaction, still needing to be fully resolved.

As well as the technical challenges outlined in this report, it is probable that SAF-specific policies will have the greatest impact on SAF expansion. Although the lipid-to-biojet process supplies the vast majority of SAF that is used to date, there will be increasing competition for lipid feedstocks from bio/renewable diesel producers. While technology developments, aiming at a broader feedstock base, will play a role in resolving this dilemma, it will likely be the use of enabling policies that will facilitate the aviation sector to attain its 2030 and 2050 decarbonisation targets.

Some highlights related to the different SAF production pathways:

• Although the lipid derived HEFA pathway has been fully commercial for some time, it has been primarily used to produce renewable diesel rather than SAF. The decision to shift to increased SAF production will likely be based on financial considerations, with policy playing a key role. The availability of waste/lower carbon Intensity (CI) feedstocks (e.g. Fats, Oils and Greases) will soon limit the production of bio/renewable diesel and SAF via the HEFA pathway as crop-derived lipids

typically come at a higher CI or may have other sustainability challenges.

• Gasification of biomass produces syngas that can be used in multiple pathways to produce SAF. Syngas can be used for SAF production via Fischer-Tropsch synthesis or via a methanol intermediate and methanol-to-jet conversion. Alternatively, the syngas can be fermented to ethanol, with the alcohols converted into SAF via the alcohol-to-jet pathway. Multiple projects that use these different pathways have been announced. While the Fischer-Tropsch process is fully commercial, the preceding processing steps, as well as the overall integration of the process, have yet to be fully commercialized. Several other gasification-based facilities are planned or under construction in North America and Europe by companies such as Velocys, DG Fuels, Enerkem, and Fulcrum Bioenergy.
• The first small-scale commercial Alcohol-to-Jet (AtJ) facility of Lanzajet is expected to be completed and commissioned in early 2024. Multiple other facilities based on the AtJ technology are planned across the globe, and several companies are offering integrated technologies that could be licensed. Facilities will differ in their approaches to ethanol production or supply. Although there is an ongoing debate around corn ethanol and its carbon intensity, sugarcane ethanol has been shown to have a very low carbon intensity (CI) and will likely be a target feedstock for SAF production (while cellulosic ethanol develops). For the case of cellulosic ethanol via gas fermentation or alternative pathways, a major challenge will be the cost of the ethanol and, therefore, the cost of the SAF.
• The Power-to-liquids (PtL) pathway is considered a sustainable route for producing SAF as it does not require any biomass feedstocks or related land use. While it can achieve low carbon intensity SAF, this will be highly dependent on the source of electricity used for hydrogen production and the source of CO₂. A significant consideration for the PtL pathway is the high cost of production, which is far higher than SAF technologies based on HEFA and ATJ. Substantial technology development still has to occur for the PtL pathway to achieve commercial status. Several companies aim to commercialise PtL technologies, most of them are located in Europe, arguably driven by the ReFuelEU policy that establishes a dedicated sub-target for SAF volumes via this route.
• Co-processing to produce lower carbon-intensive (CI) jet fuels: During 2022/23, about six refineries in Europe started producing lower carbon-intensive jet fuels through co-processing, and further plans for refinery co-processing were announced by another seven refineries. Refinery co-processing is based on the insertion of 5% lipids in the hydrotreater (as approved by ASTM), with plans to increase the level to 30%. It should be noted that the 5% bio-intermediate inserted will not translate into a 5% actual jet fraction as it will depend on the carbon chain-length of the bio-intermediate and the specific processing carried out in the refinery.
• Direct thermochemical liquefaction pathways for SAF production (pyrolysis, catalytic pyrolysis and hydrothermal liquefaction): Production of SAF via a bio-oil/biocrude intermediate has been challenging and is at a lower development stage than other pathways. Projects in the EU and US continue to explore the usage of sewage sludge and hydrothermal liquefaction as a pathway for SAF production, but this is still at a low TRL level.