Decarbonisation Technology November 2026 issue

Making biomass work for Sustainable Aviation Fuels Integrating torrefaction into the biomass-to-liquids process to convert biomass into a consistent gasifier feed

Harold Boerrigter Shell Catalysts & Technologies Patrick Bergman Yilkins

G lobal aviation is facing a significant requirements, and long-haul flight depends on high-energy-density liquid fuels, such as Jet A1. For these reasons, liquid hydrocarbons are likely to remain essential for long-haul aviation for many years ( IEA, 2020 ). Shell sees four main levers for reducing aviation emissions: lowering fuel consumption, developing electric and hydrogen-powered aircraft, scaling Sustainable Aviation Fuels (SAF), and using high- quality carbon credits to help bridge the timing gap while other options mature. Each has a role to play, but each also has its limitations. Newer aircraft can be significantly more efficient than previous generations. However, efficiency improvements can be outpaced by growth in air travel. Electric and hydrogen- powered aircraft are progressing, but their early impact is expected to be concentrated mainly in domestic and shorter-range aviation because of range and payload constraints ( IATA, 2024 ). SAF, by contrast, can be used within existing aircraft and fuel infrastructure without modification, although production will need to scale substantially to make a meaningful contribution to aviation decarbonisation ( IATA, 2026 ). The biomass opportunity decarbonisation challenge. Aircraft must meet stringent safety and performance SAF can be produced through several routes, each with different feedstock requirements and deployment considerations. An established pathway is hydroprocessed esters and fatty acids (HEFA), which use feedstocks such as vegetable oils, used cooking oils, and animal fats. These feedstocks are important, but their availability

may become increasingly constrained as SAF demand grows ( IATA, 2026 ). Alcohol-to-jet (ATJ) provides another route for expanding SAF production beyond HEFA. However, in the European market, first- generation ethanol derived from crop-based feedstocks is not eligible under the relevant advanced-fuel requirements. ATJ production would therefore need to rely on second- generation, or cellulosic, ethanol, which makes second-generation ATJ an important comparator for gasification-based biomass to liquid (BTL) pathways. Fischer–Tropsch synthesis is a third route, which could be competitive with second- generation ATJ in terms of levelised production cost under specific assumptions. Scaling SAF production will require routes that can move beyond limited pools of these types of feedstocks ( IATA, 2026 ). That is why attention is also turning to pathways that can use a wider range of carbon sources. In BTL, agricultural residues, wood waste, fractions of municipal solid waste, and other organic carbon resources are converted into synthesis gas (syngas) through gasification. This syngas can then be converted into hydrocarbons using the Shell Fischer–Tropsch Process, followed by downstream upgrading through the Shell Wax Hydroconversion Process to produce bio-SAF. The additional hydrogen required for the process is generated via shifting part of the syngas. The BTL line-up is similar to the power-to- liquids (PTL) concept, but in PTL the starting point is different. The carbon source is carbon dioxide (CO 2 ), which is combined with hydrogen produced by water electrolysis using renewable power. From this CO 2 and hydrogen, syngas is