The role of SAF in decarbonising the aviation sector

As with other heavy industries and transportation sector participants, the aviation sector, which is responsible for 2% of global CO2 emissions, sees the expanded use of SAF as a pathway to reducing the sector’s carbon footprint.

Sustainable aviation fuel (SAF), which is derived from bio-based feedstocks, leads to substantially lower CO2 emissions compared to conventional jet fuel. To qualify a fuel as SAF in the United States, the fuel must provide at least a 50% reduction in greenhouse gas emissions over conventional fuels.

Currently, SAF is produced from fats, oils and greases (FOG), but second-generation feedstocks, including wood residues, hold promise for even greater emissions reduction and can even result in “carbon negative” fuels if coupled with carbon capture and sequestrations (CCS). As such, wood residues, including forest and sawmill residues, are poised to play a crucial role in reducing the carbon intensity of aviation fuels.

Exploring pathways for SAF production

Currently, the only commercially available pathways for sustainable aviation fuel (SAF) production are the hydrogenated vegetable oil (HVO) and hydrogenated esters and fatty acids (HEFA) processes, which use vegetable and waste oils as feedstocks. These pathways have been extensively validated, with frequent announcements of new capacity. However, the availability of these fats and oils is restricted. To satisfy the growing demand for SAF, the development of new feedstocks, often necessitating novel production pathways, will be essential.

One such pathway that holds promise is the expanded use of gasification platforms to produce Fischer-Tropsch (F-T) liquids. Wood residues from logging and sawmill operations are especially attractive for producing F-T liquids due to their relative abundance and processability. Pyrolysis oil from wood also presents an opportunity, particularly as bio-intermediates gain acceptance under regulatory frameworks such as the Renewable Fuel Standard (RFS).

Challenges and opportunities in meeting the growing demand for SAF

By 2050, passenger miles in the aviation sector are anticipated to more than double and will require nearly double current fuel volumes. Based on public announcements, AFRY predicts that by 2030, 11 million tonnes of SAF, valued at $70 billion, could come online. However, the feasibility of these projects remains uncertain, despite government subsidies and incentives.

In the United States, the Department of Energy’s SAF Grand Challenge for the aviation sector aims for the production of 3 billion gallons of SAF by 2030, escalating to 35 billion gallons by 2050, thus satisfying the entire annual domestic aviation fuel demand. However, only 160 million gallons of SAF production are currently available globally.

In terms of the supply/demand balance for woody biomass, AFRY emphasises the importance of the end-user’s “ability to pay”, with fibre and kraft mill co-products like crude tall oil expected to be the most valuable materials from woody biomass. Heavy industries, like steel and cement, are expected to place increasing demands on woody biomass as bio-based solutions pose the least technology risk and can be cost-effective.

In conclusion, the demand for SAF from woody biomass hinges on overcoming technical and economic barriers, with potential disruptions such as pyrolysis oil accelerating the demand for wood residues. Public policy, industry perception and economic feasibility will collectively shape the future trajectory of sustainable aviation fuels and their impact on wood supply.