Feb-2025

Driving SAF production with feedstock diversity

Routes to producing SAF and the importance of having a diverse range of feedstocks to support the scale-up of this fuel for decarbonisation of the aviation sector.

Paul Ticehurst
Johnson Matthey

Article Summary

As the aviation sector strives to reduce emissions, sustainable aviation fuel (SAF) has emerged as a key enabling solution (IATA, 2024). With global mandates and targets for SAF production increasing, relying on a single feedstock to make SAF is neither practical nor sustainable. Scaling up the industry requires a diversified feedstock approach and innovative technologies.

Hydroprocessed esters and fatty acids (HEFA), derived primarily from used cooking oil, have been a key focus for SAF production. Yet, the availability of HEFA feedstocks is limited, with 80% of HEFA feedstocks in the EU being imported (Stratas Advisors, 2024). As other regions establish their own domestic SAF targets, this dependency on imports creates risks to supply stability. Countries such as the US, the UK, and those in Europe, which have led the way with SAF mandates and incentives, must now diversify their feedstocks to ensure resilience and domestic production capabilities.

The Fischer-Tropsch (FT) process provides a scalable solution. This ASTM-approved technology converts syngas, a mixture of carbon monoxide (CO) and hydrogen (H2), into hydrocarbons that can be upgraded into SAF. Syngas can be derived from a wide variety of feedstocks, including municipal solid waste (MSW), agricultural residues, forestry waste, and captured carbon dioxide (CO2) combined with green hydrogen. By embracing the FT process, countries can expand their SAF production capabilities and reduce reliance on HEFA and feedstock imports. Companies like Johnson Matthey (JM) are leading advancements in syngas technology, helping SAF producers realise the benefits of feedstock diversity.

Fischer-Tropsch technology: Unlocking feedstock potential
The FT process is a transformative technology that enables SAF production from diverse feedstocks. The feedstocks below all qualify under the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA):
• Municipal solid waste (MSW): Gasification of MSW not only provides syngas for SAF but can also reduce landfill use, addressing waste management challenges. JM’s proprietary technology ensures syngas is cleaned and conditioned effectively.
• Forestry residues: Gasification of forestry waste utilises renewable resources and supports responsible forest management practices aimed at reducing wildfire risks (USDA, 2024).
• Captured CO₂: CO₂ emissions, combined with green hydrogen produced through renewable-powered electrolysis, can create syngas. JM’s HyCOgen (reverse water gas shift) technology enables this process, promoting carbon reuse and climate change mitigation.
• Agricultural residues: Biomass such as corn stover, wheat straw, and rice husks can be converted into syngas, unlocking value from agricultural byproducts.

The SAF production process involves several stages: syngas production, FT catalysis using iron or cobalt-based catalysts, chemical reactions under controlled conditions
(200-350°C and 10-40 bar) to form hydrocarbons, and upgrading through hydrocracking and distillation to produce SAF.

JM’s FT CANS technology, developed in collaboration with bp, offers a step-change in the FT process. This superior catalyst and reactor design reduces catalyst requirements by 50%, lowering capital and operational costs. Its scalability allows plant sizes to be tailored to match available feedstocks, while advanced heat management improves reaction efficiency and product quality thanks to its innovative radial flow reactor design. The technology achieves CO conversion rates exceeding 90% (Johnson Matthey, 2021).

FT CANS technology has already been licensed to several large-scale projects. The Louisiana Green Fuels project will convert 1 million tonnes of forestry waste into 32 million gallons of biofuel annually while incorporating carbon capture and sequestration (CCS) to minimise carbon intensity. DG Fuels’ plant in Louisiana is the largest announced SAF facility using FT CANS technology, converting sugarcane biomass into synthetic crude for SAF production. In Spain, Repsol and Aramco’s eFuel plant integrates FT CANS with HyCOgen technology to produce synthetic fuels from CO₂ and green hydrogen. 

Typically, biomass gasification plants produce a 1:1 mixture of CO and H₂ with insufficient H₂ to feed the FT process. Often, a water gas shift (WGS) reactor is used to increase the ratio of H₂, ensuring the correct ratio enters the FT reactor. However, this process also converts valuable CO into CO₂, which must be removed before FT synthesis, effectively acting as a carbon leak and reducing the overall carbon efficiency of the process. To avoid this leakage of valuable carbon from SAF feedstocks, additional H₂ can be added to ensure the correct ratio of gases. This removes the need for the WGS reactor, and operating the process in this way can comparatively increase SAF output, increasing the overall liquid product yield by around 60%. However, even this leaves a portion of the valuable carbon behind.

HyCOgen technology can use the CO₂ produced during biomass gasification and convert it into syngas with the addition of H₂. This not only prevents what could otherwise be waste CO₂ from potentially being released into the atmosphere but also transforms it into a valuable syngas feedstock for further fuel production. This capability can significantly enhance the economic viability of hybrid SAF plants, able to produce SAF from both biofeedstocks and via power-to-liquid. The overall result can be an increase in SAF output to more than 250% compared with the base case using WGS, without the need for additional feedstock carbon.

Overcoming challenges and ensuring a sustainable future
The potential for feedstock diversification to transform SAF production is immense, but challenges remain. Securing a consistent and scalable feedstock supply requires robust logistics and supply chain infrastructure. Additionally, achieving cost competitiveness with fossil fuels will demand economies of scale, technological advancements, and supportive policies. The environmental impacts of feedstock collection and processing must also be carefully managed, with practices such as responsible forestry and lifecycle carbon assessments ensuring sustainability.

Governments worldwide are introducing policies to accelerate SAF adoption. In the US, the SAF Grand Challenge targets 3 billion gallons of SAF production by 2030 and 35 billion by 2050, supported by significant federal investments in research and development. The EU has set SAF mandates requiring 6% of aviation fuel to be SAF by 2030, rising to 70% by 2050, with specific quotas for renewable fuels of non-biological origin. In the UK, the Government has committed to a 10% SAF target by 2030, promoting domestic production and capping HEFA usage to encourage feedstock diversification.

Estimates from the International Air Transport Association (IATA) suggest that using SAF can reduce lifecycle greenhouse gas emissions by more than 80% compared to fossil-derived jet fuel (IATA, 2024). By diversifying feedstocks and deploying advanced technologies like FT CANS and HyCOgen, the aviation industry can stabilise supply chains, meet global SAF targets, and significantly reduce emissions.

Achieving these goals will require collaboration between governments, industry leaders, and researchers. By unlocking the potential of diverse feedstocks, the SAF industry can create a more sustainable future for aviation while supporting energy security and global climate objectives.

CANS and HyCOgen are trademarks of Johnson Matthey.