Nov-2024

Diversification of feedstocks essential for sustainable aviation fuel production (ERTC 2024)

Relying on a single feedstock for sustainable aviation fuel (SAF) production is not a realistic option.

Javier Torroba
Johnson Matthey

Article Summary

The amount of SAF needed for the aviation sector to meet the growing number of mandates and targets around the world is likely to require contributions from all feedstocks and multiple process routes. While a lot of focus to date has been on hydroprocessed esters and fatty acids (HEFA) from used cooking oil, there is a limited amount of this feedstock, with around 80% of the feedstock used in the EU coming from imports.¹

Although regions including the US, Europe, and the UK have led the way with mandates and incentives for SAF production, which has attracted feedstocks from around the world, as other regions inevitably bring in their own domestic targets, the reliance on importing feedstocks is a big threat to meeting SAF targets. Relying too heavily on HEFA and importing feedstocks is not a long-term solution. Quite simply, the status quo is flawed.

Diversification of feedstocks is vital for the resilience of the biofuels industry. Relying on a single type of feedstock may leave fuel suppliers vulnerable to market volatility and supply chain disruptions in an emerging market. Fuel suppliers are the obligated parties under mandates in the EU and UK and are expected to deliver against SAF targets in regions like the US, Japan, and a growing list of others. By incorporating a variety of feedstocks, both fuel suppliers and countries can take control of their own destinies and secure the SAF they need from domestic feedstocks.

However, is there an alternative that can use a wide range of feedstocks, available around the world, to unlock domestic SAF production at scale and ensure countries can produce the SAF they need?

Feedstock Diversity to unlock SAF at scale
The Fischer-Tropsch (FT) process is based on a syngas platform and is an ASTM-approved route to produce synthetic SAF blendstocks. Syngas is a mixture of carbon monoxide (CO) and hydrogen (H₂), and the FT process builds the hydrocarbon chains needed for SAF. Syngas can be produced from a huge range of feedstocks, such as municipal solid waste (MSW), waste biomass, and captured carbon dioxide (CO₂) emissions (when combined with H₂). This means the FT process provides a route to produce the SAF required to meet mandates around the world and avoids over-reliance on a single feedstock. Companies such as Johnson Matthey (JM) are leading the way in delivering syngas technology and the versatility provided by the FT route to SAF.

Feedstocks for syngas production
MSW can be gasified to produce syngas. This process not only provides a valuable source of syngas but also aids in waste management by reducing landfill use. JM’s proprietary technology ensures efficient cleanup and conditioning of the syngas, preparing it for subsequent FT synthesis.

Forestry waste can provide another abundant and renewable feedstock. Gasification of forestry biomass produces syngas, which can then be processed through the FT process to yield high-quality synthetic fuels. This approach supports responsible forest management that reduces the risk of wildfires by utilising waste materials.² Utilising captured CO₂ in combination with green hydrogen, produced via electrolysis using renewable energy, can provide a viable route to syngas. JM HyCOgen™ (reverse water gas shift) technology facilitates this, helping to reuse CO₂ emissions and contributing to climate change mitigation.

Agricultural residues, such as corn stover, wheat straw, and rice husks, are another significant source of biomass that can be converted into syngas. Using them as feedstocks for SAF can create value from waste materials. MSW, forestry, and agricultural residues are all eligible SAF feedstocks under CORSIA with qualifying default life cycle emissions below the fossil jet fuel benchmark (89 gCO₂e/MJ).³

Technical Overview: Converting Diverse Feedstocks into SAF
The FT process is a key technology for converting syngas into liquid hydrocarbons, which can then be refined and blended into various fuels, including diesel, kerosene, and SAF. The FT process requires several crucial steps:
υ Syngas production: Syngas, a mixture of CO and H₂, is produced from various feedstocks such as MSW, biomass, or CO₂ and H₂. This syngas is then fed into the FT reactor.
ϖ Catalysis: Inside the FT reactor, the syngas contacts a catalyst, typically iron or cobalt-based. The choice of catalyst depends on the desired product slate and the type of feedstock used.
ω Chemical reactions: Under temperature (200-350°C) and pressure (10-40 bar), the catalyst facilitates the chemical reactions that convert syngas into longer-chain hydrocarbons. The primary reaction typically includes the formation of paraffins following the general reaction formula:

(2n + 1)H₂+nCO ® CnH(2n + 2) + nH₂O

ξ Product formation: These hydrocarbons are typically primarily straight-chain alkanes, which can be further processed into different types of fuels through hydrocracking and other refining processes.
ψ Product upgrading: The FT process can produce waxes and lighter hydrocarbons that need upgrading to meet fuel specifications. Hydrocracking, isomerisation, and distillation are common upgrading processes that convert FT products into high-quality diesel, naphtha, and kerosene.

FT CANS, a Step-Change Improvement in FT Technology
The FT CANS™ technology developed by JM and bp represents a significant advancement in FT technology. This reactor design offers several technical benefits that enhance the efficiency and scalability of the FT process.

The FT CANS technology utilises a modular reactor design that significantly reduces the amount of catalyst required. This reduction leads to lower capital costs by approximately 50% versus traditional fixed-bed FT, and lower operational expenses, making the process more economically viable for large-scale applications. Furthermore, the modular design allows for easy scalability, readily enabling plant size to be adapted to match available feedstock quantities. Our largest announced project to date has an expected capacity of 13,000 barrels per day once operational.

Heat management is a critical factor in the FT process due to its highly exothermic reactions. The FT CANS reactor features a unique configuration that enhances heat transfer and control. This design minimises temperature fluctuations within the reactor, ensuring optimal reaction conditions and improving product yield and selectivity. The efficient heat management also reduces the risk of hot spots and thermal degradation of the catalyst.

The FT CANS reactor also boasts a high conversion rate, with CO conversion efficiencies exceeding 90%.⁴ This high conversion rate is achieved through an innovative radial flow design that maximises contact between the syngas and the catalyst. The reactor’s design facilitates efficient mass transfer, allowing for higher productivity and selectivity towards desired hydrocarbon products.

Case Studies and Real-World Applications
○ Louisiana Green Fuels Project: The Louisiana Green Fuels project illustrates the application of FT CANS technology using forestry waste as feedstock. Once operational, this project is expected to convert one million tons of forestry waste into 32 million gallons of biofuels annually. The project plans to incorporate carbon capture and sequestration (CCS) to further reduce emissions, with the aim of achieving one of the world’s lowest carbon footprints for fuel production.
○ Repsol and Aramco eFuel Plant: Another notable project is the Repsol and Aramco eFuel plant in Bilbao, Spain. This facility plans to produce synthetic fuel using green H₂ and CO₂ as feedstocks by integrating FT CANS technology with HyCOgen. The plant is designed to demonstrate commercial-scale production, converting more than 2,000 tons of CO₂ annually into high-quality synthetic products, which can be refined into transportation fuels.
○ DG Fuels Project: DG Fuels has chosen FT CANS technology for its first SAF plant located in Louisiana, USA. This plant is the largest announced SAF production facility in the world planning to use FT technology. With an expected capacity of 13,000 barrels per day once operational, it plans to utilise waste sugar cane biomass as feedstock, converting it into synthetic crude, which will be further processed to produce SAF. This project highlights the scalability and efficiency of the FT CANS technology in large-scale SAF production.

Evolving Policy and Regulatory Support
The success of feedstock diversification depends on supportive policies and regulatory frameworks. Governments around the world are recognising the importance of sustainable fuels and implementing mandates and incentives to drive their production and adoption.
○ United States: The US government is promoting the production of biofuels through various initiatives. The SAF Grand Challenge is targeting the production of 3 billion gallons by 2030 and 35 billion by 2050. The Department of Energy (DOE) is investing in research and development to improve biofuel production technologies and expand the range of eligible feedstocks.
○ European Union: The EU has set targets for SAF production, with mandates requiring 6% of aviation fuel to be SAF by 2030, increasing to 70% by 2050. These targets include specific quotas for renewable fuels of non-biological origin (RFNBO, or e-fuels) produced via power-to-liquids processes, which use CO₂ and electrolytic H₂.
○ United Kingdom: The UK aims to achieve a 10% SAF target by 2030, with a focus on creating domestic production capabilities. It also has a sub-mandate for e-fuels and recognises the need for feedstock diversity by introducing a cap on the use of HEFA feedstocks.

Positioning the SAF industry for success
The potential for feedstock diversification and the FT process is immense, and the technology is currently being licenced for deployment at scale. However, the industry must address several challenges to fully realise the benefits of feedstock diversity.
○ Feedstock supply and logistics: Ensuring a consistent and long-term supply of diverse feedstocks requires efficient logistics and supply chain management. Support to develop robust supply chains and infrastructure is essential to enable large-scale production.
○ Economic competitiveness: Production costs for synthetic fuels are currently higher than conventional fossil fuels. Bridging this cost difference requires economies of scale, deploying the best available technology, and supportive policies to drive projects to completion and supply the SAF needed to meet international targets and mandates.
○ Environmental impact: The environmental impact of feedstock cultivation, collection, and processing must be carefully managed. Practices such as responsible forestry management and minimising land-use changes can align and enable biofuel production. Ultimately, internationally recognised and standardised full life cycle carbon intensity assessments are essential to support the overall environmental benefits of biofuels.

Conclusion
Processing eligible SAF feedstocks and capturing CO₂ for SAF production can reduce greenhouse gas emissions and provide economic benefits. Estimates by the International Air Transport Association (IATA) show that the use of SAF can lead to more than an 80% reduction in net carbon emissions over the full life cycle compared to fossil-derived jet fuel.⁵

Adopting diverse feedstocks for fuel production offers a long-term solution for creating synthetic fuels and meeting the increasing SAF targets around the world. Utilising a variety of feedstocks stabilises fuel supply chains and reduces vulnerability to market fluctuations.
Overall, harnessing feedstock diversity is an important accelerator to produce synthetic fuels at scale, and the syngas-based FT CANS technology can play a key role in delivering this ambition.

The continued deployment of FT CANS technology will be pivotal in meeting the increasing global demand for synthetic fuels. As the industry evolves, collaboration between governments, industry stakeholders, and research institutions will be crucial to overcome challenges and unlock the full potential of feedstock diversity for SAF.

This short article originally appeared in the 2024 ERTC Newspaper, which you can VIEW HERE