Emerging technology in detail: sustainable aviation fuel

Sustainable aviation fuels (SAF) represents a significant advancement in reducing the environmental impact of air transportation. SAF is produced from renewable resources, such as biomass, waste oils and agricultural residues, providing an alternative to conventional jet fuels derived from fossil fuels. ⁽¹⁾Bauen, A., N. Bitossi, L. German, A. Harris and K. Leow (2020). Sustainable aviation fuels: Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnson Matthey Technology Review, 64(3), 263–278. Currently, demand for aviation fuel is dominated by jet kerosene, with SAFs accounting for less than 0.1% of all aviation fuels consumed. Manufacturers and operators are increasingly testing flights entirely fuelled by SAF, that be deployed in current infrastructure, engines and aircraft with minor adjustments to fuel delivery equipment. However, planned production capacities will provide just 1–2% of jet fuel demand by 2027. Increasing SAF use in aviation to 10% by 2030 in line with the Net Zero Scenario will require a significant ramp-up of investment in capacity to produce SAF plus supportive policies in respect to fuel tax and low-carbon fuel standards. ⁽²⁾IEA (2023). Aviation. International Energy Agency. Available at: www.iea.org/energy-system/transport/aviation . The adoption of SAFs is crucial if the aviation industry is to achieve its sustainability goals, reduce greenhouse gas emissions and mitigate climate change impacts. ⁽³⁾Chiaramonti, D. (2019). Sustainable aviation fuels: The challenge of decarbonization. Energy Procedia, 158, 1202–1207.

There are several types of SAF currently under development and in use, each with unique characteristics and production processes. Biofuels are derived from biological materials, such as vegetable oils, animal fats and waste greases (Figure C57). Examples include hydroprocessed esters and fatty acids (HEFA) and Fischer-Tropsch (FT) fuels. Synthetic fuels, or e-fuels, are produced through chemical processes using renewable energy sources, such as wind or solar power, to generate hydrogen, which is then combined with carbon dioxide to create liquid hydrocarbons. Alcohol-to-Jet (ATJ) fuels are produced by converting alcohols, such as ethanol or butanol, into jet fuel through a chemical process.

Figure C57 Alternative aviation fuel routes

Source: Bauen et al., 2020.

The core benefits of SAF include reduced greenhouse gas emissions, improved air quality and enhanced energy security. SAF can reduce life cycle greenhouse gas emissions by up to 80% compared to conventional jet fuel. ⁽⁴⁾IATA (2024). Developing sustainable aviation fuel (SAF). International Air Transport Association. Available at: www.iata.org/en/programs/environment/sustainable-aviation-fuels. For example, the Fischer-Tropsch (FT) and HEFA pathways have shown potential in reducing CO2 emissions by between 50–90%. ⁽⁵⁾Chiaramonti, D. (2019). Sustainable aviation fuels: The challenge of decarbonization. Energy Procedia, 158, 1202–1207. Additionally, SAF contributes to improved air quality by producing fewer particulate emissions and sulfur oxides. By diversifying fuel sources, SAF enhances energy security and reduces reliance on fossil fuels. ⁽⁶⁾IEA (2023). Aviation. International Energy Agency. Available at: www.iea.org/energy-system/transport/aviation. The use of local and renewable feedstocks for SAF production can mitigate the risks associated with geopolitical instability and fluctuating oil prices. ⁽⁷⁾Chiaramonti, D. (2019). Sustainable aviation fuels: The challenge of decarbonization. Energy Procedia, 158, 1202–1207. The development and scaling of SAF production can also create new economic opportunities, including job creation within the agricultural, industrial and technological sectors. ⁽⁸⁾Bauen, A., N. Bitossi, L. German, A. Harris and K. Leow (2020). Sustainable aviation fuels: Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnson Matthey Technology Review, 64(3), 263–278.

Despite its their advantages, SAF has several current limitations. The production costs of SAFs are higher compared to conventional jet fuels, primarily due to the limited availability of feedstock and the complexity of the production process. Additionally, there are technical challenges related to the compatibility of SAFs with existing aircraft engines and fueling infrastructure. Ensuring a consistent supply of high-quality feedstocks is also a significant challenge. ⁽⁹⁾Chiaramonti, D. (2019). Sustainable aviation fuels: The challenge of decarbonization. Energy Procedia, 158, 1202–1207. SAF currently has a higher production cost than conventional aviation fuels. This is mainly due to the high costs of feedstock, a complex production processes and the need for extensive certification. ⁽¹⁰⁾Shehab, M., K. Moshammer, M. Franke and E. Zondervan (2023). Analysis of the potential of meeting the EU’s sustainable aviation fuel targets in 2030 and 2050. Sustainability, 15(12), 9266. The ASTM certification process, necessary for ensuring the safety and compatibility of new fuels with existing aircraft, is both time-consuming and expensive. The availability of sustainable feedstocks is a major concern. Large-scale production of SAF requires a significant quantity of biomass, which can compete with food production and other land uses. ⁽¹¹⁾ICAO (2018). Feasibility Study on the Use of Sustainable Aviation Fuels. International Civil Aviation Organization. Available at: www.icao.int/environmental-protection/Documents/FeasabilityStudy_Kenya_Report-Web.pdf. There are also technical challenges in integrating SAF into existing fueling infrastructure and aircraft engines. Ensuring the stability and performance of SAFs under various operating conditions is critical. ⁽¹²⁾Chiaramonti, D. (2019). Sustainable aviation fuels: The challenge of decarbonization. Energy Procedia, 158, 1202–1207. Significant investments are required to scale up SAF production to a commercial levels. This includes building new biorefineries and upgrading existing facilities to process different types of feedstocks. ⁽¹³⁾Chiaramonti, D. (2019). Sustainable aviation fuels: The challenge of decarbonization. Energy Procedia, 158, 1202–1207.

Sustainable aviation fuels: scientific publications

The scientific community has shown increasing interest in SAF, as evidenced by the growing number of publications on the topic. Research focuses on improving production processes, assessing environmental impacts and enhancing the performance of SAFs in aviation applications. Figure C58 displays the number of scientific documents related to SAFs published annually from 2009 to 2024. Data shows there has been a steady increase in the number of publications, with a significant surge starting around 2020. This trend indicates a growing interest in SAF and its potential to transform the aviation industry.

Figure C59 shows the number of scientific publications related to SAF by country. The United States leads with a significant number of publications, followed by European countries Germany and the United Kingdom. China, Brazil and Canada also contribute substantially to the research effort in this field.

Sustainable aviation fuel: patent data

Patenting activity in the field of SAF already increased at the end of the 2000s peaking in 2010 at 115 patent families (Figure C60). In the years that followed, patenting activity declined, but reached a new height in 2023 at 156 patent family publications.

At a country level, most patent family publications were developed in the United States (Figure C61). China, Germany, Japan and France are other important research locations.

Sustainable aviation fuel: patent examples

Leading companies in the aviation and energy sectors, such as Boeing, Airbus and Neste, are at the forefront of patent filings, focusing on various aspects of SAF technology, including producing renewable aviation fuel, plant infrastructure as well as refuelling aircraft with SAF.

The core idea of patent WO2023126564A1 from Neste is to develop a method for producing SAF through a combination of bio-based feedstock and a chemical catalysts. This method aims to optimize the feedstock-to-fuel conversion process in order to improve fuel yield and reduce production costs. The patent focuses on enhancing the efficiency and effectiveness of the SAF production process, ensuring that the fuels can be seamlessly integrated into existing aviation infrastructure and used in current aircraft engines with minimal modifications. The ultimate goal is to provide a commercially viable and environmentally friendly alternative to conventional jet fuels, reducing the aviation industry's carbon footprint and dependency on fossil fuels.

The invention described in WO2022171643A1 from Topsoe involves an innovative method for producing SAF. This method focuses on using bio-based feedstock, such as vegetable oil and animal fat, and employs advanced chemical catalysts to optimize the conversion process. The goal is to enhance the efficiency of the feedstock-to-fuel conversion, resulting in a higher fuel yields and reduced production costs.

Source: WO2022171643A1.

Additionally, SAFs produced using this method are designed to be compatible with existing aviation infrastructure and engines, requiring only minimal adjustments to fuel delivery systems. This approach aims to provide a commercially viable and environmentally-friendly alternative to conventional jet fuel, thereby reducing the aviation industry's carbon footprint and reliance on fossil fuels.

The invention from Airbus described in patent EP4382431A1 involves the development of a novel method for producing SAFs from bio-based feedstock, such as vegetable oils and animal fats. This method leverages advanced chemical catalysts in order to enhance the efficiency of the conversion process, resulting in a higher fuel yield and reduced production costs. SAFs produced through this method are designed to be compatible with existing aviation infrastructure and engines, requiring only minor adjustments to fuel delivery systems.

Source: EP4382431A1

This innovative approach aims to provide a commercially viable and environmentally friendly alternative to conventional jet fuel, thereby reducing the aviation industry's carbon footprint and dependence on fossil fuel. The process outlined in the patent emphasizes optimizing the feedstock-to-fuel conversion to ensure high efficiency and sustainability.

The adoption of SAF in air transportation is influenced by evolving regulations and standards aimed at promoting sustainability and reducing environmental impacts. Organizations like ICAO and IATA are working on developing standards specific to SAF, addressing production processes, fuel quality and sustainability criteria to assure their reliable integration into commercial aviation. ⁽¹⁴⁾ICAO (2017). Sustainable Aviation Fuels Guide. International Civil Aviation Organization. Available at: www.icao.int/environmental-protection/knowledge-sharing/Docs/Sustainable%20Aviation%20Fuels%20Guide_vf.pdf.   ⁽¹⁵⁾IATA (2024). IATA SAF Registry. International Air Transport Association. Available at: www.iata.org/en/pressroom/2024-releases/2024-06-02-02.