Are you curious about Sustainable Aviation Fuel (SAF)?

Sustainable aviation fuels (SAFs) are pivotal in the fight against climate change and effectively reducing the aviation industry’s substantial carbon footprint. The aviation sector accounts for a significant portion of global greenhouse gas emissions, contributing around 2-3% of total CO2 emissions. With air travel demand on the rise, the imperative to cut these emissions has never been clearer.

SAFs are engineered to replace conventional fossil-based jet fuels, providing a powerful lower carbon alternative that can drastically lower lifecycle greenhouse gas emissions. By harnessing renewable feedstocks and leveraging advanced production technologies, SAFs can reduce CO2 emissions by up to 80% compared to traditional jet fuels. This shift is not just beneficial; it is essential for the aviation industry to meet international climate commitments, such as those established in the Paris Agreement, and to comply with initiatives like the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), which pursues carbon-neutral growth in the sector.

What is Sustainable Aviation Fuel?

Sustainable Aviation Fuel (SAF) is a type of aviation fuel made from renewable or waste-derived sources. One of the key features of SAF is that it can be used as a “drop-in” fuel, which means it can be blended with traditional jet fuels without the need for modifications to existing aircraft engines or fuel infrastructure.

It encompasses a variety of fuel types, including:

• Biofuels: These fuels are derived from biological materials, including plant oils, agricultural residues, and used cooking oil.
• Synthetic Fuels: These are produced through chemical processes that convert renewable energy sources into liquid fuels. An example is Power-to-Liquid (PtL) fuels, which utilize green hydrogen and carbon dioxide (CO₂) captured from the atmosphere or industrial processes (Kurzawska-Pietrowicz & Jasiński, 2024).

The most promising technological pathways for producing sustainable aviation fuels.

1. Hydroprocessed Esters and Fatty Acids (HEFA):

• Efficiency: HEFA technology is currently the most mature and widely used, with a high technology readiness level (TRL) and fuel readiness level (FRL) of 9, indicating its readiness for commercial deployment.
• Cost: Production costs for HEFA are generally higher than conventional jet fuels, averaging at least 120% more, but it is considered economically viable due to its established infrastructure.
• Environmental Impact: HEFA can achieve significant reductions in greenhouse gas (GHG) emissions, with studies indicating reductions of at least 27% compared to fossil fuels (Watson et al., 2024).

2. Fischer-Tropsch (FT) Synthesis:

• Efficiency: FT synthesis converts biomass or other carbon sources into liquid hydrocarbons. It has shown promise in producing high-quality jet fuel.
• Cost: The costs associated with FT processes can be high due to the complexity of the technology and the need for significant capital investment in infrastructure.
• Environmental Impact: FT fuels can provide substantial GHG reductions, but the overall impact depends on the feedstock used and the energy sources for the conversion process (Ansell, 2023).

3. Alcohol-to-Jet (ATJ):

• Efficiency: ATJ processes convert alcohols (like ethanol) into jet fuel. This pathway is still under development but has potential for scalability.
• Cost: The cost of ATJ production is currently high, primarily due to the need for advanced processing technologies and the variability in feedstock prices.
• Environmental Impact: ATJ can reduce GHG emissions significantly, especially when using renewable feedstocks, but the overall sustainability depends on the lifecycle analysis of the feedstock (Kurzawska-Pietrowicz & Jasiński, 2024).

4. Power-to-Liquid (PtL):

• Efficiency: PtL technology utilizes renewable electricity to produce hydrogen, which is then combined with CO2 to create synthetic fuels. This pathway is promising for long-term sustainability.
• Cost: The costs are currently high due to the need for renewable energy sources and the infrastructure required for hydrogen production and storage.
• Environmental Impact: PtL has the potential for very low GHG emissions, especially when powered by renewable energy, but it requires significant advancements in technology and cost reduction to be viable at scale (Su-ungkavatin et al., 2023).

5. Biomass-to-Liquid (BTL):

• Efficiency: BTL processes convert biomass into liquid fuels through gasification and subsequent synthesis. This pathway can utilize a variety of feedstocks.
• Cost: The production costs can be high, influenced by feedstock availability and processing technologies.
• Environmental Impact: BTL can provide substantial GHG reductions, but the sustainability of the feedstock and the energy used in the process are critical factors (Emmanouilidou et al., 2023).

Comparison Summary:

• Efficiency: HEFA and FT processes currently lead in efficiency and readiness for commercial use, while ATJ and PtL are emerging technologies with potential for future scalability.
• Cost: All SAF production methods are generally more expensive than conventional jet fuels, with HEFA being the most economically viable at present. ATJ and PtL face higher costs due to technological and infrastructure challenges.
• Environmental Impact: All pathways have the potential to significantly reduce GHG emissions compared to fossil fuels, but the extent of these reductions varies based on feedstock, production methods, and energy sources used.