From plant to plane and waste to wingtip: What is sustainable aviation fuel?

In order to reach net-zero carbon emissions by 2050, the aviation sector is undergoing a significant transformation and exploring alternatives to traditional jet fuel.

Central to this shift is sustainable aviation fuel (SAF), a lower-carbon alternative to fossil-based fuels. With the ability to reduce greenhouse gas emissions on a lifecycle basis, the increased usage of SAF underscores the industry’s commitment to combating climate change.

What exactly is sustainable aviation fuel?

SAF is derived from renewable resources, known as feedstocks. Unlike traditional jet fuel, which is made from fossil fuels extracted from the earth, SAF uses more sustainable materials and is produced through various technologies called processing pathways. It is blended with conventional jet fuel and can be used as a drop-in fuel in current aircraft engines without modifications, offering an immediate solution for reducing emissions.

What makes SAF “sustainable”?

For SAF to be considered sustainable, it must meet several criteria:

1. Resource conservation: Produced without depleting natural resources, ensuring minimal impact on freshwater supplies, food crops, and the environment.
2. Alternative materials: Uses materials other than crude oil.
3. Lifecycle carbon reduction: Demonstrates a net reduction in carbon emissions through lifecycle analysis (LCA).

Depending on the feedback and processing pathway, SAF can reduce lifecycle carbon emissions by up to 80%, making it a significantly more sustainable, low-carbon option to fossil-based fuels.

What are feedstocks?

Feedstocks are raw materials for energy conversion and biofuel production, categorized into three main types: waste, biomass, and carbon capture. Examples include:

• Fats, oils, and greases from cooking waste and meat production
• Municipal solid waste
• Agricultural and forestry residues

How is SAF produced?

SAF is produced using conversion technologies, known as processing pathways. The most common is HEFA (Hydrotreated Esters and Fatty Acids), which refines oils, waste, and fats into SAF using a hydrogen-infused process. Other pathways include Fischer-Tropsch and alcohol-to-jet processes, which use catalytic chemical reactions.

As SAF development and adoption grow, feedstocks and production technologies will evolve. Future advancements could include eSAF, created by capturing atmospheric carbon and converting it into fuel. However, significant progress in production capabilities is needed before this becomes scalable.

The SAF cycle: Reducing emissions on a lifecycle basis

By utilizing renewable feedstocks, SAF reduces the carbon footprint of flying on a lifecycle basis, unlike fossil fuels that increase overall CO2 levels by emitting carbon previously locked away.

Plants absorb CO2 during biomass growth, offsetting the carbon emitted when SAF is burned. Even considering emissions from crop cultivation, transportation, and fuel refinement, SAF still offers substantial CO2 reductions compared to traditional jet fuel.

The path forward

As the aviation industry moves towards a more sustainable future, understanding SAF’s feedstock sourcing, production processes, and lifecycle emissions reductions is essential. With the potential to significantly impact carbon emissions, SAF is crucial for industry stakeholders to support and champion.

Sources: IATA (1) (2) (3), World Economic Forum (1), ICAO (1)