How Does Sustainable Aviation Fuel Reduce Emissions?

Sustainable Aviation Fuel (SAF) reduces greenhouse gas emissions primarily by lowering lifecycle carbon emissions. The reduction does not occur because less carbon dioxide is produced during the flight but because the carbon entering the fuel production cycle comes from non-fossil sources.

Lifecycle Carbon Reduction

Conventional jet fuel is produced from crude oil and the carbon contained in the fuel has been stored underground for millions of years. When burned, this carbon is released into the atmosphere, increasing total atmospheric CO₂ concentration. On the other hand, SAF uses carbon that already exists in the current carbon cycle. Depending on the production pathway, this carbon may come from:

Direct air capture of atmospheric CO₂
Point source captured industrial CO₂
Biological sources such as waste oils or biomass

Because the carbon is recycled rather than extracted from fossil reserves, the net increase in atmospheric CO₂ is lower over the full lifecycle.

Lifecycle emission reductions typically range from:

Up to approximately 90% or more for eSAF when low-carbon electricity is used
60–80% reduction for waste-based biofuel SAF pathways

Actual reductions depend on feedstock source, processing energy, and transport emissions.

Closed Carbon Cycle Concept of eSAF

When eSAF is produced from captured CO₂, a circular carbon flow is created:

CO₂ is captured from the atmosphere or industrial emissions.
The CO₂ is converted into eFuel, i.e. eSAF.
The eSAF is burned in an aircraft engine.
CO₂ is released back into the atmosphere.

Because the carbon originated from the atmosphere rather than fossil reserves, there is minimal net addition of new carbon.

Reduction of Non-CO₂ Emissions

SAF can also reduce certain non-CO₂ climate impacts. Compared with fossil jet fuel, SAF generally contains lower sulphur content and lower aromatic compounds. This results in reduced particulate matter formation, lower soot emissions and potential reduction in contrail formation and contrail radiative forcing. So in the end, these effects contribute additional climate benefits beyond CO₂ reduction.

SAF Compatibility with Existing Aircraft

SAF is designed as a drop-in fuel, which means that no aircraft engine modifications are required within approved blend limits. Furthermore, existing fuel infrastructure can be used and emission reductions can be achieved without new aircraft technology.

Importance of the Energy Source for SAF Production

The amount of emission reduction depends on the energy used during eSAF production. If fossil electricity is used in hydrogen production or processing, emission benefits decrease. If renewable or nuclear electricity is used, lifecycle emissions are substantially reduced.

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