Sustainable aviation fuel (SAF), also known as alternative jet fuel, describes non-conventional jet fuels that are derived from renewable resources, known as feedstocks. Unlike traditional fossil-based jet fuels, SAF uses alternative feedstocks and is produced through various technologies, known as processing pathways.
SAF is a drop-in fuel substitution, meaning it can be blended with conventional jet fuel in current aircraft engines without modifications. This substitution offers an immediate solution for helping to reduce lifecycle emissions from aviation. SAF has the potential to provide a lifecycle emissions reduction of up to 80% compared to the traditional jet fuel it replaces.
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How is SAF produced?
SAF is produced using conversion technologies, which transform a range of feedstocks into fuel that can be used in airplanes. These conversation technologies are also referred to as processing pathways.
The most common processing pathway today is Hydrotreated Esters and Fatty Acids (HEFA), which refines oils, waste, and fats into SAF using a hydrogen-infused process. Other pathways include Fischer-Tropsch (FT) and Alcohol-to-Jet (AtJ) processes, which use catalytic chemical reactions. In addition, SAF can be produced without extensive infrastructural changes via co-processing, which is the simultaneous processing of fuels using non-petroleum and petroleum feedstocks at existing fuel refineries.
As SAF development and adoption grows, feedstocks and production technologies will evolve. Future advancements could include eSAF, created by capturing atmospheric carbon and converting it into fuel.
How does SAF reduce emissions?
Today, all commercially produced SAF on the market leverages biogenic feedstocks, also known as biomass. Biogenic feedstocks are renewable organic materials from plants and animals – including forestry and agricultural residues, municipal solid waste, used cooking oil, etc.
In contrast, the production of conventional jet fuel requires the extraction of fossil fuel, resulting in a release of carbon that has been sequestered in the ground for millions of years. When burned, SAF and conventional jet fuel produce similar levels of emissions, but the emissions generated from SAF are already part of the carbon cycle (because they are made of biomass) and not extracted specifically for creating aviation fuel. This results in reduction of emissions when using SAF compared to conventional jet fuel when considered over the lifecycle of the fuel.