Sustainable aviation fuel (SAF) is a type of renewable aviation fuel that is produced from sustainable feedstocks rather than traditional petroleum sources. The exact composition of SAF can vary depending on the feedstock used and the production process, but it typically consists of a mixture of hydrocarbons similar to conventional jet fuel.

Some common feedstocks used to produce SAF include:

1. Biomass:
   • Plant oils (e.g., camelina, jatropha, algae)
   • Agricultural residues (e.g., corn stover, wheat straw)
   • Forestry residues (e.g., sawdust, tree branches)
2. Municipal solid waste:
   • Non-recyclable plastics
   • Paper and cardboard
   • Textiles
3. Industrial waste gases:
   • Carbon dioxide (CO2)
   • Carbon monoxide (CO)
4. Other sources:
   • Used cooking oil
   • Animal fats
   • Municipal green waste

The production processes for SAF typically involve one or more of the following technologies:

1. Hydroprocessed Esters and Fatty Acids (HEFA): This process converts plant oils and animal fats into renewable jet fuel through hydroprocessing.
2. Fischer-Tropsch (FT) synthesis: This process converts solid biomass, municipal solid waste, or gasified industrial waste gases into liquid hydrocarbons suitable for jet fuel.
3. Alcohol-to-jet (ATJ): This process converts alcohols (such as ethanol or isobutanol) derived from biomass into jet fuel through dehydration, oligomerization, and hydroprocessing steps.
4. Catalytic hydrothermolysis (CH): This process converts lipids and fatty acids from biomass into jet fuel through a catalytic process involving water at high temperature and pressure.

The resulting SAF has a similar composition to conventional jet fuel, consisting primarily of hydrocarbons and meeting strict technical and safety standards for aviation use. However, SAF is considered more sustainable because its production process has a lower carbon footprint and utilizes renewable or waste-derived feedstocks.