What is saf?

Sustainable aviation fuel (SAF) is a type of jet fuel that is manufactured from biological and non-biological resources. It includes a number of ASTM approved fuel production pathways utilizing different manufacturing technology in the aviation sector. SAF is the most commonly used term, however there are several other terms that are used to represent SAF which have the same meaning i.e., renewable jet fuel, sustainable alternative jet fuel or biojet fuel.  Sustainable aviation fuel seeks to reduce CO2 emissions throughout its lifespan while also benefiting airlines economically and socially. It is a net-zero carbon jet fuel solution that offers a reduction of carbon dioxide levels of up to 80% in the total lifecycle of the fuel. Without the need for any technological or mechanical changes to the aircraft designs, SAF acts as a drop-in fuel to replace the currently used fossil derived jet fuel. In order to be categorized as a drop-in fuel, SAF manufactures have to meet the ASTM D7566 fuel standard. ASTM D7566 ensures that the fuel manufactured is safe to be used in aircrafts when blended with conventional jet fuel. Conventional jet fuel, either Jet A or Jet A1, that are used in the aviation industry which are certified to ASTM D1655 have similar fuel properties with an ASTM D7566 certified SAF. Up to date, there are 7 ASTM approved pathways in manufacturing SAF as listed below. Nevertheless, numerous other pathways are currently under review by ASTM.

  1. Fischer Tropsch synthesized isoparaffinic kerosene (FT-SPK)
  2. Fischer Tropsch synthesized kerosene with aromatics (FT-SPK/A)
  3. Hydroprocessed fatty acid esters and fatty acids (HEFA)
  4. Catalytic Hydrothermolysis Jet fuel (CHJ)
  5. Alcohol to jet (ATJ)
  6. Synthesized isoparaffins (SIP)
  7. Hydroprocessed Hydrocarbonssynthesized isoparaffinic kerosene (HH-SPK or HC-HEFA)

Most of these pathways have blending capability of 50% except the SIP and HC-HEFA route which is only approved to a blending ratio of up to 10%. Currently, SAFs are more costly compared to conventional jet fuel. The estimated cost range of SAF varies from 2x for certain waste-based sources to 6-10x for carbon-captured synthetic fuels. Nevertheless, in the mid to long term, the cost of SAF is bound to drop as more production facilities are being built, and a number of major airlines are negotiating big advance offtake agreements to enable new energy providers secure supply certainty.


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