Conversion processes

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Annex 16 Vol IV defines a conversion process as "a type of technology used to convert a feedstock into aviation fuel".  


SAF conversion processes are evaluated and approved by organizations such as ASTM International. As of July 2023, 11 conversion processes for SAF production have been approved and 7 other conversion processes are currently under evaluation.


In order to be eligible for use within the ICAO Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), SAF must also meet a set of sustainability criteria. More information on CORSIA eligible fuels is available on the dedicated CORSIA Eligible Fuels webpage.  Specific details on the conversion processes that already have CORSIA default Life Cycle Emission values (FT, HEFA, SIP and ATJ) are available in the CORSIA supporting document "LCA methodologies" 

Approved Conversion Processes

ASTM reference
​Conversion process
​Possible Feedstocks
Maximum Blend Ratio
​ASTM D7566 Annex​ 1

​Fischer-Tropsch hydroprocessed synthesized paraffinic kerosene


Coal, natural gas, biomass​


​ASTM D7566 Annex 2

Synthesized paraffinic kerosene from hydroprocessed esters and fatty acids​


Bio-oils, animal fat, recycled oils​


​ASTM D7566 Annex 3

​Synthesized iso-paraffins from hydroprocessed fermented sugars


Biomass used for sugar production​


​ASTM D7566 Annex 4

​Synthesized kerosene with aromatics derived by alkylation of light aromatics from non-petroleum sources


Coal, natural gas, biomass​


​ASTM D7566 Annex 5

​Alcohol to jet synthetic paraffinic kerosene


Biomass from ethanol, isobutanol  or isobuthene


​ASTM D7566 Annex 6

​Catalytic hydrothermolysis jet fuel


​Triglycerides such as soybean oil, jatropha oil, camelina oil, carinata oil, and tung oil


​ASTM D7566 Annex 7

​Synthesized paraffinic kerosene from hydrocarbon - hydroprocessed esters and fatty acids




​ASTM D7566 Annex 8

ATJ derivative starting with the mixed alcohols

​ASTM D1655  
Annex A1

co-hydroprocessing of esters and fatty acids in a conventional petroleum refinery

​co-processed HEFA

​Fats, oils, and greases (FOG) co-processed with petroleum


ASTM D1655  

Annex A1

co-hydroprocessing of Fischer-Tropsch hydrocarbons in a conventional petroleum refinery

​co-processed FT

Fischer-Tropsch hydrocarbons co-processed with petroleum


​ASTM D1655  

Annex A1

co-hydroprocessing of biomass
​co-processed biomass​5%

Conversion processes under evaluation

Various conversion processes are currently under evaluation by ASTM. More information is available on the article "New Sustainable Aviation Fuels (SAF) technology pathways under development", published on the ICAO Environmental Report 2022. Work is also ongoing to allow the use of 100% SAF in aircraft, as well as to increase the maximum blending for co-processing (from 5% to 30%). 

A detailed description of the ASTM qualification process is provided in the ACT-SAF Training Session #3.

Conversion process under evaluationAbbreviationLead developers
synthesized aromatic keroseneSAK
Integrated hydropyrolysis and hydroconversionIH2Shell
Alcohol-to-Jet (ATJ) derivative utilising biochemical production of isobutene-Global Bioenergies
Single Reactor HEFA (Drop-in Liquid Sustainable Aviation and Automotive Fuel)DILSAAFIndian CSIR-IIP
Pyrolysis of non-recyclable plasticsReOILOMV
Co-processing of pyrolysis oil from used tires 
Methanol to jet



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