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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 11 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
| Abbreviation
| Possible Feedstocks
| Maximum Blend Ratio |
ASTM D7566 Annex A1
| Fischer-Tropsch hydroprocessed synthesized paraffinic kerosene
| FT | Coal, natural gas, biomass
| 50% |
ASTM D7566 Annex A2
| Synthesized paraffinic kerosene from hydroprocessed esters and fatty acids | HEFA
| Vegetable oils, animal fats, used cooking oils | 50%
|
ASTM D7566 Annex A3
| Synthesized iso-paraffins from hydroprocessed fermented sugars
| SIP | Biomass used for sugar production | 10% |
ASTM D7566 Annex A4
| Synthesized kerosene with aromatics derived by alkylation of light aromatics from non-petroleum sources
| FT-SKA | Coal, natural gas, biomass
| 50%
|
ASTM D7566 Annex A5
| Alcohol to jet synthetic paraffinic kerosene
| ATJ-SPK | Ethanol, isobutanol and isobutene from biomass | 50% |
ASTM D7566 Annex A6
| Catalytic hydrothermolysis jet fuel
| CHJ
| Vegetable oils, animal fats, used cooking oils
| 50%
|
ASTM D7566 Annex A7
| Synthesized paraffinic kerosene from hydrocarbon - hydroprocessed esters and fatty acids
| HC-HEFA-SPK | Algae
| 10%
|
ASTM D7566 Annex A8
| Synthetic Paraffinic Kerosene with Aromatics
| ATJ-SKA
| C2-C5 alcohols from biomass’
| |
ASTM D1655
Annex A1 | co-hydroprocessing of esters and fatty acids in a conventional petroleum refinery
|
| Vegetable oils, animal fats, used cooking oils from biomass processed with petroleum’
| 5%
|
ASTM D1655 Annex A1 | co-hydroprocessing of Fischer-Tropsch hydrocarbons in a conventional petroleum refinery |
| Fischer-Tropsch hydrocarbons co-processed with petroleum
| 5%
|
ASTM D1655 Annex A1
| Co-Processing of HEFA
| Hydroprocessed esters/fatty acids from biomass’ | | 10% |
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. A general evaluation protocol is being developed to facilitate approvals of new feedstocks for co-processing, which are evaluated separately from the ASTM D4054 process’
