Process Technology Training Series
SAF
Module from the Process Technology Training Series curriculum.
Sustainable Aviation Fuel (SAF) — ASTM D7566 Pathways · Approved Conversion Routes
| Pathway | Feedstock | Max Blend (% jet fuel) | ASTM D7566 Annex | Commercial Producers | TRL* | Cost Range ($/gal) |
|---|---|---|---|---|---|---|
| FT-SPK (Fischer-Tropsch) | Natural gas, biomass (GTL) | 50% | Annex 1 | Sasol, Shell, Nouryon | 9 | 3.50–5.50 |
| HEFA-SPK (Hydroprocessed esters/fatty acids) | Carinata, algae, used oil | 50% | Annex 2 | Neste, Total Energies, REG | 9 | 2.80–4.50 |
| ATJ-SPK (Alcohol-to-jet) | Sugar, cellulose, power-to-alcohol | 50% (blend requirement) | Annex 3 | Gevo, LanzaJet, Air Company | 8 | 4.00–6.50 |
| CHJ (Catalytic hydrothermolysis jet) | Carinata, jatropha, used oil | 50% | Annex 4 | Joule, SAFRAN Partnership | 7–8 | 3.50–5.50 |
| HC-HEFA (Hydrocracked HEFA) | Carinata, algae, animal fat | 50% | Annex 5 | Neste, Shell Avancore | 9 | 3.20–4.80 |
| Direct Sugar-to-Jet (DSJ) | Sugar cane, sugar beet (via fermentation) | 50% | Annex 6 (provisional) | Gevo (partnership w/ partner airlines) | 7 | 4.50–7.00 |
| Fuel Specification (ASTM D7566-23) | ||||||
| Property | Requirement | Units | Rationale | Test Method | ||
| Density (15°C) | 775–840 | kg/m³ | Match Jet A-1 (800–840) for system compatibility | ASTM D1298 | ||
| Viscosity (–20°C) | ≥8.0 | cSt | Fuel system pump clearance | ASTM D341 | ||
| Flash Point | ≥38 | °C | Safety, transport, handling | ASTM D56 | ||
| Sulfur content | <24 | mg/kg (ppm) | Engine deposit control | ASTM D2622 | ||
| Thermal stability (JFTOT) | ≥600 | °C / 25 °C min | Heat exchanger fouling prevention | ASTM D3241 | ||
| Copper corrosion | Pass | — | Material compatibility (cu/Zn tanks) | ASTM D130 | ||
| Net heat of combustion | ≥43.15 | MJ/kg | Min energy content vs. Jet A-1 (43.4) | ASTM D3241 | ||
| Freeze point | ≤–40 | °C | Arctic/high-altitude ops | ASTM D2386 | ||
| Smoke point | ≥25 | mm | Combustor emissions/smoke | ASTM D1322 | ||
| Blend & Approval Path | ||||||
| All ASTM D7566 pathways approved for 50% maximum blend with conventional Jet A-1. Higher blends (100% drop-in) under review (Annex 7). Approvals require: airframe OEM certification, engine OEM approval, national authority endorsement (FAA, EASA). Commercial availability (2024) concentrated in FT-SPK and HEFA-SPK; ATJ-SPK scaling rapidly. |
Source: Process_Technology_Training_Series_v1.xlsx · Sheet: SAF
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