Sustainable Aviation Fuel (SAF)

What Is Sustainable Aviation Fuel?

Sustainable aviation fuel (SAF) is a category of jet fuel produced from non-petroleum feedstocks — including agricultural and forestry waste, municipal solid waste, algae, hydrogen, and captured CO2 — that meets the same technical specification as conventional Jet-A or Jet-A1 fuel (ASTM D1655 or DEF STAN 91-091). Because SAF is chemically near-identical to fossil jet fuel, it requires no aircraft or engine modifications and can be blended with conventional fuel or, in certified cases, used neat.

How It Works

SAF is produced through several certified conversion pathways, each approved under ASTM D7566:

• HEFA (Hydroprocessed Esters and Fatty Acids): hydrotreating animal fats, used cooking oil, or plant oils; currently dominant pathway, up to 50% blend
• FT-SPK (Fischer-Tropsch Synthetic Paraffinic Kerosene): biomass or municipal waste gasification + synthesis; up to 50% blend
• ATJ-SPK (Alcohol-to-Jet): fermentation of sugars/cellulose to ethanol or isobutanol, then dehydration and oligomerization; up to 50% blend
• PtL (Power-to-Liquid / e-SAF): green hydrogen + captured CO2 via Fischer-Tropsch or methanol synthesis; theoretically 100% blend; not yet at commercial scale

The lifecycle CO2 reduction vs. fossil Jet-A ranges from 40% (some HEFA pathways) to over 90% (PtL with renewable electricity and direct air capture), depending on feedstock and production energy source. Crucially, SAF contains near-zero sulfur and reduced aromatics, which also reduce contrail formation and particulate emissions.

Performance Specifications

• Maximum blend ratio (current certification): up to 50% SAF with 50% Jet-A (most pathways); ASTM Annex A1 for 100% HEFA approved 2023
• Energy density: comparable to Jet-A (~43.2 MJ/kg); some pathways slightly higher
• Lifecycle CO2 reduction: 40–80% for HEFA/FT/ATJ; up to 90%+ for e-SAF
• Price premium (2025): 2–5× conventional jet fuel cost, depending on pathway and scale
• Global SAF production (2024): approximately 600 million litres (400 million US gallons) — under 0.5% of aviation's ~300 billion litre annual demand

Aircraft Examples

• Airbus A380 — flew a 100% SAF demonstrator flight on one engine (Air France/Total Energies, October 2021)
• Boeing 787-9 operated by Virgin Atlantic — first transatlantic 100% SAF flight, November 2023 (London Heathrow to New York JFK), using Rolls-Royce Trent 1000 engines on SAF
• All major commercial aircraft are certified for 50% SAF blend without modification

SAF is aviation's primary near-term decarbonization lever, with IATA targeting 2% of fuel supply by 2025 and 65% by 2050. The European Union's ReFuelEU Aviation regulation mandates 2% SAF blend by 2025, rising to 70% by 2050. Turbofan engine manufacturers have confirmed compatibility with current and anticipated SAF pathways without hardware changes, though combustor optimization for high-SAF blends is ongoing.