Renewable diesel and SAF: Techniques
HEFA rules today; gasification and alcohol-to-jet are still first plants
What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.SAF reached about 1.9 million tonnes (2.4 billion litres) in 2025, 0.6% of jet fuel use, mostly from HEFA plants that also make renewable diesel. Gasification, alcohol-to-jet and co-processing are at first-plant stage.
Comparison
| Method | Efficiency | Cost | Life-cycle emissions | Maturity | Scale |
|---|---|---|---|---|---|
| HEFA renewable diesel (HVO)1345 | 80-85% of output is diesel when jet is 15-20% (calculated) | Feedstock is about 80% of total cost | EU typical savings: rapeseed 51% (about 46 g CO2eq/MJ, calculated), waste cooking oil 87% (about 12), palm with open effluent ponds 34% (about 62) | mature | US renewable diesel capacity 4,989 million gallons a year (September 2025); output down 12% Q1 2024 to Q1 2025 |
| HEFA sustainable aviation fuel126785 | 15-20% jet as standard, up to 50% | USD 1.7 per litre (Rotterdam, September 2020); in 2025 SAF cost about twice fossil jet, and up to five times in mandated markets | ICAO defaults including land-use change: used cooking oil 13.9, tallow 22.5, soybean 61.1-62.9, rapeseed 70.2-71.3, palm 74.0-96.6 g CO2eq/MJ, against 89 for fossil jet | early commercial | 1 Mt in 2024, 1.9 Mt in 2025; US capacity about 30,000 barrels a day (May 2025); IEA forecasts 9 billion litres by 2030 |
| Co-processing in oil refineries72 | Not quantified | Not quantified | ICAO, biogenic share: used cooking oil 16.7, tallow 27.2, soybean 61.4-63.2 g CO2eq/MJ | early commercial | 13 facilities announced |
| Gasification with Fischer-Tropsch synthesis21710 | 14-18% distillate by mass from residues | USD 4,560-5,560 per kW for early US plants; over USD 1 billion per plant | ICAO: agricultural residues 7.7, forestry residues 8.3, municipal waste 5.2 g CO2eq/MJ | pilot | The only commercial plant (Fulcrum Sierra, from 2022) shut in May 2024; 20 plants (2.24 billion litres a year) announced |
| Alcohol-to-jet17211 | Up to 70% jet in theory | Not quantified | ICAO: sugarcane ethanol 32.6-52.9, corn ethanol 72.4-100.6 g CO2eq/MJ | early commercial | First commercial-scale plant (LanzaJet Freedom Pines, US) produced fuel in November 2025; 21 plants (2.84 billion litres a year) announced |
HEFA dominates because it is a simple refinery process, but feedstock limits it: scarce waste oils give about 14 g CO2eq/MJ against 89 for fossil jet, while crop oils with land-use change approach fossil levels. Fischer-Tropsch has the lowest emissions and largest feedstock pool but costs over USD 1 billion per plant and yields only 14-18% fuel by mass. Alcohol-to-jet inherits ethanol's land-use emissions. SAF costs roughly two to five times fossil jet.
How each method works
HEFA renewable diesel (HVO)Oils and fats are reacted with hydrogen over a catalyst to remove oxygen, and the paraffins are isomerised into a drop-in replacement for fossil diesel.1345
HEFA sustainable aviation fuelThe same paraffins are cracked and isomerised more severely, distilled to the jet range and blended with fossil jet (approved 2011).126785
Co-processing in oil refineriesUp to 5% fats or oils are fed into an existing refinery hydrotreater with fossil fractions.72
Gasification with Fischer-Tropsch synthesisWood, residues or waste are gasified to syngas (carbon monoxide and hydrogen), cleaned, and synthesised over a catalyst into hydrocarbons that are cracked to jet and diesel.21710
Alcohol-to-jetEthanol or isobutanol is dehydrated to light olefins, which are joined into longer chains and hydrogenated to jet fuel.17211
Sources
- Reaching Zero with Renewables: Biojet fuels IRENA, 2021
- Progress in commercialisation of biojet / SAF (van Dyk, IEA Bioenergy workshop presentation) IEA Bioenergy Task 39 (hosted by DBFZ), 2023
- Directive (EU) 2018/2001 (Renewable Energy Directive II), Annex V: typical and default greenhouse gas savings for biofuels; fossil comparator 94 g CO2eq/MJ. Default values not changed by amending Directive (EU) 2023/2413 (RED III); a Commission revision was in draft in 2026 European Union (EUR-Lex), 2018
- Monthly Biofuels Capacity and Feedstocks Update, Table 1: U.S. biofuels operable production capacity US Energy Information Administration, 2025
- Renewables 2025: Renewable transport International Energy Agency, 2025
- SAF Production Growth Rate is Slowing Down, Essential to Correct Course Ahead of e-SAF Mandates (press release, 9 December 2025) IATA, 2025
- CORSIA Default Life Cycle Emissions Values for CORSIA Eligible Fuels (ICAO document 06) International Civil Aviation Organization, 2025
- U.S. sustainable aviation fuel production takes off as new capacity comes online (Today in Energy, 6 May 2025) US Energy Information Administration, 2025
- Fulcrum BioEnergy shuts down Sierra BioFuels plant in Nevada (5 June 2024) Waste Dive, 2024
- LanzaJet produces first jet fuel from ethanol at a commercial scale (19 November 2025) Hydrocarbon Processing, 2025