Achieving carbon-neutral aviation by 2050 requires a combination of emerging technologies, infrastructure changes, and policies. Sustainable Aviation Fuels (SAF) are among the most promising near-term solutions for reducing carbon emissions in aviation. They are produced from biomass, waste oils and fats, municipal solid waste, and e-fuels (CO₂ + renewable hydrogen).
SAF can be used in existing aircraft engines with little or no modification and can reduce lifecycle carbon emissions by up to 80% versus fossil jet fuel. Drop-in capability means airports and airlines can adopt SAF without significant changes to infrastructure. The challenges are scale, cost, and feedstock availability.
The need for SAF and the EU mandates
While some technology developers are pursuing SAF on idealistic grounds, the main near-term driver is European legislation. From 2025, 2% of all fuel uplifted from EU airports must be sustainable, rising to 6% by 2030, 20% by 2035, and 70% by 2050. ReFuelEU additionally requires that 1.2% of fuel be of synthetic origin (eSAF) by 2030, rising to 35% by 2050.
Approved pathways and where MTJ fits
The main commercial ASTM D-7566 approved pathways are Hydroprocessed Esters and Fatty Acids (HEFA), Alcohol-to-Jet (ATJ), and Fischer–Tropsch (FT). These rely on biogenic carbon and therefore do not qualify as eSAF under ReFuelEU.
Methanol-to-Jet (MTJ) does not yet hold ASTM D-7566 approval, but is technically and commercially attractive. When the methanol is produced synthetically, from CO₂ and green hydrogen, the resulting fuel qualifies as eSAF.
The Methanol-to-Jet process
Methanol is converted to aviation fuel in a sequence of steps. First, methanol is converted into olefins (short unsaturated hydrocarbons such as ethylene and propylene) via dimethyl ether (DME), with water eliminated as part of the chemistry. After an initial fractionation that removes light methane and heavy aromatics, heavier unsaturated hydrocarbons are produced from the olefins via oligomerization and isomerization on a ZSM-5 catalyst. A second fractionation step yields gasoline and a heavier distillate. The raw distillate is hydrotreated and may need further treatment to meet ASTM D-7566.
Indicative process conditions
- MTO reactor: ~2 bar, ~450 °C, ZSM-5
- MOGD reactor: ~40 bar, ~200 °C, ZSM-5
- Hydrogenation: ~40 bar, ~300 °C
The most important parameters are the SAF yield per unit feedstock and the overall energy intensity. Catalyst development drives the first; integration with energy-demanding facilities drives the second, the process is a net energy producer.
A 20 kta business case
We developed a case for a 20 kta SAF facility based on the MTO–MOGD MTJ pathway. The process was simulated in AspenPlus, producing heat and material balances that fed preliminary equipment design and plot plan development. A crude economic analysis was then built on top.
Economic viability depends greatly on feedstock and product pricing, both set by the competitive marketplace, not by the scale of an MTJ plant. For biobased fuels, HEFA and ATJ are more price-competitive and that gap is unlikely to close in the short to medium term. For the e-fuels route, however, MTJ is likely to outperform FT on carbon and energy efficiency. With expected pricing of around 1,400 EUR/t for e-methanol and 4,000 EUR/t for eSAF, an MTJ business case may be feasible.
Outlook
Carbon-neutral aviation in 2050 will require widespread adoption of SAF, supported by strong policy. All currently available production pathways suffer from feedstock limitations, so additional production technologies will be needed. MTJ is built on already-proven methanol conversion chemistry, but further catalyst and process improvements will be necessary to be competitive. Securing methanol availability is critical, which makes the closing of Ørsted's FlagshipONE e-methanol project (55 kta, the largest commercial-scale facility under construction in Europe) a meaningful setback for the field.