Carbon-neutral jet fuel — specifically synthetic aviation fuel made by capturing CO₂ directly from the atmosphere and combining it with green hydrogen — is currently the most credible long-term decarbonization pathway for commercial aviation. Electric and hydrogen aircraft remain structurally limited by energy density physics at commercial scale. SAF (Sustainable Aviation Fuel) derived from atmospheric carbon is the only solution that fits inside existing aircraft, existing airports, and existing economics — at least in theory.
The gap between "in theory" and "on the tarmac" is where almost everything interesting, and troubling, lives.
The Physics Problem Nobody in Aviation Marketing Wants to Talk About
Aviation is, by almost every measure, one of the hardest sectors to decarbonize. This isn't a political statement. It's a thermodynamics statement.
Jet fuel carries roughly 43 megajoules per kilogram of energy. The best lithium-ion batteries available today sit somewhere around 0.7–0.9 MJ/kg at pack level. That's not a gap that gets closed with incremental battery chemistry improvements. Liquid hydrogen gets closer on energy density by mass, but its volumetric density is terrible — a hydrogen-fueled aircraft would need fuel tanks roughly four times larger than a conventional one, which structurally doesn't fit inside a narrowbody fuselage without a complete redesign.
So the aviation industry is, somewhat by process of elimination, pointing itself toward synthetic liquid fuels — specifically e-fuels or power-to-liquid (PtL) SAF made from captured CO₂ and green hydrogen. The argument is elegant: you pull carbon from the atmosphere, you combine it with hydrogen made from electrolyzed water using renewable electricity, you synthesize hydrocarbons through Fischer-Tropsch or methanol-to-jet pathways, and you burn them in an aircraft. The carbon released during combustion was carbon you pulled from the air. Net zero, in principle.
In practice, the energy math is brutal.
The Energy Accounting Nobody Shows You on the Infographic
To make one liter of synthetic jet fuel via the PtL pathway, you need — depending on process efficiency and carbon capture technology — somewhere between 6 and 10 kWh of renewable electricity. That number includes electrolysis losses, CO₂ capture energy, synthesis energy, and compression. It does not include logistics, distribution, or the energy cost of building the infrastructure.
Commercial aviation consumed approximately 360 billion liters of jet fuel in a near-normal year before COVID disruptions. If you tried to replace all of that with atmospheric PtL SAF today, you'd need renewable electricity capacity that doesn't currently exist at any scale remotely close to that. You'd also need direct air capture (DAC) infrastructure that the entire world hasn't yet deployed even a fractional percentage of.
The honest version of the carbon-neutral jet fuel story isn't "we have a solution." It's "we have a chemistry that could be a solution if we build the energy infrastructure of several industrial revolutions in the next two to three decades."
What's Actually Being Built Right Now
Despite the scale gap, real infrastructure is going in the ground — slowly, expensively, with a lot of engineering pain.
Climeworks in Iceland has been running DAC operations commercially, pulling CO₂ from ambient air using geothermal-powered systems. Their Mammoth plant, commissioned in 2024, has a nameplate capacity of around 36,000 tonnes of CO₂ per year — which sounds impressive until you remember that global aviation emits roughly 900 million tonnes of CO₂ annually. Mammoth could offset about four seconds of global aviation emissions per year.
Haru Oni in Chile — a joint venture involving Porsche, HIF Global, Siemens Energy, and others — is producing synthetic e-methanol and e-gasoline using wind power and DAC. Their pathway isn't optimized for jet fuel yet, but the process engineering overlaps substantially.
Norsk e-Fuel in Norway is building a dedicated PtL jet fuel facility targeting 12.5 million liters per year initially. That's roughly 0.003% of pre-COVID European aviation fuel demand.
These aren't failures. They're genuine first steps. But the gap between first steps and the scale aviation needs is so vast that it strains credibility to present current SAF production numbers as progress toward a solution, rather than progress toward proof-of-concept.
Why Airlines Are Buying SAF Anyway — And Why the Incentive Structure Is Broken
Airlines are buying SAF certificates and small volumes of blended fuel, and they're doing so for reasons that aren't primarily about decarbonization. They're doing it because: