Air travel is really hard to decarbonize: Efficiency improvements can cut carbon emissions per mile flown but are swamped by more people flying; biofuels require massive amounts of land; and hydrogen- and electric-powered aircraft won’t be ready for wide use for a while.
In a new study, researchers analyze what they argue are the only solutions that could feasibly meet the scale of the problem: pulling carbon out of the air and storing it in some permanent form, or pulling carbon out of the air and using it to make synthetic jet fuel.
“Until now, truly ‘green’ synthetic fuels have been considered too expensive and energy-intensive to serve as a practical solution for aviation,” says study team member Nicoletta Brazzola, a postdoctoral researcher at ETH Zurich in Switzerland. “As a result, airlines have increasingly turned to carbon dioxide removal (CDR) to offset their emissions.”
But synthetic fuel has some big environmental advantages over carbon dioxide removal: it reduces climate-warming contrail clouds, and is in line with the broader societal goal of shifting the economy away from fossil fuels.
Brazzola and her collaborators compared the costs and benefits of the two strategies in various economic and public policy scenarios, searching for what conditions would make synthetic jet fuel cost-competitive.
If the goal is to achieve carbon neutrality – that is, eliminate the carbon dioxide emissions associated with aviation – then carbon storage is cheaper, the researchers report in Nature Communications. Synthetic fuel is expensive mainly because it requires a lot of energy and equipment to produce.
But if the goal is the more ambitious – climate neutrality – then the carbon-dioxide-to-jet-fuel strategy wins on cost. That’s because about two-thirds of the climate impact of flying comes from sources other than carbon dioxide, especially contrails.
Other efforts are underway to reduce the climate impact of aviation, and there could be tradeoffs among these approaches. Adding strategies such as reducing air travel demand and changing flight paths to avoid producing contrails to the mix makes synthetic fuel less attractive from a cost point of view, the researchers found.
On the other hand, cheap electricity or expensive fossil fuels shift the cost-benefit analysis in favor of synthetic fuel.
When it comes to what an individual passenger would pay for a carbon- or climate-neutral flight, the cost premium of synthetic fuel is only a little bigger than that of carbon storage. Synthetic fuels would increase ticket prices by about 50% compared to conventional fossil kerosene – a surprisingly modest proportion, Brazzola says, that is “within the range of seasonal fluctuations in ticket prices.”
Still, the findings don’t change the overall picture of air travel and climate change. “Flying less is still one of the most effective ways to reduce aviation’s climate impacts in the short term,” Brazzola says. In the longer term, “Synthetic fuels and carbon removal will likely play an important role” in decarbonizing the industry, “but reducing air travel demand would significantly lower the scale of these technologies required, making the challenge more manageable.”
Source: Brazzola N. et al. “The role of direct air capture in achieving climate-neutral aviation.” Nature Communications 2025.
Image: ©Anthropocene Magazine
