Cutting carbon emissions from planes is going to be difficult—but not impossible. With enough funding, policy support, and alternative fuel, aviation can make enough progress to help the world reach global climate targets by 2050, according to a new report.
Today, aviation makes up about 3% of greenhouse-gas emissions worldwide. Some airlines and industry groups have made pledges to reach net-zero emissions by 2050, but these plans often don’t include details on how to get there.
The new report, published by the International Council on Clean Transportation (ICCT), a nonprofit research group, outlines possible paths for aviation to reduce emissions enough to do its part in keeping global warming at less than 2 °C above preindustrial levels, the target set by the Paris agreement. Reaching that goal will require quick action within aviation and significant policy support for technologies like alternative fuels that don’t currently exist at industrial scale.
Aviation is an industry that’s notoriously difficult to decarbonize. Strict operating and safety requirements limit what technology can be used. Equipment has a long lifetime, so a plane built today will still be flying in 2050. That means technical progress needs to happen quickly to make a dent in emissions decades in the future.
“If you want to decarbonize aviation, you have to start now,” says Lynnette Dray, a principal research fellow at University College London.
Keeping emissions low enough to stay under 2 °C of warming would mean cutting aviation’s annual emissions in 2050 to about half of currently projected levels—a daunting task for an industry that’s expected to grow swiftly in the next few decades. For the industry to hit that target, its emissions would need to peak and start falling by 2030, says Brandon Graver, one of the report authors and a senior aviation researcher at the ICCT. And to further limit warming to 1.75 °C, emissions will need to start falling as soon as 2025.
In the ICCT analysis, about 60% of emissions reductions are projected to come from low-carbon fuels.
But new fuels have a long way to go to reach that kind of impact. The supply of alternative jet fuel represents about 0.05% of the total fuel supply in 2020. Judging from 2018 numbers, a full year’s supply of non-fossil fuel would power global aviation for about 10 minutes.
To keep up with demand in 2050, even in the most conservative estimate, alternative fuel supply would need to grow by about 3,000 times from 2020 levels.
The small amount of commercial alternative fuel produced today derives largely from waste fats, oils, and greases. But the supply of these waste oils is limited, so further fuels will need to come from other sources.
Other biofuels will also play a role, but the actual impact of biofuels on emissions reductions can vary widely depending on their source, says Praveen Bains, an aviation analyst at the International Energy Agency. And biomass sources like agricultural waste will also be too limited to power global flight.
So the aviation industry is also counting on technology like synthetic kerosene as an alternative fuel. At least half of alternative fuel supply in the ICCT projections is from that technology, in which electricity is used to convert carbon dioxide into fuel that planes can burn. While parts of this process are done industrially today, there are huge questions about the technology and its future cost.
In order to make up the rest of the emissions cuts needed to stay below 2 °C by 2050, airlines will need to improve both technical efficiency (for example, how much fuel a plane burns per mile) and operational efficiency (how full flights are). And demand will likely need to slow, either because people travel less or because they shift to other modes of transport, like high-speed trains.
“It’s going to take a lot of work,” Graver says, “and I don’t want people to think that it’s a hopeless cause and that nothing’s going to happen. But we need to take action now.”