The second option is sustainable aviation fuel which could, ideally, be used by existing airplanes and emit fewer greenhouse gasses. At least, that’s the idea. One study of four alternative aviation fuels by researchers in the UK concluded that none would be able to replace fossil fuels in the near term. Biofuels would require a massive portion of arable land, and options like hydrogen would require significantly more renewable energy than the UK currently produces.
It’s worth noting that year over year, new airplane models are using less fuel. But the challenge with incremental improvements to emissions—like making a fuel that releases, say, 10 percent less carbon, or a plane that requires 15 percent less—is that demand for air travel is still growing, and quickly. Any gains are quickly offset by increased use. According to the International Energy Agency, new aircraft models are up to 20 percent more efficient than the older planes they’re replacing. But aviation emissions still keep increasing every year because additional flights make up the difference.
You don’t have to know much about decarbonization or the airline industry for the combination of ‘sustainable’ and ‘air travel’ to set off some greenwashing and oxymoron alarms. But that’s not to say that a combination of less-polluting technologies, thoughtful and limited expansion (Amsterdam’s Schiphol airport, for example, capped the number of flights allowed in and out each year), and curbing demand couldn’t ultimately lead to fewer aviation emissions.
