EMILY FENG, HOST:
Travel depends on fossil fuels, but the war in Iran has disrupted the global fuel supply, and that has sent prices soaring, which is why European airlines like Lufthansa and KLM have announced they are cutting flights. And other airlines could follow. This got us wondering. Could another fuel source help take us to the skies? We've brought in someone with the science chops to help us dig through this, Short Wave co-host Emily Kwong. Hi, fellow Emily.
EMILY KWONG, BYLINE: Hello, fellow Emily.
FENG: I want to start with the basics...
KWONG: Yeah.
FENG: ...Which is what is alternative aviation fuel, or what some people call sustainable aviation fuel or even SAF for short?
KWONG: Yeah, so these are jet fuels made from nonpetroleum sources. The most common is cooking oil, but you can also make SAF out of agricultural crops, municipal waste. There's even synthetic possibilities. And these fuels are compatible with today's airplanes. So the idea is to basically supplement what fuels planes with something cleaner.
FENG: Like, do to planes what we've done to cars by making a hybrid electric vehicle, for example?
KWONG: Yeah, it's like a blend of energy sources. That's a great comparison. And I got to say, even I, science believer, was skeptical at the idea of a plane powered by leftover french fry oil.
FENG: Really?
KWONG: Yeah. So the first thing I wanted to know is, is this even safe?
JOSHUA HEYNE: Absolutely. And, Emily, I'm pretty confident you have flown on a plane with some of this stuff on there.
KWONG: This is Joshua Heyne, the director of the Bioproducts, Sciences and Engineering Lab at Washington State University.
HEYNE: If you flew out of LAX within the last few years, it's likely been on a plane you've been on. So roughly 0.6% of the global jet fuel consumption is this used cooking oil and other fats, oils, greases.
KWONG: But the economics, the supply side of this, is really tricky.
FENG: Right. Is there enough leftover cooking oil in the world to power the entire global aviation industry?
KWONG: Not at all, no. Cooking oil is not going to be a silver bullet to decarbonize aviation. Heyne says what's needed is a diverse portfolio of different technologies so SAF can be produced at scale and be affordable enough for airlines to even want to buy it. I heard something similar from Nafisa Lohawala, a fellow with the think tank Resources for the Future.
NAFISA LOHAWALA: Basically, de-risking this market is a big challenge for investors, for private investors, to feel comfortable, you know, spending their money here.
KWONG: And that's why a new venture in the Pacific Northwest is trying to break through. So earlier this year, Alaska Airlines and Washington state leaders announced the Cascadia Sustainable Aviation Accelerator. The goal of this project is to diversify that alternative jet fuel portfolio. Heyne is the technical lead for the project and a self-described fuel nerd.
HEYNE: We are working with companies that take postanaerobic-digested human sewage and turn that into jet fuel.
KWONG: It's a real twist on another man's trash, but for planes.
FENG: Using human sewage? Wow.
KWONG: That is something that a team (ph) might explore in the lab. Yes, yes, yes.
FENG: How much of all this is aspirational, Emily?
KWONG: Yeah. I mean, so much more science needs to be done. It's so early. And these projects, I mean, they can fail. A recent Reuters investigation found that of the 165 SAF projects announced by airlines over the last few years, only 10 reported producing commercial volumes of SAF. Also, another critique of these fuels that's important to say - the biobased ones - is that they have a potential impact on land use and food prices. But the biggest hurdle, of course, is whether all these different groups - government, industry, scientific institutions - can even come together to develop SAF at scale.
FENG: That's Emily Kwong, the co-host of Short Wave, NPR's science podcast. Thank you, Emily.
KWONG: Thanks so much.
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