Short Wave - Is sewage the future of green aviation?

Episode Date: June 17, 2026

The war in Iran has disrupted the global fuel supply. That has sent airline prices soaring and cancelled scores of flights. This got Short Wave host Emily Kwong wondering: Could another fuel source help take us to the skies? Today on the show, we explore the chemistry and cost of sustainable aviation fuel. Along the way, we highlight two initiatives to create a regional SAF supply – one in Washington and one in Pennsylvania.  Interested in more stories about the future of flying? Email us your question at [e-mail] to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, Shire Waver is Regina Barber here. And Emily Kwong, and today we are taking to the skies on the wings of cooking oil. Well, today, Flight 100 is flying from London to New York on sustainable fuel. Okay, that's Richard Branson. Yes. Okay. The co-founder of the Virgin Group.

Was this the first flight run entirely on alternative jet fuel? Yes. Wow. Virgin Atlantic in 2023 operated a flight powered by biofuel. and a synthetic alternative made from planet sugars. This flight was incredibly expensive, receiving up to 1 million British pounds from the UK government, all to prove a scientific point that a plane can fully run on something other than jet fuel, which, as you know, comes from fossil fuels.

I love this, because what's getting us into the air now, it's not great for a planet. No. At any given moment, there are thousands of planes in the air, and jet fuel is the only thing energy dense enough and cheap enough to keep that industry. a loft. But the war in Iran has put a damper on those economics. Brian Spees, the managing director of sustainability for Alaska Airlines, is definitely feeling the pinch. We were on track for a really, really great year. And fuel prices have, you know, put us back hundreds of millions of dollars. Right. The Strait of Hormuz has been effectively closed for months. So some airlines

are running low on fuel. Ticket prices have gone up. This has already affected my travel this year. I've cut back. Oh, really? Yeah. Well, honestly, that is. an airline company's worst nightmare. They need our butts in those seats to meet their bottom line. So in a strange way, this global crisis has kicked down the door for a new kind of conversation about alternatives to jet fuel. And someone who pointed this out to me is Annie Petzank, the former Assistant Secretary of Transportation for Aviation and International Affairs under the Biden administration. Because of the Iran War fuel price shocks, a number of airlines and a number of policymakers are starting to see alternative fuel as a national security matter.

We can produce our own fuel here in the United States and not be dependent on foreign oil producers. Today on the show, Greener flights. We explore a bunch of alternatives to jet fuel. Their chemistry, their cost, and what it would actually take to decarbonize the aviation industry for good. I'm Emily Kwong.

And I'm Regina Barber, and you're listening to Shortwave, the science podcast from NPR. All right, Emily. Let's start with basics. Okay. So the chemistry of alternatives to jet fuel. So some people call this fuel sustainable aviation fuel or SAF, so SAF. SAF. What's it made out of? Yeah. So the most commonly used saff is made from cooking oils, fats and greases. I love those. Yeah. At a molecular level, they're similar to jet fuel. These long chains of hydrocarbons go through a chemical glow up to be something that airplanes can fly on. Cool. This process is known as Hefa, which is a lot. stands for hydro process esters and fatty acids. And by the way, that Virgin Atlantic flight we mentioned earlier was mostly powered by Hefa fuel. And this fuel is chemically similar to renewable diesels, which are already used in land and aquatic vehicles.

And this fuel works for planes. Yeah? It does. And the way it works is refineries will blend Hefa with regular jet fuel. And Emily, I'm pretty confident you have flown on a plane with some of this stuff on there. Wait, so they're already using this kind of jet fuel, this blend. right now. A very small amount. Yes. Okay. 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. Joshua Hine is the director of the Bioproduct Sciences and Engineering Lab at Washington State University. And he explained to me that the main problem with SAF isn't the chemistry. It's not the science. It's the economics. Yeah, so what is the supply like for leftover cooking oil? I'm guessing there's not enough. No, there's not enough. So what we need is a diverse portfolio of lots of different technologies that will enable the scale of SAF production globally to occur. So the scale question is hard. And for Nefisa Lohoala, a fellow with the think tank resources for the future, the supply chain problem exists because of the underlying cost issues. SAF is just extremely expensive to make. Basically, derisking this market is a big challenge for investors, for private investors

to feel comfortable, you know, spending their money here. Yeah, you said that the UK government granted one million British pounds to the Virgin Atlantic flight. So are there other ways to make SAF, this sustainable aviation fuel besides cooking oil? There are. In fact, 11 conversion processes for SAF production have been approved by regulators. One of the most promising is the alcohol to jet process, where you convert starches like corn or cellulose biomass into ethanol, which then gets converted into jet fuel. It's technically possible. But to scale it, again, that scale question for airplanes would take a lot of financial investment and raw material. Right, because all of this requires a lot of land.

Yes, yes. And that is a major critique of bio-based fuels overall. Their potential negative impact on land use and even food prices. I mean, we need land for crops. Do we also have enough to fuel cars and planes, too? Yeah, I remember in the early 2000s, I was at Washington State University, a big agriculture school. And there was this huge push for biofuels made for things like corn. But then there were these environmental concerns. Like, some people thought it could be better to use the land for other things, like solar panels, for instance, instead of crops.

Although I should say, Emily, this debate was mostly about cars and the huge fuel demand that would create. That's fascinating. Yeah. So is there a way to use something other than biofuels? It's a very good question. Yes, there is a way to make SAF out of thin air. What? Yeah, the way you do this is you combine captured carbon dioxide, say from direct air capture,

with hydrogen atoms found in water. And those liquid hydrocarbons can be converted into SAF. However, this synthetic process is even more expensive than the bio-based processes. So it's just not practical right now to scale. Yeah. Honestly, M, all of this sounds like a chicken and an egg problem. Like, SAF is too expensive and resource intensive to make. So supply is low.

So planes keep running on jet fuel. And the cycle just kind of repeats. Yeah. Yeah, yeah. And I suppose that is where a new $20 million venture in Washington State is trying to break through. State and aviation leaders launched the Cascadia Sustainable Accelerator. It's a new nonprofit designed to help grow the region's clean fuel industry. The goal of the Cascadia Accelerator in your home state of Washington is to make SAF for the Pacific Northwest.

Alaska Airlines is a partner. Washington State University is a partner. They want to create a reference library. Basically that portfolio Joshua was talking about of all the different ways that SAF can be made in the future. Being able to source and find these reference materials, that's what we're hoping to really. enable here in the next year. Joshua is the technical lead for this

project and a self-described fuel nerd. His lab has already received SAF samples from 40 different institutions. You know, we are working with companies that take post anaerobic digested human sewage and turn that into jet fuel.

It's a real twist on another man's trash, you know. This is so cool. Honestly, like sewage seems like the best fuel I mean, I love it because humans are always going to poop. Let's fly on it, you know? You make a good case. Thank you. But how much of this is like aspirational? Because planes only run on this tiny amount of SAF now. Yeah, also true. I mean, exciting as this venture is, it has a lot to prove.

A recent Reuters investigation found that of the 165 SAF projects that have been announced by airlines over the last few years, only 10 reported producing commercial volumes of SAF. Wow. Just 10. Just 10. Because there's so many obstacles to doing this. There's high upfront costs. We have the raw materials question. And also just the amount of cooperation needed between so many different groups, government, industry, and research to truly make SAF at scale and reinvent flying as we know it. And that's kind of what I want to spend the rest of the episode talking about Gina, just the sheer amount of collaboration and political will that would have to happen to decarbonize. aviation. That would be amazing if it happened, though. The ultimate solution to all of this is just to

like not fly, right? Cut back on flying. Yeah, climate experts would definitely back you up on this. Driving emits much less carbon than flying. So we should just road trip more, right? Yeah, yeah. Short distances maybe drive instead of fly. This, of course, doesn't solve the problem, though, of decarbonizing aviation in the first place. That would take federal policy. Now, there were SAF credits put in place by the Biden administration in an effort to insuff. incentivize airlines to find alternative fuels. But last year, the Trump administration cut the SAF tax credit almost in half. Kind of took the heart out of the policy to make SAF desirable for U.S. Airlines. So the political will is just not there anymore?

Not at the federal level right now, no. But at the state level, in the state of Pennsylvania, it's a slightly different story. The grid is our backup. We can operate in any situation where the grid might go down. Christina Cosotis is the CEO of the Allegheny County Airport Authority, which operates Pittsburgh International Airport. Now, this airport's kind of interesting. Back in 2021, Pittsburgh became the first major airport in the world to be powered by its own microgrid. Oh. Run on five natural gas turbines and eight acres of solar, which is super helpful when the main grid that connects Pittsburgh goes down like happened last year. The lights flickered for a couple of seconds and it kicked into gear and we didn't even notice until, a few weeks later. When London's Heathrow Airport had to shut down for a day for a similar reason.

And somebody on my staff said, oh, you know, that just happened to us. And we were like, what? We didn't even know. They're just living off the grid. This airport is living off the grid. They are. Yeah. And this self-sufficiency, this can-do attitude, has now inspired the airport to figure out how to make SAF to fuel their planes. So last year, the airport announced it was teaming up with a company to build a plant to one day turn these start. into jet fuel. So they're going to use this alcohol to jet fuel process. Yes. Though they are also exploring the waste to fuel pipeline too. They just want to make SAF for Pittsburgh planes. It's the sewage. I'm telling you, I love it. Yeah, we'll see what they come up with. By the way, Christina told me in an email that she doesn't anticipate any land use

changes or impacts to existing commodities for the sake of this SAF production plant. She wants to see that plant built near the Pittsburgh airport in the next two years. All of this to make the airport even more self-sufficient. Because Pittsburgh is a health care town. People need to get reliably flown in, and organs, too. Every day, there are live organs coming in, transplant teams coming in, and I feel like we have an obligation to make sure that no matter what, we don't close. It's the same energy we bring to making sure that no matter how much snow is falling, those runways stay open. There's a real need for airports to be resilient, and I feel like let's just go. I mean, they did, make this microgrid happen, right? So maybe they could make a breakthrough with SAF too.

Someone's got to do it. And maybe we'll be Washington, maybe Pennsylvania. Who knows? We're in a race. We probably should race for this. The planet may be counting on us. Emily Kwong, my shortwave co-host, thank you so much for reporting. Oh my gosh. Thank you so much, Gina. This was really fun. This episode was produced by Hannah Chin. It was edited by Brent Bachman and our showrunner, Rebecca Ramirez. Special thanks to Daniel Offman, Sarah. Robbins and Julia Simon. Tyler Jones checked the facts. Quasi Lee was the audio engineer. I'm Emily Kwong. And I'm Regina Barber. Thank you for listening to Shorewave from NPR.