Pod Insights Short Wave Is sewage the future of green aviation? About this episode 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 [email protected] mailto:[email protected] .
Listen 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 http://plus.npr.org/shortwave.
See pcm.adswizz.com https://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 https://www.npr.org/about-npr/179878450/privacy-policy
Transcript Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
0:00 Speaker 00 This message comes from Avalara Aviator. Aviator is the agent hub for tax and compliance. Purpose-built AI agents work around the clock and across business systems to help execute the work. Visit avalara.com/aviator.
0:15 Emily Kwong? You're listening to Short Wave from NPR.
0:20 Regina Barber? Hey, Short Wavers. Regina Barber here.
0:22 Emily Kwong? And Emily Kwong. And today, we are taking to the skies on the wings of cooking oil.
0:27 Speaker 03 Well, today, Flight 100 is flying from London to New York on sustainable fuel.
0:32 Regina Barber? OK, that's Richard Branson.
0:34 Emily Kwong? Yes.
0:34 Regina Barber? The co-founder of the Virgin Group.
0:36 Emily Kwong? Was this the first flight run entirely on alternative jet fuel?
0:40 Regina Barber? Yes.
0:40 Emily Kwong? Wow.
0:41 Regina Barber? Virgin Atlantic in 2023 operated a flight powered by biofuel and a synthetic alternative made from plant sugars.
0:47 Emily Kwong? 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.
1:01 Regina Barber? I love this because what's getting us into the air now, it's not great for our planet.
1:05 Emily Kwong? 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 aloft. But the war in Iran has put a damper on those economics. Brian Spies, the Managing Director of Sustainability for Alaska Airlines, is definitely feeling the pinch.
1:24 Speaker 04 We were on track for a really, really great year. And fuel prices have, you know, put us back hundreds of millions of dollars.
1:32 Regina Barber? 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.
1:42 Emily Kwong? Oh, really?
1:43 Regina Barber? Yeah.
1:43 Emily Kwong? 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 Petsonk, the former Assistant Secretary of Transportation for Aviation and International Affairs under the Biden administration.
2:06 Speaker 05 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.
2:25 Regina Barber? 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.
2:37 Emily Kwong? And I'm Regina Barber, and you're listening to Short Wave, the science podcast from NPR.
2:48 Speaker 00 Stay tuned for the following announcements and messages from our sponsors.
2:52 Speaker 06 This message comes from Edward Jones. Where they believe rich is more than caring about the latest and greatest, it's also about taking care of what gives your life meaning. That's why your dedicated financial advisor meets you where you are with personalized financial strategies that help protect what matters so you can preserve your progress while creating a path forward. The key to being rich is knowing what counts. Let's find your rich together. Edward Jones. Member SIPC. This message comes from NPR sponsor, Lynda Mood Bell. Lance was bright, but he struggled to read words. Michelle was the opposite. She could read words easily, but struggled to understand what she read. Like so many students, they struggled not only with learning,
3:37 Speaker 06 but with self-confidence. Personalized one-to-one instruction at Lynda Mood Bell Learning Centers changed that. Today, they read with confidence and they understand what they read. Instruction is available online or in person. Learn more at lyndamoodbell.com/NPR.
3:54 Speaker 00 This message comes from EasyCater, making it easy for organizations to order food for meetings and events from favorite restaurants, set up meal programs for their employees, and manage food spend all in one place at easycater.com.
4:09 Regina Barber? All right, Emily, let's start with basics.
4:11 Emily Kwong? Okay.
4:11 Regina Barber? So the chemistry of alternatives to jet fuel. So some people call this fuel sustainable aviation fuel, or SAF. So SAF.
4:19 Emily Kwong? SAF.
4:20 Regina Barber? What's it made out of?
4:21 Emily Kwong? Yeah, so the most commonly used SAF is made from cooking oils, fats and grease.
4:26 Regina Barber? I love those.
4:26 Emily Kwong? 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.
4:35 Regina Barber? Cool.
4:35 Emily Kwong? This process is known as HEFA, which 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.
4:52 Regina Barber? And this fuel- Works for planes.
4:54 Emily Kwong? Yeah, it does. And the way it works is refineries will blend hefa with regular jet fuel.
4:59 Speaker 07 And Emily, I'm pretty confident you have flown on a plane with some of this stuff on there.
5:04 Regina Barber? Wait, so they're already using this kind of jet fuel, this blend, right now?
5:09 Emily Kwong? A very small amount, yes.
5:11 Regina Barber? Okay.
5:11 Speaker 07 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.
5:25 Emily Kwong? Joshua Hine is the director of the Bioproducts 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.
5:37 Regina Barber? Yeah, so what is the supply like for leftover cooking oil? I'm guessing there's not enough.
5:42 Speaker 07 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.
5:55 Emily Kwong? So the scale question is hard. And for Nafisa Loahuala, 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.
6:17 Regina Barber? Yeah, you said that the UK government granted £1 million British pounds to the Virgin Atlantic flight. So are there other ways to make SAF, this sustainable aviation fuel, besides cooking oil?
6:28 Emily Kwong? 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.
6:52 Regina Barber? Right, because all of this requires a lot of land.
6:55 Emily Kwong? 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?
7:08 Regina Barber? 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 from 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.
7:32 Emily Kwong? That's fascinating, yeah.
7:35 Regina Barber? So is there a way to use something other than biofuels?
7:38 Emily Kwong? It's a very good question. Yes, there is a way to make SAF out of thin air.
7:42 Regina Barber? What?
7:43 Emily Kwong? 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 at a scale.
8:04 Regina Barber? Yeah. Honestly, Em, all 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.
8:16 Emily Kwong? And the cycle just kind of repeats.
8:17 Regina Barber? Yeah.
8:18 Emily Kwong? Yeah, yeah. And I suppose that is where a new $20 million venture in Washington State is trying to break through.
8:25 Speaker 05 State and aviation leaders launched the Cascadia Sustainable Accelerator. It's a new nonprofit designed to help grow the region's clean fuel industry.
8:35 Emily Kwong? 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.
8:55 Speaker 07 Being able to source and find these reference materials, that's what we're hoping to really enable here in the next year.
9:03 Emily Kwong? 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.
9:13 Regina Barber? Oh!
9:14 Speaker 07 You know, we are working with companies that take post anaerobic digested human sewage and turn that into jet fuel.
9:22 Emily Kwong? It's a real twist on another man's trash, you know?
9:24 Regina Barber? This is so cool. Honestly, sewage seems like the best fuel source. I mean, I love it, because humans are always going to poop. Let's fly on it, you know?
9:37 Emily Kwong? You make a good case.
9:38 Regina Barber? Thank you. But how much of this is aspirational? Because planes only run on this tiny amount of SAF now.
9:45 Emily Kwong? 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.
10:01 Regina Barber? Wow, just 10.
10:03 Emily Kwong? 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.
10:31 Regina Barber? That would be amazing if it happened, though. The ultimate solution to all of this is just to not fly, right? Cut back on flying.
10:38 Emily Kwong? Yeah, climate experts would definitely back you up on this. Driving amidst much less carbon than flying.
10:44 Regina Barber? So we should just road trip more, right?
10:45 Emily Kwong? 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 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 US airlines.
11:11 Regina Barber? So the political will is just not there anymore?
11:14 Emily Kwong? 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 Kasotis 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, 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.
11:55 Speaker 05 Into gear and we didn't even notice until a few weeks later.
11:59 Emily Kwong? When London's Heathrow Airport had to shut down for a day for a similar reason.
12:04 Speaker 05 And somebody on my staff said, oh, you know, that just happened to us. And we were like, what? We didn't even know.
12:09 Emily Kwong? 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 starches into jet fuel.
12:30 Regina Barber? So they're going to use this alcohol to jet fuel process?
12:32 Emily Kwong? Yes.
12:33 Regina Barber? Wow.
12:33 Emily Kwong? Though they are also exploring the waste to fuel pipeline, too. They just want to make SAF for Pittsburgh planes.
12:38 Regina Barber? It's the sewage. I'm telling you, I love it.
12:41 Emily Kwong? 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 healthcare town. People need to get reliably flown in and organs, too.
13:05 Speaker 05 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, let's just go.
13:25 Regina Barber? I mean, they did make this microgrid happen, right? So maybe they could make a breakthrough with SAF, too.
13:31 Emily Kwong? Someone's got to do it. And maybe it'll be Washington, maybe Pennsylvania. Who knows?
13:36 Regina Barber? We're in a race.
13:37 Emily Kwong? We probably should race for this. The planet may be counting on us.
13:41 Regina Barber? Emily Kwong, my Short Wave co-host, thank you so much for reporting.
13:45 Emily Kwong? Oh, my gosh. Thank you so much, Gina. This was really fun.
13:49 Regina Barber? This episode was produced by Hannah Chin. It was edited by Brent Bachman and our showrunner, Rebecca Ramirez.
13:54 Emily Kwong? Special thanks to Daniel Offman, Sarah Robins, and Julia Simon. Tyler Jones checked the facts. Kwasi Lee was the audio engineer. I'm Emily Kwong.
14:02 Regina Barber? And I'm Regina Barber. Thank you for listening to Short Wave from NPR.
14:13 Speaker 00 Stay tuned for the following announcements and messages from our sponsors. This week on Up First, we're in the final days before the midterm elections. And this is one of the wonderful things about politics, one of the wonderful things about humanity. We have all this data, we have all this information, and nobody really knows what's gonna happen.
14:32 Speaker 06 We're gonna follow it day by day, through Election Day and beyond. And you can listen to Up First every morning on the NPR app or wherever you get your podcasts. I'm Kevin Roos. And I'm Casey Newton. And together, we've been tech journalists for decades. Now, we're your hosts of Machine Gods, a new podcast from NPR that makes sense of what AI means for your work, your life, and all of our futures. Twice a week, we'll be exploring the biggest moves in tech and give you unmatched access to the real titans of industry. Listen to Machine Gods from NPR on the NPR app or wherever you get your podcasts.
Previous Could air pollution make your memory worse? Next Why scientists launched two little robots to the moon Page updated October 30, 2026 · transcript and summary are machine-generated