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Emily Kwong
You're listening to Short Wave from NPR. Hey, shortwavers, 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.
Regina Barber
Richard Branson is the co founder of the Virgin Group. Was this the first flight run entirely on alternative jet fuel?
Emily Kwong
Yes.
Regina Barber
Wow.
Emily Kwong
Virgin Atlantic in 2023 operated a flight powered by biofuel and a synthetic alternative made from plant 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.
Regina Barber
I love this. Because what's getting us into the air now? It's not great for a planet.
Joshua Hein
No.
Emily Kwong
And 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. Ryan Spies, the managing director of sustainability for Alaska Airlines, is definitely feeling the pinch.
Joshua Hein
We were on track for a really, really great year. And fuel prices have, you know, put us back hundreds of millions of dollars.
Regina Barber
Right. The Strait of Hormuz has been effectively closed for months, so some airlines are running low on fue. Ticket prices have gone up. This has already affected my travel. This year, I've cut back.
Emily Kwong
Oh, really?
Regina Barber
Yeah.
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.
Regina Barber
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
Emily Kwong
fuel, their chemistry, their cost, and what it would actually take to decarbonize the aviation industry for good. I'm Emily Kwong.
Regina Barber
And I'm Regina Barber. And you're listening to Shortwave, the science podcast from npr.
Angie
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Regina Barber
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 S a F saf. What's it made out of?
Emily Kwong
Yeah, so the most commonly used SAF is made from cooking oils, fats and greases.
Regina Barber
I love those.
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.
Regina Barber
Cool.
Emily Kwong
This process is known as hefa, which stands for hydroprocessed 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.
Regina Barber
And this fuel works for planes?
Emily Kwong
Yeah, it does. And the way it works is refineries will blend HEFA with regular jet fuel.
Joshua Hein
And Emily, I'm pretty confident you have Flown on a plane with some of this stuff on there.
Regina Barber
Wait, so they're already using this kind of jet fuel, this blend right now?
Emily Kwong
A very small amount, yes.
Regina Barber
Okay.
Joshua Hein
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. Is this used cooking oil and other fats, oils, greases.
Emily Kwong
Joshua Hein 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.
Regina Barber
Yeah. So what is the supply like for leftover cooking oil? I'm guessing there's not enough.
Joshua Hein
No, there. 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.
Emily Kwong
So the scale question is hard. And for Nafisa Lohualla, 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.
Regina Barber
Basically, de risking this market is a
Christina Cassotis
big challenge for investors, for private investors
Regina Barber
to feel comfortable, you know, spending their money here. 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?
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 scale it again. That scale question for airplanes would take a lot of financial investment and raw material.
Regina Barber
Right. Because all of this requires a lot of land.
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?
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.
Emily Kwong
That's fascinating.
Regina Barber
Yeah. So is there a way to use something other than biofuels?
Emily Kwong
It's a Very good question. Yes, there is a way to make SAF out of thin air.
Regina Barber
What?
Christina Cassotis
Yeah.
Emily Kwong
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, it's just not practical right now to scale.
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
Emily Kwong
and the cycle just kind of repeats. Yeah, yeah, yeah, yeah. And I suppose that is where a new 20 million venture in Washington state is trying to break through.
Regina Barber
State and aviation leaders launched the Cascadia Sustainable Accelerator. It's a new nonprofit designed to help grow the region's clean fuel industry.
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, being
Joshua Hein
able to source and find these reference materials, that's what we're hoping to really enable here in the next year.
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.
Joshua Hein
You know, we are working with companies that take post anaerobic digested human sewage and turn that into jet fuel.
Emily Kwong
It's a real twist on another man's trash.
Regina Barber
You know, this is so cool. Honestly, like sewage seems like the best fuel source. I mean I love it. Because humans are always going to poop. Let's fly on it.
Emily Kwong
You know, you make a good case.
Regina Barber
Thank you. But how much of this is like aspirational? Because planes only run on this tiny amount of stuff now.
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.
Regina Barber
Wow. Just 10.
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.
Regina Barber
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.
Christina Cassotis
Yeah.
Emily Kwong
Climate experts would definitely back you up on this. Driving emits much less carbon than flying.
Regina Barber
So we should just road trip more, right?
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 U.S. airlines.
Regina Barber
So the political will is just not there anymore.
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.
Christina Cassotis
The grid is our backup. We can operate in any situation where the grid might go down.
Emily Kwong
Christina Cassotis 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 micro grid.
Regina Barber
Oh.
Emily Kwong
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,
Christina Cassotis
the lights flickered for a couple of seconds and it kicked into gear. And we didn't even notice until a
Emily Kwong
few weeks later when London's Heathrow Airport had to shut down for a day for a similar reason.
Christina Cassotis
And somebody on my staff said, oh, you know, that just happened to us.
Regina Barber
And we were like, what?
Christina Cassotis
We didn't even know.
Regina Barber
They're just living off the grid. This airport is living off the grid.
Emily Kwong
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 they're 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.
Regina Barber
So they're going to use this alcohol to jet fuel process? Yes.
Emily Kwong
Though they are also exploring the waste to fuel pipeline, too. They just want to make SAF for Pittsburgh planes.
Regina Barber
It's the sewage, I'm telling you. I love it.
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 health care town, people need to get reliably flown in. And organs too.
Christina Cassotis
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.
Regina Barber
I mean, they did make this micro grid happen, right? So maybe they could make a breakthrough with SAF too.
Emily Kwong
Someone's got to do it. And maybe it'll be Washington, maybe Pennsylvania. Who knows?
Regina Barber
We're in a race.
Emily Kwong
We probably should race for this. The planet may be counting on us.
Regina Barber
Emily Kwong, my shortwave co host, thank you so much for reporting.
Emily Kwong
Oh my gosh, thank you so much, Gina. This was really fun.
Regina Barber
This episode was produced by Hannah Chin. It was edited by Brent Baughman and our showrunner, Rebecca Ramirez.
Emily Kwong
Special thanks to Daniel Offman, Sarah Robbins and Julia Simon. Tyler Jones checked the facts. Kwesi Lee was the audio engineer. I'm Emily Kwong.
Regina Barber
And I'm Regina Barber. Thank you for listening to Short Wave from.
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Date: June 17, 2026
Hosts: Emily Kwong & Regina Barber
This episode of Short Wave dives into the world of sustainable aviation fuels (SAF), specifically exploring wild new possibilities: could leftover cooking oil—or even human sewage—one day fuel your cross-country flight? Emily and Regina break down what it would take (chemically, technologically, economically, and politically) to decarbonize the aviation industry, spotlighting innovations, challenges, and the real numbers behind “greener” flying.
Virgin Atlantic's Milestone
Industry Pressures & Geopolitical Impact
Chemistry & Types of SAF
How Prevalent Is SAF?
Supply Limitations
Economic Hurdles
Land Use Concerns
Alternative Pathways
Limited Commercial Scale
Ultimate Solution: Fly Less?
The Power of Poop
Reality Check on Flying
The Race to the Future
The episode ends on a mix of optimism and realism, highlighting both technological promise (from cooking oil to human sewage) and the massive economic, political, and logistical hurdles to decarbonizing flight. As the hosts quip about the “race” between states and institutions, listeners are reminded that every step counts on the path to climate action—but for now, flying green remains more aspirational than accessible.