Ian McKay: How do you get rid of contrails?

In this episode of Solving for Climate, the founder of Orca Sciences reveals the surprisingly easy fix for reducing contrails.

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Hannah: Hello and welcome to Solving for Climate, a podcast where we chat to scientists and innovators developing solutions to climate change. I'm data scientist Dr. Hannah Ritchie. On today's podcast I'm chatting about the science club backing big climate ideas with Ian McKay, founder of Orca Sciences. Orca is an incubator for projects looking to get off the ground. They ask big questions like how do we get rid of sky graffiti and can we just eat carbon?

As a data scientist, I'll be thinking about the numbers on the solutions he’s backing, from polluting airplane contrails to low emissions hydrogen.

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Hannah: Now Rob can't join us today, so I'll briefly explain a couple of the problems we'll be chatting to Ian about. His incubator covers lots of different solutions, but we're going to focus mostly on two. So first, what's the deal with contrails? So when we're thinking about aviation's influence on climate change, there are two parts to it. The one that people always think about is burning jet fuel, and when we burn jet fuel, we release CO2.

And if you remember, one of our previous episodes, we looked at the solution of sustainable aviation fuels, which looked at basically how do you replace jet fuel? And one of the alternatives might be cooking oils and waste fats, right? So that's the solution we were talking about there. But aviation also contributes to global warming through what we call contrails. So if you look at a plane that's in the sky, you might often see these kind of white lines in the sky behind it.

And these white lines, they look very unassuming, but they actually have quite a strong warming impact. So that adds additional warming on top of the CO2, so the aviation contributes around three and a half to 4%, right? So this is actually relatively substantial for those tiny white streaks that you see in the sky.

And then the other solution we'll be talking about is hydrogen. There's probably some sectors where it's maybe been overhyped. Maybe there are some sectors where hydrogen can still play a role. But basically, we produce hydrogen using energy in the first place. So we can either use fossil fuels to produce hydrogen, or you can potentially produce that through using clean electricity, right? And then you have this fuel, I'm not a fan of using it in cars, you can use it for heating, you can use it for industrial processes. So there's a range of ways that you could use hydrogen, especially if you produce this in a clean way.

One of the big downsides to hydrogen, as I'll ask Ian about, is that in order to produce hydrogen you often waste quite a bit of energy.

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Hannah: So Ian, founder of Orca Sciences, welcome to Solving for Climate.

Ian: Thanks for having me, great to be here.

Hannah: So you previously described Orca as a science club. Can you give us the climate pitch for what Orca does?

Ian: Sure, yeah. I think more officially, Orca is kind of a research group slash startup incubator, but it really does feel like a science club on the inside. You know, just a bunch of people, you know, a group of friends, mostly tossing back and forth weird ideas and materials, energy, chemistry. We definitely have a focus, not just on like around the corner science ideas. I think we're not the most advanced scientists in any category.

But more of like, okay, what are the kind of weirder, edgier, what are the research questions that other scientists haven't thought to ask? And so mostly that's a formula for making a big long list of ideas that don't work or things that nobody will want. But occasionally it's felt like we've hit on something that needs to be more than just a research paper. And so we started, I think, six startups now. One of them was Savor. I think you talked to Kathleen Alexander about that project turning, you

know, captured carbon or methane into fats and oils. So no two are like happy to talk about any of them or anything else as you like.

Hannah: I'm wondering, so you have this kind of portfolio of solutions or companies, what role do you play there? Are you a sounding board? Do you provide financial investment? What's the role of Orca within this kind of science club?

Ian: We're definitely kind of co-creators. So Orca started as just a word document with a bunch of ideas started by me and friends. And eventually now we do have our own basic financial support. But the idea is we kind of create the idea, get the right person to work on it, maybe start starting the team and then throw it out into the world where they'll need to get the invisible hand to invest in it somehow.

Hannah: So let's start with contrails then. First, could you maybe just explain to us, like I'm five years old, what a contrail is and what the solution you're backing, how does that help to solve that?

Ian: So it's kind of a surprising and unknown topic to a lot of people, but you know, about half the climate impact of aviation, it isn't the CO2 that comes from burning fossil fuels to drive commercial planes. It actually involves the clouds that are seeded by the exhaust of the plane. So condensation trails, contrails, are those white lines you see in the sky left behind commercial planes. It's basically the same as when you exhale on a cold day, you can see your breath, right? The steam condenses into little droplets and starts interacting with light and becomes visible.

Basically, when a plane flies through a colder region of the, like the tropopause, between 30 and 40,000 feet high, the water vapor and its exhaust condenses into this line-shaped cloud. And those clouds themselves don't have a particular climate impact. It's like 0.1 % of all climate change. But about 2 % of the time, and if you look up, like once you see it once and know what it is, you'll never forget, that cloud kind of spreads out into an artificial cirrus cloud. And cirrus are a naturally forming kind of cloud, but these contrails cirrus are completely artificial. They're totally opaque in the infrared. So they're like a greenhouse cloud, basically a greenhouse aerosol, just like CO2 is a greenhouse gas. And so worldwide contrails are about 2 % of anthropogenic climate change, the radiative impact of contrails.

But the crazy thing about them and what really got us working on them was just realizing how simple they were to avoid. So the US military has been issuing what are called contrail meteorological forecasts for decades, saying like, okay, here are the weather conditions where a contrail is likely to form, just fly a little bit higher or lower to avoid those regions. And for them, it's about, you know, they don't want a big line shaped cloud pointing out where their jets are in the sky.

But for us, it's more about climate. And our first big result with a big trial was pretty shocking. Like cost-wise, move about 2 % of planes up or down 2,000 feet, which is the ordinary increment for altitude changes for commercial flights. And you can cut the contrail impact of flights by 80%. So cut total climate impact of aviation by like 40%.

And so what that translates to is a cost of like $5 per flight or you know, it's always a little bit dodgy to equate a cloud that lasts for eight to 12 hours with a greenhouse gas that lasts for hundreds of years. But on CO2 terms, the cost of that intervention is something like one ton or one dollar per ton CO2 equivalent on like a hundred year CO2 basis. So it's just an incredibly high leverage climate solution. It's just an app. We publish this weather forecast, it's a region of the sky planes can avoid just like they avoid turbulence or bad weather now.

Contrails are harmful engineering, geoengineering that we do now. These are artificial clouds. It's like sky vandalism. It should be easy to erase them.

Hannah: Yeah, I think it's funny and interesting that you call it sky vandalism. Like I never really thought about it that way before.

Ian: Isn't it like that, graffiti up there?

Hannah: Yeah, yeah and I think that's quite an appealing way to talk about it because people generally don't like vandalism. So we should get rid of it, right?

So just to get this straight, the main point is that a very small percentage of flights contribute basically most of this contrail impact. So maybe 2 % or 5 % or something is responsible for around 80%. And the point there is that basically like flying at a particular altitude or flying in particular weather conditions creates these conditions where you get these large clouds. Is that the point?

Ian: Well, that's exactly right. You know, we have this contrails.org project now and our group's main contribution initially was just let's make a grid voxel by voxel of the whole atmosphere and say, okay, if we flew here and added these, you know, contrail aerosols, would we form a cloud? And if so, what would the climate forcing be? And it turns out just the vast majority of the time, you don't have to change anything. You're not flying through one of those regions.

Hannah: So basically the solution is you basically have this quite high resolution weather map, a flight is about to fly through one of these zones where it would form this and you basically say to the pilot or air controller or whatever, you go up a little bit or go down a little bit so you avoid this zone and basically you just avoid that warming impact that you would have had.

Ian: Conceptually right, but it's even easier than that. So we found that you can forecast these areas like 10 hours in advance with pretty high fidelity. The pilot doesn't even have to know. This is done like at the flight planning stage when the airline is using a software package that helps them determine the ideal altitude for the fuel burn and the air traffic areas and the winds aloft and the turbulence. It's just another layer that the flight planner clicks on at that stage.

Hannah: So as a passenger, it's not like I'm going to be rerouted and add another hour to my journey.

Ian: No, no, we well that would be a net negative from extra co2 burn.

Hannah: And I guess what's so exciting about this and what I'm still trying to get my head around is how cheap this is. And because it's so incredibly cheap, why, it's just, we're not obviously doing it? So I mean, you said earlier that it was about five dollars per flight, is that right?

Ian: That was in a big trial with American Airlines of moving, of looking at moving flights around and you know, how many do you actually have to move? You know, cause these altitude changes are quite small. You know, if that's $5 every flight, you know, the flights that do reroute cost a little bit more, but compared to the other things people, you know, say they're prepared to do for climate change, it's an incredibly low cost. And that's the sincerity test aspect.

Hannah: So what's going on there? So like one, you could ask per passenger on that flight. I'm sure most people would be willing to pay that. Per passenger, it's a few cents. Right. It's cents! Or even the airline itself. Why would an airline not just want to pay five extra dollars? I mean, for them, that's quite this big kind of announcement that they're actually taking climate change seriously. Decarbonizing jet fuel is quite hard and aviation industry has been quite slow on that.

But this seems like such a huge win to be able to say you're taking action on and it would be five dollars a flight. I just don't understand why this is not obvious.

Ian: 100%. I mean, $5 a flight does turn into a hundred million or more dollars per year, you know, to do it fleet wide. And so you could see why airlines wouldn't want to, you know, take on that cost. They have razor thin margins. So far, you know, contrails aren't very useful virtue signaling material. You know, even though they are just sky graffiti, people don't tend to know about them as a climate cause. And at this point, most airlines would rather the issue just go away rather than being, you know, actually, it's twice as bad as you thought with your climate impact. But I definitely see it the way you do is like, this is an incredible opportunity.

Hannah: So if airlines in the aviation industry are maybe not super keen, because maybe it also just highlights that contrails exist, as you said. Maybe people realize that their impact on warming is bigger than they had previously thought. I could see from a government perspective, this is an incredibly cheap solution relative to, as you say, some other, you know, parts of their pie that they need to solve, right? Often you're at solutions that are more than a hundred dollars per ton of CO2 equivalents. What role do you think governments could play in this?

Ian: It could play such a huge role, right? And you already see some action from the EU at least quantifying the non-CO2 impacts of aviation. Finding a way to have airlines paid to do this or finding a way to have it legislated the, okay, in this airspace, that shall not leave contrails could be one of the ways that this gets solved quickly. But I think what we see from regulators so far, at least in the U.S. is like, okay, maybe we can study this for 20 years and then press a button and turn it off. When in reality, I think that button is basically there already in all the flight planning apps and we just have to ask them to press it now.

Hannah: Okay, so I'm very now excited about the potential to abate contrails. I wanted to move on a bit to hydrogen. So you're also supporting Peregrine, a company that's producing clean hydrogen. Can you tell us about how this works and why you're excited about it?

Ian: Definitely, definitely. Peregrine, they're in the phosphate fertilizer industry. And it involves hydrogen. You know, you'll see hydrogen is involved in so many world industries. Peregrine is definitely a little bit in the weeds in the chemical industry of how phosphate fertilizers are made. Phosphorus is the P in NPK fertilizers. It's probably the second most important fertilizer in the world. So phosphorus is still a fossil fertilizer. We dig up ancient sea beds to get our phosphorus.

And phosphorus is actually kind of doubly a fossil fertilizer because the way we get it is we take sulfur, which is a byproduct of fossil fuel extraction. We oxidize it to make sulfuric acid, the world's number one commodity chemical. And then we pour that on these phosphate rocks we've dug up in order to make phosphoric acid. So Peregrine really comes from this question of like, how are we going to feed the world?

And you know, provide food security with phosphate fertilizers in a post-fossil era when we don't have all this free sulfur from making fossil fuels anymore. And so, Peregrine is a way of co-producing sulfuric acid and hydrogen in an electrolyzer in a way that's kind of fundamentally advantaged in a way that like is one piece of like, okay, here's how we'll keep getting phosphate, which will stay a finite resource, but will become a lot harder to extract.

Hannah: At least from previous conversations it's become quite clear that hydrogen is not going to win on cars or in heating, but what you're describing there is kind of industrial processes. Are there other areas where you see lots of potential for hydrogen?

Ian: Yeah, 100%. There's no tech push and there's no market pull for hydrogen outside of where we use it now, right? There's no tech push or like, like we have dollar per kilogram hydrogen from fossil fuel sources now. And there's no kind of technical enabler that's going to get us even Peregrine's approach, sub dollar per kilogram hydrogen from clean sources. And there's also no real market pull for it, right? People using that super cheap fossil hydrogen for things like heating or transport or you know, shipping or trucking - places they don't use it now. So it's definitely challenged in those sectors. And that really leaves manufacturing and agriculture is where, you know, the really hard things and that's where hydrogen is actually already indispensable. So in the manufacturing of ammonia, in making phosphate fertilizers, and then in other places in manufacturing as the places like you just don't have an alternative and so we need to find something.

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Hannah: So XLinks have this big project, and I've had it on my radar for some time, the Morocco to UK Power Project. The plan is to transport renewable energy from sunny Morocco to the dreary UK. In June, the UK government decided not to go ahead with a contract for difference for the project. And there's a but incoming. But Xlinks are still looking at other delivery options. And they're also doing feasibility work on separate projects which could benefit other parts of Europe. To find out more, you can follow their journey on LinkedIn by searching Xlinks, capital X, lowercase links.

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Hannah: Yeah, so one of the barriers for hydrogen has been cost. It's often hard to get it cost comparable with what we have now or what alternatives would be. But I think Peregrine claims that they want to or they can make clean hydrogen without the green premium. Is that correct? How do they do that?

Ian: It's correct. You know, one of the big candidates and it's not the only way of making hydrogen rather, you know, that's not using fossil fuels as via electrolysis, which is basically splitting water with two electrodes. So basically you're stealing an electron from the oxygen in water and stuffing it onto hydrogen where it doesn't want to sit very well to make hydrogen and oxygen. And this is, you know, a hundred year old process. We have a hundred or more startups making electrolytic hydrogen.

In theory, this is a way of turning cheap renewable energy into renewable chemical reducing agent, hydrogen that could make fertilizer, fuels, et cetera. In practice, electrolysis is a tough process, right? Most of your energy is going to the reaction where you create oxygen. And so Peregrine's approach is saying, okay, what else is there that we can combine with water to take the electrons from that makes a second valuable product, that makes the whole thing pencil economically.

And so that's where sulfur comes in. So for Peregrine, we're co-electrolyzing the sulfur with water to produce both sulfuric acid and hydrogen. And that has two effects. One is, okay, you get two value centers per electron you pass rather than just one, but also sulfur being a chemical reducing agent, the process takes vastly less energy. And so that's the really big advantage there.

Obviously, you're not selling Peregrine as a negative-green premium way to decarbonize the whole economy with hydrogen, because it's really useful only where hydrogen and one of these oxidized co-products are used. And so hydrogen sulfuric acid is a great first market, because those two are used together to make phosphate fertilizers. But the idea that this could be a negative-green premium way of making hydrogen for syn fuels or for ammonia in general isn't I don't think it's on the table.

Hannah: Where is Peregrine now in its journey and what would be, I guess, the barriers for its scaling?

Ian: They just closed the first part of their series A fundraise as a startup. And so they're working really closely with the Moroccan phosphate company, OCP, to do a pre-pilot of their electrolyzer. You know, Morocco has 70 % of the world's like economical phosphate reserves. And so it's like they're one of the big players.

Hannah: So Morocco has 70 % of basically the phosphate, which is pretty wild, no?

Ian: Yeah, so there's been a recent discovery in Norway of like a lot more phosphate rock. You know, this is kind of like the Paul Ehrlich, you know, research. Yeah. The more you look, the more you'll find. But Morocco has really high grade phosphate really close to the surface. And so as they are definitely the gorilla in the room.

Hannah: Cool.

We've talked there about two specific solutions. We could go on and talk about many, because they're all really exciting. But you had previously wrote a piece about all the ideas that misfired at Orca. And I just love that idea. I love learning about ideas. I don't think we hear a lot about ideas that didn't work and why they didn't work. I'm wondering, could you talk us through some of those and what you might have learned from that process?

Ian: Yeah, gosh, there are so many and it could go in so many directions. I got really interested in looking at using the techniques of fracking to pump water underground and lift up new islands in the ocean.

Hannah: Woah.

Ian: As both like, you could make sea walls to stop sea level rise or just, know, land is more valuable than water, more valuable ecologically, more valuable to people.

Hannah: And how did you discover what was the sticking factor there? Why would that not work?

Ian: Well, it is interesting and it's actually looked at very seriously in the case of things like Venice, where it's like, okay, we have this one hyper valuable city. We can pump sand under there and maybe raise it back up. But the earth is a lot like powdered snow where you take, you crunch it down once and it stays there. There isn't really a way to fluff it back up. So a lot of those approaches to fracking, to raise up land are going to require you to continuously pump water or a prop down there.

We couldn't figure, maybe someone will, but we couldn't get that one to work out.

Hannah: What about edible microalgae? What was the sticking factor there, that people wouldn't eat it?

Ian: I mean, that's one where there would just have been many, many shots on goal. It seems like of photosynthetic ways to produce food, it seems like, I mean, that people would talk about producing fuels with algae, right? There are some thorny chemical problems in making that stuff palatable. And the fact that many people have tried and failed in that one, I think warned us off of that one. A lot of other conventional ones like, you know, solar power from space or muon catalyzed fusion are, you know, fun to look at.

Hannah: Give us the debrief on solar power from space. Some people still take that reasonably seriously.

Ian: Yeah, I think if you, that one, you concatenate some optimistic assumptions around the cost of getting mass to space and the efficiency and how light you can make solar panels and then the down links from space to earth, you can get that to converge as the cheapest electricity on earth. But this is a way of making energy that's dispatchable in space across kind of a field of view. And so it could interact with the grid in a really interesting way.

The question of the downlink becomes really important. There are multiple startups. I think there's three categories of startups in this space. Now there's the giant mirrors, you know, focusing light from the sun onto existing solar installations. There's microwave phased arrays, basically giant microwave emitters coupled to towers on to receiving huge antennas on the ground. And then there's what I think is the most promising, the idea of using near IR lasers to illuminate existing solar farms.

And that one leverages, there have been some really interesting cost decreases in lasers in recent years, but definitely some startups to watch in that space that we didn't end up making one.

Hannah: Yeah, so you've, I guess, thought about a lot of crazy climate ideas and some of them have turned out to be not that crazy, right? And are actually potentially going to win or play a big role. I feel like, at least from the emails that land on my inbox, I feel like a lot of people have this sense that they have this kind of a crazy climate idea that might work. What would your advice be to someone that thinks they have an idea? How do they go about the process of working out whether it's viable or like what would be your advice on what they should do next?

Ian: Hmm. So I feel like that ideation process has gotten harder recently, right? Cause we have these LLMs that will immediately give you the right answer to any question. In our group, like we used to have this naive questions channel, which, you know, people would post their naive questions and it seemed like that was always the most fertile area. You know, someone would be like, why aren't we eating algae or something? And then you get 50 different answers and many of them would be wrong, but it allows you to suspend your disbelief and learn, you know, why the accepted answer might not be a hundred percent correct.

But in recent years, or maybe the last year and a half, that naive questions channel has been completely dead because there are no naive questions anymore. Everyone, you know, you get the correct answer immediately from the LLM. And so my only advice would be suspend disbelief as long as you can and find out why you might be right before you let the machine tell you why you're wrong.

Hannah: Like as a final question for our listeners, there's like one question that's really stuck in your head at the moment and you just, you think that we should be able to solve it but we just are not quite there yet. Is there anything that our listeners could work on?

Ian: Boy, I gotta say the one that's radicalizing me the most is this idea of food without agriculture ever being just the highest alpha. And there's so many potential products in that area and so many molecules now that we make in huge quantities and absolutely crazy ways. So I feel like that's a really, really fertile area for the imagination.

Hannah: Ian, thank you so much. I've really, really enjoyed this conversation. It was a lot of fun.

Ian: Great, thanks Hannah.

Hannah: I thought that was such a fun conversation, also just because we, especially at the end, went off in many different directions. And I love just thinking about, I guess, cool innovative ways of tackling different parts of the climate problem. I also thought that Ian was just very good and knowledgeable, like on a technical level about, I mean, he's also just looking at a range of very different solutions, right? Often when we speak to people, they have their one thing that they're super knowledgeable on. He kind of has this... breadth across many many different solutions so that was great to have him on.

I think I still can't get my head around contrails in the sense of how it can be so cheap and yet we're not doing it like it just seems so obvious I mean the numbers he were quoting like less than one tonne per CO2 equivalent like his perspective for people that's like so low often we're talking about solutions that are more than a hundred dollars per tonne of CO2 so this is incredibly incredibly cheap.

So with the numbers on contrails, I think what he was quoting was that, like if you got rid of the contrails, it would basically have evasions, warming impact. I would say that's maybe slightly too high, but not that far off. So the numbers I have in my head, and maybe they're actually a few years out of date now, the contribution from CO2 is around two and a half of the world's emissions, and then the additional kind of non jet fuel impacts increase it to around three and a half to four percent. Maybe halfing emissions is a little bit too high but maybe not hugely far off I'd say between a third and a half of aviation's warming impact if you can get rid of basically all of the contrails.

Ah, I mean I'm just thinking if I was on a flight I would be so happy to just pay the five dollars for that entire flight and I feel like lots of people on that plane would be more than willing to do that so I feel like this should be something that we can do.

And then I also thought like hydrogen in many circles gets quite a bad name I think now because I think there's a feeling that it has been overhyped for stuff like road transport or heating and its role has been very much squeezed out of the potential suite of solutions. But I think there are just some very specific industrial applications and Peregrine, which Ian was talking about, is basically looking at its role in fertilizer and fertilizer is very hard to decarbonize.

So think it was really interesting there to get his take on what role hydrogen can play. Yeah, I'm actually a little bit jealous that he has this little science club and I would really, really like to join. So I'm hoping that you listeners found that conversation interesting or maybe inspired to think a bit more about your wacky climate ideas as well.

Thank you for listening to this season of Solving for Climate. To find transcripts of this episode, go to our substack in the description. Goodbye.

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Xlinks have sponsored this series of Solving for Climate.

Hannah: Xlinks have quite an impressive team, led by a board that includes Sir Dave Lewis, former Tesco CEO, ex-Rolls-Royce chairman Sir Ian Davis, and founder of ACWA Power, Paddy Padmanathan. And to top it all off, Time Magazine recognised Xlinks as a world-top green tech company in their 2025 rankings. I hope they stuck that on their LinkedIn.

To find out more, you can follow their journey on LinkedIn by searching Xlinks, capital X, lowercase links by searching Xlinks, capital X, lowercase links.