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The future of greenhouse gases

A chemical engineer explains why he thinks a better approach to greenhouse gases in the sky is to turn them into other chemicals.
Detail of a modern power plant fueled with coal and biomass
Can we transform greenhouse gases into benign chemicals? | iStock/zhongguo

Guest Matteo Cargnello approaches the challenge of greenhouse gases from a different perspective.

He doesn’t study how harmful chemicals got in the skies, or even the consequences. Instead, Cargnello is using his skills as a chemical engineer to turn them into other benign or useful chemicals. So far, he’s turned greenhouse gases into valuable industrial chemicals, polymers, renewable fuels, and even ethanol. Useful products from greenhouse gases, that's the dream, Cargnello tells host Russ Altman on this episode of Stanford Engineering’sThe Future of Everything.

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Matteo Cargnello: Take CO2 and create more complex molecules. For example, hydrocarbons. So then we could make fuels like gasoline that powers our cars from CO2 and hydrogen, and, uh, make our fuels less damaging for the atmosphere.

Russ Altman: This is Stanford Engineering's The Future of Everything, and I'm your host, Russ Altman. If you enjoy The Future of Everything, subscribe or follow it on your favorite listening app. It will help us grow and it'll make sure you don't miss any episodes.

Today, Matteo Cargnello will tell us how his lab is developing new materials to catalyze the transformation of greenhouse gases into benign chemicals like water, nitrogen, and even alcohol. It's the future of greenhouse gases.

Before we jump into this podcast, let me ask you to please rate and review it. It helps us improve and it helps spread the word about The Future of Everything.

We have all heard about greenhouse gases. These are the chemicals that enter the atmosphere and create an insulation layer around the earth. Although many of these gases are naturally occurring, the rate at which they're being produced has remarkably increased in the last 200 years, and now they've accumulated to the point where the planet is heating up.

Global temperatures are increasing and threaten lots of changes to both land, sea, and air as a result. So that makes a double challenge. First, we wanna reduce our creation of these gases, but secondly, we need to figure out ways to remove them from the atmosphere. Matteo Cargnello is a professor of chemical engineering at Stanford University.

His group creates new materials that can catalyze the transformation of greenhouse gases into benign chemicals. These main greenhouse gases are carbon dioxide. Methane and nitrous oxide. He's also creating methods to store these gases, either for productive use or just to keep them away.

Mateo, let's start out with a very simple question.

What is the problem that your research is trying to help solve?

Matteo Cargnello: Thank you Russ, for having me here. The problem is kind of like very simple to explain. Uh, it's of course much harder to, uh, solve. It's the problem of greenhouse gas emissions and reducing the concentration of greenhouse gases in the atmosphere.

That can be done in several, many different ways. It's through energy usage, through avoiding greenhouse gases from getting into the atmosphere in first place, and also being able to capture those greenhouse gases that are already in the atmosphere. So all of that is. What I'm trying to solve and, uh, at the end of the day, it's about reducing global warming and all the problems associated with it.

Russ Altman: Great. So for people, I think everybody has heard this phrase "greenhouse gases" and we sometimes hear about specific gases. But I think it would be useful as we start for you to tell me like what the major targets are of these gases and what are our opportunities to kind of improve this situation?

Or is the cat already out the cow already out of the barn and there's nothing to be done?

Matteo Cargnello: Yeah. By the way, cows are very important in this discussion too, but we can get to that later. Probably many people know that one of the main, um, uh, culprits of this problem is a gas called carbon dioxide, CO2. Uh, this is the gas that has increased in concentration tremendously in the last 150 years since the Industrial Revolution.

And, uh, the problem is that this particular gas traps heat from, uh, the sun, uh, within the atmosphere. And this increases the temperature of the planet with all the consequences that, uh, we are, uh, probably aware of in terms of catastrophic disasters, ocean warming, increasing of ocean levels. Uh, it's not just CO2 though.

One thing that is important to keep in mind is that CO2 is the main one that is anthropogenic. It means that human beings increase the concentration of these gas. There are others as well that we are, uh, working on, um, as well as CO2. For example, methane is the second most prevalent, greenhouse gas and, uh, nitrogen oxides in the atmosphere.

So there's a variety, a few of them that are extremely important to controlling concentration. But absolutely, CO2 is by far the one that is the most relevant.

Russ Altman: Now. Um, do those other, you just mentioned methane, uh, does it a act in the same way in terms of like, uh, sealing in the heat or are there other negative consequences that it has that are different from the CO2?

Matteo Cargnello: Yeah, in principle, when we, uh, think about global warming. The, uh, principle by which these molecules act in increasing the temperature in the atmosphere is very similar in the sense that they trap the heat, that comes from the sun. Their effect though, uh, can last, uh, for different, uh, periods of time.

CO2 has an effect that can last for many, many decades because of the stability of this molecule. Uh, methane, uh, lasts for less than CO2 because it gets converted into other molecules in the atmosphere. But for example, it has an immediate larger effect than CO2 that is equivalent to roughly 20 to 80 times dead of CO2, uh...

Russ Altman: oh

Matteo Cargnello: ...with nitrogen oxide that's even higher.

Uh, so this is the so-called greenhouse gas, uh, power of, um, or potential of these gases that is varied. So it really depends in terms of time and intensity, but overall, the effect by which they warm the atmosphere is similar.

Russ Altman: So let me just ask one more kind of setting up of the, of the whole discussion, which is what are the major sources for these three gases that, uh, I think we all have a rough idea that combustion engines produce something and, but why don't you just kind of give us a rundown of what the major sources are?

Matteo Cargnello: Yeah. There are natural processes that, uh, involve these gases and they've been around, uh, even before humanity was around on this planet. But clearly there are, um, artificial processes that increase or change the concentrations and the equilibria around this specific gases. And when it comes to CO2, the main source is, uh, human activities, especially energy generation, combustion of, uh, Oil and uh, related products for energy generation.

Uh, in term, when it comes to methane, it's, uh, the activity of extracting oil and, uh, agriculture and, um, uh, farming. Those are huge, uh, sources of methane. And when it comes to nitrogen.

Russ Altman: This is where the cows come in?

Matteo Cargnello: It's when the cows come in, and that's, uh, a big issue because that methane is, despite being dilute in the atmosphere, it's about 200 times less concentrated than CO2, but because of its higher global warming potential, then it turns out to be a big offender when it comes to, uh, global warming. Um, so these are, there are these natural sources, but certainly, uh, farming, agriculture those are huge sources of methane and, uh, nitrogen oxides.

Russ Altman: Okay, so now let's get into your work and it's very exciting because my understanding is you're using the principles of chemistry to actually try to remediate all of these compounds. Um, what is the gen, what is the approach there? Tell us, uh, enough chemistry so that we can see both the challenge and the promise.

Matteo Cargnello: Yeah. So there's two facets, uh, in my research, uh, work.

On one side because the emission of greenhouse gases come from the generation of energy and, uh, when it comes to energy generation, we're talking about converting chemical species into others that would release with the release of energy that we can utilize, then we can, um, find out ways to, uh, run this chemical processes with less energy consumption.

Which means that is then directly giving us the opportunity to reduce the, uh, energy emissions, uh, or the greenhouse gas emissions, sorry, from, from energy generation. So that's, uh, essentially an indirect pathway to reduce the greenhouse gas emission.

Russ Altman: Sure.

Matteo Cargnello: On the other side, we can find chemical processes to convert these molecules such as methane into others that would be less damaging to the atmosphere. And that's another facet.

And the third one is, can we use chemical principle to directly grab these molecules from the atmosphere and store them and sequester them into appropriate reservoirs that could, uh, then last for a long time so that it don't get back into the atmosphere. So it's the chemistry of these small molecular compounds that is either in their conversion into others with lower emissions or directly converting them to remove them from the atmosphere.

Russ Altman: So that was a great overview and I know that, I don't know if it's for all three of these challenges, prefer at least some of them you're also creating new materials, so-called nano materials that have special properties.

And a lot of people hear about nanoscience and maybe they're thinking about computers or other things, but it's very interesting to find out that this might have implications also for chemical catalysis and global warming. So what's the connection between nano materials? Why are they special?

Matteo Cargnello: Mm-hmm. Yeah, nano materials are very special.

And by the way, we started, uh, as humanity. I mean we started working on this chemical processes at industrial scale using nanomaterials long before we recognize that these materials are nano.

Russ Altman: Huh?

Matteo Cargnello: That are small, small scale. And the reason why that's the case is because when we want to run chemical transformations on molecules, then we need to have materials that interact with these molecules and to the highest possible extent.

And the way to do that is to reduce the size of the materials. To the level of a few atoms, because then these materials will show the highest efficiency in interacting with these gauges molecules.

So that's why we need to use materials that are very small at the nanometer scale in order to make them very efficient for, uh, interacting with, uh, molecules in these chemical processes?

Russ Altman: Is it basically a surface area situation that if you have tiny things, if you have a large volume, but if it's all tiny particles, then they have a lot of opportunity to interact with like the air around them.

Matteo Cargnello: Exactly.

Russ Altman: Is that the idea?

Matteo Cargnello: So the usual, uh, comparison or analogy we make is that if you take a cube, uh, that has macroscopic dimensions, most of those of the material in the cube will be in the internal space, volume of the material, and that will not be able to interact with the atmosphere, which is in the end what we're trying to do. But when we start cutting down this, uh, cube into smaller and smaller pieces or bits, then we are able to expose more of the surface area, uh, which is one of the primary needs for, um, materials that we want to use for chemical transformations.

Russ Altman: Okay. So what kind of chemical transformations, like what are we turning the CO2 into? I know, for example, that plants can turn it into sugar. Uh, yeah. Uh, and also what are we turning the meth methane into? I'm doubting that you're making sugar, but I don't want to pre-judge.

Matteo Cargnello: Well, there's, there are different pathways that are imagined in the, in our field in order to turn CO2 into something useful.

Uh, there are some. Let's say low hanging fruit in terms of compounds that can be made, such as carbon monoxide, which is one step away from CO2. Carbon monoxide is actually a poison. It's very toxic for human beings it can kill us. But in the chemical industry, it's a very crucial building block to prepare a variety of compounds, fuels, in other chemicals.

So CO is one. Uh, we can, however, one, some of the most interesting compounds are those that have carbon, carbon bonds. So if you can take CO2 and create more complex molecules, for example, hydrocarbons, so then we could make fuels like gasoline that powers our cars from CO2 and hydrogen and, uh, make our fuels less damaging for the atmosphere, uh, in...

Russ Altman: it's almost like recycling the fuels?

Matteo Cargnello: ...exactly. Although it's not the best way we have in order to reduce the, um, amount of green or CO2 that we put into the atmosphere but it's a way to go. And more recently, um, I'm excited to share with you that we've also been making ethanol, which is basically alcohol from CO2.

So I ...

Russ Altman: now you're talking.

Matteo Cargnello: ...yeah, exactly. So I joke with my students, they were making booze from air. So in principle, the idea is to take CO2 from the atmosphere and hydrogen from sustainable renewable processes and make ethanol.

The reason why we want to make ethanol is because, first of all, it can be used as a fuel. It's already used in some countries as a hundred percent, uh, fuel for internal combustion engines, but it can also be used as a sustainable chemical for the production of a variety of important building blocks in the in industries for polymers, for example, in other applications.

So there's clearly a variety of things that we can do with CO2 but there's a few ones in particular that are relevant when we want to solve the problem of CO2 emissions.

Russ Altman: So let me go on a little tangent because this is very exciting and I just wanna make sure I kind of see the, kind of the use case. So you, as you develop these chemistries, can you do it like on the land in a factory or are you gonna have to get this stuff up into the sky to interact with all of the CO2 and for the other reactions, the methane or is that not necessary?

This can all be done like terrestrially. I I'm just wondering how, what your vision is for how this gets scaled once you develop all the technologies.

Matteo Cargnello: Uh, it depends on the final goal. There are actually researchers that are looking at the possibility of running this chemistry in the sky, in the atmosphere.

Uh, for us, when we think about chemical engineering and producing chemicals from CO2, uh, we see it as an opportunity to do it, um, on land. So the idea is to...

Russ Altman: Yes.

Matteo Cargnello: ...try and grab that CO2 from the atmosphere or from seawater, by the way. We can talk about that later on.

Russ Altman: Ah.

Matteo Cargnello: But then doing it in a factory and making useful chemicals then could replace other chemicals that we're using today that come from fossil fuels.

That will be really the vision and, uh, the, the dream.

Russ Altman: Gotcha. And, uh, and, and before, before I went on that tangent, I wanted to also ask about methane. What are the kinds of things that we would, might be able to turn methane into?

Matteo Cargnello: Yeah. Methane is a very interesting compound. Together with, uh, some colleagues, uh, from Stanford a few years ago, uh, we did some calculations on the methane concentration in the atmosphere and realized that, or demonstrated that if we were to magically remove methane from the atmosphere, we would be back to the greenhouse gas potential at, of like 1850.

So methane is a big offender.

Russ Altman: Huh

Matteo Cargnello: now the question is what do we do though, given the fact that it's such, that's such low concentration in the atmosphere?

So there are some ideas that we're working on to turn methane into CO2. Uh, and now one will say, okay, why CO2? Well, because methane is 20 to 80 times more powerful than CO2. So even being able to convert that methane to CO2 would reduce the greenhouse gas potential of gases in the atmosphere and really help us, uh, solve, uh, this problem.

So that's one idea that we are working on.

Russ Altman: Yes. It actually makes sense if it's 20 or 30 times worse and you can turn a methane into one or two CO2 s and now you're also developing CO2 remediation.

You have created a pipeline towards, uh, towards a solution.

Matteo Cargnello: Right.

Russ Altman: I just wanted to make sure, by the way, Um, is the carbon monoxide and these other things that you're turning, um, the CO2 into, are they gonna have the same greenhouse house problems or is the idea to capture them and store them so that they never get into the

Matteo Cargnello: uh, exactly. So this is an important point that, um, you mentioned. We have to ensure that whatever conversion we, uh, work on, it is we convert CO2 into, first of all, a useful chemical compact, but on the other side, we have to ensure that carbon is not going to end up in the atmosphere right away because otherwise any chemical process requires energy.

And energy in principle means that we are, uh, emitting CO2 in using energy. So if we use energy and emit CO2 to make a chemical that would turn back into CO2 right away, that's not a great way to solve this problem. So CO is. Um, so some of these gases, um, are not as, um, powerful as greenhouse gases as CO2, but we have to ensure that we turn them into compounds that, uh, would allow us to at least semi permanently store CO2 in chemical bonds that are not going to end up, uh, in the atmosphere again.

So I emphasize the ethanol, for example, in polymers because in principle, uh, polymers that we use, um, all every day and they're all around us are a way to semi permanently store carbon.

Although we have. Lots of other problems with plastics for sure, but that's also why in principle, turning CO2 into fuels that we use, uh, right away directly is not the best way to remediate, uh, this issue. So there's very many considerations around the use and storage and, um, conversion of CO2. And we're just discussing the tip of the iceberg essential.

Russ Altman: This is The Future of Everything with Russ Altman. More with Matteo Cargnello next.

Welcome back to The Future of Everything. I'm your host, Russ Altman, and I'm speaking with Professor Matteo Cargnello from Stanford University In the last segment, Matteo told us about how greenhouse gases are accumulating, how they cause trouble, and how some of the materials that his group is developing can transform these gases into benign chemicals, which are far less dangerous and destructive.

In this segment, Matteo will tell us about the process of catalysis, how it relates to catalytic converters, and how he's basically building a catalytic converter for the entire earth. He'll also tell us about some exciting new projects with seawater, which turns out is a sponge from greenhouse gases.

So the key to this, Matteo is catalysis. And so I think it's now time for you to tell us about the chemistry. What is Catalysis and what is the chemistry of catalysis?

Matteo Cargnello: Yes, catalysis is a very crucial, uh, science in allowing us to fight global warming catalysis. The definition is that catalyst accelerates the rate of a chemical reaction. Now, the weight works is that any chemical reaction in order to occur as to overcome with some energy barrier.

So we need to give it a kick in order for that to start. Now, a catalyst is a substance in principle, in my case, a nanomaterial, that would allow this, um, this reaction to start with a lower energy of activation. And it is clear then to imagine that when we, uh, think about less energy to run chemical transformations, we're talking immediately, we are thinking immediately about reducing the CO2 footprint. Uh, of, uh, some of these chemical processes.

And so then the trick or the important part of my research is in finding the appropriate materials that would work as the most efficient catalyst for the processes that involve greenhouse gases.

Russ Altman: Now we all have a car with a catalytic converter, uh, and a lot of them are being stolen.

Does this relate to the work that you are doing, or is it entirely different kind of catalysis?

Matteo Cargnello: Absolutely yes. I, uh, I think catalytic converter is one of the most important inventions of the last century. Uh, we, if we are familiar with photos from cities in the US from the seventies, there was, uh, there were high concentrations of smog and pollution.

And, uh, really the invention of the Cali converter allowed us to have, um, uh, better, clearer skies and, uh, better, um, air that we breathe in the cities and these devices take, um, uh, pollutants and toxic gases such as hydrocarbons, carbon monoxide, and nitrogen oxides, and turn them into harmless compounds that we can breathe, such as, uh, nitrogen, uh, CO2 and, uh, and water. Uh, and this is an incredibly important, uh, discovery that allowed us to make these materials with this very, very high efficiency for turning these gases.

The fact is that most of these materials, most of these, uh, cali, um, or cali converters in particular, uh, work with, um, precious metals.

Such as platinum, palladium, and roadium. And these metals are very, very precious and that's the reason why Cali converters get stolen, because they're very valuable.

Russ Altman: And they're not using nanomaterials is my guess. But you are?

Matteo Cargnello: They are. No, even in Cali converters we have nanomaterials.

Russ Altman: Okay.

Matteo Cargnello: So again, in order to increase the efficiency of these, uh, metals in particular to work on, uh, gasses, uh, compounds and convert those, we need to make them very, very small and tiny.

And these particles are in the order of like, uh, 5 to 50 nanometers in size. Which is about, uh, a thousand times, uh, smaller than the diameter of one of our hair. That's the size that we're talking about.

And it is important to recognize that this, uh, materials play a crucial role in, not just in cali converters, but in many, many industrial processes that we run at the million ton scale on a daily basis.

And it's all based on the, and these small, tiny particles, uh, that we use as catalyst.

Russ Altman: Yes. So when you're building these nano materials, is it correct that you're actually in, are you, uh, integrating some of these precious metals into the nano materials that you build? And then we talked before about the importance of making sure that the surface area is appropriate for the, for making a large volume.

Uh, is that the kind of work that you're doing?

Matteo Cargnello: Yeah, exactly. So we use a so-called bottom up approach. A chemical approach that would allow us to start from single individual atoms of a material and build the materials atom by atom with, uh, a precision that would allow us to tune the properties of these materials because whether the particle is a certain size or another matter tremendously for the final efficiency and selectivity of these materials.

So we're using these chemical tools. They would allow us to, uh, build the materials atom, by atom and really get to on one side, under the fundamental understanding of how the size and morphology of the nanomaterials matter for a final application as well as engineering the properties of these materials.

Russ Altman: Yes, I can imagine that in addition to making sure that it can catalyze the reaction that you want to happen, there are all kinds of operating conditions in terms of temperature and pressure and all those other things that you have to make sure you get it just right to optimize the reactions.

Matteo Cargnello: Correct. Exactly.

And these conditions will also affect the performance of the catalyst. So we also need to study how the material is going to get affected by the operating conditions and make it last for a long time, which is one of the main issues. For example, in Cali Converters, we don't want, uh, the people to have to replace that expensive Cali Converter every 10,000 miles.

It has to last at least 150,000 miles, if not more.

Russ Altman: Right. Okay, great. Well, in the last two minutes, I want to change topics cuz I know that you've also written and done work with seawater and you might, people might not think of seawater as a big issue or a big opportunity. Where does seawater come into your, uh, professional life?

Matteo Cargnello: Yeah, seawater is a project that we are starting to consider now and we go back to capturing CO2 from the atmosphere. That is like one of the biggest challenges that we have to really solve as a humanity and in this generation. So the fight that seawater is a storage medium for CO2. The CO2 from the atmosphere gets dissolved into the ocean water. And then we can try and take the CO2 from seawater rather than the atmosphere.

The reason why that's appealing is on one side, the concentration of CO2 is higher in seawater than it is in the atmosphere.

Russ Altman: Oh, that's interesting.

Matteo Cargnello: Yeah, because seawater is a liquid and the atmosphere is a gas, so we can, uh, process less volumes of seawater to get to extract the same amount of CO2.

On the other side, uh, the CO2 is not just the only. Um, if you want resource that we can harvest from seawater, there's other compounds that are very important, uh, chemical compounds for industry and for processes. So we could in principle utilize, uh, seawater not just as a reservoir of CO2, but also to extract other important components such as lithium salts, for example, that are so critical for lithium ion batteries.

So now there's quite a few researchers around the world, uh, focusing their attention on the, uh, seawater and, uh, the resources that we can extract from it.

Russ Altman: And is it possible that you'll actually be doing catalysis in the water or, uh, and would it be water? I guess my question is, does the principles that you use, uh, for the, uh, non-aqueous, um, catalytic reactions do I, my guess is they have to be modified, but they still might be applicable in water?

Matteo Cargnello: It's possible there are some ideas in doing chemistry on the seawater or doing chemistry. With the CO2 that is removed from the seawater.

So one of the dreams I think that many people have is to have potentially these floating islands that can capture renewable energy. For example, with solar panels, to power the processes to extract these important compounds, CO2, lithium matters from seawater, and then process them on this island and then, Using that to feed, um, and then populations, uh, on the coast and transport that.

So that's one vision of how we could have this, uh, islands to remediate greenhouse gas emissions and global warming in hopefully not too long from now.

Russ Altman: Very exciting. So these are catalytic converters, not just for your car, but catalytic converters really for the earth and for the environment.

Matteo Cargnello: Absolutely.

Russ Altman: Thanks to Matteo Cargnello, that was the future of greenhouse gases. If you enjoy the podcast, please consider subscribing or following it on your favorite app. You'll receive news of new episodes and you'll never be surprised by the future of anything. Maybe tell your friends about it as well and definitely rate and review it.

We have more than 200 episodes in our archives and you might wanna check those cuz there's a lot of good stuff. You can connect with me on Twitter @RBAltman, or with Stanford Engineering @StanfordEng.

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