Advanced science.  Applied technology.

Technology Today Podcast
Go to Technology Today Podcast Episode 54: Targeting Transportation Emissions

Episode 54: Targeting Transportation Emissions

How to Listen

Listen on Google Podcasts, Apple Podcasts, or via the SoundCloud media player above.


April 22 marks Earth Day, an annual call to action to preserve natural resources and protect the planet. On this Earth Day episode, we’re discussing new SwRI technology in development that targets rising greenhouse gas emissions, which cause disruptive changes in Earth’s climate. The transportation sector is a major contributor of carbon emissions. SwRI engineers are developing a potential solution, a membrane that removes and captures carbon dioxide before it escapes into the atmosphere, leaving cleaner air. They envision it will be outfitted on a range of vehicles, from compact cars to ships.

Listen now as SwRI Staff Engineer Dr. Graham Conway discusses going beyond a zero-emissions solution to develop a novel carbon capture membrane, a negative-emissions technology.

Visit Decarbonization Technology Services to learn more about SwRI’s research and development to lower carbon emissions.


Below is a transcript of the episode, modified for clarity.

Lisa Peña (LP): April 22 marks Earth Day, so we're highlighting SwRI research and development underway to protect the environment. Hear about a solution to decrease greenhouse gas emissions. It's not a zero emissions technology, but even better, a negative emissions technology. We'll explain next on this episode of Technology Today.


We live with technology, science, engineering, and the results of innovative research every day. Now, let's understand it better. You're listening to the Technology Today podcast presented by Southwest Research Institute. From deep sea to deep space, we develop solutions to benefit humankind. Transcripts and photos for this episode and all episodes are available at Share the podcast and hit that Subscribe button on your favorite podcast platform.

Hello, and welcome to Technology Today. I'm Lisa Peña. You may have heard of zero-emissions vehicles that don't add carbon dioxide to the atmosphere, but have you heard of negative-emissions vehicles that remove greenhouse gases from the air? It's possible with technology and development right now at SwRI. Our guest today is SwRI Staff Engineer Dr. Graham Conway. We first heard from him in Episode 21, Examining Zero Emissions. He's back for this special Earth Day episode to discuss the environmental problem we're up against and a solution his team is working on. Welcome back, Graham.

carbon trajectory graph

The graph shows the trajectory of atmospheric carbon dioxide (CO2) in parts per million since 1990 and the potential increase of CO2 concentration if we continue adding carbon emissions to the atmosphere at the current pace.

Dr. Graham Conway (GC): Hi, Lisa. It's great to be here.

LP: So I've seen some alarming information about our current climate situation from the National Oceanic and Atmospheric Administration website. Earth's average surface temperature has risen by about 1.8 degrees Fahrenheit since 1880. From NASA, they say the current warming is happening at a rate not seen in the past 10,000 years. So let's start with a climate change refresher for listeners. What are greenhouse gases? How do greenhouse gases impact climate change? And how do greenhouse gases differ from other pollutants?

GC: Yeah, that's a great starter. So greenhouse gases are simply gases in the Earth's atmosphere that trap heat and prevent it from escaping into further areas of the atmosphere and into space, and that is causing the planet to have some shift in its climate patterns. And so it's climate change. The most common greenhouse gases that we see are carbon dioxide, methane, nitrous oxide, and fluorinated gases, as well. And so all of these go into trapping that heat into the atmosphere.

LP: And those are different from some of the other pollutants that cause health problems, like asthma. Can you talk to us about that difference?

GC: Exactly. So greenhouse gases, they're in the atmosphere at a high level. They're trapping in heat. They're causing the planet to warm. Generally, we called it a global problem. So a CO2 emitted somewhere over the other side of the world will cause problems to me here in the United States. Criteria pollutant emissions are much more localized in their problem. So they tend to occur or be most severe in densely populated cities, where a lot of localized emissions are produced. And they can cause problems with asthma, they can cause problems with the lungs. It's much more localized and more immediate of a problem.

LP: So today, we're going to focus on those greenhouse gases causing global warming. So let's talk about the consequences of global warming. What are we seeing because of it?

GC: So global warming, I guess we started calling it global warming because we saw the average temperature starting to increase around the world, but that led to several different events. We started to see rising sea levels because the ice caps were melting and causing the sea levels to rise, but we're also now seeing more frequent severe weather events. And that can also include extreme cold conditions, as well as the hot conditions. And so we've kind of shifted from global warming to climate change, because it covers both the hot events and the cold events. So we're really seeing a big shift in the range of temperature events we're seeing.

LP: All right, so we want to talk today about those carbon dioxide emissions in the atmosphere. Looking at our current situation, what trajectory are we on? What will happen if we don't make any changes?

GC: Yeah, so currently, the atmosphere is at about 420 parts per million of CO2, which doesn't sound like a lot, but it seems to be really closely related to temperature. And that's linked back to all the problems we just spoke about. It's important to mention that previously in history, the Earth has been at a much higher level of CO2, as high as 1,500 parts per million about 250 million years ago, but today, we're in a very different place. And so we've recognized that we need to slow the rate of CO2 increase down. A lot of government bodies come together and discuss this because it is a worldwide problem. And the consensus is we need to limit further increases in average temperatures to about 1 and 1/2 degrees Celsius.
membrane under microscope

Researchers studied the carbon capture membrane under a microscope. It is made up of lithium zirconate suspended in a ceramic structure. Developed with internal research funding, SwRI has a patent on the underlying technology.

LP: So 2050, I keep hearing that year as a goal year. What are the goals to reach by 2050?

GC: So many of the goals are that individual companies, countries, and individuals should be at net zero. So that means we're not putting any more CO2 into the atmosphere if we can at all help it. CO2, once it's in the atmosphere, it stays there for a very, very, very long time. And so the challenge is, even if we get to net zero where we're not putting any more in, we still already caused some damage that is going to need reversal.

LP: All right. So the search is on for good solutions to help us reach those goals. So how does the transportation sector contribute to greenhouse gas emissions?

GC: So the transportation sector is a very large contributor to greenhouse gas emissions. Around 1/3 of the greenhouse gas emissions produced in the United States come from the transportation sector. And around 50% of those emissions come from passenger cars, the cars you or I drive to work. And so there's lots of different ways they come from. The main pathway to the greenhouse gas is from the fossil fuels that these vehicles use that produce CO2 in an engine that goes into the atmosphere.

LP: So whether it's the gas we use in our passenger vehicles, or diesel used in big rigs, they all contribute. Explain the process to us. An engine burns fuel, and what happens after that? Where do carbon emissions end up?

GC: Yeah, so fossil fuel comes from under the ground, and it is made up of hydrogen atoms and carbon atoms, and we call it a hydrocarbon. When you react to that on the high temperature in air or in an oxygen environment, you produce CO2, or carbon dioxide and water. Those are the main products of that process. And so, the hydrocarbon and the carbon that's trapped under the ground gets converted into a gas that we release into the atmosphere. And so it floats up in the atmosphere through diffusion, not through buoyancy, and then ends up high up in the atmosphere.

LP: So are we too far gone? What are our options at this point? What are potential transportation solutions to rescue the atmosphere, so to speak?

GC: Yeah. So, are we too far gone? That's a whole episode on its own. I think it's safe to say we need to limit the amount of CO2 we're putting into the atmosphere as a really high priority. The next part, as I mentioned earlier, if any CO2 that is in the atmosphere is going to be there for hundreds of years, and so we really want to start looking at technologies that remove CO2 from the atmosphere, or negative-emissions technologies.

LP: You did touch on zero-emissions technology, but you're talking about what you've called negative-emissions technology. So what is a negative-emissions vehicle? How do you achieve negative emissions?

GC: Yeah, so that's a great question. I know all the listeners remember my podcast when I did it before word for word, but as a quick refresher, when we talk about emissions in this context, we need to consider all of the source of emissions in the life cycle of the vehicle. So we call a zero-emission vehicle a zero-emission vehicle because it has no tailpipe and it has no engine, so it is not releasing CO2. However, to make the electricity for some of these vehicles, we do produce CO2. And so, by framing things like that, we just need to understand that we need to look at the entire context of the vehicle. When that comes to a negative-emissions vehicle, this is a vehicle that, through its use, will have reduced its carbon footprint to the point that by the end of its life, it will have consumed CO2 rather than released it. And it does this by being very careful and clever about the fuel it uses, and also, it must store any CO2 it produces itself, and then, at the end of it, it needs to bury that CO2 back into the ground.
Dr. Graham Conway

SwRI Staff Engineer Dr. Graham Conway and a team of researchers are developing a new carbon capture membrane that targets CO2 engine emissions. The technology is described as a negative-emissions solution since it is built to remove carbon emissions from the atmosphere.

LP: So is it also capturing any CO2 from the air around it, or just its own emissions?

GC: It is capturing CO2 from the air around it, but not directly. So this is the special fuels that we need. So one of those fuels would be ethanol, for example. So ethanol that comes from corn, the CO2 that was in the atmosphere has been absorbed by the plant to grow. And so that's captured some of the CO2. If we just burnt that in the engine and released it again, that's kind of a circular economy. The CO2 just goes round and round and round. But the technology we're looking at will store that CO2 on the vehicle, and then, at the end of the life of that fuel tank, we'll release the CO2 underground and store it, hopefully, forever.

LP: All right. And that's called sequestration.

GC: That's sequestration.

LP: All right. Sequestration. So this brings us to SwRI's carbon capture membrane technology, which is doing just that, capturing the carbon of the vehicle that it's installed on. So how does it work? Tell us a little bit more about it.

GC: Yeah, so the CO2 membrane that we worked at Southwest Research Institute, we've been working on it for several years. The membrane itself works by a chemical reaction process whereby it converts the CO2 into something that is very selective towards CO2. So only CO2 can pass through this membrane. No other gases can pass through. And so that allows us to very easily remove CO2 from an exhaust stream, such as would find on an engine, or in a whole host of other applications where there is hot exhaust gas that contains CO2.

LP: OK, so can you tell us more about the material the membrane is made from?

GC: So the membrane itself is made up of lithium zirconate, which is suspended in a porous ceramic substrate. And so you can think of that as a sponge. And we fill the sponge with water, and then it holds that water. And then, you squeeze it, and the water comes out of it. We're doing the same thing with CO2, just with some slightly different physics to drive the process. So the CO2 is analogous to the water. The ceramic is analogous to the sponge. And the chemistry is what causes the sponge to absorb the CO2.

LP: So once the CO2 passes through the membrane and it's captured, what happens next? What do you do with it? Is it stored in, like, a tank? Or how does that work?

GC: So on the vehicle demonstration program we're looking at, we will be storing the CO2 on board the vehicle in a tank. The end goal is to have that tank offload that CO2 into a sequestration pipeline network where it will eventually be stored underground. The Inflation Reduction Act of last year has placed an extremely high value on sequestered carbon, and so a lot more commercial entities are looking at pathways to execute on that 45Q tax credit to put CO2 back under the ground.

LP: Yeah, can we talk a little bit more about that act? What is the name of it again? And what does it spell out?

GC: So the Inflation Reduction Act came about in Q4 of last year. It was a government program looking at how we can, in some ways, look towards decarbonization in different industries. So it brought around many incentives for electric vehicles, but it also started looking at other alternatives and other options. And so the value placed on capturing CO2 and putting it under the ground became much, much higher after that act passed. So before the act passed, every ton of CO2 captured was worth $50 in a tax credit. Now, it can be as high as $180 for that same ton of CO2 captured. And so it's a significant increase in the value of it.

LP: So describe what this off loading process would look like. Would you drive the vehicle tank on board to like a station of some kind, and then, maybe there's an underground, you said, pipe network, and it would just be secured there and released? Is that how it would work? What does that look like?

GC: So, essentially, if we think of a commercial application, let's think of something that has a route-based operation or duty cycle, the Amazon Prime trucks that come round to my neighborhood 400 times a day. 399 of those are for me. They will come around with the truck, and then, they will go back to the depot. The idea is there will be an off loading site at their depot which is part of a pipeline network. Now, we're an extremely long way away from that network being a reality, but starting to move forward with it would put it in parallel with other technologies, such as hydrogen, which also needs a big infrastructure build out to become a reality.

LP: So you're not just filling up anymore. You're offloading.

GC: You're offloading, ideally, at the same time you fill up. So the end user, now, instead when they grab the pump, it will have two nozzles, not one nozzle. One will refill the vehicle, one will offload the CO2. That's an idealized case. Again, we're a very long way away from that. But that's how we would envision it working.

LP: That's the vision. That's what we like to talk about on the podcast. What's coming up. So would did this membrane work on all size vehicles, from passenger vehicles, to, again, the 18 wheelers?

GC: Yes. So the membrane scales. The membrane scales with the size of the vehicle. And I think we need to consider a much wider scope of applications for this technology. In fact, as you scale in size, the larger you get, the more sense it makes to apply this technology. So if you could consider a leaf blower with an engine, if you wanted to put in a supercritical CO2 storage system and pumps on it, that's going to be pretty difficult to carry because it's already a small unit. If you go to the other end of the scale, which is maybe a ship or something in the marine space, then it becomes a lot more feasible to see where you can put the CO2 that you're going to store. And so we think most of on-road applications would be a fantastic fit, and some off road, including marine. Aviation, it's not really applicable to aviation. We're going to have to find other decarbonization solutions there.

LP: And you say this is a while away, but how soon could we see this technology outfitted on vehicles?

GC: So the technology itself could be in a demonstration form within 12 to 18 months. The biggest challenge is the offloading part of once you've captured and stored the CO2, what does the network, at a commercial scale, look like to offload that? Again, a demonstration of that could be achieved in a very small timeline, but to have something that we can truly rely on for a mass adoption decarbonization strategy, we are probably, honestly, decades away from achieving that.

LP: So are there any opportunities here for landowners who would want to dedicate space to achieve sequestration on a larger scale?

GC: I think there's opportunities, especially given the value that has now been placed on sequestered carbon for large companies. And so there are ventures looking at building out pipeline networks. So there's a joint program by BlackRock and Navigator, looking to build out 1,200 miles of supercritical CO2 sequestration pipeline in the Midwest. And so they're currently negotiating with farmers to bury the CO2 pipeline in their land so that we can have somewhere that the CO2 can go. So, yes, there should be interest in adopting that.

LP: So this is unfolding as we speak.

GC: It is, yes.

LP: What will it take to get this technology adopted around the world?

GC: So I think the Inflation Reduction Act was a big step forward in the adoption of it because it gave motivation to commercial entities to go after it. I think the other thing that is happening is we're seeing an increase in environmental social pressure. We're seeing an increase in the ESG pressure that companies are facing. And so there's pressures on companies to do something and show decarbonization strategies. On a larger scale, it is still going to need regulations to help the technology matter to end users. And so I think a combination of the increase in incentives from the government, pressure for companies, and regulations to force it will eventually lead to an increase in public awareness, which is ultimately going to help fulfill the continued push towards it.

LP: So let's compare this membrane technology to electric vehicles. Should we be working to get everyone on board with electric, or is this a more viable solution long term to solve our carbon emissions problem?

GC: So should we look at electric vehicles, or should we look at carbon capture? The answer is yes. So we need -

LP: All of the above.

GC: We need all of the above and more. And so there's many, many situations where the electric vehicle just makes a lot of sense. If we go to my earlier example of a handheld leaf blower, that makes a lot of sense for a battery-operated piece of equipment. Even when we get into cars, it makes a lot of sense for battery electric vehicles, especially those that operate around cities, can go home and charge overnight. The user doesn't have huge concerns with range anxiety because they've got a public infrastructure for charging if they ever need it. That makes a lot of sense.

As we start to scale up the technologies and we go to larger trucks, we go to off-road applications, then we go to trains and marine, that's where the batteries become a lot more challenging. There's very expensive batteries, very heavy weight of batteries, and a long time, in cases, to charge these batteries. And so in these applications, this is where we're looking at a host of different decarbonization strategies, of which, the carbon capture is certainly one of them.

LP: So SwRI really shines on multidisciplinary projects. We have talent from several areas coming together to develop this membrane technology. Tell us more about the different disciplines cooperating on this membrane.

GC: It's one of those projects that really does span all of the physical sciences that the institute is so famous for. We are working on this particular project across three divisions. We are working with our colleagues in the chemistry and chemical engineering division, Division 1, to develop the membrane technology itself, to get it to a stage where it's operating at the best it possibly can. We're also working with colleagues in Division 18, in mechanical engineering groups, to look at how we can take the CO2 and we can then compress it, we can cool it, we can store it in the smallest possible amount of space using the least possible amount of energy to do so. And then, in 3, III the powertrain engineering division, we're looking at how we can ultimately get this into a demonstration vehicle to show people the technology.

LP: All right. And are there any other technologies aimed at protecting-- aimed at protecting the environment in the works that you can preview for us?

GC: There are lots of other technologies out there, and there needs to be. As I've mentioned, we need a host of different decarbonization strategies. I know we've spoken on the podcast, not me, but I know Angel has spoken about the hydrogen economy and where hydrogen goes. And so hydrogen is a pretty interesting prospect right now for transportation, either in an internal combustion engine or in a fuel cell electric vehicle. And I think, like the CO2, there's a challenge with where does the hydrogen come from? There's challenges for both.

For the hydrogen, it's where do you get the hydrogen? You need an infrastructure to get the hydrogen. For the CO2, it's kind of the opposite. You've already got it. You need to get rid of it. And so whichever approach we go down, we're going to need significant buildout or investment of the infrastructure. But definitely, hydrogen is another area that the institute is starting to really ramp up in because it will help us towards our decarbonization goals.

LP: All right. Exciting things coming up. So while you and your team are working on this potentially world-changing technology, what can the rest of us do? Maybe we're not scientists or engineers. How can we help lower carbon emissions? Is it as simple as maybe carpooling, or walking and biking? What do you suggest?

GC: Yeah. There's lots of things we can do. The industry, 10 years ago, when internal combustion engines were the big driving force, if you could get a 1% reduction in CO2, that was a really, really big deal. But if you think about it in a different way, if you got two people to drive in one car rather than two people driving a car each, that's a 50% reduction immediately, and we're really, really excited about 1%. So there is a huge power to be explored in carpooling or car sharing. And so I think for many people, especially people who work at the institute, there are opportunities.

Find someone who might live near you find, someone who's on a similar schedule. Even if it's one day a week where you carpool in, that eventually makes a difference. I like to ride my bike to work sometimes. It's about 35 miles on the greenway, but it's enjoyable. I enjoy the ride to work. I know I'm missing the traffic, I'm getting some exercise, and I do have a lower CO2 footprint from doing it.

LP: So that's a lot of motivation to get you on that bike and get you to work that way. It's really neat.

GC: It definitely helps.

LP: So as we celebrate Earth Day this month, what is your message for our listeners? How can we better protect our planet?

GC: I think this is another approach where we have to consider the impact that we can all make. So there's the quote, many hands make light work, and I think that's really applicable here. I could, myself, strive to be a zero-emission person. I could do everything I possibly could to achieve that. Would it make a difference on a global scale? Unfortunately not. But if every single person aimed to reduce their emissions by 1%, that would go a huge way to reducing the climate change problem we have. And that could be as simple as setting the AC 1 degree higher. It could be as simple as planting a few plants. It could be as simple as the carpooling that we've just discussed. There's lots of different ways we can make a big difference if we come together as society.

LP: All right, so many great ideas there. And as you said, we need all the solutions. So we're excited about all the technology in the works that has the potential, as we said, to make a difference, not just for us, but for future generations, and to get us to those 2050 goals. So thank you so much for joining us today, Graham.

GC: Thanks again, Lisa.

And thank you to our listeners for learning along with us today. You can hear all of our Technology Today episodes and see photos and complete transcripts at Remember to share our podcast and subscribe on your favorite podcast platform.

Want to see what else we're up to? Connect with Southwest Research Institute on Facebook, Instagram, Twitter, LinkedIn, and YouTube. Check out the Technology Today Magazine at And now is a great time to become an SwRI problem solver. Visit our career page at

Ian McKinney and Bryan Ortiz are the podcast audio engineers and editors. I am producer and host, Lisa Peña.

Thanks for listening.


Decarbonization refers to the widespread adoption of solutions that contribute to a carbon-neutral society. Southwest Research Institute offers advanced science and applied technology that aid in lowering carbon emissions through development of decarbonization technology, including energy storage, carbon capture, and hydrogen combustion and compression.