The reality of capturing carbon

Kara Miller: From the MIT Energy Initiative, this is What if it works?—a podcast looking at the energy solutions for climate change. I’m Kara Miller.

Robert Stoner: And I’m Rob Stoner.

KM: And this is What if it works?

We’re going to talk in a few minutes about some cutting-edge ways to take carbon out of our world. Well, why would you want to do that? Carbon dioxide, of course, is a powerful greenhouse gas that contributes to climate change. In fact, its levels in the atmosphere have increased nearly 50% just since the 1950s. The Earth does have biological systems that can remove carbon, but they cannot keep up with the sheer scale of the stuff that is being dumped into the atmosphere from industrial systems, from our various modes of transportation, and on it goes.

So, what ideas do scientists and engineers have for removing it? We will get to that.

But first, to get a sense of where this whole line of thinking got started, you’ve got to go back at least to the mid-1980s. In 1985, an incredibly well-known scientist, a star in the general public, named Carl Sagan, testified before Congress.

Unknown: We’re very pleased that you would take the time out of your schedule to come to a place like Washington where everything seems to be living in today and not in tomorrow to share with us your particular view of how our past and our present may well affect our future. Carl, thank you very much.

KM: Sagan was an astronomer at Cornell who had narrated a big series on TV called Cosmos, and he showed up in D.C. in 1985 to testify about climate change, which was just starting to get on more and more people’s radars.

Carl Sagan: The power of human beings to affect and control and change the environment is growing as our technology grows, and at present time, we clearly have reached the stage where we are capable both intentionally and inadvertently to make significant changes in the global climate and in the global ecosystem.

KM: A few years later, in 1988, NASA scientist James Hansen would also warn Congress about the fact that the climate was changing. And that was right about the time that our guest today, Howard Herzog, arrived at MIT.

Howard Herzog [00:02:29] The first summer I was here, back in 1989, I came here to work on a variety of energy projects. But the first summer I was here, there was a researcher here from Japan, actually, doing nuclear research. But some of his colleagues back in Japan asked him a question, can you capture carbon dioxide emissions coming out of a power plant?

KM: Howard is an engineer. A senior research engineer here at MIT, he has now written a book called Carbon Capture. He’s the co-author of an upcoming book on carbon removal, and this struck him as a very interesting question. Can you capture CO2 emissions coming out of a power plant?

HH: Three of us formed a team and issued a report and said, yes, it is feasible. Costs a little money, but you can do it. And we published and we were one of the first people to publish in this area. There were a few other groups publishing. And that field eventually became known as carbon dioxide capture and storage or CCS for short. But that first project led to another project and a big research-needs assessment for the Department of Energy in 1992 with some co-authors here at the, back then it was called the Energy Lab, and that just kept going after about 10 years. It was a major part of my research portfolio and has remained that way for the past 25 years or so.

KM: During that time, Howie has seen the interest in climate change grow.

HH: We organized a big symposium called “Energy and environment in the 21st century.” So, it was back in 1990 and our big keynote speaker was Al Gore and he was a senator. And all I remember him talking about was this trip underneath the Arctic ice in a submarine.

KM: But he has also seen interest in climate change splinter.

HH: Back then, it was a bipartisan issue. It was the first George Bush that was president when the framework convention was to be ratified that came out of the Rio back in 1994. He signed it. I forget it was overwhelmingly approved by the Senate. So it wasn’t a political issue back then. It became that over the years. I can’t pinpoint anything, but I think all of our politics has become more polarized and this was just part of the polarization, which is too bad because it affects everybody, red states, blue states. It’s not something that’s easy to solve unless you have everybody on board to really have good climate policy. It really has to be bipartisan and bought in by a majority of the people. And unfortunately, that’s not where we’re at today.

KM: We’re going to talk about pulling carbon out of the atmosphere. But to know whether that makes any sense, you really have to think about how much it costs to both put carbon into the atmosphere and to pull it out. Fossil fuels, Howie says, are a pretty great energy source. And if you don’t acknowledge the fact that they’ve got a downside by putting a price on them, people will turn to them, which is logical. Europe has put a price on carbon, which can go up to $100 per ton of CO2, Howie says, but of course, people are resistant to pay that kind of tax.

HH: It’s going to cost more to reduce our carbon emissions, but the real question is, if we don’t reduce our carbon emissions, what’s the cost there?

KM: And that cost can be high. But still, there’s a lot of interest in removing carbon dioxide from the atmosphere. So, what do the range of options look like once the carbons already out there? Howie laid it out for us.

HH: There’s two ways to get CO2 out of the air. One is biological, and that’s through photosynthesis. Plants do this all the time. They record the CO2 level in the atmosphere at the Mauna Loa Observatory. If you look at that, it’s not a straight line. It’s squiggles going up and down. In the spring, all of a sudden, the plants come to life, and they suck up a lot of the carbon dioxide, and when they die in the fall, it goes back up. And you can actually see it in the measurements in the atmosphere. Plants…

KM: I saw a visualization of this, I have to say, at the MIT Media Lab. Rachel Connolly works on NASA stuff. It was amazing. During the spring and the summer, there’s so much less carbon dioxide in the air, right, than in the winter when there’s just so many fewer leaves to suck it up.

HH: And for people who think, well, there’s a southern hemisphere too, but most of the lands in the northern hemisphere, and that’s what really controls that. And the measurements are being made in the northern hemisphere. So you have photosynthesis, and the other is chemically. And the way you do a chemically is you do it with what I call alkali. And alkali just means it’s a chemical that’s basic. And CO2 is an acid. So think of when you’re a kid and you did the volcanoes with baking soda and vinegar. Vinegar is an acid, baking soda is a base, and they react together. Same with alkali and carbon dioxide in the atmosphere. The problem is we don’t have alkali lying around. Why don’t we have alkali lying around? Because if it was, the CO2 in the atmosphere would react with it and neutralize it. So we have to create it, and that costs money. And there’s several ways to create this alkali. And so what you have are things like direct air capture, which uses a sorbent. Talk about things like enhanced weathering. People talk about liming the ocean. Lime is an alkaline material.

KM: I’ve heard of weather forecasting. What is enhanced weathering?

HH: I’m sorry, enhanced rock weathering. So the way that nature takes CO2 out of the atmosphere is by reacting with alkaline rocks. And a lot of these alkaline rocks are silicate type rocks. And the problem is the time scale for this is 100,000s of years. So that’s slow. So there’s always been a slow removal of CO2 into rocks over time. But they want to enhance that. They want to get this thing from taking 100,000 years to taking days.

KM: Pressing fast forward on nature.

HH: If I could take this rock and really crush it up so it’s fine, so a lot more sees the air, it will speed up the reaction. But the problem is to crush it up that fine, it takes a lot of energy. Whatever we look, at those ways take energy. So those are the things. Now, when we go back to photosynthesis, there’s two ways to think about it. One is let’s just plant a tree and leave it there. And so there’s a concept called stocks and flows. Stocks means how much you have in a given place. Flows is the flow going between.

So what we’re doing with climate change is we have flows of CO2 in the atmosphere primarily from our fossil fuel use. And that increases the stock of CO2 in the atmosphere. Some of that will get also absorbed in the trees and vegetation and the ocean. But about half of it stays up in the atmosphere. So if we stop emitting CO2 today, we stop the flow, but the stock is still up there. You know, that’s the issue. That’s why it lasts a long time. And it’s the stock that’s in the atmosphere that determines how severe climate change can be, how the temperature rise and the other impacts.

So one thing we can do is we can just plant more trees. We can figure out how to get more trees or more stocks of carbon on a certain area. Actually, the soils contain about twice as much carbon as the trees and vegetation. So if we want to get into there, wetlands, for instance, contain a real lot of carbon. And a lot of the wetlands have been degraded over the years. So restoring those wetlands could really absorb carbon. So that puts it all in the atmosphere. But we can also harvest the carbon from the trees and the vegetation and do other things with it. One thing people talk about doing is making biochar, which is like a soil supplement, and putting that in the soil. But basically where we are today, that’s it. And in general, it’s a lot cheaper to reduce emissions.

RS: Don’t let it get up in the atmosphere in the first place.

HH: Right. But there are some removals that are fairly inexpensive. And if they are, like planting trees is one of them. But there are other issues that we can come back to, specifically the permanence issue. That’s a fine role today. But most of these other ones are very expensive. So you really want to reduce first. But once we reduce 70, 80, 90 percent, it starts getting very expensive to reduce the last 10 or 20 percent. And these are what people sometimes call residual emissions. So it may be cheaper instead of trying to eliminate these residual emissions to offset them or counterbalance them with carbon removals. So to get fossil fuels off an airplane is not going to be easy. If they electrify airplanes, it will only be for small planes. All these airplanes are made for jet fuel. There’s a lot of issues of safety and everything. So it may cost $1,000 to try to get it off a plane, but we can remove it from the atmosphere for a few hundred dollars. That’s a real benefit.

RS: So the IPCC, which is this international panel of scientists to which you belong or have belonged at times, chartered by the UNFCCC, the United Nations Framework Convention on Climate Change, has become very clear in their last couple of reports about just what that removal rate has to be by the middle of the century. And they’re talking about something like 10 billion tons a year net are going to have to be removed by us and put somewhere where it can’t get back into the atmosphere. Are you saying that that’s overstated because they’re underestimating how fast technology will move?

HH: Well, I’m saying there’s a lot of uncertainty in that number. And it’s a debate to have in mid-century when we’re going to be a lot smarter on the cost and benefits of all this because we can’t start lowering the stock of CO2 in the atmosphere until we get to net zero. So I think our full focus should be getting on net zero. And we haven’t been reducing emissions fast enough. And I don’t think it’s good to say, oh, that’s okay, because if we overshoot, we’ll be able to remove it. And then they try to prove it. I think we should focus on reducing our emissions as quickly as feasibly possible. There’s technical feasibility, but there’s also political feasibility here. That should be our focus. And we’re developing these things to remove it from the atmosphere right now, and we should continue doing that. Modeling out to 2100 has a lot of assumptions.

RS: So we create the technologies. And I know that you’ve gone around the world visiting some of the startup companies that are trying to perfect technologies that can work. What have you learned? What are your feelings about what they’re doing and the odds that we’ll really have the capacity?

HH: Well, I mean, I think you’re talking…I mean, what I focused on a bit recently is direct air capture. And I don’t know how many companies are out there, but I think it’s probably over 30.

RS: DAC, they call it, direct air capture.

HH: DAC. And I have visited a couple of the leading companies, and there’s one company, Climeworks, that’s actually doing it.

KM: So what air are we talking about here? Are we talking about air that comes out of, like, power plants? Are we talking about just, like, the regular air around us?

HH: It’s just that regular air around us. These are big machines, and they push the air through the machines with big fans to move it. But basically, the air is pretty much the same everywhere. It has about 420, 430 parts per million CO2. It goes through the machines, and it comes out the other side. They take out maybe 60 to 75 percent of the CO2 in the air that goes through the machines.

KM: Wow. So then if that works for getting the carbon dioxide out of the air, why are we not running these machines 24/7 every country? Is this the solution?

HH: Well, that’s what some people would like, and that’s why this technology has sort of become a darling with billions of dollars being invested in it. But the bottom line is very costly. So we talked about, like, the European trading system having a carbon price of about $100 per ton. If you go online today to Climework’s website, you can buy offsets, and the cost there is $1,500 a ton of carbon. So that’s a lot of money.

RS: Is that because they’re gouging consumers when they buy carbon offsets?

HH: No. Actually, they may be charging less than the real cost.

KM: So is the deal then that, okay, yes, they can run these machines 24/7, but it’s going to cost them so much to do it, we can’t afford it?

HH: Yeah, and it’s not just money. It also costs a lot of energy. So you have to use clean energy. If you hooked up one of these machines to a coal-fired power plant, you would actually put more CO2 in the atmosphere from the coal-fired power plant than you would capture from these machines. So you really need…

KM: Seems like a bad decision.

HH: And the question is, if we have that carbon-free energy, is it better today to use that to take CO2 out of the air, or is it better to supplant fossil fuels we’re using today with that clean energy? And it’s almost the latter that’s the case. So as I say, carbon removal becomes important as we start approaching net zero, get the last 20 % or so of residual emissions compensated for. But today where there’s a lot cheaper ways to reduce emissions, that’s where our focus should be. And some people call things like direct air capture a dangerous distraction because of that, because we’re not focused on reducing the emissions today.

KM: So, okay, so if you’re a government or you’re a wealthy investor, investing fund, and you’re thinking how to deploy money, you work in thinking about carbon capture, would you say, like, this is not where to spend your money? Go spend it somewhere else.

HH: Well, I mean, carbon capture is different from carbon removal. I’m saying that I think there’s good reason to invest in carbon removal today to develop the technology. But to deploy it at large scale, I don’t think the time is right yet. But on the other hand, it could take 10, 20 years to really get these technologies commercially ready. There’s a lot of carbon removal technologies. We don’t know what are the best. And so working on them, we’re not really spending a lot of money today in the development of it. Now, of course, if you have a company in trying to develop this, you want to deploy it as much as possible.

RS: You better have some patient investors.

HH: Yeah, but you either got to get the cost way down, which I think in some of the things are going to be hard because to do it chemically, it costs a lot of money to develop this alkali. You need to process a tremendous amount of air to get out a good amount of CO2 because it’s so diluted in the air. So if you want to capture a million tons a year, we put out in the United States five billion tons of CO2 a year. So just to capture…

KM: We put out five billion. If you want to capture a million…

HH: A million tons.

KM: Which is okay, but not so great. All right.

HH: The cross-sectional area is sort of the thing perpendicular. So let’s think of it like a building. You need like a three-story building that’s three miles long, all covered with fans.

RS: That’s to capture one million, which is one one-thousandth of a billion, of course. And we got to get to something like 40 billion.

HH: So if you want to capture all the CO2 we’re putting out, it would take… We don’t produce enough electricity to drive these things to even get our… In the United States, to get our five billion.

RS: But as I’m hearing you talk, I mean, your message is sort of on different time frames. Let’s right now, today, reduce our emissions of CO2 where we can. But in the future, when we need to start doing removals, use the low-cost options available to us, like growing biomass, making biochar, sticking it in the ground, and then look to the future when we might have the electrical capacity and the efficiency in these machines to start doing it actively.

HH: Correct.

RS: It’s this tiered system. We’re buying time.

HH: Right. And of course, as analysis, we can say that, but the real world’s messy. So when you have 30 companies out there developing direct air capture technologies, they don’t want to wait.

RS: So there’s direct capture, but a lot of our colleagues here lately have been talking about the idea of direct ocean capture.

KM: Yeah.

RS: DAC and DOC. Yeah. What’s the idea there?

HH: In a given volume, there’s maybe a hundred times or a little over a hundred times more carbon in that volume of water than in the air.

KM: Wow.

RS: Why?

HH: Why? Because water is a thousand times denser than air.

RS: Ah, okay. So you’ve got to move the same amount of mass.

HH: That’s what drives it, but that doesn’t guarantee you anything. Actually, the mass fraction in air of carbon is higher than it is in the ocean. Also in the ocean, it’s not in the form of CO2. It’s dissolved carbon. It is carbonates and bicarbonates primarily. And so therefore the technology to get it out is different. And once again, from things that I’ve read, this is very early stage of this, but what I’ve read on the subject so far is it takes a lot of energy and maybe even more energy than direct air capture.

RS: Right, but from what you were saying earlier, because the carbon is more concentrated in the water, the volume of water you have to move through is much smaller.

HH: Yes.

RS: And therefore the machine is much smaller.

HH: Not necessarily.

RS: Oh. Why?

HH: Well, it depends on how it comes out, and the main thing that they’re using to have it come out now is electrochemistry. So yeah, so your cross-sectional area is smaller, but that’s, it takes energy to move air, but it also, when you’re putting these through electrochemical devices, those devices take a lot of energy too. Not necessarily to move the air, but to get that carbon out of there. Then there’s a whole problem once you get the carbon out of a certain amount of seawater, you got to put the seawater back in the ocean. What does that do? Because will that affect the ocean flux with the atmosphere? Will that give you environmental impacts? When you’re taking it out of seawater, you’re changing the chemistry of that bit, and when you put it back in, that’s going to have some impact. So we got to really understand that. Plus, you know, it’s tough enough getting a permit for a wind turbine. When you’re going to try to do things in the ocean like that, it’s going to take some time getting a permit.

RS: I see. Fishermen and so on might be pushing back a little bit if you’re going to start…

HH: I mean, that’s why it’s worth the research now to understand these things, to answer these questions. So when you do go for a permit, you have the answers.

KM: Do you think, I mean, I know this is projecting forward and I know we don’t have the answers, but do you think when we eventually figure out in mid-century how we’re going to address climate change, that the idea of actually taking carbon out of the atmosphere or out of water or whatever is going to be a big player here, and it won’t just be, let’s switch to wind, let’s switch to solar, and let’s switch the kind of cars we drive, and etcetera.

HH: Because of the physics of the problem, it’s hard for me for saying it’s ever going to be cheap. But what are the impacts? So we talked today, they talk about the social cost of carbon, which is really, people give numbers to it, we don’t know, but the concept is every time we emit some carbon dioxide to the atmosphere, there’s a cost to that. It impacts from climate change. So if we want to remove it in the future, there’ll be benefits. How much are those benefits compared to the cost of removing it? That’s the decision people will make at that time and say, is it worth doing that? I keep an open mind about it, but I don’t feel strongly one way or another. I just hope we decrease emissions fast enough so it’s not going to be necessary for us to remove too much.

KM: Then we don’t get to your research yet. You’re the just-in-case research.

HH: Well, no.  I started on carbon capture, and I think carbon capture is a way to reduce emissions to the atmosphere. We’re using more coal today. Coal keeps increasing. The U.S., we’re closing coal plants, but China and India are still building it. People are always going to want energy, and the question is, for them to do their emissions, capturing a power plant can be cost-effective. That’s a lot less, but I think once you build up carbon capture and get the supply chains right, you can do it for under $100 a ton at a power plant. Maybe even get it closer to $50 a ton. That’s different than we’re talking numbers up now in the hundreds of dollars.

RS: We haven’t really talked about where you put the CO2 once you capture it. We talked about biochar a little bit.

HH: Basically, where can you put it? As I say, there’s three reservoirs that they call atmosphere, ocean, and the terrestrial biosphere. The more we put in the ocean or terrestrial biosphere, the less is in the atmosphere. Planting trees is one way to keep it in the terrestrial biosphere. Biochar is another way to do that. Once again, those are issues of permanence. Will you really keep it there for the length of time you need? Or will things like pestilence and fires disrupt some of it or even changes in land use? But if you keep up there, at least, that has the effect. The other places are, like I mentioned, enhanced rock weathering. You turn it into rocks, or you can put it back into geologic formations. These geologic formations are where we take out oil and gas. We can put them into those same reservoirs, or there’s a lot of geologic formations and a lot more of these than oil and gas reservoirs that are basically deep and they’re filled with brine. You want to go over 800 meters deep. That’s the way the CO2 stays in a dense phase, a liquid-like phase. You can put them in those geologic formations. Hopefully, we’ve had the oil and gas stay on the ground for literally millions of years. Hopefully, that’s a permanent solution. So those are what you can do.

RS: Is there enough space down there? Do you have reservations about the limits?

HH: There’s a lot of space down there. The theoretical space is very large. There’s two issues. One, how much of that theoretical space can we use? And secondly, it’s not everywhere. It’s in all parts of the world, but it’s not in every place. For instance, here in New England, we don’t really have a lot of that formation. A lot of those formations are where you see oil and gas production today. We do potentially have some capacity here in New England offshore, but it hasn’t really been explored because the places people have explored underground are where they’re trying to get out fossil fuels.

RS: I guess that’s another big application of CO2, once it’s captured, to use it to pump into active oil and gas reserves to produce more efficiently.

HH: CO2 is good at…you pump CO2 into an active oil reservoir, what they call “mobilize the oil,” it changes the oil viscosity so it flows better.

RS: So there’s an irony there. But is that also potentially a pathway to almost have a circular flow of carbon from the reservoir, out to where we use it, and back in again?

HH: It depends. You can maybe produce carbon neutral oil that way, but that’s not a negative emission, or in the long run, you really got to cut back. But what that’s been useful for, it’s been a stepping stone to help some of these initial projects, which are financially challenged to begin with because it helps to finance those projects because they can actually sell the CO2 and get a little money for it.

RS: In fact, Occidental Petroleum bought, what was it, carbon engineering?

HH: Carbon engineering, correct.

RS: To do precisely that.

KM: To inject carbon into their wells to get more oil out?

RS: For producing more oil. With the idea that it’s a stepping stone, I guess.

HH: Well let’s just say Oxy’s a little more bullish on all this than I am. They want to have a half a million ton a year plant operating by the end of next year. Well, we’ll see.

RS:] I saw Vicki Hollub talking about this recently. She’s quite convincing when you hear her, but yeah, it’s a fraught path.

HH: I’m going to go back to the old British proverb, the proof is in the pudding.

RS: Well, Warren Buffett’s bullish. He’s so sold on the story that Oxy’s putting out that he’s acquired most of the company.

KM: Wow. Well, he’s often right.

HH: I take a wait and see attitude.

KM: I know we wanted to, I think, finally talk about some of the maybe more fringe ideas of how to really geoengineer. If we think, wow, things are getting too hot, there’s too much carbon out there, what can we do? I feel like these efforts to change clouds, change the weather, these kinds of things, they get a lot of media attention. I don’t know if they deserve the media attention, but they seem, I think, so interesting and exciting that people can’t resist talking about them. So, just, first of all, talk about what kinds of things do people talk about that you might be able to do, and then tell us if you can really do that.

HH: The most common one people talk about are solar radiance management, putting up a sun sheet. The most common there is putting aerosol particles up in the stratosphere, and so it reflects sunlight. So, this doesn’t do anything to the carbon dioxide, but it cools the earth.

KM: So the idea is you’ve got the sun’s rays coming down, and you’re like, no, let’s reflect them back. We don’t want them here.

HH: Right. And there’s a whole series of things to do it. So this goes back a long time. There was a National Academy study sometime around 1990. I can’t remember the exact date, and it was really thick. It might have been 1,000 pages. And they had like a 15 or so page appendix. They had a lot of appendices, and one was on geoengineering. So there’s a really thick report, this one appendix. There was an article, and I still have the article in my drawer, an article in Newsweek called “The Wings of Icarus,” a two-page spread, and all they talked about from that report were the geoengineering ones. They talked about shooting Navy shells up in the atmosphere to do sulfates and putting a sunshade, actually putting things in space at some of these Lagrangian points.

RS: They’re still talking about it.

HH: I know, they’re still talking about it. And it’s something people like to talk about. I actually have a section in the new book saying, is carbon removal geoengineering? And I think the answer, there’s an array, and it depends how you define geoengineering.  People don’t know. So people say when we’re emitting CO2 up our chimneys or our tailpipes is a geoengineering experiment, because we’re changing the Earth, it’s causing climate change. In that case, any time we remove it would be too. But probably the most benign in terms of that is direct air capture, because you’re really not affecting anything except taking the CO2 out of the air. And I think that’s another reason people like it a lot. And the other extreme is this ocean alkalinity enhancement, where you’re putting alkaline subjects in the ocean so you can get more carbon stored there.

RS: Accelerated sort of dissolution of CO2 into the ocean.

HH: Yeah, when you put more alkali in the ocean, it will absorb more CO2 from the atmosphere. And also it will neutralize a little of the ocean acidification that’s being caused by the extra CO2 going in the ocean right now. So it looks pretty interesting, but there’s a lot of questions on what the impacts. So it will be something that goes slow. But that really is geoengineering. Even though there, once again, you are affecting the CO2 in the atmosphere, as opposed to trying to, you know, when you’re trying to manage the solar radiation, there’s no guarantee it’s going to be an exact match. So some places may make climate change impacts worse, while make it better in other places. And then, of course, I would suggest you become a lawyer so you can take all the law cases suing the people that did the solar radiance.

KM: It sounds like you’re skeptical. And it’s also, I would think, impossible to test many of these things out. Like until you just do it. Do you decide we’re going to pull the trigger and do this?

HH: Down the street, or maybe I should say up the river at Harvard, they were going to do an experiment on this in Sweden. And it ran into opposition, and they never ran the experiment because of the local opposition. I think it’s hard to run an experiment on that. There’s research you can do to better understand it. The best experiments are natural experiments. So when a volcano erupts, that’s basically what they’re trying to do. So we have data from that. But it’s what I said in my first book. Geoengineering is a Hail Mary pass in football. And you ask any football coach, you want to avoid the Hail Mary.

RS: So I guess that same caution…

HH: Because it doesn’t work most of the time.

RS: But that same caution applies to direct ocean capture as well, from what you were saying earlier. We’re going to be affecting the alkalinity of the ocean and its biology very locally.

HH: That’s right.

RS: That could have real impacts, unlike capturing it from the atmosphere. The dilute nature of what’s in the atmosphere is actually advantageous.

HH: So I think when you work in the ocean, you are much more on the geoengineering fringe than, say, planting trees or restoring wetlands.

RS: So can we do it? I mean, can we use these techniques to address this increase we have in our emissions and head off climate change? Or is that even the right way to think about it?

HH: There’s a person that I worked with in the past from Oak Ridge named Greg Marland. And once again, this is back 25 years ago. He ran a little symposium. And in the morning, it said, can we geoengineer the climate? And then the afternoon session was, should we geoengineer the climate?

RS: What could possibly go wrong?

HH: So, I think the most important thing we can do now is reduce emissions as quickly as possible. And so maybe I can end with the last statement of the new book we wrote. And the best way to remove CO2 from the atmosphere is not to put CO2 in the atmosphere in the first place.

RS: Great advice.

KM: Howard Herzog is a senior research engineer at the MIT Energy Initiative. He’s the author of the book Carbon Capture and of an upcoming book on carbon removal. Howard, thanks so much for being here.

RS: Thank you.

KM: What if it works? is a production of the MIT Energy Initiative. If you like the show, please leave us a review or invite a friend to listen. And remember to subscribe on Apple Podcasts, Spotify, or wherever you get your podcasts. You can find an archive of every episode, all of our show notes and a lot more at energy.mit.edu/podcasts and you can learn more about the work of the Energy initiative and the energy transition at energy.mit.edu. Our original podcast artwork is by Zeitler Design. Special thanks to all the people at MITEI and MIT who make this show possible. I’m Kara Miller.

RS:  And I’m Rob Stoner.

KM: Thanks for listening.

Fact check: Rio was 1992.