Why CO2 ‘Air Capture’ Could Be Key to Slowing Global Warming

Physicist Klaus Lackner has long advocated deploying devices that extract carbon dioxide from the atmosphere to combat climate change. Now, as emissions keep soaring, Lackner says in a Yale Environment 360 interview that such “air capture” approaches may be our last best hope.

For two decades, Klaus Lackner has pioneered efforts to combat climate change by pulling carbon dioxide from the atmosphere. Now, after years of watching the global community fail to bring greenhouse gas emissions under control, Lackner — director of the Center for Negative Carbon Emissions at Arizona State University — is delivering a blunt message: The best hope to avoid major disruptions from global warming is to launch a massive program of CO2 “air capture” that will begin to reverse the buildup of billions of tons of carbon in our atmosphere.

Trained as a theoretical physicist, Lackner developed a device while at Columbia University that was patterned after a tree, absorbing the carbon dioxide that passed through it as wind and releasing it in a stream of water.

Klaus Lackner. BRUCE GILBERT

Lackner says he is continuing to perfect this design, which he hopes will one day serve as a prototype for millions of such devices around the globe.

In an interview with Yale Environment 360, Lackner says that while the development of renewable energy is essential in slowing global warming, these alternative sources are being deployed far too slowly. He contends the best course of action — and one that will become more palatable as the costs of rising seas and other climate upheaval mounts — is for governments to require the petroleum industry, the coal sector, and other emitters of CO2 to remove the same amount of carbon from the atmosphere that they release as emissions.

“If you pump a ton of carbon out of the ground, you will need to take a ton out of the air,” says Lackner. “We need to have the ability to walk this backwards. I’m saying this is a war, and we need to use all the weapons at our disposal. You don’t want to get into this fight with one hand tied behind your back.”

Yale Environment 360: In Paris last year, delegates agreed to attempt to limit global warming to 1.5 degrees Celsius. Are we anywhere near on track for that?

Klaus Lackner: Let me ask that the other way around: Are you sure that we are not at 1.5 C already? Keep in mind, if we were to quit by magic our C02 emissions tomorrow, it would still get warmer for decades [because of the C02 already in the atmosphere]. So I don’t think we stand a chance of 1.5 degrees unless we have a way of actually reducing C02 in the air. The IPCC [Intergovernmental Panel on Climate Change] itself has said that without a significant period of negative emissions, we won’t make a 2-degree C target either. So in reality, we’ve probably already overshot the goal because of the inertia in the system. At this point, we need to figure out how to go backwards, and that is where air capture plays a big role.

e360: We can’t get there with wind and solar?

Lackner: We might be able to in the long term, but the question is: Can we phase it in that fast? We are nowhere close to doing that. So I would argue that no matter what we do, we will go past 450 ppm [parts per million of C02, a level most scientists regard as dangerously high]. Certainly, we need to grow alternatives as fast as possible. But to stay below 450 ppm, I’ve done the calculations and we would have to cut carbon emissions by 8 percent every year. You show me how — with the global population increasing, with countries like India and China coming up, with the push for economic growth — we can possibly do that?

‘‘‘We’ve run up a huge debt on our carbon credit card and we need to pay it back.’

e360: You pioneered the idea of building what you call mechanical trees that could be placed on the landscape to take C02 out of the air. How would that work?

Lackner: Trees have lots of surfaces called leaves, and as wind blows over those surfaces, they slightly absorb C02. So when we started, we said, ‘Maybe there are materials that absorb C02 more aggressively than a leaf surface.’ We found a plastic material, a resin, that very nicely absorbs C02. As the wind blows by, it takes CO2 out of the air. When it is dry, it loads and when it is wet, it releases C02 back. Then we pump it out of the chamber and compress it to liquid C02.

e360: What do you do with the C02 once you’ve captured it?

Lackner: You can feed some of it to algae, which can be used for food and fuel production, or you feed it into a greenhouse where it stimulates plant growth, or pump it into oil wells in a process called enhanced oil recovery. There is an $800-million yearly market for what I call merchant C02 in the U.S. But much of the greenhouse gas would need to be sequestered in geological formations underground. In the long run, underground storage may not be sufficient, so I am looking at another technique where you feed C02 to olivine and serpentine, which absorbs it in weathering, transforming it into geologically stable carbonates.

e360: Some people object to talk of taking C02 out of the air, saying that it diverts the discussion from where it should be — namely developing alternative energies.

Lackner: We could have had this conversation in 1980 and you might have convinced me that I shouldn’t put air capture out on the table because it might be used as an excuse to delay cutting our emissions. But now that we have delayed, it’s too late to have this argument. We need to have the ability to walk this backwards. I’m saying this is a war, and we need to use all the weapons at our disposal. You don’t want to get into this fight with one hand tied behind your back. The IPCC has said we cannot solve this problem unless we have what it calls ‘negative emissions,’ which means we take more C02 out in a given year than we put into the atmosphere. And if you want to do that, you need air capture.

e360: Some environmentalists would call this ‘geo-engineering’ and say it’s the wrong approach.

Lackner: [Climate scientist] Jim Hansen is saying that we should go back to 350 ppm. 350.org wants to do that, but they don’t want to take C02 out of the atmosphere. However, there is no other way to get back there. To roll back 100 ppm, we may already be obliged to put away more C02 than we made in the entire 20th century. So I would argue that we have to take C02 back simply to balance old conditions. We’ve run up a huge debt on our carbon credit card and we need to pay it back.

‘We need to change the way we think about C02 and recognize that it is a waste disposal issue.’

e360: One technology that is in use in a few pilot plants is taking C02 directly out of the exhaust gases from power plants and factories.

Lackner: There is an advantage to capturing C02 in power plant and industrial flue gases, where it is concentrated. The cost of taking C02 out of the air will generally be higher than scrubbing it from flue gas. However, getting C02 from power plants doesn’t make you carbon neutral — far from it. Half of all emissions come from smaller sources, and there you don’t have much choice. An airplane can’t carry home the C02 it makes, even if you could figure out how to capture it, because it can’t handle the weight. Neither can a car. You would have to have 6 cylinders of C02 in your trunk. So we have to deal with this C02, as well. And direct air capture is the way.

e360: The big criticism of air capture is that it is too expensive and that it hasn’t been adopted commercially on any scale yet.

Lackner: Why would I adopt it if there isn’t yet a price on carbon? What incentive do I have as a company to do this? Never mind what the price is, even if you tell me it is 1$ a ton, why would I do it? My view is we need to change the way we think about C02 and recognize that it is a waste disposal issue. If we called it ‘C02 dumping’ rather than ‘C02 emissions,’ maybe we would have solved the problem by now.

e360: How would that change the discussion?

Lackner: If I go out and dump my garbage in the street, my neighbors would complain about it. If I went to them and said, “Look, guys, I thought about ways to make my processes more efficient and I’m only dumping 80 percent of what I used to onto the street,” they wouldn’t take that as a good answer. Because they would understand that it is a waste problem and you are not allowed to put it out — period and end of discussion. If you create garbage, you are responsible for taking it out.

I would argue that if you want to take oil, coal, or gas out of the ground, you have to present a certificate of sequestration, which certifies that an equal amount of carbon has already been put away. If you pump a ton of carbon out of the ground, you will need to take a ton out of the air. Ultimately, you need a regulation that says you have to buy that offset.

e360: So government regulations are the answer?

Lackner: There is no question of business as usual here. Eventually the pain [of climate change] will get too high, and we’ll be forced to act. Carbon regulations may be a tax, may be a carbon price on a cap and trade [system], or the certificate of sequestration that we just talked about. But unless there is a regulation, there is no money to be made in this. And if there is no money to be made, nothing will happen, you can be sure of that.

‘You would need 100 million air capture devices to take out all the C02 that we putting into the atmosphere today.’

e360: Some have argued that planting trees is better for the environment and cheaper than mechanical air capture.

Lackner: Is it really better for the environment? If you really wanted to get the C02 that we produce back, you would need to have more acres in trees than we now use for farming for food production. The environmental footprint would be huge. A good-sized tree collects a few tens of tons of carbon in its lifetime. We can produce a device of the same size and collect a ton a day, which is roughly 1,000 times more C02 than the tree. The analogy I use is: Can you pull a plow with a horse? Of course you can. But wouldn’t you rather use a tractor?

e360: You are not saying that we shouldn’t plant trees, are you?

Lackner: Planting trees is part of the mix, as are other forms of bio-sequestration, like biochar and growing microalgae in the ocean. I’m not saying you shouldn’t do it, I’m just saying it won’t scale up to the size where you need it to be at. I mean, look at bioethanol — we get less than 10 percent of our total fuel consumption from it. But look at what it has done to our agricultural system. Growing trees is a form of agriculture that will compete for land with food agriculture. There is just not enough land to go around.

e360: You have been working on developing a viable air capture device for many years, but it is not yet in use. What needs to happen now?

Lackner: With $10 million to $20 million worth of engineering R&D, we can get off the ground. My hope would be that we then would have a device that can take out a ton a day of carbon from the atmosphere. If you take out a ton a day, you would need 100 million air capture devices to take out all the C02 that we putting into the atmosphere today. And I would argue that it would be a lot less than that because we would also be capturing carbon at the flue stack, and not making the C02 in the first place by developing solar and wind technologies.

e360: Still that’s a huge number. But maybe not in comparison to the number of cars.

Lackner: Yes, that’s the argument that I would make. There are about 1 billion cars out there. We are building 70 million cars and light trucks a year. So that kind of industrial production is quite possible. Eventually we should be able to produce an air capture device for roughly what it costs to manufacture a car.

e360: How long will it take to develop a workable air capture unit?

Lackner: In 1935, people said jet planes can never get there, because a jet engine is so inefficient that it can’t even carry its own weight. By 1938, the first one flew. By 1951, jet planes went into commercial service. So there was some delay between the time when it was demonstrated that it worked and when it went into commercial production. Wind turbines today are 40 percent cheaper than they were in 1960, and photovoltaics are 100 percent percent cheaper. There is far less of a gap in air capture today than we faced for renewables back then.

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So the characteristic time frame from development to large-scale commercial application is 20 to 30 years.

e360: Given the current state of the atmosphere, we don’t have 20 to 30 years to develop air capture, do we?

Lackner: That’s why I’m arguing that it is silly to say that we shouldn’t do it. There’s no question in my mind that we are going to be too late. If you wanted to hold this to 1.5 degrees C you should have started in 1980.

e360: So you are saying we are already too late, but…

Lackner: If you have to be in hot water, you at least want to come out again on the other side. Once the devices are out there, it will still take years to roll back C02 in the atmosphere. If you [reduce the carbon load by] 2ppm a year, you are doing very well. If you want to come back 100 ppm, at 2ppm a year, that’s fifty years. So I’m saying that every year that we don’t have this technology things are going to get worse, the cost of dealing with it will get larger.