Experimenting with Carbon Sequestration Each year, the world releases more than 25 billion tons of carbon dioxide. Scrubbers exist to strip pollutants such as sulfur from smokestack emissions — could a carbon dioxide scrubber be built to suck CO2 out of the atmosphere and help combat global climate change?

Experimenting with Carbon Sequestration

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You're listening to TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow.

Yesterday, President Bush spoke about global climate change, and the president has consistently called for greater research into technological solutions to climate change. And, well, we've uncovered a couple of new ideas that you may not have heard about - high-tech answers that are still in the early developmental stages but certainly hold out promise. Let's go to the first one.

The first one is an answer to a common question: Why can't we just suck up the extra CO2 out of the atmosphere the way trees do it? You know, they suck it up during photosynthesis. Can we make something like, you know, synthetic trees that use it? Well, one answer could be to plant a lot more of these trees, but now high-tech solutions come from laboratories at Columbia University where scientists say they have done just that - developed a way to suck the CO2 right out of the air.

Joining me now is Klaus Lackner. He developed a technique along with the company Global Research Technologies. He is the Maurice Ewing and J. Lamar Worzel Professor of Geophysics, director of the Lenfest Center for Sustainable Energy at The Earth Institute at Columbia. And he joins us today by phone.

Welcome to the program.

Dr. KLAUS LACKNER (Maurice Ewing and J. Lamar Worzel Professor of Geophysics; Director of Lenfest Center for Sustainable Energy, The Earth Institute, Columbia University): Thank you so much for having me.

FLATOW: This is - tell us in brief, how you do this? I know that you've been developing this for years.

Dr. LACKNER: Yes. The basic idea is actually quite simple. If you have a material like sodium hydroxide or calcium hydroxide and you expose it to air, it will collect the CO2 out of that air. This is done by analytical chemists to determine how much CO2 is in a gas mixture. So that CO2 can be collected has been known for quite some time. The question really is, can I do it in an affordable way where I don't spend more energy in doing that? And I got out making the CO2 in the first place.

FLATOW: And I've seen pictures and diagrams of it. It looked something like - it's been described as a goal post with Venetian blinds strung across.

Dr. LACKNER: Yeah, that's probably a pretty good description of one potential device. Go a little closer to it and you see sort of a big box filled with what you might think of - the leaves of the synthetic tree. You have the air blowing through this box, and as it goes through, it comes in contact with the surfaces, which are coated with a sorbent, the absorber which binds the CO2. And as the air goes out it, has lost maybe 30 percent of the CO2 it had to start with. And that's the CO2, which has been collected.

Now, you can arrange this in different forms and the Venetian blinds on the goal post, which pivots to face into the wind is just one example of how it might look.

FLATOW: And how much CO2 can you actually pull out of the air using something like this?

Dr. LACKNER: Well, there's actually a surprising amount. If you sort of go into a place where you would put a windmill and you can hold up a wire frame and say, I want to make it big enough, that one personal CO2, that 25 tons or 22 tons per year you are personally responsible for will blow through that. It's about the size of a television screen. If you allow for the fact that you're not 100 percent efficient, you need to be three to five times bigger than a television screen, the normal 24-inch screen, and you get a feeling for how big it has to be to collect one person's CO2. You would probably be, with a typical sorbent, about a meter deep as the air has to go through it.

FLATOW: And how much CO2 can you suck out of that?

Dr. LACKNER: Well, that object the size of a little smaller than the door could take out one person's CO2 so in the order of 20 tons a year.


Dr. LACKNER: If you have a 10-by-10 meter area, you can conservatively pull a thousand tons of CO2 out of the air per year.

FLATOW: And you could create - do you see this as CO2, farms or do you see this as everybody having one around their house or in their lawn or something?

Dr. LACKNER: I would see them as CO2 collector farms for the simple reason that you have to put the CO2 somewhere after you've collected it.

FLATOW: Right.

Dr. LACKNER: The hard step is actually not to collect the CO2, but once you have collected it, to pry it loose from the sorbent. And that step requires energy, and that is where you have your costs and where you consume energy. And the advance Global Research Technologies has made is to find a sorbent that binds no more tightly than a sorbent you would use in a flue stack of a power plant. So therefore, we expect that in the long term, the cost of collecting the CO2 with that particular sorbent will not be much different than it is for scrubbing.

A flue stack, the fact that the air is much more dilute makes the collector much bigger but the collector is only 20 percent of the total cost. So even if the air had much more CO2, the collector would get smaller, but the effort of prying the CO2 off the sorbent again is actually not much different than it would be for a power plant.

FLATOW: 1-800-989-8255. Does it collect as a powder on a surface of the absorber, then you dust them off or shake them? How does it work?

Dr. LACKNER: No, not quite. But you can sort of wash it off. And you can use, actually, a solution is simple as sodium carbonate, and it will, in the process, be turned into sodium bicarbonate. And then you have to free that CO2 again from the bicarbonate.

FLATOW: And how would you do that?

Dr. LACKNER: Well, one process we have developed is an electro-chemical process. With that, we are consuming electricity. I wouldn't recommend using a coal plant, but even if we did, the coal plant would make less CO2 than we collected. But the next step we are working on is to have a thermal process where we actually control the CO2 emissions of that step itself and collect not just the ton of CO2 we pulled out of the air but the extra 20-30 percent of CO2 we generated in the process of recovering our sorbent and separating the CO2 from it.

But to come back to your earlier question, I want to do that at the location where I can get rid of that CO2 either because you want it for enhanced oil recovery or where you inject it underground to put it away safely or permanently, or maybe in the future where you form a mineral carbonate to stabilize the CO2 in a solid form.

FLATOW: Are you saying that it turns into bicarbonate of soda?

Dr. LACKNER: In the intermediate step or according…

FLATOW: Can you just sell that, you know, as a product?

Dr. LACKNER: Not in the quantities you are talking about.

FLATOW: I see.

Dr. LACKNER: You won't bake enough cakes to fill the 22 tons of CO2 in a year.

FLATOW: I see. It makes - that makes sense. But one of the problems with disposable CO2 we keep hearing about is that it is a gas, you know, and you have to pump it underground. You seem to be saying that you may have it in a solid form that you could store at some place as a solid?

Dr. LACKNER: Well, yes. I think the immediate way of dealing with a carbon dioxide will be injecting it underground, because we know how to do this and we know how to do it in an affordable fashion. I have been working for probably 15 years now on the idea of taking the CO2 and bind it to certain minerals like magnesium oxides, which you find in magnesium silicates, and let the magnesium react with the CO2 to form magnesium carbonate, which indeed is stable and is a solid. And so you can - rather than have to control it underground, you can now sort of literally pile it up. It still is a mountain, but you know where the CO2 is, and you know it won't go away. And again, you have something which is, environmentally, a fairly harmless substance.

So I see that as a long-term option, but right now, it's probably a factor five too expensive. And one of the challenges is to do enough research to drive the cost of that down. But then again photovoltaic cells are much more than a factor five too expensive right now, and we are willing to do research on it.

FLATOW: Let's go to Yutan(ph) in Columbus. Hi, welcome to SCIENCE FRIDAY.

YUTAN (Caller): Hi, thank you for taking my call. It sounds like you're doing some good solid chemistry, and I appreciate that as a chemist myself. I have a question. It's a little bit a question of kinetics in terms of the concentration of CO2 in the air…

Dr. LACKNER: Mm-hmm.

YUTAN: …and whether you can actually pull it out of the air fast enough to make this really a competitive process. How much surface do you have to cover to get any appreciable amount out? And I should give credit to this question a little bit. It was raised in my mind by a visit recently of Nate Lewis, who's a professor of chemistry at Cal Tech. And he was talking about this as out of the potential issue in terms of some things with carbon sequestration.

Mr. LACKNER: We have worked this out quite in some detail earlier, and this was published for sodium hydroxide. In that case, you need roughly 300 to 1,000 square meters of surface per square meter of front layer area where the wind blows through. So think of having sheets of about one square meter stacked a hundred high and a hundred vertical so you have tubes going through, and you have about the right amount. So you end up with a block where the spacing is typically a centimeter to half a centimeter to a centimeter, and a meter's (unintelligible) you have enough surface in the block to actually collect a substantial fraction of the CO2, which blows in with the air.

So that works well. The new sorbent the GRT came up with is about the same strength as sodium hydroxide in terms of the kinetics of picking it up, but the binding energy is substantially lower. If you were to coat with sodium carbonate, then it would be far, far too big and too much surface to make it happen. Compared to a tree, by the way, you are about a thousand times better.

FLATOW: We're a thousand times better.

YUTAN: That's good. Thanks a lot.

FLATOW: Wow. Thanks for calling, Yutan. So how practical is this? I mean, if we could - if you can iron out all the ifs, ands or buts - and I know there are a few of them there - can you actually suck enough CO2 out of the atmosphere? Could you make enough of them, distribute them around the world enough that you could reverse to build up?

Dr. LACKNER: I believe, well, you would first start with compensating for existing emissions. And you probably would not go after that power plant, because I think it is smarter to collect the CO2 before you diluted it. But if you think of airplanes and of cars, it's very, very difficult to deal with the emissions on board. So there, it's better to collect after the fact because the weight of the CO2 is about three times better than gasoline you've started with.

So it's actually better to collect after the fact at a location where you actually can deal with the CO2. And so you would start phasing it gradually in one ton at a time, and for every car over its lifetime, you would have to collect on the order of a hundred tons.

Now as you move on and you have dealt with the transportation sector in that way, you would not deal with particularly many units. I calculated one piece -50-by-60 meter, big units - you have - you referred to as Venetian blinds and goal posts; the world, we need are roughly 250,000 of them. That's less than there are water towers. That's less than we have containers in the world's shipping containers.

And it's a small number compared to other structures of this size we have built. So I do believe that it could be done. Now if you can do that, you can go the next step and say, you've weighed every ton of CO2 you emit, you have to pull one and a half tons back. And then indeed, you would gradually drive the CO2 in the atmosphere back down. But in a sense, that's futuristic, and at first, we have to hold the rise before we can start driving it back down.

FLATOW: And tell us what needs - what technological hurdles have to be overcome? What do we need to develop to make this to work now?

Dr. LACKNER: Well, I feel strongly that we have to present to the world a thermal process, because the electricity process only works with renewable electricity. Otherwise, chasing down that CO2 - which you made in the production of the electricity - is not canceling you completely out but makes it prohibitively expensive. And so I would like to see a thermal process, but I think that will happen soon.

Then afterwards, it's a matter of scaling it up to get from the bench to the demonstration scale - where we are sort of in between right now - and then go through what I would think is sort of the equivalent to Altamont Pass, where you built your first windmill farm. You are - now have to build your first collector farm, and then you move forward from there. What it really needs is a price on carbon, because without that, there is no economic incentive to make it happen.

FLATOW: Right. Talking with Klaus Lackner at this hour on TALK OF THE NATION: SCIENCE FRIDAY from NPR News. So you're saying - when you say thermally run, you're talking about solar power?

Dr. LACKNER: Well, or for that matter, it could be ordinary fuels. I want to stress at the game. The system itself, as it collects, doesn't need energy. But you now need to process the spent sorbent, which has CO2 attached to it. You want to recover that sorbent, and that's where your cost and where your energy penalty is, and you can do that in principle with heat. Recall that if you bake a cake, the sodium bicarbonate turns back into sodium carbonate, and that's precisely the reaction we try to induce as well. Now that heat could come from burning ordinary fuels, natural gas or even coal. But I do need to have control over this process so that I can collect that CO2.

FLATOW: Yeah, you're just been making the CO2 all over again.

Dr. LACKNER: Right. And, well, that's an additional 20, 30 percent CO2, so rather than delivering you one ton of CO2 for the disposal, I will deliver you 1.2 or 1.3 tons of CO2.

FLATOW: But you're saying that we need to look at the bigger picture here, and we've talked - every time we talk about energy, we talk about having some sort of political drive or some sort of leadership to make these things happen. Is that - you're saying we need some sort of carbon tax to make it competitive.

Dr. LACKNER: We need some form of bringing the ability of actually pricing this in, right? At some level, if you buy a gallon of gasoline, you have to pay for the collection of the CO2, which will happen presumably afterwards. And if we can get the price down to what - where I would hope it goes to, which is around $30 per ton of CO2, this would add $0.25 to the gallon of gasoline. But there has to be a mechanism in place to make that happen.

The advantage it gives you is you can run the transportation sector on the very convenient and very energy-rich liquid hydrocarbons, which otherwise you would have to abandon because without this option, they emit CO2 to the atmosphere and it's going to stay there.

FLATOW: And so the advantage you're saying is we don't have to give up oil or hydrocarbons. We can suck it out of the CO2 out of the air if we're willing to add a few more sense to a gallon of gasoline.

Dr. LACKNER: That's correct.

FLATOW: And it's quite feasible to do this; we just need a plan of action.


FLATOW: And somebody has to run with the ball now that you've invented this.

Dr. LACKNER: Well, that ball, and there are plenty of other balls. I don't want to give you this feeling that it's the one and only solution to the problem. I would argue we need many arrows and - as quiver, and this is one. This will help with the distributed dilute emissions, which is very difficult to plug one hole at a time.

And you deal with them in their fashion. You still have to deal with power plants. You still have to deal with the rest of the energy economy. And in the long term, we have to find ways of being carbon neutral. Now, fossil fuels can play a role in such an energy economy, provided that the CO2 is captured and safely and permanently disposed of.

I'm skeptical that in the next 50 years we can wean ourselves off of fossil fuels. They're very plentiful. Oil may not last, but coal and tars and shales will last for another 100 to 150 years. And so we need to have technological solutions in place which allow us to deal with the CO2 emissions, because they are not tolerable on that time scale.

FLATOW: There you have it. Thank you, Professor Lackner.

Dr. LACKNER: Thank so much for having me.

FLATOW: And we'll follow this, good luck to you.

Dr. LACKNER: Thanks so much.

FLATOW: Great interesting idea from Maurice, from Professor Lackner, who is the Maurice Ewing and J. Lamar Worzel Professor of Geophysics and director of the Lenfest Center for Sustainable Energy at the Earth Institute at Columbia University.

We're not done about talking about energy and global warming. We're going to go, take a short break and come back and talk about scientists at Purdue University, who have come up with a way of taking hydrogen out of water with an alloy that could drop the pellets into the water and out comes the hydrogen. Interesting. See if that's ready for primetime. Stay with us, we'll be right back.

I'm Ira Flatow. This is TALK OF THE NATION: SCIENCE FRIDAY from NPR News.

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