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Stashing Carbon Dioxide In Rocks

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Stashing Carbon Dioxide In Rocks

Stashing Carbon Dioxide In Rocks

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IRA FLATOW, host:

You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

If you had to find a place for a billion tons of carbon dioxide, where would you stash it? Not in your closet. Why not rocks? Yeah. Scientists are reporting in the Proceedings of the National Academy of Sciences and they say that basalt, basalt formations deep within the sea floor could work as CO2 sponges. They estimate that one basalt face right here in Sandy Hook, New Jersey, right at the gateway to New York City, there's enough basalt there that they can hold roughly 40 years worth of emissions from four coal-fired power plants. Well, of course, if we can do that, how do we get the CO2 into the rock? Why won't it leak out?

Well, here to tell us more about it is Paul Olsen. Dr. Olsen is the Arthur D. Storke Memorial Professor of Earth and Environmental Sciences at Columbia University's Lamont-Doherty Earth Observatory and author of the study, coming from just up - just up the road a piece, right?

Dr. PAUL OLSEN (Columbia University): That's right.

FLATOW: Welcome to SCIENCE FRIDAY.

Dr. OLSEN: Thank you. It's a pleasure to be here. I'm a big fan.

FLATOW: Thank you. Well, let's talk about - what is basalt and why is that a good place to store it?

Dr. OLSEN: Basalt is hardened lava.

FLATOW: Mm-hmm.

Dr. OLSEN: When the lava comes out and pools on the Earth's surface, it cools rather rapidly. The upper surface is foamy because there's gas in the basalt. And it hardens into a rock we call basalt.

FLATOW: And it's the stuff you can see just driving around and...

Dr. OLSEN: In the East coast...

FLATOW: ...all around us.

Dr. OLSEN: In the East coast, many of the quarries from which we get crushed rock to make roads are in basalt. Ancient lava flows about 200 million years old.

FLATOW: So your idea is to find this layer of the bubbly, it's not really foam - it looks foamy like...

Dr. OLSEN: It looks foamy.

FLATOW: ...it looks like lava.

Dr. OLSEN: That's right. It is lava.

FLATOW: It's very hard lava, not the kind we have in Hawaii that's floating on the waters, it's sort of denser?

Dr. OLSEN: Well, actually the foamy part is very much like the pumice...

FLATOW: Is that right?

Dr. OLSEN: ...that would be floating on water. It's not quite that foamy, but it's close.

FLATOW: And there's enough of it around that you could pump in CO2 and it would soak it up like a sponge.

Dr. OLSEN: Every place that there were these ancient lava flows, the top of every single one is foamy. There are also fractures in the rock as well. And that means there's pore space in the foam and in the fractures, and it's a place you could store CO2.

FLATOW: And how far down below the ground do you - would you have to find it?

Dr. OLSEN: You - well, it occurs at the surface. But it also occurs underground as well. And there are several places, many places in fact, off the Atlantic Coast where it's thousands of feet underground, under the sea floor, actually, and where you could safely store the stuff. It's abundant. It's easy to get to. It has known, rather simple properties, so it's a kind of an ideal place to do it.

FLATOW: This place that you talk about, Sandy Hook, which is right out here in Jersey, you studied that place and you found that you could store a vast amount - I mentioned how many - how much CO2?

Dr. OLSEN: Well, enough, 40 years worth of that.

FLATOW: Forty years worth.

Dr. OLSEN: Forty years worth from four coal-burning power plants. But the -remember, that's a very crude estimate.

FLATOW: Yeah.

Dr. OLSEN: We don't really know that much about what's under Sandy Hook. There are some geophysical measurements of what's under there and it's a guess that there's basalt under there. We know that basalt's abundant up and down the East Coast. It's probably there, but you'd have to drill to find out for sure.

FLATOW: Right. And something fascinating happens when you pump the CO2 into the rock.

Dr. OLSEN: Oh, that's one of things that's very special about basalt. It has calcium and magnesium silicates that react with the carbon dioxide to form another compound, which is basically calcium carbonate, and that's just common limestone. So people have talked about storing CO2 in rocks before. Mostly they're talking about places that gas or oil has been extracted from. There's known pore space in the rock and you'd pump down CO2 and store it in that kind of reservoir. Those can leak through time. Any reservoir can.

FLATOW: Mm-hmm.

Dr. OLSEN: However, if you put it in basalt, the reaction with the basalt makes the reservoir more and more stable through time, instead of unstable.

FLATOW: So over time the CO2 morphs into this...

Dr. OLSEN: Limestone.

FLATOW: ...limestone?

Dr. OLSEN: Yes.

FLATOW: So it's locked up forever?

Dr. OLSEN: It's locked up forever. It becomes inert. It would not be released into the atmosphere again until that crust got subducted in 60 or 70 million years just like limestone does in sea floor normally.

FLATOW: Wow. And did the CO2 start out in that?

Dr. OLSEN: Oh, that's one of the really sort of fascinating ironies, is that the CO2 that's in the atmosphere ultimately comes from deep in the earth, and basalt is one of the places it comes out of. So where you have lava pouring out on the surface of the earth, that's where CO2 is coming back into the atmosphere, because all the time there are processes that remove it. And if CO2 didn't go back in, it would have eventually be consumed and all plants will die. And then that would be the end of life on Earth.

But instead what happens is the places that lava comes out constantly add little bits of CO2 all the time. So it's a real irony if we're going to pump it right back in where it came from.

FLATOW: Mm-hmm. So over time though, if you're pumping this stuff into the foamy basalt and it's turning into calcium carbonate, into limestone, aren't you going to fill up that spot? And...

Dr. OLSEN: Yes. Eventually you would fill it up. But you know, you'd fill it up anyway with the carbon dioxide and you'd have to move to another place. The important thing is that it stabilizes itself through time with a very benign substance.

FLATOW: Where did all this come from? Where did all this basalt come from?

Dr. OLSEN: Well, that's a really interesting story. The basalt came from an eruption, a series of eruptions that occurred between eastern North America, Africa, and South America 200 million years ago when all the continents were united in the supercontinent Pangaea and they began to split up.

FLATOW: Right.

Dr. OLSEN: And what's really amazing about these particular lavas is they came out over an enormous area, 11 million square kilometers, one-third the area of the moon. And it came out in less than 600,000 years and spread over this gigantic area. So much CO2 was released in that process that it probably resulted in a mass extinction that killed off about 50 percent of all plant and animal life on the Earth.

FLATOW: Wow. So that - and that basalt is still there waiting for us to go back and put the CO2 back in...

Dr. OLSEN: Yes.

FLATOW: ...that came out.

Dr. OLSEN: Right. Exactly. And, of course, the CO2 that we're breathing now and plants are using to make their tissue, that CO2 is partly coming from the burning of fossil fuels and not coming from the basalt. The CO2 that was poured out in the atmosphere 200 million years ago, that's been recycled many times already in the Earth's system.

FLATOW: Here's a tweet coming in from Mtadder(ph) - wants to know what are the downsides? Is there any danger of the basalt carbon internment, interconnection?

Dr. OLSEN: There is no danger to the basalt conversion into limestone. There are always risks when you're drilling that occur all the time when you're drilling into rock, but they're very small risks, less risks than you'd have when you're drilling for hydrocarbons, for example. Furthermore, of course, when you drill down into the crust, then there's pore space at depth that isn't empty. There's something there. There's water.

FLATOW: Right.

Dr. OLSEN: And that water is generally salty at depth. If you drill on land and you put CO2 down there into basalt, which is certainly possible, the problem is you then have to dispose of the water that you're displacing. If you do this in the ocean, you're displacing seawater that's in the basalt and it's just seawater in seawater, which is fairly benign. So that's why the seawater...

FLATOW: Right.

Dr. OLSEN: ...the ocean is a better place to put this than on land.

FLATOW: It's also a better place, as you say, because it's really deep and the pressure of the water...

Dr. OLSEN: That's right.

FLATOW: ...is great.

Dr. OLSEN: Then what the pressure of the water and the depth in the crust allows you to do, it allows you to store CO2 in a liquid form, and at the right depth it is actually heavier than water.

FLATOW: You don't have to chill it down or anything.

Dr. OLSEN: We have to compress it.

FLATOW: You compress it. The water will compress it.

Dr. OLSEN: Yes, that's right. So - at that pressure, it'll be liquid and it'll be heavier than water so it won't have a tendency to rise up, which is another advantage of putting it in the oceans.

FLATOW: So if any of it leaks out, it's just going to stay down there.

Dr. OLSEN: Yeah, that's right. And the basalt reaction to the limestone...

FLATOW: Right.

Dr. OLSEN: ...through time makes it inert and incapable of moving again.

FLATOW: So this would be an answer to people who say, well, if we have to sequester CO2, if we can scrub it out of our coal-fired power plants, where are we going to put it? We can put it in these basalt formations.

Dr. OLSEN: Probably basalt formations are not going to solve the whole problem. One of the greatest problems with have with this is transportation. You want to be close to the sources of CO2 or at least close to scrubbers so that it's possible, for example, to remove CO2 directly from the atmosphere rather than the more efficient way of removing it directly from the source, of a power plant or so. But a big cost of it is getting to where you want to sequester it.

FLATOW: But what's interesting about your discovery being - we're right in a giant metropolitan area where you might create a power plant and you don't have to move it very far. Could you just drill down CO2, take it right out and put it right down into the basalt right where we need it?

Dr. OLSEN: That's the basic idea. You - well, we probably want to pipe it offshore...

FLATOW: Right.

Dr. OLSEN: ...a distance and then put it in the ground. But the advantage of these particular rocks is they're so common that almost every single major city on the East Coast, there's some of this offshore.

FLATOW: You know, sometimes things sound too good to be true.

(Soundbite of laughter)

Dr. OLSEN: There's a lot of basalt, not every place you drill is going to be the right place. You have to have enough porosity and permeability to allow this stuff to be stored. It's - we don't have enough experimental experience to know how easy or hard this process is going to be. There has to be a program of getting samples specifically in places that this basalt exists. There have to be tests. We're very far, not enormously far, not decades and decades but we need to do enough research to be able to really understand the system before we go willy-nilly starting storing this stuff.

FLATOW: And that's what you're doing. You're doing that basic research.

Dr. OLSEN: Yes. That's what we're trying to do.

FLATOW: And you need to do more of it.

Dr. OLSEN: A lot more. The most difficult part is getting the samples of rock to work on and getting the holes in the right setting to do the actual tests. It's quite expensive and it's experimental.

FLATOW: And you'd - so you have boreholes in various places?

Dr. OLSEN: Well, my colleagues at Lamont-Doherty Earth Observatory, which is part of Columbia, have done tests of - at Lamont in Palisades, New York, in the Palisades sill, which is some lava that never got out of the ground basically. And so some those tests have actually been done, but it's still very much in its infancy.

FLATOW: I want to bring on Flora Lichtman, our video producer who's here with us. And I know that Flora is going to talk about our Video Pick of the Week, which is you went out on a field trip.

FLORA LICHTMAN: Yes. Dr. Olsen took us out to a basalt quarry in New Jersey. And so we actually saw the types of rock that we're talking about today.

FLATOW: Mm-hmm. And you sort of gave us a tour guide. You took them out, and he's like a tour guide so he's showing us the different layers.

LICHTMAN: Yeah. What was amazing to me was actually the differences between the basalt - so the bubbly basalt versus the non-bubbly, you know, because you want to pump it into the holey one, basically.

FLATOW: Right.

LICHTMAN: You could actually see it. I mean, it was visibly different. And we saw that intersection between these two types of basalt when we were in the quarry.

FLATOW: And there was a special layer that you were showing her in the video. If you go to our video at sciencefriday.com, look at the video on Pick of the Week on the left, you'll see the terrific video with Dr. Olsen there. There has - it's better to have a cap on it, you were saying in the video?

Dr. OLSEN: Yes. You have to have some kind of seal on that bubbly surface, otherwise the carbon dioxide would just move around. And you don't want it to move around, you want it to sit right there where it will react with the basalt. So another lava flow on top is usually a lot less bubbly at the bottom than it is at the top, so that provides a very convenient seal.

By the way, that's another advantage to putting the stuff offshore where there's a thick pile of much younger clay-rich sediments to keep that entire package of basalt under wraps.

FLATOW: Mm-hmm.

Dr. OLSEN: But in this quarry, you could see that bubbly surface beautifully, and you could hold it in your hands and you could see the size of the bubbles, about an eighth-inch across each, and there were thousands and thousands and thousands of these. And we have taken samples of that basalt and we've looked at how much porosity there is. There's about 10 to 15 percent by volume of open space in that rock.

FLATOW: Talking to you about carbon sequestration in basalt this hour on SCIENCE FRIDAY from NPR News, here with Dr. Paul Olsen of Lamont-Doherty Earth Observatory, and with Flora Lichtman, our video producer.

LICHTMAN: One thing that you were talking about when we were in the quarry is that how that bubbly layer was formed. And I thought that was pretty interesting. So how does that happen?

Dr. OLSEN: Well, the lava, as it comes up through the earth's crust, is being under less and less pressure, and there are dissolved gases in the magma as it's rising through the earth's crust. The pressure is released, it starts literally to boil. The gases come out of solution. They form bubbles. The bubbles are rising to the top and they make a foam. But the basalt is also cooling so that foam gets frozen in place, and that's what we were looking at in the quarry, this foamy surface.

LICHTMAN: It was like a basalt float.

Dr. OLSEN: Yes, or a basalt sundae.

(Soundbite of laughter)

FLATOW: A basalt sundae, so - the basalt of the earth, so to speak.

Dr. OLSEN: Oh, yeah.

FLATOW: Oh, you've heard that a few times.

Dr. OLSEN: A few times.

(Soundbite of laughter)

FLATOW: Shucks.

LICHTMAN: And then what caused - what is the cap? What actually was on top of it? Why is the layer on top not bubbly?

Dr. OLSEN: Because it's - the layer on top isn't bubbly because the lava flow is heavy. So the bottom part is under greater pressure than the top part, which is open to the air, so the bubbles go to the top. There are some bubbles that are at the bottom, especially if the basalt heats what's under it enough in the water that's absorbed in the rock below, steams up and pops up through the -into the basalt. And we saw some of those little pipes and vessels, too. But there are far fewer of those than the bubbles that are on top of the flow.

FLATOW: Do you have to have an area of geology where there was a rift and of this volcanic action?

Dr. OLSEN: You know, you don't have to have a rift valley. But in - off New Jersey and in New Jersey and Pennsylvania and Connecticut and Massachusetts, there were such rifts, and they hold enormous volumes of rocks. Some of the single lava flows are over 600 feet thick, so they're enormous. And the foamy parts can be 50 or 60 feet thick and cover thousands of square kilometers.

FLATOW: So Flora when we see your video pick of the week, will we see you taking a tour with Dr. Olsen on the rock?

LICHTMAN: We'll see Dr. Olsen leading a tour.

(Soundbite of laughter)

LICHTMAN: How do these rocks relate to the palisades? I think people have seen the palisades as sort of photogenic on the...

FLATOW: Hudson.

Dr. OLSEN: Hard to miss when crossing the George Washington Bridge or the Tappan Zee. And what you're looking at is you're looking at a cross-section, caused by relatively modern erosion, of what's called a sill. A sill is a body of igneous rock that was molten and injected into previously existing older material. It spreads out horizontally, like squeezing toothpaste between two pieces of bread - or I guess you'd want to squeeze peanut butter, not toothpaste.

FLATOW: Mm-hmm.

Dr. OLSEN: But in any case, you squeeze it into the bread and it makes a little sandwich. And that lava never - that magma never made it to the surface. It's compositionally the same as the basalt flows, but it lacks a bubbly layer. It has fractures in it that could, in fact, hold CO2 - that's why we did the test at Lamont. But it doesn't have a foamy layer, so it's not ideal.

FLATOW: That foamy layer is the secret.

LICHTMAN: That's the key, and you can see it, actually.

FLATOW: On our video at SCIENCE FRIDAY's Pick of the Week at sciencefriday.com that little video, our new video up there on the left side. Just click on it and then watch the tour of the quarry of - are there other quarries like that? Is that a typical quarry in that part of New Jersey?

Dr. OLSEN: It's a very typical quarry because the basalt, often called trap rock, is a valuable resource and an important resource because it's hard. It meets engineering specifications for hardness and compressibility. And it's an ideal material to mix into cement or tar to make roads.

FLATOW: And one great part of the video is that - is Flora showing that you're holding an actual piece of basalt that started the transition to have the limestone in it.

Dr. OLSEN: That's right. Under quite common conditions, that transformation of basalt to limestone occurs in nature. It can occur in the ground if there's very rich - water very rich in carbon dioxide circulating. Or more commonly, in arid areas, it forms on the surface and you'll get a crust of limestone right on top of the basalt.

FLATOW: A pretty black rock with a lot of white specks in it. Thank you, Dr. Olsen, very much, fascinating.

Dr. OLSEN: My pleasure. Great to be here.

FLATOW: Dr. Paul Olsen is a professor of earth environmental sciences at Columbia University's Lamont-Doherty Earth Observatory. And Flora Lichtman was here with our Video Pick of the Week. Go to our Web site at sciencefriday.com and watch the tour of that quarry with all that basalt.

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