MS. DIANE REHMThanks for joining us. I'm Diane Rehm. Last month, in Paris, world leaders pledged to dramatically cut greenhouse gas emissions. The final agreement also described the need for greenhouse gas sinks or methods of removing carbon already in the atmosphere. This is the latest acknowledgement that simply decreasing output won't prevent devastating climate change.

MS. DIANE REHMFor this month's Environmental Outlook, the future of carbon removal. Here in the studio, Thomas Armstrong of the Madison River Group, a science policy consulting firm. From a studio in Berkeley, California, Jane Long, former associate director of energy and environment at Livermore National Laboratory and also Noah Diech of the Center For Carbon Removal.

MS. DIANE REHMI do invite you, as always, to be part of the program. Give us a call at 800-433-8850. Send us an email to drshow@wamu.org. Follow us on Facebook or Twitter. And thank you all for joining us.

MR. THOMAS ARMSTRONGThank you.

MS. JANE LONGThanks.

MR. NOAH DIECHThank you.

REHMGood to see you all. Noah, I know that your company is very, very focused on carbon removal. You must be very interested in what happened in Paris. Tell me what you believe were the most important factors related to carbon removal coming from those talks.

DIECHSure. So when I was in Paris, I think the most exciting thing to me was the headline of the goal that was set by the 195 countries who agreed to the Paris Agreement of not just aiming to keep climate change below 2C above preindustrial levels, but to aspire to go much below that and really aim for 1.5C, which I think the scientific literature is increasingly certain is what the real threshold for save climate change really is.

DIECHAnd this is a really important acknowledgement by leaders across the world that our response has to be very aggressive to climate change.

REHMAnd to you, Jane, how important do you believe the idea of carbon removal technologies are going to be in this whole effort to make sure to stay at or below 2 degrees Celsius in the atmosphere?

LONGWell, Diane, you know, the United Nations sponsors a group, the IPCC, to assess all the literature on climate change and to come up with projections from that literature about what's going to happen. And for the first time -- they do this every few years and for the first time, the assessments about what's going to happen in the future show that it's really not possible to, according to these models, not possible to stay below 2 degrees, not to mention 1.5 degrees without some kind of intervention in the climate, in other words, taking carbon dioxide out of the atmosphere.

LONGSo I think recognition of that fact in this Paris talks was very influential and is probably one of the most important things to come out of these assessments in a very long time.

REHMSo Jane, what you're saying is the idea of planting more trees or simply lowering emissions is just not going to do it.

LONGWell, lowering emissions was never going to do it. It's stopping emissions is what's going to do it because one of the most important facts about climate change is that pretty much all of the carbon dioxide that you put in the atmosphere either goes in the ocean or stays there. Some of it is taken up by plants, but basically, the concentration of carbon dioxide in the atmosphere continues to grow as long as you keep emitting.

LONGAnd so the problem gets larger as long as you keep emitting. So it's really stopping emissions. And then, all that stuff we've put up there since the 18th century is still there, still causing climate change and that's where we have to do something about it.

REHMThomas Armstrong, I know that you are the former executive director of the White House office of science and technology policies U.S. Global Change Research Program. You helped to create President Obama's climate change plan. Was there any mention then of carbon removal? Why or why not?

ARMSTRONGWell, Diane, the plan really focuses on being proactive on trying to reduce emissions, the first step as both Noah and Jane said, towards being successful in dealing with climate change. The U.S. Global Change Research Program, which I was the executive director of, has a strategic plan and ironically it, right now, is in the process of being publically reviewed for revision.

ARMSTRONGAnd it does discuss in there carbon removal and climate engineering and the need for more research on both understanding what are the interdependencies of removing carbon across different fiscal and biological chemical parameters, but also what can we do beyond just removing carbon today moving into the future and realizing that this problem, as Noah said time and time again to many of us, that this is a gigaton problem.

ARMSTRONGThis is a problem of finding ways to deal with -- at the scale of the problem, removing gigatons of carbon. And just to put that into perspective, a gigaton of something is the weight of elephants, trunk to tail, from here to the moon and halfway back again. That's one gigaton. So we're talking about a lot of carbon that has to be removed and our program did start to deal with the issue of how do we do this in a scientifically viable and safe and effective way.

REHMHelp me to understand the moral hazard question involved here.

ARMSTRONGWell, I think everybody can chime in on this, but let me just tell you, from my perspective, part of the moral hazard and that is it's akin to a football game. That is, at the beginning of the game, you're very conservative and you have a very conservative approach because the risks are low, but as the game goes on and your team is down on the scoreboard, your propensity for taking a Hail Mary pass or onside kick, something risky, increases dramatically because you've waited so long in order to fulfill your game plan.

ARMSTRONGAnd I think that's part of the problem we're faced today is that we're looking into trying to do things in an engineering fashion regarding removing carbon before scientifically we may really understand the system thoroughly and all its interdependencies. And frankly, Diane, I think the problem is we're worried about doing something or implementing something that may have unintended consequences that are as big as the problem we're trying to fix.

REHMNoah Diech.

DIECHYeah. Diane, I would add that right now it's the new year. Many of us are making resolutions, some of us, to lose weight. And I think when you think about losing weight, your doctor says, you go on a diet and you exercise. And I think very analogously, the IPCC that Jane has mentioned has said, the planet needs to stop emissions and enhance carbon sinks. And it's not an either/or. You don't diet until you can't diet anymore and then start exercising. You do both and you ramp up both slowly.

DIECHAnd I think what we're realizing now is that there's another side of these equation, that we can't just cut emissions, that we need to figure out new strategies and that's what this idea of enhancing carbon sinks really is.

REHMSomebody's got to explain to me exactly what a carbon sink is.

LONGA carbon sink is when you take the carbon out of the atmosphere and you put it someplace that it's no longer in the atmosphere. So for example, if you grow a plant, it takes carbon dioxide out of the air and then if you allow that plant to grow and it dies and it begins to decay, that decay process, it becomes a carbon source. It emits carbon dioxide back into the atmosphere. If you filter carbon dioxide out of the atmosphere and then you pump it into an old oil and gas reservoir and put it underground where it can't get into the air, then that oil and gas reservoir becomes a carbon sink.

REHMBut that's what...

LONGAnyplace that takes it up.

REHMIsn't that what you're worried about, Thomas?

ARMSTRONGYeah. And I want to be very clear that I completely agree with what Noah and Jane said before. We need to have a multifold strategy for dealing with this problem. It's very clear -- and I was one of the co-leads of the U.S. delegation to IPCC for working group 2 where we dealt with this issue. It's very clear from the science now that just dealing with emissions and the reduction, even the outright total reduction of emissions is not going to get us to a solution at 2 degrees C, let alone 1.5 degrees C.

ARMSTRONGBut I think that the issue we face here is first, understanding what are the technologies out there that will actually help us to remove gigatons of carbon from the active part of the system and being part of the sink means being inactive. It means you're no longer able to interact with the system, be it in geologic substrate, the deep part of the ocean, whatever it may be. So you're right, Diane. I think the dilemma here is making sure that we really have a scientific -- clear scientific understanding about the technologies before we implement them.

REHMAnd what could be the outcome of these huge carbon sinks?

ARMSTRONGSure, sure. I mean, you know, we've talked about geologic sequestration or geologic carbon capture storage for years and Department of Energy, the U.S. Geological Survey have been working on these things for a long time. As a geologist, I can tell you that some people's idea of a sealed sink is different than others and we just need to be clear that in the timeframe we're talking about that these things really do serve as sinks.

REHMThomas Armstrong, he's president of the Madison River Group. Short break here. After that break, we'll talk further, take your calls. Stay with us.

REHMAnd welcome back. We're talking about carbon removal from the atmosphere, discussion certainly at the Paris Climate Change Summit. And here is our first email from Lloyd in Winterville, North Carolina. He puts it flat out there. Is carbon capture real? It has seemed like fusion reactors, it's the future and always will be. Even more cynically, says Lloyd, it seems like a move to distract. Keep burning because eventually because eventually we will suck it all back and put carbon in the closet. And what do you think of that, Noah?

MR. NOAH DEICHWell, so I think that we certainly have actual carbon capture projects today. You can go put on a hard hat and go see projects that are taking carbon out of flu gas streams and power plants, even directly out of the air in some pilot facilities. So this technology works. The question is will anyone will pay for it. And I think that's the...

REHMHow expensive is it?

DEICHIt really depends on what your source is. Right now we're doing first-of-a-kind projects. So many of these projects cost a lot of money. There's a project in Mississippi at the Kemper Coal Power Plant that's cost over $5 billion to build just a single carbon capture installation. So projects like that make the price tag sound very, very high. But I think it's really important to keep in mind that if you looked at solar power just 30 years ago, the cost of those projects were 100 times or even greater what they are today.

DEICHAnd what we saw with solar simply has not happened with carbon capture, where we've built projects, and we've provided incentives for industry to learn how to do these effectively. And I think it's not just carbon capture on fossil energy but carbon capture on renewable energy, either through biomass or through direct air capture, as well. We simply have not seen enough projects to understand how much it will really cost.

REHMAnd Jane, here's a question for you from Vicky in Dallas, Texas. She says, geological carbon sequestration, have we learned nothing from burying hydraulic fracturing waste?

LONGWell, hydraulic fracturing waste is actually not a bad analogy for some of the issues that take place in storing carbon dioxide in the geological formations underground. What happens when you pump waste or pump any fluid, and in the case of carbon dioxide you compress it until it's a fluid to put it underground, what happens when you do that is if you keep pumping it underground, you increase the pressure underground, and that can open faults and allow them to slip and cause an earthquake.

LONGBut the fact is that when you set up a carbon sequestration project, you wouldn't do it in a way that would cause that problem. First of all, you need to characterize the geologic system carefully to understand that you're not near earthquake faults, and you need to control the pressures. And one way to control the pressures is to pump water out of the formations at the same time that you're pumping carbon dioxide into the formations. So this is not an unsolvable problem. It does requirement management, and one of the highlights of this whole problem is that we are talking about learning how to manage better, and that's the critical issue.

LONGWe can't just do these things willy-nilly, and clearly, for example, disposal of oil field waste, waste waters coming up with the oil in Oklahoma, has been causing earthquakes because people have been injecting it near faults, and we shouldn't be doing that.

REHMAnd the question is how clearly those faults can be identified before you even begin such a project. I mean, there are literally hundreds of earthquakes going on in Oklahoma, where in the past there have been four or maybe five a year, and now already hundreds.

ARMSTRONGIronically a lot of those earthquakes or small disharmonic tremors are being caused by either the injection of fluids into the substrate or their removal through, you know, what we call human-induced or anthropogenic processes. So there's sort of an irony there. But the point is still well taken, and I think again Jane described this very effectively, that at the end of the day, the science needs to be done, and we're not doing this in a willy-nilly fashion. We're trying to understand and control the environment while we conduct these experiments.

ARMSTRONGAs Noah said, there's a lot of implementation already going on across the country. I think carbon capture is a proven technique, a proven implementation. The question is can you get enough out, or can you get enough into the ground to make it really tractable. And second, a problem that we've dealt with when I was at U.S. Geological Survey, is can you also transport the carbon to the place where you can actually put it in the ground because where you emit the carbon isn't the same place as where you might effectively store it.

REHMDo you have to solidify that carbon before you can transport and store it?

ARMSTRONGI don't really know the details, to be honest with you. I know that it's usually done in a fluid, and Jane may know more of the details, having worked on this before. But typically it's injected as a fluid back into the substrate.

LONGBut you're...

REHMAnd go ahead, Jane.

LONGBut your emailer, you know, is correct that this is an issue, and the question is really, when we start to think about the scale of this problem, where we have essentially -- Tom talked about the elephants on the way to the moon, well, that was one gigaton. We've emitted and more or less have to deal with something like 2,000 gigatons of carbon dioxide since the beginning of the Industrial Revolution in the 18th century. And so you're really talking about first of all not making that problem bigger, so you want to stop emitting, and then secondly getting rid of the problem that we're -- we've already bought.

LONGSo it's not quite like the football game we bought -- we bought a bad score, I guess maybe is the way to put it. But we -- you know, so if you think, well, maybe over some period like 100 or 200 years, we're going to be wanting to get rid of that pollution we already have in the atmosphere, then we're talking about, you know, doing tens of gigatons every year, pulling out tens of gigatons every year. And that is -- that's not going to be solved by any one technique. I just want to re-emphasize this.

LONGSo for example in geologic storage, we have a lot of depleted oil reservoirs, and they're under-pressured because we took the oil out. And so we could put a lot of carbon dioxide in there, and maybe for the next few decades it could be a really, really good solution to help us move along. But maybe geologic storage to solve this whole problem is not the answer. So there -- but what's really important about that part of the topic is that it's not enough to take it out of the atmosphere. You have to put it someplace. And if we can't put it underground, we've got to start thinking about where else we can put it, and that is -- that's a research question of just absolute importance, where can it go and not get back into the atmosphere.

REHMAnd?

DEICHAnd I think that's the piece that actually has the most traction, especially in Paris and associated conversations, which is how do we put carbon back in soils and in forests and in ecosystems that our modern, industrial, agricultural system actually emits a lot of carbon itself. This isn't just an energy sector problem. So how do we start to think about the myriad new techniques that we can encourage farmers to use across the globe to start to build up those soil carbon stocks, which certainly aren't as secure as deep underground storage, but they can provide us with an important buffer, and they can remain in the soil for decades, if not centuries, too, which will be incredibly important because this is an all-of-the-above type of challenge.

REHMI guess my question would be, what about the potential of volatility to that much stored carbon dioxide? Are there concerns about that, Thomas?

ARMSTRONGSure, there are always concerns about the volatility of something that you put into the ground that wasn't there before.

REHMExactly.

ARMSTRONGIt's really taking an equilibrium environment and providing disequilibrium to the system. But...

REHMI would put it more simply, messing with nature.

ARMSTRONGWell, we already messed with nature. As Jane said, we've got a lot of catching up to do. We were given a 30 -- the other team was given a 35-point spot over us in this football game, and we've got a long ways to go. But I would say on the volatility issue, like any other issue regarding the science, that this is exactly why we need to conduct the science. Every geologic environment is different and unique in its own way. So there's no one size fits all. We really need to understand, very systematically, what we're doing with this carbon, where it's going to be stored.

ARMSTRONGAnd I agree with what Noah said. It's got to be a multi-path portfolio. There's no one silver bullet in this. It's got to be all these different technologies working together.

REHMAll right, and joining us now is David Keith. He's professor of applied physics at Harvard. He's president of Carbon Engineering, a start-up company developing industrial-scale technologies for direct air capture of CO2. David Keith, welcome.

MR. DAVID KEITHHi there, thanks for having me.

REHMTell us about your company and exactly how it works.

KEITHWe're developing ways to capture carbon dioxide from the atmosphere and use it for making fuels to attack the kind of heavy end of the transportation problem. So let's start with what problem we're trying to solve. How do you de-carbonize, say, heavy vehicles and aircraft, say, mid-century? So we want to stop emitting carbon, and we've got fantastic improvement in, say, solar power, but batteries really aren't going to work on airplanes. So we need a way to take the low-carbon energy we have from, say, solar power and use it to make fuels in a way that doesn't have other big environmental footprints the way biofuels do.

KEITHSo one way to do that is you go solar power to make hydrogen, and then you take CO2 from the atmosphere to make fuels. And that's the focus of our company's efforts.

REHMSo as I understand it, you've got some fans working that suck air into a mesh filled with a trickle of potassium hydroxide and pulling carbon dioxide into the solution, pumping it through a tank with sand-like balls of lime, and it's there that the CO2 hardens into a limestone coating. Is that correct?

KEITHYeah, more or less. I think the key -- technically there's no big issue about capturing CO2 from the air. It's been done commercially as a pre-step in what's called cryogenic air separation for half a century. The issue is can you do it cheaply. And the focus of our company has been to adapt existing industrial technologies that we know are cheap. And so there's not much CO2 in the air. You must make the thing, that first so-called contact, that first takes it out of the air, must have low capital and operating costs, or you're death.

KEITHAnd our focus has been to build on the technology of so-called force-draft cooling towers. These are things lots of your viewers would have seen associated with power plants or cooling equipment on building, and we're basically adapting that technology, and the key thing is we know, from the partners that we have, SBX and others, who build these cooling towers that we can make them very cheap. And so the issue is really to prove that we can adapt that cooling tower technology to capturing CO2, which it itself a weak acid, it's called carbonic acid, into a basic solution and then back end of our process getting the CO2 back out of that liquid.

KEITHIt is important to say it's actually, in terms of chemical terms a lot of physical terms, more or less the same as part of the back end of pulp and paper. And so there's, you know, a kind of 75-year history that we're building on.

REHMAnd you're listening to the Diane Rehm Show. David Keith, is -- do you believe that this technology could really be employed on a very large scale?

KEITHWe've got to define what very large means, but we think we're making very good progress and could plausibly build a first-of-a-kind plant that would be able to produce -- be a sort of a 100,000-tons-of-CO2-a-year-scale plant would probably the size of our first of a kind. And we think this pathway, there's competitors to our particular way to do it, but the pathway that says we deal with the heavy part of the transportation sector by taking low-carbon power from wind or solar or nuclear power, and making fuels with it, we think that pathway is very scalable to tackle, say, you know, that segment of the transportation, which is sort of 20 percent or so, depending how you measure it, of the global CO2 emissions.

REHMJane Long, what do you think of this approach?

LONGI think that what David's talking about illustrates a really important point, which is that there are kind of crossovers in technology between what some people would call mitigation, which is the term we use for talking about stopping emissions or reducing emissions, and what we were talking about on your show, Diane, which is what we call carbon dioxide removal from the atmosphere, just actually lowering removal. So they're -- they have very different strategic roles, but the technologies overlap, and David's company is doing a marvelous job of trying to figure out the very, very difficult problem of removing it from the air, which is -- takes quite a bit more energy than removing it from, say, flu gas, where it's more concentrated but which we will eventually likely want to be able to do.

LONGAnd meanwhile he's playing in the mitigation market to try to produce what are essentially low-carbon fossil fuels, or actually hydrocarbon fuels, not fossil fuels.

KEITHYeah, not fossil fuels is the whole point.

LONGExactly. Yeah, they're not fossil fuels, but they're chemically equivalent to fossil fuels, but they're not fossil, they're coming out of the air, using renewable energy in this air-capture technology. And so he's going to work on this technology. The technology could eventually transfer over to this climate-engineering-type application. So I think he's -- it's a great illustration of how research will proceed. It won't be neatly focused on one application that applications -- different applications will lead to different parts of the solution used in different ways over time.

REHMAnd Thomas, your view?

ARMSTRONGYeah, I want to say I have been on panels and committees with David before, and I can say that the thing that I like about this approach is it's a multi-scaled approach. It's starting out at a small scale, understanding the science, understanding the boundary conditions, understanding the interactions and scaling up from there towards the implementation of the technology. So I applaud the way that he handles this. This is the way to make sure that people don't get scared and that we consider these technologies appropriately.

REHMDavid Keith, I thank you so much for joining us. Good luck on your project.

KEITHThank you very much.

REHMAnd short break here, your calls, your questions when we come back. Stay with us.

REHMAnd I must say one of the questions that has haunted me throughout this whole investigation into carbon removal from the atmosphere is that we as humans take in oxygen, breathe in oxygen, breathe out carbon dioxide. So with all these people on the planet earth, how can you remove enough carbon dioxide, Thomas?

ARMSTRONGWell, I think, Diane, it's a good question, but the issue is really the population itself. And we talked about this before, that nature has sort of a buffer, accommodation zone built around its processes that allows for some stakes or unintended consequences or whatever you want to call it.

ARMSTRONGBut when the population goes from 2 to 7 to up to 9 billion people, and we have that kind of anthropogenic or human induced processes going on that are causing climate change that everybody agrees on in terms of the science community as far as I'm concerned, the real issue becomes population. It becomes a real quandary. And the truth of the matter is that Mother Nature can buffer the system so far, but we've gone just too far.

REHMJane Long, do you agree?

LONGYeah, that's absolutely true, but I think to come back to your question, the amount that we respire every time we bring in oxygen and breathe out carbon dioxide, it's nowhere near what we do by burning fossil fuel essentially. I mean, the fact nature has stored all this carbon for millions and millions of years underground, and within a matter of a couple hundred years, we're burning huge quantities of it.

LONGJust to give you a feeling, every time you fill up your car and drive through that tank of gasoline, that's probably 300 to 500 pounds of carbon dioxide, which is something like at least twice your weight maybe, hopefully three or four times your weight. And so basically, you know, this -- and that represents something like 30 to 40 percent of our emissions from energy are coming from transportation and fuels.

REHMAll right. And here's an email, Noah, for you, from Donald who wants to know, is it possible to convert captured carbon into building materials? Could this make capture efforts more economically viable?

DEICHIt certainly can, and I think we see exciting initiatives to turn CO2 into cements, into plastics and other types of new composite materials, as well as just using sustainably harvested timber, which the tree pulls the CO2 out of the air as it's growing and locks that timber in a building when it is used for construction. The question here is scale. So I think initially this is a great opportunity for companies to make the market and start to build early uses for CO2.

DEICHBut as Tom mentioned, this is a billion ton problem, and we simply don't consume that much CO2 today. And we don't consume that much material that even has carbon in it. And I think this is a question of how do we use the carbon in the air, not in the ground to make these materials today. We could, in theory, expand how much we use, given that we find a use for it to sequester CO2, but it's only going to be a piece of the puzzle, that we have to start thinking about geologic storage, about terrestrial storage, in agriculture, in forestry as well, that all of these pieces add up.

DEICHAnd it's very similar to renewable energy today. Nobody's saying we just put solar panels everywhere and we'll be fine. This is you put solar where it's sunny, wind where it's windy. It's the same type of thing with carbon sequestration. You want to use the resources that are of most high value where you are and what fits best within the local context.

REHMAll right. Let's go to the phones. First to David. He's in Syracuse, N.Y. David, you're on the air.

DAVIDGood afternoon, thank you, Diane, for taking my call.

REHMCertainly.

DAVIDFirst, I think -- I have serious concerns about geological sequestration. I think every discussion about that should include the safety issue highlighted by the 1986 Lake Nyos disaster. I know from personal experience what it feels like to be within high ambient CO2 levels. You can't breathe in at all. That's very scary. Well, my question is, is there any comprehensive, physical, mathematical analysis showing that carbon scrubbing technology and geo-sequestration can really be more viable than nature's approach? That is (word?) forestation and reforestation.

DAVIDMy impression is that carbon scrubbing is all very hypothetical. And I'd expect it could be impossible to take more CO2 out of the atmosphere using that technology than the energy required to manufacture and operate that technology and to manage the geological sequestration. I would love to hear that my concern is not a concern at all.

REHMJane.

LONGWell, let me go after one at a time here. The Nyos situation is a situation where there was an overturning of a lake that had high concentrations of CO2 at the bottom, and the lake overturned and CO2 was emitted. And CO2 is heavier -- is a heavy gas, and it can flow along the topography, and it killed a lot of people, as the caller represents it. It is true that this is not a great thing to be around, and concentrations of CO2 are dangerous.

LONGWhat the research has shown for carbon sequestration -- deliberate carbon sequestration, that the only way that you could have some kind of an eruption like that, of carbon dioxide, would be if you started to store CO2 near a source of heat, like in a volcano or a geothermal area. So that would be something to avoid. Again, you can't do this willy-nilly. You have to manage the situation.

LONGAlso we know that any kind of leaks would accumulate in low areas of topography, and it's possible to put together detection systems to have early detection of problems and then perhaps de-pressure areas that were problematic. I think these things can be managed. I don't know that they can be managed on the scale of 2,000 gigatons of carbon dioxide that we want to eventually take out of the atmosphere or that we likely will want to. So, you know, geologic storage is going to be part of the problem.

LONGDoes the technology work? Yes. Noah brought up before, we are already doing on the order of millions of tons of carbon dioxide in storage. There are projects underway now to add several million more. We know how to work the technology. We know how to -- as David pointed out, we know how to get it out of the air, and we're trying to make that an affordable system. None of these things work without some kind of a price for carbon in the economic system. But physically they can be made to work. And if we design them well and monitor them well and manage them well, each of them can have some part of the global solution.

REHMAll right. To Tim in Lambertville, Mich. You're on the air.

TIMHi, Diane and guests.

REHMHi.

TIMThe scale of the CO2 removal problem is so great that intervention between any mechanical, chemical apparatus and the air mass is incapable of enough interface area. But the air, ocean interface, on the other hand, is so huge, millions of square miles, and is already taking CO2 out of the atmosphere by dissolving it, we should accelerate the (unintelligible) rate, by reducing the partial pressure of CO2 in water, below that of CO2 in air, which is doable by simple chemistry, using calcium oxide, Lyme, which removes CO2 from dissolution in seawater and sequesters it geologically into bicarbonate ions which is where most of the planet's carbon is already residing.

TIMIt's absolutely stable, geo-molecular sequestration, unlike underground caverns.

REHMAll right. And, Jane, I'll let you have that one.

LONGAgain. Well, you know, first of all, having carbon dioxide in the ocean isn't a freebie, so as Noah or Tom pointed out, I can't remember now, when carbon dioxide dissolves in water, it becomes a acid, a weak acid, but that acid changes the whole ecology of the ocean. So ocean acidification, as commonly called, is one of our serious environmental problems of climate change, so that's not a freebie.

LONGThe idea of putting carbon dioxide into the deep ocean, into trenches, is probably one of the things that hasn't been discussed very much, but it will have to come up. Because if we're going to pull a significant amount of carbon dioxide out of the air, probably the geologic conditions, although the upper limit on what could be the total capacity might be very large, we might not want to use all that capacity, because it might be that the good sites are used up first, and the others are riskier, and we don't want to take those risks. So, yeah, the ocean will play a role.

LONGIn terms of getting enough limestone to do what the caller suggests, these ideas have been talked about, and the amount of material that would have to be moved is sort of equivalent to everything that we pull out of the ground now for mining and for construction and all of that volume, do all of that volume and put it into the ocean to make a difference of a few gigatons.

REHMAll right.

LONGSo I think it's a big problem.

REHMTo Thomasville, Ga. Henry, you're on the air.

HENRYHey, Diane. Thanks for taking my call.

REHMSure.

HENRYI was just wanting to bring up something. After the Dust Bowl period, the federal government started a program called the Soil Bank Program. The Soil Bank Program finally matured into what's now called a CRP Program. And that's to stabilize our soil to protect our natural resource of water. Well, what's happening as a result of that, those trees are also sequestering carbon. So it would just stand to reason that, not a solution to the whole problem, but one solution would be to further fund the cost share programs for planting trees, to take care of part -- to sequester more carbon.

REHMAll right. Thomas Armstrong, how many trees would you have to plant?

ARMSTRONGWell, it would be a lot of trees, but, again, I think the issue is we're not looking for the silver bullet. All of these activities, including a cost share program, a public-private partnership that would allow for some of the carbon to be sequestered and sunk into trees in order to alleviate the CO2 problem is just one of the possible implementations that would make up the whole portfolio. Again, it's that we're not looking for the silver bullet. We need to take all these things into consideration. I can tell you from my days at the Department of the Interior, the U.S. Fish and Wildlife Service and the National Park Service were doing these very same kinds of activities.

REHMAnd a question for you, Noah.

DEICHDiane, I'd like just to...

REHMWhat do you think about the agriculture footprint on the climate and soil?

DEICHWell, and I think it's an important area to tackle. And both Tom and the caller previously bring up an important point, which is that the federal government is already doing a lot of things that can be adapted to encourage carbon sequestration. So it's not just in USDA and thinking about planting more trees or restoring ecosystems. But there are initiatives around forestry and other initiatives to help build up soil carbon stocks.

DEICHAnd so I think that, in particular, agriculture offers really interesting opportunities. In Paris there was the announcement of a launch of a project called the "4 per 1000" Initiative, which is all about building up organic matter in soils. And through changing farming techniques across the world, even by building up a little bit of carbon in the soils, we can sequester a lot of carbon from the air.

REHMAnd you're listening to "The Diane Rehm Show." Here's an email from Erin and perhaps we've touched on this, but it's an interesting question. She says, "I'm wondering how much energy is used to pull carbon out of the atmosphere. Does it use a lot less energy? Is a lot less carbon released to perform the job than the amount of carbon that is retrieved?" Jane.

LONGSo one of the things that you have to take account of is where you're getting the carbon dioxide. So if you get it out of flu gas from a power plant, it can take what we call parasitic energy. In other words, it's a parasite on your energy production system. And it could be as much as 20 or 30 percent. But almost all of that energy is from industrial processes that are amenable to innovation, and so this is where we really -- in all of this, we really need research and trials and demonstration projects, so that we can find out what are the ways in which we can reduce it.

LONGIf we try to get it out of the air, it's too, too -- ten times more energy to get it out of the air. But the upside of that is you can do what David has suggested. He could go anyplace where it was sunny and put in solar panels. And that's what we might call stranded energy. In other words, you can't that solar power into the grid to power your homes, but you might be able to use it out in the desert someplace to capture CO2. So he's got -- these things are complicated and it depends on the setting...

REHMSure.

LONG...that you put them in. But it does take energy. And if you get that energy from fossil fuel, then it's less effective than getting it from, say, a stranded solar plant in the desert.

REHMNoah, do you want to add?

DEICHYeah, and I will just add that it really depends on what you're looking at. So plants take sunshine and water and they take CO2 out of the atmosphere. They're not particularly efficient at it, but they've had a few billion years of R and D to get to the point where they are very passive and they're very efficient with the resources that they do have. And so I think that we can learn from this and adapt our industrial systems to take these principles and not necessarily focus on the efficiency of conversion, but the cost-effectiveness of that conversion, and make it as economical as possible.

REHMI wonder is there any thought of how many trees you would have to plant in order to balance this carbon sequestration or...

LONGOne of the -- Diane...

REHM...carbon removal from the atmosphere? Any thoughts about that, Jane?

LONGOne of the things you have to be -- you have to be really careful about planting trees. If you took some bare land and you planted a forest, you could take a lot of carbon dioxide out of the air for, say, 40 years. But then the forest becomes mature, and the trees die, and they rot. And so after a while it's not clear that it continues to be a sync. And so the actual management of how you would use forestation as part of this problem is not straightforward, and it depends on where you're doing it, what kind of trees you're planting, and what the long-term history is. So I think one of things that's really important for your listeners to understand is that just planting trees is not the answer.

REHMIs not the answer. All right. We'll leave it at that with Jane Long, Noah Deich and Thomas Armstrong. Fascinating discussion. I hope we'll hear more about this as time goes on. Thank you all for being with us. And thanks for listening. I'm Diane Rehm.