By John Rennie
Posting in Energy
Inexpensive carbon-capture systems may soon be able to pull excess CO2 out of the open air faster than burning fuels can add it. Yet coping with global warming will still be a challenge.
Everyone who has thought about industrially driven climate change has at some point, however briefly, wondered why we can't solve the problem by pulling the unwanted carbon dioxide back out of the air. Surely, if burning fossil fuels can blast so much extra carbon dioxide into the atmosphere, some other act of chemistry on an equally gargantuan scale ought to be able to recapture the gas.
Recent news out of the University of Southern California suggests that science is getting closer to making that antidote to global warming feasible. A close look at the technology, however, also shows why it would probably not be a perfect remedy all by itself.
Finding ways to draw carbon dioxide (CO2) out of the air is not in itself a terribly difficult problem. A variety of substances, such as calcium hydroxide, sodium hydroxide, and aminosilicas will under the right conditions spontaneously adsorb the gas. Submarines and spacecraft have long used filtration systems based on that principle to help keep their air supplies breathable.
But replicating that success on a massive industrial scale to offset the emissions from burning coal and oil gets problematic. Unless one has a bottomless, cheap supply of the sorbent material (and a place to store it once used), recycling it becomes a priority. Driving the CO2 back out of the sorbent usually entails raising its temperature, often by hundreds of degrees Celsius, which drives up the cost prohibitively.
Because of pressures to curtail CO2 release, the energy industry has nonetheless been working on chemical systems based on ammonia or amines for scrubbing the carbon out of flue gases at coal- or oil-burning power plants. Currently, these approaches often cost about $100-150 per ton of CO2 abated, though expectations are that as the technology matures, costs will fall into the $35-50 per ton range.
Even so, that technology can only be fitted to stationary, concentrated sources of carbon emissions: adapting it for use on CO2 sources that are more mobile (like cars) or more diffuse (like cooking stoves and home heaters) isn't practical or affordable. It would therefore miss about half of all CO2 emissions from human activities. The ideal version of carbon capture would work independently of the sources. It would -- somehow affordably -- process the open air.
The latest advance in that direction has now come from Alain Goeppert, G. K. Surya Prakash, Nobel laureate George A. Olah and their colleagues at USC's Lokar Hydrocarbon Research Institute, as reported in the Nov. 21, 2011 issue of the Journal of the American Chemical Society. They have developed a new adsorbent plastic material that they maintain is inexpensive to produce and so voraciously hungry for CO2 that, until it fills up, it can thoroughly strip all the CO2 out of any surrounding air. Moreover, a temperature of only 85 °C is sufficient to release the CO2 and leave the plastic ready for reuse.
Their material consists of a highly branched organic compound called a polyethylenimine (PEI) that has been coated onto grains of silica, so that it offers lots of surface area. In humid, room-temperature air, each molecule of PEI reacts with CO2 and shifts into a stable bicarbonate form. (Even under more arid conditions, the PEI continued to take up CO2 well.) In tests, the material took up a bit less than 10 percent of its own weight in CO2 (1.71 mmol CO2 per gram of adsorbent).
The USC lab's technique is the latest of many developed to remove CO2 from air, and much more work still needs to determine whether it -- or something else yet to be invented -- is practical enough to deploy widely. Klaus S. Lackner of Columbia University has been a pioneer in the field, and Global Research Technologies, a company he founded, is attempting to commercialize his approach based on a carbonate polymer material. Other efforts (and compounds) are the focus of work at the Georgia Institute of Technology, Brookhaven National Laboratory, the University of Calgary, the Swiss Federal Institute of Technology, and elsewhere.
Assuming that any such approach pans out, what impact might it have on climate change? In a 2010 article on the subject for Scientific American, Lackner extrapolated from his technology to envision a time when 10 million air capture machines around the world, each extracting 10 tons of CO2 a day, would affordably collect 36 gigatons of CO2 per year. That would be enough to reduce the atmospheric concentration of CO2 by 5 parts per million annually -- more than twice the current rate at which CO2 is being added today. Lackner estimated that the initial costs might be about $200 per ton of CO2, but that as the technology matured, they might fall to around $30 per ton.
What technology alone can't do
Appealing as those projections sound -- and they do sound encouragingly good -- they shouldn't suggest that effective carbon capture makes global warming trivial to solve. First, developing and deploying the technology at that literally world-altering scale will take decades. Even a transient period of higher global temperatures could disrupt some ecosystems, contribute to natural disasters, and cause other headaches.
Then there's the issue of cost. An abatement cost of $35 per ton of CO2 may be reasonable; it should raise the cost of electricity by only a couple of cents per kilowatt-hour. But in recent U.S. policy discussions about cap-and-trade CO2 credits and carbon taxes, the idea of setting prices at even $20 per ton or less has met intense opposition. Who will be willing to foot the bill for building and operating the massive carbon capture infrastructure that Lackner described? As critics of carbon capture have argued for years, it might be less expensive simply to shift away from fossil fuels and to solar, wind, or other carbon-light energy sources.
Successful carbon capture also obliges us then to do something with the collected CO2. As Goeppert, Prakash, Olah, and Lackner have variously written, that CO2 has many industrial applications, including potential uses as an alternative to petrochemicals in the manufacture of polymers and fuels. A sizeable amount of it, however, will probably need to be sequestered -- for example, by pumping it underground into tapped-out oil fields or other sealed geological formations.
Yet carbon sequestration is still barely past its infancy. The Sleipner project has been storing more than 10 million metric tons of CO2 in formations under the North Sea off the coast of Norway for the past decade, and dozens of other projects are in various stages of execution or planning. But effective sequestration will need to work indefinitely, and concerns have arisen that at least some sites under consideration might not only leak CO2 but could lead to contamination of aquifers. Geologists are still determining how many formations around the world would be suited to sequestering carbon over the long term.
None of these objections means that scrubbing CO2 out of the atmosphere won't work well in practice. That the technology would allow the capture of CO2 to be delinked from the production of CO2 might actually be a point in its favor: it would pose less of an immediate thorn in the side to powerful energy interests and it might be more appealing this way to entrepreneurs. Removing CO2 from the air may in fact turn out to be an essential adjunct to curbs on CO2 production, such as switching to solar power: that combination might turn out to be the best hope for keeping greenhouse gas concentrations below catastrophic levels.
Even so, carbon capture doesn't represent a simple tech solution to climate change that can bypass the political and economic obstacles that have dogged the issue to date. The military theorist Carl von Clausewitz observed, "War is the continuation of politics by other means." The same can probably be said for technology.
Image: The earth's atmosphere, as photographed from the International Space Station. (Credit: ISS/NASA)
Jan 16, 2012
This reminds me of a catalyst that was supposed to be applied to car radiators that would convert ozone to oxygen by splitting off the extra atom. What if we could get the cost down and do the same? Then find a way to split the carbon and ozygen atoms apart; use the carbon to make "stuff" and release the oxygen into the air. It will all boil down to the cost/benefit which may be why we never saw the introduction of the ozone catalyst for radiators even though they were predicting it would only come to $35.00 per car extra.
Trees sequester carbon. Some trees live for hundreds of years, not mere decades, so plant the right trees. Furniture can last for hundreds of years if we want it to, so use it to make antique furniture. Or stockpile it. It is easier to keep than liquid or solid CO2. If we use some of it for fuel, leaving the fossil carbon where it is instead of using it to build and power high tech carbon capture plant, that is as good as sequestering it. The point is that with a bag of seeds we could put people to work tomorrow planting up empty spaces and be actually doing something - instead of grinding political and commercial ax-heads at the expanse of green concepts.
1) As I was growing up in the 60's the worry was that we were going into a mini Ice Age. The science around "Global Warming" is not as hard as people want you to think. We have less than 200 years observation on what appears to be an 11,000 year cycle. "Global Warming" makes for some good headlines, but the actual proof is not as solid as the popular media would want you to believe. On the other side, try to publish something that contradicts global warming. You will lose all hope of tenure and, if tenured, you will gradually be forced out or be declared a radical teacher. 2) Plants produce carbon dioxide as well as oxygen. They produce a lot more oxygen when in sunlight, but it drops way off during dark periods and CO2 is the major expirant. 3) The whole idea of sequestering excess carbon dioxide under ground scares the hell out of me. Add a little water and you get carbonic acid, the same stuff that made caves worldwide. The stuff that made the caves was pretty weak. I can see double digit concentrations from one of the sequestration sites, and huge caves forming in human time scales, not geological. I once lived in a coal-mining area where it was fairly common to have sink holes the size of houses form when the old tunnels collapsed. Imagine sink holes the size of counties. My house is built on limestone. Would your house, and everything around it, be safe?
The development and production costs, maintenance and management costs have yet to be announced, but this solution can't compete with the ultimate self-building, self replicating plant that recovers carbon from the atmosphere, stores it as solid fuel, runs 24/7 unattended and grows its own extra capacity at no cost. But who gets famous for telling people to plant trees. It seems we are looking for an expensive risky investment-needing invention rather than a simple solution to the problem.
If you want to remove CO2 from the sky, plant trees and crops. More CO2, more plant life. It's part of a self-regulating system. We should focus on removing contaminants from our air, water, and food.
In other words, keep the coal in the mines,natural gas in the shale, and oil in the ground as much as is humanly possible and use your investments to drastically decrease waste and improve efficiency. The money saved can then bootstrap the development of true renewables, which is much more promising than trying to stick the CO2 back into the ground and make it stay there.
1) It was those concerns about an ice-age that prompted scientists to devote more data collection to the issue, and the resultant new data indicated that the opposite was happening. This is well documented history, and the data collected indicating anthropogenic effects on climate is overwhelming now. 2) And the models incorporate this dynamic. Doesn't change the outcomes, I'm afraid. 3) I agree with you: the volumes of CO2 that would be needed to make a dent in increased CO2 atmospheric levels in the next century would be unreal, but nothing that I've seen proposed is even remotely economical, so I wouldn't be too worried about it. Best to keep all that carbon geologically sequestered by not digging it up in the first place.
Trees have been shown to have stunted growth in a higher CO2 environment while vines (not very good at sequestering carbon because of their small biomass) thrive. and actually kill surrounding trees by smothering them. It has been looked at as a major cause of increased poison ivy and kudzu growth!
The problem with plants is that they die and release their CO2 back into the air. Even trees store CO2 for only a few decades. Thus you can only sequester as much CO2 as you can plant extra crops on average. Right now, most arable land is already being used. Then there's the problem of water to get these plants to grow. Other schemes have explored getting extra plants to grow in the ocean. One such idea is that some kinds of plants are inhibited by lack of iron, so adding iron to the ocean promotes their growth. But nobody know the long-term effect of doing this on a massive scale.
Actually, all the activities you mention produce net money (AKA profits). There's no money to be "saved" by not doing them. Nobody drills or builds a mine if they think they won't make money. Those investments aren't free, they are a net loss to society if they don't ultimately return a profit. Unfortunately, right now it's far more profitable to mine carbon than it is to invest in renewables.
There are trees that are several hundred years old. As Wikipedia states: "The record-holders.....are Great Basin bristlecone pine trees from California and Nevada, in the United States. Through tree-ring cross-referencing, they have been shown to be almost 5,000 years old." When trees die they don't release the carbon right away. They can be used for a number of different purposes such as houses, furniture, paper and so on. Some of them turn to coal, which is where we get some of our fuel from today. Planting new trees instead of the ones cut down is very easy and efficient, if people would only do it. Where trees once grew, they can grow again. After all, it is people who have been cutting them down, so it should be people who plant new ones. And for heaven's sake human kind, start using condoms. There are 7 billion of you already on the earth. What does it take to make you see the real problem here?
As to sequestering CO2 in plants: Plants primarily convert CO2 into sugars and release O2. The more CO2 the more FOOD stock they produce...but this is beside the point. CO2 may moderate aerosols which drive coolng, which by the way, has been going on for the last almost 2 decades: Not that any of the "climate warming" Goreean types are apt to admit. The science has been settled: Global Warming is caused by a star in the center of our solar system in the complete range of things. This reality is lost on the chicken little's inability to process an entire set of concepts. So doesn't it make more economic sense that if we really need to interfere with the "change" part of the equation, it is easier to shade the earth via aerosols? We can start by releasing particles by using solar powered lasers against all those empty water bottles soccer moms generate everyday (rolling eyes). Better yet solve 2 problems at once..laser away the soccer mom breeders and deal with the over-population and food shortages vanish in a generation! Yeah that's the ticket.... If you are shocked enough to respond tome with indignation then your ability to process satire is diminished below a threshold which indicates all your faculties are too diminished to be participating in this discussion in the first place. Besides I would not laser splat soccer moms before politicians and Teeny-Bopper/Toddler pageant moms!
And there's even more money in retrofitting existing commercial and residential buildings, manufacturing processes, and transportation systems in order to make them more efficient and waste less. I'm not disagreeing with you so much as saying that we need to shift priorities from making a buck off of high carbon sources to making a buck from low carbon sources as well as making a buck from efficiency measures.
Large forests in the American Southwest were clear cut to produce the railroad ties that laid the foundation for the great rail expansion into the west. Another major use of lumber was in mines. The mines at the Comstock Lode by themselves used several forests of lumber to shore up the walls to keep mine shafts from collapsing. You could say that carbon is squestered. The lumber is still in the mines today.
Much of Arizona and New Mexico were once covered in old growth pine forests. When native americans cut these trees down (which grew VERY SLOWLY) they ended up altering the more humid, high precipitation microclimate and the rich top soil quickly blew away. Now the environment would simply not support trees. Sometimes actions are just plain irreversible!
Nobody said that the sun isn't central (pardon the pun) to the earth's climate. But to disparage the larger scientific community by blowing off humanity's role in climate change is, well, bad science. Dismissing legitimate science as "Gorean" doesn't impress anyone. Show me a legitimate study that explains our current understanding of climate dynamics without including humanity's role in that dynamic, and we'll talk. But judging from the rest of your post, It seems that you are interested primarily in providing as much hot air as possible....