Giant Carbon Dioxide Vacuums

Wally Broecker, Columbia University

Now a company called Global Research Technologies, working with Columbia University scientists including Broecker and Klaus Lackner, has demonstrated a working prototype of a carbon air capture device. Allen Wright, president of the company, points out that many other research groups are working on capturing CO2 from concentrated sources like power plants, as well as on ways to sequester or store it. But this device addresses CO2 that has already been dispersed in the air.

"We know that carbon dioxide in the atmosphere is very dilute, yet there are innumerable sources of carbon dioxide that can't be captured any other way other than removing it from the atmosphere," says Wright. "So for the first time, we now have a machine that not only collects CO2 from the atmosphere, but we have been able to separate it from its adsorption chemistry and deliver a pure stream of CO2 as an end product.

"The entire system is a closed loop system, so the end product, what we deliver, is CO2 gas," says Wright.
The CO2 could then be stored-- perhaps by pumping it underground-- or even sold. "Our first markets will probably be commercial in nature," Wright says. "One of the largest is likely to be the field of enhanced oil recovery, where carbon dioxide is used as a solvent to extract additional oil from wells that have become depleted... you might be able to put an air capture park next to a wellhead that has been depleted and extract additional oil from that well."

30 million tons a day?

The machine in their shop is just a prototype. "We've done some preliminary calculations, and if you assume…that the machine is going to be the size of lets say a 40-foot shipping container or a tractor trailer semi rig, that you see on the highway, a collector of that size would capture and produce on the order of a ton of CO2 per day," says Wright.

He says they can also be made to look more attractive, and that millions of them could be parked around the planet.

This artist's rendering shows how CO2 collectors might be made to look attractive for deployment in urban centers image: GRT

The machine uses acid-base chemistry to attract CO2, dissolve it into a water-based solution, and then separate it as a pure gas. Earlier research used caustic sodium hydroxide to absorb the CO2, but research by Lackner and others (described in a 2002 Los Alamos National Lab news release with the optimistic headline, "Imagine no restrictions on fossil-fuel usage and no global warming!") showed that milder bases such as sodium carbonate are both safer and more efficient.

"We use a chemical system, and it attracts and absorbs carbon dioxide from the atmosphere," he says. "In that sense, it is stuck to the surface of a panel which we then wash off with a liquid chemistry, and that chemistry is then pumped over to a separator which splits that liquid into its carbon dioxide gas and the liquid then gets sent back to the collector for another round of air capture."

Since the machine runs on electricity, Wright says it's important that it removes more carbon dioxide from the atmosphere than it adds by using non-green power.

"We have been successful in arriving on that correct side of the carbon balance," Wright says. "So we're very excited. Now, does that mean that we are as far on that side that we need to be? No, unfortunately not-- the technology as it stands today probably would not be amenable to deployment using electricity that comes from a coal-fired power plant."

Allen Wright (left), president of Global Research Technologies, is working on a prototype of a carbon air capture device.

Wright says some of the actual chemistry in GRT's machine is "proprietary." He says the company's goal was to develop the technology so it will be available for when we decide we need it.

Lackner and Broecker think that time is now, and Broecker says to his knowledge GRT is the only company in the world dedicated to carbon air capture. "I'm trying to encourage that other people do this," says Broecker. "I'm not happy that they have no competition, because I think that the more groups that are working on it the more innovations made and the cheaper the price would be.

"I'm very confident that this will be part of the solution," Broecker says. "Otherwise, you'd have to wait for the ocean to suck it up and [CO2] to go back down again and that would take hundreds of years-- a long time. During that long time, there would be a substantial melting of the ice caps... raise the sea level... which would be an enormous expense in property damage all over the world. Greenland, if it would entirely melt, would raise the sea level about 20 feet-- and of course, 20 feet would take away all the beachfront property in the whole world, and the value is enormous."

Broecker published his article in the March 9, 2007 issue of Science. Wright's research is funded by the Gary Comer Science Foundation.