Friday, March 28, 2008

Spongelike Air-Capture Gadget Scrubs Away Carbon Emissions

The Atmospheric Carbon CapturE SystemS (ACCESS) Air-Capture System, developed by Global Research Technologies in Tucson, Ariz., holds sheets of material capable of capturing CO2 molecules directly from open air.

To remove the molecules, the sheets are sprayed with a chemical solution that bonds to the carbon dioxide. The solution is then drained off to a separation unit, where the CO2 is isolated as pure gas through electrodialysis. A design goal was to avoid using toxic or corrosive chemicals that would require special handling, so ordinary PVC pipe is used to transfer the solution back to a collection unit so that it can be recycled.

Ideally, the ACCESS machines would be placed in clusters, similar to windmill groupings, near facilities capable of storing the carbon permanently. Unlike turbines, however, these devices can be placed anywhere. Locating them in windy areas would increase their efficiency by moving air across the surfaces more quickly, but they are not dependent on a strong breeze.

The current prototype captures less than 100 kilograms of CO2 per day, but Lackner predicts future models will capture 1 ton per day—several hundred times the amount saved by an equal-size windmill. New versions of ACCESS could capture carbon at a rate of about 3 kg per second, the same amount an average tree absorbs in a year.

Skeptics of the technology point to carbon emissions coming from ACCESS and similar devices themselves. Because it uses electricity from the grid to separate gas from the solution, the prototype barely breaks even in CO2 savings. The price of capturing the CO2 is also high, predicted to cost several hundred dollars per ton once commercially developed. "In the long term, the price will come down to $30 per ton," Lackner says, "but this will not happen overnight."

Lackner says the ACCESS system could be paired with any form of carbon sequestration being developed, including underground or underwater storage. His preferred method is to pack carbon away Han Solo-style with mineral carbonation, a process that turns CO2 into a solid by mixing it with other compounds.
I first became aware of Lackner and his idea 2 years ago. Glad to see that he is getting close to a commercial version. But, at a cost of several hundred dollars per ton of CO2 sequestered, I don't see much of a use for it. If they can get it down to $30 a ton, then this would be a game changer.

via Popular Mechanics

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