Much of the attention of late has been focused on finding new ways to scrub carbon dioxide from power plant stacks or to capture it and sequester it below ground. This, say some scientists, misses a crucial point: how to effectively - and, more importantly, cheaply - remove the carbon dioxide that is issued from millions of tailpipes and homes from the air.
Frank Zeman, an engineer at Columbia University, and his colleagues claim they may have just discovered such a solution. They report in a new study that employing the technology used by pulp and paper mills - industrial-scale "scrubbers" - could help draw down carbon dioxide from the atmosphere. The captured gas could then be stored by being pumped underground or into the ocean.Zeman's process would work by moving air through a packing material-filled chamber where it would come into contact with a sodium hydroxide solution - a liquid that absorbs carbon dioxide. The resulting solution would be combined with lime to precipitate limestone - which could then be heated to release a form of carbon dioxide ready for storage (or, if some of Zeman's other ideas pan out, for transportation fuels).
The cost for all of this, however, wouldn't come cheap: a whopping $200 per metric ton of carbon dioxide captured. Zeman and David Keith, his co-author, estimate improvements in the technology could help cut into that price tag over time, especially since it is already being used in pulp and paper mills around the world.
It won't be easy, Zeman acknowledges. Since ambient air only contains about 380 ppm of carbon dioxide, attempting to suck it out would require moving a whole lot of air through the scrubbers. These scrubbers would then have to process almost 250 times more air than flue gas to capture an equal amount. And, of course, this process would do nothing to tackle other GHG commonly spewed by power plants.
Still, if it all goes according to plan (a big "if," we know), Zeman's proposal could go a ways toward helping reduce atmospheric levels of carbon dioxide.
Via ::Environmental Science & Technology: The CO2 sponge (journal)