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Art: Joe Zeff Design. Source: David Goldberg, Lamont-Doherty Earth Observatory, Columbia University
Government studies suggest there is room underground for many decades’ worth of CO2—though the idea has not been tested on the massive scale required. Click the labels above to see more about each method.

CO2 scrubbers that rely on similarly simple chemistry already recycle human exhalations in submarines and space shuttles. Devising an economic way of scrubbing the outside air, though, is harder. Lackner’s plastic offers two advantages, he says, over schemes that other labs are working on. It sponges up CO2 quickly— the porous material has lots of surface area to contact the air—and holds on to it lightly. The latter is crucial. The CO2 must be separated from the sponge for disposal, and in most schemes that step takes a lot of energy. But Lackner and Wright just rinse their plastic with water in a vacuum chamber, and the CO2 comes off.

What to do with it? Most likely, compress it to a liquid and pump it underground—the same option being studied for coal-fired power plants, which could capture CO2 at the smokestack. That’s not practical for cars and planes; there wouldn’t be room on board to store the gaseous stuff until you got to the CO2 dump. A scrubber that pulled CO2 out of the air, on the other hand, could be located anywhere—right above the most convenient dump site, say.

Another option would be to add hydrogen to the CO2 and convert it back into liquid hydrocarbons. If the energy for that came from renewable sources, engines that burned the fuel would emit no new carbon. Jet travel would become guilt free again. We could keep our cars and gas stations—no need for a whole new hydrogen- or electric-powered infrastructure. Subversive thought: We could keep our lifestyles. “That’s historically what we’ve done,” Lackner says. “We’ve run into environmental issues that seemed insurmountable— and we’ve found a solution.” One day, he says, when we’ve finally stopped the rise of CO2, we might even be able to reduce its concentration in the atmosphere, back to a level that won’t melt glaciers. —Robert Kunzig

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