"Trees can take CO2 back out again-but even covering the planet with forests wouldn't solve our problem, and there would be an awful lot of wood to preserve. (If allowed to rot or burn, trees release their carbon again.) Physicist Klaus Lackner thinks he has a better idea: Suck CO2 out of the air with 'artificial trees' that operate a thousand times faster than real ones.
They don't exist yet, and when they do, they probably won't look like real trees. But in Lackner's lab at Columbia University he and colleague Allen Wright are experimenting with bits of whitish-beige plastic that you might call artificial leaves. The plastic is a resin of the kind used to pull calcium out of water in a water softener. When Lackner and Wright impregnate that resin with sodium carbonate, it pulls carbon dioxide out of the air. The extra carbon converts the sodium carbonate to bicarbonate, or baking soda."
The artificial trees could absorbs the carbon dioxide, but only hold it until it is removed for proper disposal, another as-yet-unanswered question.