The units, demo versions of which already exist (this is assuredly not a concept), take CO2 in from the air and turn it into liquid, which is easier to store and manage. Professor Klaus Lackner, lead developer, notes that the synthetic trees are not designed to replace, say, coal plants that reduce emissions from the inside, but this could be one very useful plastic plant if it sees mass production. [CNN]

The scrubber takes in air and binds the CO2 to sodium hydroxide. The heavier concoction is then sent through a few more chemical intermediaries, eventually resulting in a batch of separated CO2 that can be piped away, while the hydroxide gets fed back into the machine.

According to the university, the scrubbers can capture around a ton of carbon dioxide for less than 100 kwh of electricity, about ten times as much CO2 as was released to keep it running. Unfortunately, that's not quite enough to keep it from being prohibitively expensive. The cheapest way to keep CO2 emissions out of the air is still not generating it in the first place. [Popsci]