University of Calgary scientists are working on a machine that would pull carbon dioxide from the air in an attempt to scrub out emissions from diffuse sources, such as car exhaust and home heating. These "diffuse emissions" account for roughly half of the CO2 that goes up into the sky every day, contributing to global warming.
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]