Let It Snow, Let It Snow … CO2

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Turning atmospheric carbon dioxide it into snow and burying it underground is a new way to think about capturing harmful CO2.
Corbis

What if you could build a giant refrigeration unit near the South Pole, pulling harmful carbon dioxide out of the Earth's atmosphere, turning it into snow and burying it underground. Wind turbines would power the chiller plants, converting CO2 from a heat-trapping atmospheric gas to a solid as a way of slowing down climate change.

Of all the greenhouse gases, CO2 is the "control knob" of climate change. There's currently too much of it in our atmosphere, and the more of it that there is, the greater the effects of warming.

It sounds far-fetched, but researchers at Purdue University have put together a plan on how such a device would work.

"It's kind of a novel idea and it's going to take a lot of refrigeration units and a lot of cost," said Ernest Agee, professor earth and planetary sciences at Purdue and author of the paper appearing in the Journal of Applied Meteorology and Climatology.

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Water vapor turns to snow around 32 degrees Fahrenheit, but CO2 doesn't switch from gas to solid until it gets down to a chilly -220 degrees Fahrenheit (133 Kelvin). The ambient air temperature in Antarctica can often reach -100 F, which gives the chilling process a head start.

But to transform the planet's atmospheric CO2 into snow, it would take an estimated 446 individual refrigeration units that use a closed-loop liquid nitrogen process. The units would be powered by 16 1,200-megawatt wind turbines. That's a lot of power.

Agee says the idea came to him during a discussion about Mars' south polar ice cap, which was found to consist of CO2 by the Mars Global Surveyor and Odyssey missions.

He says Antarctica's coastline would be the best place to put the chiller plants and the turbines since the coast gets blasts of high-powered winds that cascade down from the higher South Polar ice cap toward the ocean. The CO2 snow would be stored in insulated landfills. The winds can power the turbines, while excess heat from the chillers and electricity from the turbines can be harnessed to keep Antarctic research stations warm and dry.

Russell Donnelly, a University of Oregon physicist, is intrigued with Agee's idea."It's quite exciting," Donnelly said. "It's certainly thinking big."

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"You look at the hot gases of a stack, it would look impossible," Donnelly said. "But you can cool them off with water sprays and down to room temperature without spending much money. Then if you start to refrigerate, you need to put just enough refrigeration to get the job done."

Donnelly and colleagues published a paper in the July 12 issue of the journal Physical Review E that spells out how he would build such a device.

He said the electricity would cost 25 percent more to produce, "but you would have an environmentally-friendly power plant."

Carbon sequestration schemes are not new. Utilities have been looking at burying excess CO2 beneath the ground or in deep wells or algae ponds for years, but efforts have not paid off because of the high associated costs.

Richard Branson's Virgin Earth Challenge is offering $25 million to any company or group that can sequester a billion tons of CO2 from the atmosphere per year. That's the same amount that Agee says he can pull using his Antarctic chiller system, although he did not enter the contest.

Eleven finalists were chosen in November 2011, but no winners yet.