Earth too Warm? Just Bury the CO2

Under a blazing west Texas sun, with a whiptail lizard and cattle looking on, Rebecca Smyth works with an assistant to lower a measuring line, then a hose, and finally a slender plastic capsule down an old water well 200 feet deep.

She's hoping the water samples she collects will yield clues to what is, arguably, one of mankind's most pressing environmental questions: Can nations bury their greenhouse gases?

If they can, then governments will have bought themselves a decades-long respite as they search for less carbon-intensive energy sources. If they can't, then a significant rise in global temperatures by 2100 looks inevitable, if fossil-fuel consumption continues at its current pace.

And the answer may well lie here, atop an old west Texas oil field known simply as SACROC, where more CO2 has been pumped underground over a longer period of years than anywhere else on Earth. Her efforts -- and those of the rest of a small army of scientists funded by the US Department of Energy -- are being closely watched. Energy companies want to know their options as Congress mulls over legislative options to global warming. Environmentalists are eager to find ways to slow the rise of greenhouse gases.

"If we don't sequester carbon from coal, we won't be able to stabilize the concentration of CO2 in the atmosphere," says John Thompson, director of the coal transition project of the Clean Air Task Force, a Boston-based environmental group. "It's the linchpin."

Admittedly, pumping huge amounts of carbon dioxide into underground caverns sounds audacious. If the US captured just 60 percent of the CO2 emitted by its coal-burning power plants and reduced it to a liquid for injection underground, the daily volume would roughly equal what the US consumes in oil each day -- about 20 million barrels, according to a report by the Massachusetts Institute of Technology in Cambridge. And the risks are substantial.

Inject too much CO2 and the resulting pressure could cause earth tremors or push deep super-salty groundwater up into freshwater aquifers. Once pumped in, the CO2 may not even stay put in the sandstone formations, below layers of shale and other rock.

Nevertheless, researchers sound confident. "I grew up near Love Canal, so I know the problems of putting stuff underground," says Sue Hovorka, a research scientist at the University of Texas at Austin. "But we're cautiously optimistic this is going to work."

She is one of the scientists tracking the movement of carbon dioxide underground in the nation's first deep-sequestration experiment.

Under a torrid midday sun in the old Liberty oil field south of Houston, she is tracking the progress of about 2,000 tons of food-grade CO2 that she had injected into a well in 2004 and again last fall. Unlike SACROC (Scurry Area Canyon Reef Operators Committee), no CO2 had ever been injected here before, so it should be straightforward to track. But at the moment, Dr. Hovorka is not happy.

Nearly a mile below, her sensitive instruments are trapped in a five-inch steel pipe, and the roughnecks on the rig have spent hours trying to pull them out. A colleague opts to use small explosives to dislodge them. An hour later, the instruments are on their way to the surface and water samples are being analyzed from an adjacent well.

So far, the results are positive.

"Right now the CO2 is stored as small bubbles in the pore spaces of the sandstone," Hovorka says. "We believe it's immobilized and will sit there on a 10,000-year time frame and that when we open this well later nothing will happen. We don't expect any geysers of escaping CO2 or any of the things that people worry so much about."

The amount of potential storage is vast. Three of the five US geologic storage possibilities under review -- salt basins a mile or more deep, mature oil and natural-gas reservoirs, and deep unminable coal seams -- could permanently hold at least two centuries' worth of US CO2 emissions -- about 6 billion metric tons a year, researchers estimate.