''People think, it would have been sort of sad going through all this trouble,'' said Tony Kovscek, associate professor of energy resources engineering and a researcher on a GCEP project on carbon sequestration in coal.
But studies have shown that leakage, if it happened at all, would be insignificant, Benson said. The IPCC reported that 99 percent retention of the carbon dioxide that is stored would be ''very likely'' over 100 years and ''likely'' over 1,000 years, she said.
''If you do it right, if you select the site correctly and monitor, it can be near permanent,'' Benson said.
Of greater concern to the researchers are the potential risks of carbon sequestration to human health, mainly through asphyxiation and groundwater contamination.
The threat of asphyxiation-or suffocation due to carbon dioxide displacing oxygen-is very low, the researchers said, because of the unlikelihood of a rapid leakage, which would have to occur to cause a problem.
Drinking water contamination, Benson said, is the more probable danger. For example, if carbon dioxide enters the groundwater somehow, it can increase the water's acidity, potentially leaching toxic chemicals, such as lead, from rocks into the water, she said.
To address these risks, scientists are studying reservoir geology to better understand what happens after injecting carbon dioxide underground.
''You need to carefully select places that won't leak, and do a good job of engineering the injection systems and paying attention to where the carbon dioxide is actually going,'' Orr said.
While a thorough technical understanding of the risks will reveal best practices, the scientists also stressed the need for good management to see that proper procedures are followed.
Benson points to a familiar technology as a model for thinking about and tackling risk.'"/>