Mar 9, 2009

Scientists map U.S. rocks that soak up CO2

NEW YORK (Reuters) - Certain rocks abundant on the U.S. East and West coasts may one day be coaxed to absorb emissions of the main greenhouse gas carbon dioxide at a rate that could slow climate change, scientists say.

"One day this could be an incredibly useful tool to help fight global warming," said Sam Krevor, the lead author of a new study by scientists at Columbia University's Earth Institute and the U.S. Geological Survey that maps such rocks in the United States.

Scientists have long known that rocks naturally absorb carbon dioxide over thousands of years by binding it with minerals to form solids like calcium carbonate, a common substance found in rocks and the main component of snail shells and eggshells. When their surfaces are dissolved by weathering and natural cycles, the rocks absorb carbon dioxide from the atmosphere as it recrystallizes.

Scientists have speeded up that process in the laboratory by grinding rocks and adding a catalyst like sodium citrate to dissolve them. The rocks then reform in minutes, absorbing carbon dioxide.

But that process occurs on too small a scale and requires too much energy and other inputs to tackle the vast volumes of carbon dioxide blamed for global warming.

MORE RESEARCH NEEDED

So scientists are looking to natural rock outcroppings, which they hope can be forced to absorb CO2 faster than happens naturally. One method could involve boring into rock and injecting it with hot water and pressurized carbon dioxide.

More research needs to be done to determine whether this is feasible. But if it works, it could reduce the need for an emerging sequestration industry that aims to capture carbon dioxide from such facilities as coal-fired power plants for injection deep underground for permanent storage.

The world is looking to limit emissions of greenhouse gases like CO2 as climate scientists warn that their elevated global levels could lead to higher temperatures, causing deadly floods, droughts, heat waves and stronger storms.

Some 6,000 square miles (15,540 sq km) of rocks rich in the minerals olivine and serpentine that could be supercharged to absorb carbon dioxide lie on or near the surface in California, Oregon and Washington, and along the entire Appalachian belt of eastern North America from Alabama to Newfoundland, according to the study.

Similar rocks are also abundant in Oman and in the Pacific islands of Papua New Guinea and Caledonia and along the coast of the Adriatic Sea.

Krevor said the U.S. rocks could potentially absorb 500 years' of the country's CO2 emissions. The United States is the world's second-largest carbon dioxide emitter after China.

"The problem is not going to be a lack of rocks, it's getting them to do the job," Krevor said.

By Timothy Gardner

Reuters Online

3-6-09

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