March 18, 2009 -- One possible solution to global warming is simple, abundant and just sitting around waiting to go to work: rocks.
Scattered across the country, there are heaps of rocks capable of permanently sucking tons of carbon dioxide out of the atmosphere, according to a new mapping project by the U.S. Geological Survey and Columbia University's Earth Institute.
Many of these rocks are already slowly lapping up carbon from the air.
The trick now is to find a cheap, energy-efficient way to speed up the process, said Sam Krevor, an environmental engineer at Columbia University in New York.
"There's more rock to bind carbon dioxide than you would produce with all the fossil fuels you could burn," Krevor told Discovery News.
"Whether or not this is practical will be answered in the next few years with the way research is going," he added. "But there's nothing now saying that it's dead in the water."
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Krevor and colleagues collected and pored over geologic maps that cover various parts of the continental United States. They were looking specifically for rocks with high concentrations of magnesium, which readily reacts with carbon dioxide to produce a stable, solid mineral called magnesium carbonate.
Rocks deep in the earth's mantle are particularly rich in magnesium. So the researchers focused on places where the mantle has been exposed but have remained mostly unchanged. Coastal mountain chains proved to be a particularly good source of these rocks, called ultramific. In those places, the ocean crust has been pushed up onto the continental crust.
Because of their chemical makeup, when the rocks are exposed to carbon dioxide, they react to form common limestone and chalk.
After compiling and mapping all of the information they could dig up, the researchers found a total of 6,000 square miles of ultramific rock at or near the Earth's surface around the United States. Twenty-nine of the lower 48 states have enough ultramific rock to make industrial-scale carbon sequestration possible, Krevor said.
"You could easily get out 500 years-worth of [CO2] output," he said. "Basically, any amount of carbon dioxide you might want to sequester using this method would not be limited by the amount of rock."
And the technology necessary to make it happen already exists, said Juerg Matter, a geologist at the Lamont-Doherty Earth Observatory in Palisades, New York. To begin with, he said, it is currently possible to capture carbon dioxide at large-scale power plants. And oil companies sometimes inject the gas into depleted oil reserves to get more oil out.
Matter is working on a technique to inject ultramific rocks with carbon dioxide as a warming-mitigating strategy. The potential is significant, he said, because these rocks exist all over the world, from Oman to Papa New Guinea to the Balkan states of Europe.
But turning potential into reality will require more research and more efficiency. At this point, capturing and storing carbon are wasteful, energy-intensive processes. Scientists will also need to make sure that the carbon doesn't leak out of the rocks after it has been injected.
"Globally, we emit 25 to 30 million tons of carbon dioxide each year," Matter said. "These rocks could have a significant impact in the reduction of these emissions."
Related Links:
Discovery Earth: Video, Expert Interviews, Photos and More
Discovery Tech My Take: We Need to Bury Emissions
Columbia University's Earth Institute
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