Volcanic rocks seen as storage for industrial carbon

In one potential strategy to combat global warming, scientists say carbon dioxide from power plants and other industrial sources might be safely stored in layers of deep-sea volcanic rocks off the South Shore of Long Island.

The layers of rocks 30 to 60 miles offshore were among several sites along the Atlantic coast that researchers identified as promising, in a paper published online this week in the Proceedings of the National Academy of Sciences.

The study focused on offshore and some land formations of basalt, a dense igneous rock with porous layers. Basalt has the ability to transform liquefied carbon dioxide into a limestone-like material through a series of chemical reactions that, over decades, seal the carbon in place.

Many of the study's sites, which range from offshore Massachusetts to inland Georgia, were identified through indirect methods such as seismic surveys. They haven't yet been drilled or had their geologic properties mapped.

"We would really want to do some coring and surveying, particularly in the southern area," said lead author David Goldberg, a senior scientist at Columbia University's Lamont-Doherty Earth Observatory. "There are a lot of advantages if they bear out. They're close by, and they're offshore."

Goldberg said storing carbon in undersea basalt formations offers two key advantages: depth and security.

"It's on the continental shelf," Goldberg said. "The water is probably 100 meters, or 300 feet or so, and these layers go as deep as a mile below the sea bed."

Carbon dioxide would be collected from power plants, liquefied and sent to the storage sites via a pipeline, researchers said.

The liquefied carbon dioxide has to be placed at least 2,500 feet below the surface to prevent it from reverting to a gas and potentially leaking out to the surface.

The porous layers where researchers propose injecting carbon dioxide are thought to be thousands of feet below the surface and topped by dense rock that acts as a natural geologic cap.

Undersea sediments would act as an additional blanket, sealing off the reservoir from above, Goldberg said.

He said the Sandy Hook formation off the coast of New Jersey could potentially handle 40 years worth of emissions from three good-sized power plants.

Jeffrey Fitts, a geochemist at Brookhaven National Laboratory, cautioned that the potential human health and environmental risks of storing carbon dioxide underground were still being evaluated.

The expense and difficulty of studying underwater formations means it could be some time before it happens, said environmental engineer Pete McGrail.

He has studied carbon sequestration for more than a decade at the Pacific Northwest National Laboratory in Richland, Wash.

"I would look at this more as an opportunity that could come further down the road," he said, "after the first pilot studies and commercial projects on shore."