Thursday, September 24, 2009

Bury the carbon and set off a quake

It all looked so promising - tidy carbon dioxide away underground and forget about it. But even as the US's first large-scale sequestration operation is getting off the ground at the Mountaineer plant in West Virginia, geophysicists are concerned that burying the carbon could trigger earthquakes and tsunamis.

In a carbon sequestration power plant (CCS), CO2 is extracted from the exhaust then pumped into aquifers and old gas fields several kilometres beneath the Earth's surface. So far so good. But the CO2 expands as it rises through the porous rock, increasing pressure inside. "If enough CO2is injected into an aquifer, it could increase the pressure enough to reactivate a fault and trigger an earthquake," warns Andrew Chadwick of the British Geological Survey.

Chemical reactions between the injected CO2, water and rock could also destabilise the rock, says Ernest Majer, a seismologist at the Lawrence Berkeley National Laboratory in California who briefed the Senate on CCS hazards this week. "It's such a new technology that none of these issues have been addressed," says Majer. Even storage sites far from human settlements could have disastrous effects, warns Christian Klose, a geophysicist at the Think Geohazards consulting firm in California. A CCS facility at the Sleipner gas field in the North Sea, may have triggered a magnitude 4 earthquake in 2008. Had it been bigger, says Klose, it might have triggered a tsunami.

Shanta Barley

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