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A global threat buried

The Times: A global threat buried

By Anjana Ahuja

May 20, 2004

Energy companies hope that carbon dioxide — the ‘villain’ of global warming — can be stored safely in underground rock formations for thousands of years. Problem solved?

JUST EAST of Houston, Texas, lies an abandoned oilfield. It may be barren but it is by no means redundant. It has just become a testing ground for a technology that could prove crucial in the decades ahead.

American scientists have started trucking in lorryloads of liquefied carbon dioxide from a nearby BP oil refinery and pumping it into the rocks that lie above the emptied oil reservoir. Once underground, the theory goes, the gas will invade the mile-deep alternating layers of sand and shale, and push out the salty water that currently fills its pores. Barring any leakages, the gas will remain there for thousands of years, supposedly safely tucked away from the atmosphere and so unable to contribute to climate change.

Carbon dioxide is the villain in the drama of global warming. While efforts such as the Kyoto Protocol have focused on getting countries to reduce their greenhouse gas emissions in the future, scientists claim that the pollutants currently being produced must also be dealt with. The answer, some geologists argue, is to trap them underground.

This Texan experiment in so-called carbon sequestration — capturing carbon at its point of production and keeping it hidden from the atmosphere — is called the Frio Pilot Test after the Frio Formation, the saline aquifer (water-holding rock) atop the oilfield that will hold the gas.

The idea of dumping carbon dioxide underground is not new. Since 1996 Esso and Statoil have been taking the carbon produced by the Sleipner West natural gas field off Norway and injecting it into the Utsira Sand, a saline aquifer underneath the North Sea, but until now the technique has not been tried on land. Environmental groups such as Greenpeace and Friends of the Earth condemned the Norwegian experiment as a “dangerous distraction”, claiming that leakages could destroy marine life and cause a runaway greenhouse effect. They also dispute that stowing carbon underground can make anything but a small difference to long-term efforts to stem climate change.

Trapping carbon dioxide in underground rocks is far from untested, though. The technique is already used by oil companies to squeeze every last drop from dwindling reservoirs. The principle is the same — carbon dioxide is pumped in to flush out the oil. The carbon dioxide stays put, giving encouragement to geologists who believe that rock formations really can solve the problem.

“While we expect the (carbon dioxide) plume to spread out over a few hundred metres, it should stay buried for thousands of years,” says Larry Myer, an engineer at the Lawrence Berkeley Laboratory, which, along with the Oak Ridge National Laboratory, will monitor the Texas site for leaks. “The risk of leakage is critical when storing carbon in brine formations, but I’m optimistic that our test results will show that these formations are safe for carbon sequestration.”

The Frio Formation is capped with a thick layer of shale, which should keep a lid on leaks. Sideways seepage is expected to be contained by faults at the formation’s edges. Statoil says that the carbon dioxide stored in the Sleipner experiment has not leaked.

The figures certainly look encouraging — an estimated seven billion tonnes of carbon dioxide is created globally by human activity each year. According to Susan Hovorka, a geologist with the Texas Bureau of Economic Geology, which is leading the Frio Pilot Test, the Frio Formation alone can hold between 200 and 350 billion tonnes of carbon dioxide, or at least 28 years’ worth. In the US alone there are an estimated 60,000 similar formations, providing a potential dumping ground for centuries. The Utsira Sand could hold all the carbon dioxide produced by Europe’s fossil fuel power stations for 800 years.

That, say green groups, is partly the problem — as long as there is a place to banish unwanted carbon, there is little incentive to stop producing it. However, energy companies reject the “out of sight, out of mind” argument. They prefer to call carbon sequestration a “bridging technology” that will ease the transition to cleaner energy sources while meeting soaring demand, especially from the developing world.

The CO2 Capture Project — a consortium of, among others, Shell, BP, Statoil, ChevronTexaco, the US Department of Energy and the EU — is optimistic about underground carbon storage. It says that it “intends to address the issue of reducing emissions in a manner that will contribute to an environmentally acceptable and competitively priced continuous energy supply for the world”.

Offshore carbon storage might one day become an option for Britain — in which case, says Dr Simon Shackley, from the Tyndall Centre for Climate Change Research in Manchester, the public needs to be involved now.

“Our research team interviewed 200 people about carbon capture and storage (CCS) and nobody had ever heard of it,” he says. “They said it sounded dangerous and unnecessary. But when we explained the problem of emissions, they came round a bit.

“They don’t like the idea of a quick fix or burying the problem. Most people would rather see a move to renewables and improved energy efficiency, but understand that CCS could solve a problem over the next few decades. People are more inclined to accept it as part of a package of measures, policies and ideas.

“Compared with America, the British Government hasn’t put much money into it, and we do need a proper risk assessment because carbon dioxide leakages could be harmful to health and ecosystems. The only way to learn is to do trials. But we need to have a proper public dialogue now.

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