Gas hydrates on the front burner wide store of conventional fossil fuels, most gas hydrates are disseminated at low concentrations in fine-grained sediments unsuitable for exploitation, explains Tim Collett, a geologist with the U.S. Geological Survey and a contributor to the report. USGS
Gas hydrates were highly esoteric 30 years ago, but now countries are investing tens of millions of dollars in research on this topic. Although little is known about the role of gas hydrates in regulating climate, government and industry researchers in the U.S. and Canada are hoping to begin commercial exploitation of this unconventional fossil fuel within the next 10 years. But the looming question is whether people can use and manage this novel natural gas in ways that won’t add to climate destabilization, critics say. “If Canada ignores gas hydrates altogether, more damaging ways of meeting energy needs could be adopted, and Canada could lose out competitively to other countries, perhaps even to the point of having others exploit Canadian resources,” warns a July 7 report from the Council of Canadian Academies, a nonprofit organization. Released at the International Conference on Gas Hydrates in Vancouver, the report paints a picture of a resource that has great potential, yet poses big uncertainties. When methane encounters water under high pressure and low temperature, gas hydrates form as molecules of methane are enclosed in a crystalline cage of water molecules. The ideal conditions for generating gas hydrates, also known as methane hydrates or clathrates, are found in deep ocean sediments that ring the continental margins at 500-600 meters below sea level and in Arctic permafrost, says Charles Paull, a marine geologist at the Monterey Bay Aquarium Research Institute. Gas hydrates may contain the largest pool of carbon on earth; estimates of their extent range from 35,000 to 4,200,000 trillion cubic feet (Tcf) of methane, the report notes. Although the global volume may exceed the world-
The Mallik test site in Canada’s Northwest Territories taps a gas hydrate reservoir, deep beneath the permafrost, that might prove to be a source of methane.
“Methane hydrates are a big part of the earthsoceans atmosphere system that we know little about, and [they] have the potential for big impact,” says Neil Hamilton, director of the International Arctic Programme for WWF. Gas hydrates are in constant flux as microbes and geological processes generate methane that becomes trapped in ice, which in turn melts and releases methane into the environment, he explains. The liberated methane can feed microorganisms or enter the atmosphere, where it has 23 times the greenhouse warming power of CO2 over a 50-year period. Nevertheless, most climate models ignore gas hydrate dynamics, he says. But chronic seepage of methane into the atmosphere is very likely over the next century or
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more, Hamilton says. Gas hydrates are sensitive to changes in temperature and pressure, and as global climate change heats the shallow Arctic Ocean, gas hydrates could become unstable and release methane that would further accelerate climate change, he adds. Harvesting the gas hydrate for energy use is not likely to solve this problem. “It should also be noted that the exploitation of gas hydrate could not remove sufficient quantities from the earth’s crust to prevent the possible long-term dissociation of gas hydrate due to climate change,” the report’s authors write. Until now, oil and gas companies have been focused on gas hydrates primarily as a safety hazard to be avoided while drilling for conventional fuel, says Gordon Pospisil, technology and resource manager at BP Exploration, Inc. “BP is one of the few oil and gas companies active in hydrates research and development,” he says. BP drilled a gas hydrate test well in 2007 on Alaska’s North Slope, in partnership with the U.S. Department of Energy (DOE), and plans more tests. Enough concentrated gas hydrate deposits probably exist in coarse sand formations to rival conventional oil and gas deposits, Collett says. For instance, local accumulations as large as 35 Tcf occur on Alaska’s North Slope. “But, given the challenges, unlocking the potential of hydrates is likely to take at least 5-10 years,” Pospisil says. That timeline fits well with DOE’s goal of having technologies in place so that industry could begin extracting gas hydrates in Alaska by 2015. Meanwhile, at the Mallik test site in Canada’s Northwest Territories, researchers have sunk a well under the permafrost into a gas hydrate reservoir and drawn down the pressure to release the methane. A 6-day test in March
10.1021/es802250e
2008 American Chemical Society
Published on Web 08/27/2008
exploration program manager at DOE. “In less than 20 years, we need to move away from highcarbon fuels,” Hamilton adds. Gas hydrates could be used to make the transition to a sustainable energy mix, provided there is a way to document that they are replacing a high-carbon fuel, he says. Rather than simply adding hydrates to the current fossil-fuelbased mix, Hamilton suggests that global leaders reach a compromise on what level of CO2 in the atmosphere is safe, and then not exceed that level. “The key issue is that we can’t add methane hydrates to the existing fossil fuel resources because you start to increase atmospheric CO2 to levels that are really scary,” he says. —JANET PELLEY
HARRY TURNER/NRC-CNRC
sustained gas flows ranging from 70,000 to 140,000 cf per day (cf/ day), the report says. Gas hydrate production models predict that similar deposits could eventually yield several million cubic feet of gas per day, more than the 1 million cf/day found in average conventional Rocky Mountain wells, Collett says. So far, Japan, India, South Korea, and Chinasall large energy importerssare driving the research on gas hydrates, because they may have large deposits offshore, and they see the resource as a way to gain energy independence and security, Collett says. If clean-burning gas from hydrates were used to replace coal in electric power plants, CO2 emissions from the plants could be cut by half, says Edith Allison,
This chunk of gas hydrate, synthesized in the lab by scientists, looks like ice and burns like natural gas.
October 15, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 7551
