A new idea to fight global warming / CO2 emissions could be liquefied, pumped under sea
Published 4:00 am, Friday, August 11, 2006
Global warming could be slowed by injecting carbon dioxide into the Earth's crust -- perhaps in oceanic sediments that surround the U.S. coastline, according to a new scientific report.
The United States has enough coastline to bury thousands of years' worth of carbon dioxide emissions from factories and other stationary sources, scientists report in the most recent issue of the Proceedings of the National Academy of Sciences. They propose liquefying the gas and burying it under several hundred feet of sediment. Those sediments -- located off both East and West coasts -- are beneath ocean waters about 2 miles deep.
For years, experts have also investigated and tested ways to bury carbon dioxide underground on land, for example by squirting it into abandoned oil wells. President Bush has mentioned so-called "carbon sequestration" as one potential answer to climate change.
But some environmentalists argue there are better, cheaper and more immediate solutions to global warming, such as energy conservation.
Some scientists believe carbon sequestration is worth additional study because the planet will probably continue burning fossil fuels for decades. The burning of fossil fuels in cars, factories and elsewhere generates greenhouse gases, notably carbon dioxide, which absorb infrared radiation that would otherwise escape into outer space.
Kurt Z. House, a Harvard University scientist and lead author of the study, said such deep-sea burial might safely dispose of from one-third to half of the carbon dioxide generated annually by the United States.
However, the downsides are steep. For one thing, he said, managing a nationwide carbon dioxide sequestration program could cost hundreds of billions of dollars a year. Funding it might require levying a tax of up to $50 a ton on carbon dioxide producers, he said. The average U.S. resident emits about 20 tons a year of carbon dioxide by doing things like driving a car or heating homes with natural gas.
Offshore seabeds are cold enough to keep liquid carbon dioxide from reverting back to a gas and leaking to the surface, House said. At that depth, carbon dioxide will stay liquefied up to 80 degrees, he calculated.
By contrast, on land, Earth's crust tends to be warmer, which means that carbon dioxide buried there is likelier to try to force its way through cracks and fissures, according to the article printed Tuesday.
Still, "I certainly wouldn't want to go as far as say we've solved global warming" with their proposal to bury carbon dioxide along U.S. coastlines, House said. Carbon sequestration is expensive and "would require a pretty stiff policy like a carbon tax to motivate (people to use) this (sequestration) technology."
Factories and other stationary sources emit about 7 billion tons of carbon dioxide per year, House said. He estimates that trapping and burying that much carbon dioxide could cost between $150 billion and $200 billion a year.
Authors of the Proceedings article include House, a doctoral candidate in geoscience; his Harvard colleague Daniel P. Schrag; Charles F. Harvey of MIT; and Klaus S. Lackner of Columbia University.
Ken Caldeira, a climate scientist at the Carnegie Institution's branch institute at Stanford University, expressed a mixed view. On the one hand, he said, carbon sequestration appears to be a safe way to store emissions, possibly for millions of years.
Yet "there are still questions about whether the approach is technically feasible. Nobody has ever tried to do this before," Caldeira said.
The environmental group Greenpeace attacked the idea, calling it an unproved and expensive technology.
Chris Miller, a senior campaigner for Greenpeace USA, said what's really needed is more investment in renewable energy like solar and wind power.
Peter Brewer, an ocean chemist at Monterey Bay Aquarium Research Institute who has investigated carbon sequestration, is cautious. On the one hand, he said, "it's a fascinating research area. It's important that we look at these things; otherwise society speculates forever instead of having hard knowledge to make decisions," he said.
Right now, he added, "the big challenge is, how can we do it economically? The disposal in the ground is not the major cost -- the major cost is capturing the carbon dioxide from the power plant.
"And you have to be careful which ground to put it in. Some geological areas are more safe than others."