TEMPE, Ariz. -- With its dented metal cylinders, rust-colored tanks and network of silver tubing, the Goldwater Materials Science Laboratory at Arizona State University does not look especially high-tech. But if an ongoing experiment there succeeds, this unassuming basement facility near Phoenix could offer a partial way out of the nation's greenhouse-gas problems.
Americans' prodigious energy use -- from the gas that fuels massive SUVs to the coal that keeps the light and heat on in sprawling suburban homes -- comes at a cost. Burning fuel spews carbon dioxide (CO
) into the air, which in turn traps heat and, most scientists believe, is accelerating global climate change that is melting glaciers, altering animals' breeding and migration patterns, and boosting temperatures around the globe.
Some scientists favor "carbon sequestration" using trees, which absorb carbon dioxide, as in a project underway along the Neches River in Texas.
But many business leaders and top policymakers, including President Bush, reject the idea of imposing mandatory limits on carbon dioxide emissions because, they contend, it could hurt the U.S. economy. As one alternative, some scientists, funded by government and private industry, are exploring whether they can extract carbon dioxide from the air in meaningful amounts and trap it underground, beneath the sea or on land.
But scientists are deeply divided on whether "carbon sequestration" can make a dent in the buildup of carbon dioxide in the atmosphere. Advocates say it could at least mitigate the impact of humans' insatiable hunger for cheap fossil fuels, which provide 85 percent of the globe's commercial energy. Critics say it is an unrealistic and shortsighted response to a problem that requires politicians to make hard economic choices.
Howard J. Herzog, a chemical engineer at the Massachusetts Institute of Technology who has studied the subject for more than 15 years, said sequestration methods are "not an answer to the problem" of global warming but "they're part of the answer to the problem."
"This is not 'We're going to be able to have our cake and eat it, too,' " he said. "This is one problem that's extremely hard to solve."
Experts have spent years trying to limit emissions from power plants and other sources, and the effort has taken on growing urgency as more studies suggest that industrial activity is building up ominous levels of greenhouse gases. Since preindustrial times, the atmospheric concentration of carbon dioxide has increased 33 percent, according to the United Nations' Intergovernmental Panel on Climate Change, which also projects that worldwide CO
emissions could triple over the next century.
The Bush administration is spending tens of millions of dollars on research projects such as the one at Arizona State. In its new budget, the White House is seeking $107.4 million for sequestration studies at the Energy Department, which is currently funding 65 projects at an annual cost of $80 million. The Agriculture Department is spending an additional $18 million a year on carbon research and sequestration projects and seeking $3 million more. The government also plans to spend $550 million in the coming decade on FutureGen, a coal-fired power plant that will capture all carbon dioxide emissions on site.
David Conover, senior policy adviser to Energy Secretary Samuel W. Bodman, calls carbon sequestration "a very realistic option."
"Just like any other technology," Conover said, "the key is to reduce the cost."
There are a number of ways to capture and store carbon dioxide, including pumping it into depleted oil and gas fields or deep saline aquifers, converting it into stable carbonate minerals, and planting trees to absorb it. But scientists are a long way from a cheap and effective option that will ensure the carbon will stay put.
Arizona State professors Andrew Chizmeshya and Michael McKelvy, who work in the Goldwater lab, neutralize CO
by combining it at high heat with serpentine or olivine, two common minerals, in what they call "a dirty soda pop" -- a solution of water, sodium chloride and sodium bicarbonate. The reaction produces magnesium carbonate, a stable substance that can be buried, turned into road pavement or stored in other ways.
"What we're trying to do is take what nature does over 100,000 years and do it in less than an hour for 10 bucks a ton" of sequestered carbon, McKelvy said.
But right now, it costs about $70 a ton. The two researchers, who are working with more than a dozen other scientists in four other laboratories, are trying to make the reaction cheaper by breaking down a coating that forms over the minerals during the conversion process.