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The fight against global warming in every which way possible has been resumed under the Obama administration. The Energy Department has revived the carbon burial project, earlier put on the backburner.

Carbon capture and burial from power plants and heavy industry holds promise to play a role in fighting emissions of the main gas blamed for global warming, but is expensive and unproven on a commercial scale. Last year the U.S. Department of Energy pulled funding for the FutureGen Alliance, a proposed carbon capture and sequestration plant, citing rising costs.

The start of drilling in Illinois Sunday marks the launch a geological sequestration project that will deposit a million metric tons of carbon dioxide into the ground by 2012.

While that's nothing compared to the several billion tons of CO2 that humans emit yearly, it's the geology of the site that makes the development exciting. The CO2 will be piped into a geological formation that underlies parts of Illinois, Indiana and Kentucky that could eventually hold more than 100 billion tons of CO2.

"This is going to be a large-scale injection of 1 million metric tons, one of the largest injections to date in the U.S." project manager Robert Finley said here at the American Association for the Advancement of Science meeting Sunday.

While the Department of Energy and private industry have been pushing to create cheaper renewable energy and investigating increased nuclear-power options to reduce carbon emissions, carbon capture and sequestration remains an attractive idea. It would allow regions of the country like the southeast, which don't have Texas or California-level wind or solar resources, to continue burning coal without contributing to climate change.

To do that, many technological issues will need to be solved. Some utility executives have questioned whether storing CO2 will actually make sense. The Intergovernmental Panel on Climate Change (IPCC) estimated that as much as 30 percent of the energy created by a coal plant would have to be spent on just pulling the CO2 out of its flue gas, writes Alexis Madrigal on Wired.

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The technology—carbon capture and storage (CCS)— has the capacity to curb global carbon emissions by about a third, analysts say, given that it can remove around 90% of all carbon from fossil fuel-fired power plants, which in turn account for about 40% of all carbon emissions.

Economically, CCS could also have applications beyond cleaning up coal-fired power plants, for example, helping develop low carbon-emitting transport fuels from wood, trap CO2 emissions from oil refining, or produce hydrogen fuel for cars.

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Several US states have required that all new coal-fired power plants have the “capability” for CCS.

“The problem is that the carbon capture technology isn’t here yet,” a spokesman for the office of fossil fuel energy at the US Department of Energy had said last year.

“It is remarkably difficult to define exactly what it is,” said a spokeswoman for Britain’s department for business enterprise and regulatory reform, referring to the ‘CCS ready’ label.

Some environmentalists dislike CCS, as well as coal, because they say it is a distraction from a drive to develop non-fossil fuel energy, and leaks may wipe out the point of burying gases.  

But new materials for more selectively capturing CO2 from gas mixes continue to be created in labs like Omar Yaghi's at University of California, Los Angeles and at Georgia Tech under Chris Jones. Those innovations could make the capture part of "carbon capture and sequestration" easier than it currently is. Add in a carbon tax of some form and fossil-fuel power plant operators would have the incentive to start capturing a lot of carbon dioxide. Then, they'll just need somewhere to put it.

The DOE thinks the United States has more than enough underground closet space.

"What we found in the U.S. with the research that we've done over the last 10 years is that there is a significant potential to store CO2 ... in these very large reservoirs that are underground," said John Litynski, who works in the fossil-fuel-centered National Energy Technology Laboratory's Sequestration Division.

But most current sequestration projects use the carbon dioxide to squeeze more oil and gas out of depleted fields. Those fields probably won't cut it for much larger amounts of CO2. For that, they will have to turn to huge reservoirs deeper underground. That's why the Illinois demonstration project is so important. It will test a formation called the Mt. Simon sandstone, allowing scientists to track in near real-time what happens when they start putting large amounts of compressed carbon dioxide 6,500 feet below the surface.

"We have numbers for what we think the capacity is in the U.S., but the only way to prove that is to actually drill a well," said Litynski.

Drilling a 6,500-foot well doesn't come cheap — the Mt. Simon project has a, $84 million price tag. It's a collaboration between the DOE and industrial partners including Archer Daniels Midland, which is providing the land for the test site and will serve up CO2 from its ethanol fermenters. A group of scientists from state U.S. Geological Survey known as the Midwest Geological Carbon Sequestration Consortium are leading the research.

They'll collect enormous amounts of data about how the CO2 plume moves through the pores in the sandstone. The Mt. Simon formation is particularly attractive because of a series of fortuitous events that have placed three layers of impermeable rock — known as "cap rock" — between the sandstone and the surface. Finley thinks that makes the project a very good bet to succeed in keeping CO2 buried away for what amounts to forever in human timescales.

Estimates of worldwide storage capacity range from 2 trillion to 10 trillion tons of carbon dioxide, according to the Intergovernmental Panel on Climate Change (IPCC) in its report on carbon capture and storage. Global emissions in 2004 totaled 27 billion tons, according to the U.S. Department of Energy's Energy Information Administration.

If all human-induced emissions were sequestered, enough capacity would exist to accommodate more than 100 years' worth of emissions, according to Benson, coordinating lead author of the IPCC chapter on underground geological storage.

With fossil fuels already comprising 85 percent of the world's energy consumption, and their use rapidly increasing due to the growth of developing countries, such as China and India, the need to find solutions to curb carbon emissions becomes even more crucial, Benson had observed.

''The goal of carbon sequestration is to permanently store the carbon dioxide,'' Benson said, ''permanent meaning very, very long-term, geological time periods.''

The greatest concern surrounding carbon dioxide storage is the potential for it to leak, researchers said.

The most obvious worry, said Benson, was that leakage would lead to more global warming, defeating the purpose of storage in the first place.

Of greater concern to the researchers were the potential risks of carbon sequestration to human health, mainly through asphyxiation and groundwater contamination.

The threat of asphyxiation-or suffocation due to carbon dioxide displacing oxygen-is very low, the researchers said, because of the unlikelihood of a rapid leakage, which would have to occur to cause a problem.

Drinking water contamination, Benson said, was the more probable danger. For example, if carbon dioxide enters the groundwater somehow, it can increase the water's acidity, potentially leaching toxic chemicals, such as lead, from rocks into the water, she said.

To address these risks, scientists are studying reservoir geology to better understand what happens after injecting carbon dioxide underground.

''We need thousands of projects,'' Benson said. ''That's the kind of thing that will only happen if there are global policies to address these issues. That's the number one critical thing.''

With the proper development, Benson believes that carbon sequestration could be ripe for industry in the next 20 years.

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