Fighting global warming by burying carbon dioxide

By EDIE LAU
Monday, February 12, 2007

Deep beneath the fertile soil of California's Central Valley lies what some scientists believe may be part of the defense against global warming.

Instead of letting carbon dioxide flow into the atmosphere where it traps heat, the idea goes, people could bury the gas underground.

An experiment led by the California Energy Commission aims to bury a sample of carbon dioxide somewhere near the town of Thornton, possibly as soon as this spring.

"The 21st century is here, and we're using modern tools to cure the environment," said Adam Gottlieb, a commission spokesman.

The project is one of several by a government industry coalition called West Coast Regional Carbon Sequestration Partnership, or WESTCARB, that is exploring the feasibility of stashing carbon dioxide underground.

WESTCARB is looking at two underground test sites, one in Arizona, the other in California. It has zeroed in on the Sacramento/San Joaquin Valley because of the local geology.

Below Earth's surface, impermeable caps of shale rock overlie layers of porous sandstone that once held natural deposits of gas and oil.

"The oil and gas reservoirs are good candidates because they have held oil and gas for ... millions of years," said Larry Myer, an earth scientist at Lawrence Berkeley National Laboratory and WESTCARB's technical director.

In other words, the land already has shown that it can store carbon-rich matter for a very long time.

That's important, because one of the worries about sequestering carbon underground is that it might leak out.

Project leaders and other proponents of geologic carbon storage say that the likelihood of a catastrophic eruption of gas is low to near-impossible.

"If you inject it into a reservoir full of cracks and pore spaces, the friction and forces that bind it into those cracks limit the rate at which it can escape," said Daniel Schrag, a professor of earth and planetary sciences and director of the Harvard University Center for the Environment.

"It's not like it's a giant cavern sitting underground that, take off the cork, and all of a sudden, kaboom!" he said.

A slow leak, which is more possible, is a problem only because it would defeat the purpose of preventing gas from entering the atmosphere, Schrag said.

Carbon dioxide, or CO2, is a ubiquitous gas essential to life. Plants take up CO2 to make energy from the sun, in the process releasing oxygen. Humans and other animals breathe in oxygen and exhale CO2, forming a mutually beneficial relationship with plants.

Yet CO2 increasingly is viewed as a pollutant because human activities _ chiefly the burning of coal, oil and other fossil fuels _ have altered the concentration of the gas in the air.

Carbon dioxide traps heat in the atmosphere _ a good thing in moderation and bad in excess _ in the same way that a measure of water is needed for life but a flood can destroy and kill.

The more CO2 and other heat-trapping gases accumulate in the atmosphere, the greater the chance of disrupting global climate patterns.

Schrag said that because humankind gets 85 percent of its energy from fossil fuels, solving climate change will require a three-pronged effort: cutting energy use through better efficiency and changing lifestyles; expanding use of energy sources that don't put carbon into the atmosphere, such as solar, wind and nuclear; and capturing the carbon dioxide from fossil fuel-burning and storing it.

WESTCARB is one of seven research partnerships formed by the U.S. Department of Energy to study carbon sequestration.

Worldwide, Myer said, two commercial CO2 storage projects are in place, one below the bottom of the North Sea by the Norwegian energy company Statoil; the other in Algeria by the energy company BP.

In each case, about 1 million metric tons of CO2 are injected underground each year, he said.

The Thornton project is tiny by comparison. Only 2,000 metric tons of CO2 will go into the ground.