Material injected near Price will be methane taken from from coal beds. In the test, some of the gases will be captured and injected deep underground. The program should show whether capture and sequestration is efficient.

McPherson does not see safety as a big concern.

That isn't to say carbon dioxide is a benign gas. As a San Diego State University Web site records, in August 1986, "a cloudy mixture of carbon dioxide and water droplets rose violently from Lake Nyos, Cameroon (Africa). As the lethal mist swept down adjacent valleys, it killed over 1,700 people, thousands of cattle, and many more birds and animals."

Venting like that is not seen as likely in the carbon sequestration.

McPherson points out that produced water — briny water from oil and gas wells, often containing carbon dioxide, oil and salts — "is injected into the subsurface all the time."

Commercial sequestration may require pumping carbon dioxide to a depth of 8,000 or 10,000 feet. A formation targeted for the liquefied gas would have highly porous rock, saline groundwater that wouldn't be usable, and "thousands of feet of shale or other low-permeability rocks" over it as a cap. Salt might work, too, McPherson said.

"We've actually found that a great deal of what's called sedimentary basins, which exist in all states of the western U.S. — those are the best places. ...

"Generally the injection would take place over a long period of time," he added. In several years, when the job of an injection well is finished, it would be capped. "Frequent, regular monitoring protocols would be indicated," he said.

New seismic imaging technology would give monitors a view of what is going on in depth.

Capture and sequestration requires energy, and the question is whether the process is economically viable.

"If you have enough money anything can be done, of course. But for specific types of power plants, the maximum estimated increase to cost of electricity would be about 20 percent," McPherson said.

That much added to a power bill may seem daunting. Although the federal government might add incentives such as tax breaks, "obviously you've added something to the system, the cost is going to go up."

The expense of capturing the gas is four times the expense of injection and storage, he said. "But that cost is going down because more and more research is going into it."

Altogether, electrical power costs eventually could rise by 10 percent because of capture and sequestration, once the system is ready, in his opinion.

Asked when the process can be carried out on a commercial scale, McPherson said, "I think it's going to be five or 10 years."

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E-mail: bau@desnews.com