Each day from a natural gas plant in central North Dakota, 5,000 tons of compressed carbon dioxide flow beneath the prairie, through 200 miles of pipes, to an oil field in Saskatchewan, Canada.
There, the carbon dioxide is pumped nearly a mile below ground into depleted oil reservoirs, where it is expected to remain for thousands, if not millions of years, away from the Earth's atmosphere and climate.
Most efforts at cutting emissions of carbon dioxide - one of the main "greenhouse gases" contributing to the world's rising temperatures - take one of two approaches. One is developing alternative energy sources, such as nuclear and solar power, that do not produce greenhouse gases. The other is trimming energy consumption through conservation and higher-efficiency appliances and automobiles.
Now scientists and policy-makers are exploring a third strategy: snaring carbon dioxide out of the smokestacks before it reaches the air and then storing it in the ground or deep ocean.
In his remarks Monday about global warming, President Bush said, "We all believe technology offers great promise to significantly reduce emissions, especially carbon capture, storage and sequestration technologies."
That could help the Bush administration reconcile the divergent goals of its energy and climate policies, enabling the construction of fossil fuel-burning power plants while cutting greenhouse gas emissions.
"If you want to stabilize CO2 emissions over a long period of time, we think carbon sequestration is essential," said Robert S. Kripowicz, acting assistant secretary of energy for fossil energy.
But not all the technologies are ready, and financing of research in the United States remains relatively modest, about $40 million a year. As acknowledged by Bush, carbon-dioxide scrubbers are too expensive. The Department of Energy has set $2.75 as a reasonable cost for storing a ton of carbon dioxide. Technologies cost 15 to 20 times as much.
The science of what happens to the sequestered carbon dioxide is also incomplete.
A small quantity of carbon dioxide is harmless - it provides the fizz in soda - but a cloud of it can be deadly, as in 1986 when carbon dioxide-rich waters from a lake in Cameroon in west Africa suddenly welled to the surface and suffocated 1,700 people in nearby villages. Most scientists contend a sudden, catastrophic release of carbon dioxide from a storage site is unlikely, but environmentalists worry that the carbon dioxide could harm nearby ecosystems, particularly if it is injected into the oceans.
