The technology would capture carbon dioxide released by power plants or other factories, transport it and bury it underground -- either in old oil fields or coal mines, or even at the bottom of the ocean.

Once the gas is buried, it would no longer contribute to global warming.

"That is among the options" being considered by UN experts meeting in Bangkok to find ways to ease the harshest effects of climate change, according to Renaud Crassous, a French delegate at the meeting in Bangkok.

The still-experimental technology would cut about 35 percent of the carbon dioxide emissions from steel mills, cement plants and power plants.

In 2004, those industries released some 29 billion tonnes of CO2 into the air, Crassous told AFP on the sidelines of the Bangkok meeting.

A draft of the report by UN experts on the Intergovernmental Panel on Climate Change (IPCC), obtained by AFP, highlights the interest in developing this technology for coal-fired power plants of the future.

Rapidly developing countries like China and India are expected to rely on coal and other fossil fuels to power their development for years to come.

"There is no point to go to China and say 'stop coal.' They would laugh at you," said Stephan Singer of the World Wildlife Fund.

"We must invest as soon as possible into the feasibility of carbon capture and storage," he said.

"We need investment, much investment, and as soon as possible, to look into where it can be stored."

Europe and the United States are already experimenting with the technology.

In the North Sea, Norwegian oil giant Statoil injects CO2 into an underwater cavern some 1,000 metres (3,300 feet) below the ocean floor.

In Poland, the European Recopol project plans to store CO2 in a coal mine.

And in Denmark, the Castor project led by the French Institute of Oil is developing another "CO2 trap."

The United States has developed its own carbon capture and storage programmes, according to Tom Shope, the acting assistant secretary for fossil energy in the US Department of Energy, in a recent paper.

So far, no one has proved if the technology would be economically viable on a large scale. The current cost of such a system would have to be greatly reduced to make it workable for big industries.

Environmental activists worry about the risks of storing the carbon dioxide, fearing that the gas could burst into the atmosphere if the underground caverns ever cracked.

"A burst of CO2 could be fatal, even though carbon dioxide is not poisonous," Greenpeace said in a report on renewable energy.

"CO2 concentrations of seven or eight percent in the atmosphere could cause death by suffocation in 30 to 60 minutes," the report said.

The technology will not be ready until 2020, and modernising power plants with this type of equipment would be expensive, the group said.

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