The hitch was the cost.

Electricity prices could typically rise by 25-80 percent if power plant operators, the most promising users, adopted the technology, according to the report by the UN's Intergovernmental Panel on Climate Change (IPCC).

"While the most important solutions to climate change will remain energy efficiency and cleaner energy sources ... capturing and storing carbon dioxide can supplement these other efforts," said Klaus Toepfer, head of of the UN Environment Programme.

If exploited via hundreds of thousands of storage sites around the world, the system could make up 15-55 percent of total projected cuts in emissions of greenhouse gases needed to offset climate change by 2100, the report estimated.

Other IPCC reports project that greenhouse gases from human activities may wreak havoc with the climate by 2100, spurring more powerful storms, desertification and rising sea levels. In turn, thousands of species could be driven to extinction.

To combat the warming, Monday's report said that carbon dioxide emissions needed to cost at least $25-30 a tonne for the capture and storage technologies to work. Three projects were in operation -- in Canada, Algeria and off Norway, it said.

PRICE SPUR

"We are very aware that there are non-technology constraints," Toepfer said in a briefing in Montreal broadcast on the Internet.

"One is that if you have no price, no limitation of carbon dioxide, you don't have the demand for those technologies."

In the European Union, carbon dioxide traded on Monday at 21.4 euros ($25.80) a tonne in a market backing up an EU implementation of the UN's Kyoto protocol capping emissions of carbon dioxide.

In the United States, where President George W. Bush pulled out of Kyoto in 2001, carbon dioxide is not rated a pollutant. Bush said Kyoto would cost too much and wrongly excluded developing nations from a first round of cuts to 2012.

The report said that generating electricity now costs about $0.04-$0.06 a kilowatt hour.

Using existing carbon capture and storage technology would add $0.01-$0.05 per kilowatt hour, it said. Costs could be slightly lower if carbon dioxide were injected into oilfields, helping raise pressure to force more oil to the surface.

Still, the report said that carbon storage could be up to 30 percent cheaper than some alternative strategies for fighting climate change.

Rajendra Pachauri, chairman of the IPCC, said the report was "a starting point. There's much more to be done".

And there are legal hurdles. Some environmental groups including Greenpeace say burying carbon dioxide could violate anti-dumping conventions.

"There are still far too many questions about environmental risk, safety and costs," said Gabriela von Goerne, a Greenpeace climate and energy expert.