CALGARY, Alberta - Canada's government saw only limited opportunities to cut greenhouse gas emissions from the oil sands using carbon capture and storage technology, according to briefing notes obtained by a Canadian media.

The notes, prepared by a carbon capture task force, were used by Canadian federal and provincial politicians and were obtained by the Canadian Broadcasting Corp, which said it requested them under freedom of information legislation.

Carbon capture and storage would see carbon-dioxide removed from the emissions of oil sands upgraders that turn tar-like bitumen into refinery-ready synthetic crude. The captured CO2 would be put into underground reservoirs for permanent storage instead of being pumped into the atmosphere.

The government of Alberta and the federal government are touting carbon capture and storage (CCS) as a way clean up emissions from huge energy projects in the northern Alberta oil sands region, which contains some 173 billion barrels of tar-like bitumen.

Earlier this year Alberta set aside C$2 billion (to fund CCS projects from big emitters like oil sands upgraders and power plants

But the briefing notes say the technology offers only limited solutions to greenhouse gas emissions from oil sands projects.

"Only a small percentage of emitted CO2 is 'capturable' since most emissions aren't pure enough," said a copy of the note that was posted on the CBC website. "Only limited near-term opportunities exist in the oil sands and they largely relate to the upgrader facilities."

It also said that the projects will be expensive and government will have legal liability for stored carbon-dioxide.

Some critics say the briefing notes are only acknowledging what is already known: that the technology is expensive and may not mitigate carbon emissions for the oil sands.

"This is technology that will require massive subsidies," said Dave Martin, climate and energy co-ordinator for Greenpeace "This is a boondoggle of the first order."

Still, the Alberta government is backing the technology as a way to ensure that oil sands projects don't face sanctions from any climate change legislation introduced in the United States, which buys most of Canada's oil exports.

"It's well known that there are some challenges in capturing emissions at oil sands facilities," said Jason Chance, a spokesman for Alberta's energy department. "But what our own analysis tells us is still up to 75 percent of oil sands (emissions) are capturable."

($1=$1.23 Canadian)

Reporting by Scott Haggett; editing by Rob Wilson