A plan to pipe carbon dioxide from Alberta's oilsands and store it underground could cost as much as $5 billion, says Alberta's environment minister.

The province wants to capture carbon dioxide and send it through a 400-kilometre pipeline. Intergovernmental Affairs Minister Guy Boutilier said earlier this month that the pipeline would cost $1.5 billion and the carbon dioxide would be used to help get more oil out of low-producing wells.

He was pushing for the federal government and industry to split the cost of the project.

But Environment Minister Rob Renner suggested Wednesday it could cost much more.

"The number of $1.5 billion has been floated," Renner said. "I suspect that the number — all costs included — will be significantly higher than that.

"I've seen estimates as high as $5 billion by the time it has taken into account the cost to industry to implement the [carbon] capture facilities."

In a joint news conference in Edmonton last week, Prime Minister Stephen Harper and Alberta Premier Ed Stelmach lauded the plan to capture carbon dioxide, something that's already being done with smaller projects on the Prairies.

Harper called it "a dream that could truly change the world."

Stelmach has struck a committee to look at the pros, cons and costs of expanding the process to a large scale. Renner said Wednesday that the committee will also look at who would foot the bill for the pipeline.

Critics call idea unproven and costly

Alberta Liberal energy critic David Swann said the government shouldn't be looking at exotic solutions when they could just tell industry to cut emissions.

"We need to be really serious with reducing, not simply patching up with technology the issues that we have created," he said.

Brian Mason of the New Democrats said the plan was ill conceived from the start.

"We're going to sink billions of dollars into an unproven approach whose main rationale seems to be to allow industry to continue to increase C02 emissions because we are going to fix it, pipe it all away."

Total greenhouse gas emissions in Alberta have increased by 39.4 per cent from 168.17 megatons in 1990 to 234.51 megatons in 2004, according to Environment Canada.

With files from the Canadian Press