ST. PAUL — Public debate grew heated Thursday about Enbridge Energy’s plan to nearly double the capacity of its Alberta Clipper pipeline across northern Minnesota.

The pipeline now carries 450,000 barrels of Canadian crude oil daily through a corner of North Dakota and across Minnesota to Superior, Wis. The company wants the Minnesota Public Utilities Commission to approve an increased capacity of 800,000 barrels per day.

Several hundred activists rallied in St. Paul before speaking at a PUC hearing. They object because much of the oil that the pipeline carries comes from the oil sands of Alberta, and they say extracting and refining that oil is an energy-intensive process.

Beyond the risk of spills, opponents say increasing the pipeline’s capacity takes the United States in the wrong direction when it comes to tackling climate change.

“My hope is that someday I will be able to look at that future grandchild of mine in the eye and say, ‘See, we Americans can accomplish anything we put our hearts and minds to,”’ Carolyn Ham said at the hearing. “There is no need for this expansion, and I urge you to deny it.”

Enbridge spokeswoman Lorraine Little said the Alberta Clipper currently carries about 450,000 barrels per day across Minnesota.

“But it was built and designed to ultimately carry 800,000 barrels per day should the need or the demand from our customers arise,” Little said. “And now it’s arisen, and it’s arisen because refineries in North America want to have access to secure and reliable sources of North American crude oil.”

Many pipeline supporters at the hearing argued that the oil would continue flowing from Alberta’s oil sands even if Minnesotans don’t want it.

“The country runs on oil,” said Steven Shew, a plumber and pipefitter from Wisconsin. “Good, bad or indifferent that’s the way it is and that’s the way it’s going to be for awhile.”

Shew said the project will create good paying jobs and help the country avoid another oil crisis like the one in the 1970s.

“I don’t want to see my kids have to go through that uncertainty of what it does economically, the recessions it created because somebody over across the pond decides to turn our oil off,” he said.