PORTLAND — Although there still isn’t a formal proposal to pipe “tar sands” from Alberta, Canada, to Portland Harbor, the province sent a delegation Monday to counter critics of the practice.

Diana McQueen, the Alberta minister of  environment and sustainable resource development, visited the city to meet with lawmakers and discuss the province’s experiences with tar sands and its strategy for environmental management.

“When there’s a policy that affects the use of Alberta (tar) sands, it’s important that people have the facts,” McQueen said.

Alberta is home to the world’s third-largest proven reserve of oil, and nearly all of it is tar sands, a sludge-like mixture of sand, oil, clay and an oil known as bitumen.

Some environmental advocates say Canadian energy company Enbridge intends to pump tar sands 236 miles through the 72-year-old Portland-Montreal Pipeline. But because it is more corrosive than other forms of crude oil, the advocates claim, the thick goo could damage the pipeline and endanger water resources, including Sebago Lake and Casco Bay.

Environmentalists also claim that increasing the extraction, refining and eventual use of tar sands will increase greenhouse gas emissions and be a disastrous “game-changer” for the earth’s climate.

Dangers like these drew hundreds of people to Portland streets in protest last month, and led the City Council to consider – but ultimately table – a proposal to ban the city’s use of fuel derived from tar sands.

At a breakfast meeting Monday at the Portland Regency Hotel, McQueeen said Alberta tar sands account for only a tiny percentage of greenhouse gas, and that the province has stringent industry regulations and monitoring protocols to minimize the danger of pipeline leaks.

“Developing (tar) sands is important to Alberta, but what’s equally important is our environment,” she said.

But industry regulations can do little to clean up a tar-sands spill, according to City Councilor Dave Marshall, who chairs the Transportation, Energy and Sustainability Committee that drafted the council’s proposed ban.

In the event of a spill in a body of water, the heavy oil would sink to the bottom, where it would be almost impossible to remove, he said. Unlike oil spills of light crude oil, “you can’t boom it, you can’t skim it, you can’t evaporate it away.

“My concern is that we don’t have the technology to clean it up, ” said Marshall, who was one of about a dozen people invited by the Consulate General of Canada to New England to meet with McQueen. “You can put the responsibility on industry to do that, but you’re still going to have a polluted body of water.”

Marshall mentioned a much-publicized 2010 pipeline burst that spilled millions of gallons of tar-sands oil into the Kalamazoo River in Michigan. But that spill was unique and largely the result of operator error, said Tristan Sangret, another Alberta official at the meeting.

In response to a question from state Sen. James Boyle, D-Gorham, Sangret also explained that because tar sands are diluted and processed before they are transported, they’re no more corrosive than other crude oil.

“Basically, by the time (tar sands) leave the plant gate,” he said, “they’re a diluted heavy oil that meets pipeline specs.”

Sangret also said that a study released Monday by Penspen Integrity, a British pipeline company, was new proof that tar sands are no more corrosive than other crudes.

As the meeting wound up, McQueen urged Mainers to see the big picture when it came to the use of tar sands.

“The world is looking for energy from responsible (oil) producers,” she said. “If not Alberta, then someone else is going to be doing it. … Is it fair to say to other countries that they can’t have what we have?

“Alberta has stepped up to the plate,” she continued. “I challenge other jurisdictions to (produce oil) as well, with as much transparency, as we have.”

But Marshall said he, too, is looking at the big picture.

“We’ve reached a point where our addiction to fossil fuels will ensure the destruction of the planet,” he said. “I don’t see that as sustainable for future generations.”

William Hall can be reached at 781-3661 ext. 106 or whall@theforecaster.net. Follow him on Twitter: @hallwilliam4.