Keystone XL Pipeline: Debate Over Tar Sands Oil from Canada

November 14, 2014 2:07 PM EST

The proposed Keystone XL pipeline has become the single most important environmental issue in the U.S.—even though its environmental impact may not even be that great. The pipeline would move some 830,000 barrels of crude a day from the Canadian oil sands in Alberta to Steele City, Nebraska and then down to the Gulf of Mexico. Keystone would make it easier for Canadian producers to sell their landlocked crude to the rest of the world—which is exactly what environmentalists fear. Oil sands crude is dirtier and has a bigger carbon footprint than conventional oil.

Landowners in Nebraska worry that a spill could contaminate the state’s vital aquifer, while environmentalists fear that the pipeline will speed the development of the oil sands and help add huge amounts of carbon into the atmosphere. But other experts argue that oil sands crude will come to the U.S. by another route—most likely through rail—or be sold elsewhere in the world if Keystone isn’t built, meaning the planet won’t be any better off.

Since it’s an international project, the President has to sign off on the Keystone pipeline before it can be built—and much to the consternation of the oil industry, President Obama has delayed his decision for years, claiming that he needs more time to study the pipeline. But with Republicans now firmly in charge of both houses of Congress—and many conservative Democrats in favor of the project—Obama may need to make a decision soon.

With a decision potentially on the horizon — the House passed legislation on Friday and the Senate is expected to vote on the topic next week — refresh your understanding of the debate with these three articles from the TIME archives:

Mar. 12, 2012: Cold Warrior

A profile of activist and author Bill McKibben explains why the pipeline extension drew environmentalists’ attention, and how they helped influence President Obama’s decision to reject a 2012 version of the application to build the pipeline:

Though Canada is already mining and selling oil-sands crude, McKibben saw the proposed Keystone XL pipeline–set to deliver up to 830,000 barrels a day to the U.S.–as a crucial accelerator. More practically, because the cross-border pipeline required State Department approval, he saw an opportunity to confront Obama, who dropped an early climate-change agenda in the face of stiff resistance. In late August, McKibben, along with major environmental groups, helped organize days of protest around the White House. Over 12,000 people showed up, and hundreds were arrested. In November, Obama said he would delay a decision until 2013. But Republicans tacked a provision onto a payroll-tax-cut bill mandating that the White House decide on the pipeline within 60 days. In response, Obama decided in January to reject Keystone XL altogether.

Apr. 9, 2012: The Truth About Oil

A broader look at new sources of oil explains why the crude that would travel through the pipeline is different from other oil:

Oil has never exactly been clean, but the new sources coming online tend to be more polluting and more dangerous than conventional crude. Producing oil from the sands in northern Alberta can be destructive to the local environment, requiring massive open-pit mines that strip forests and take years to recover from. The tailings from those mines are toxic. While some of the newer production methods eschew the open-pit mines and instead process the sands underground or in situ, which is much cleaner, they still require additional energy to turn oil sands into usable crude. As a result, a barrel of oil-sand crude usually has a 10% to 15% larger carbon footprint than conventional crude over its lifetime, from the well to the wheels of a car. Given the massive size of the oil-sand reserve–nearly 200 billion recoverable barrels–that’s potentially a lot of carbon. It’s not surprising that environmentalists have loudly opposed the Keystone XL pipeline, which would send 800,000 barrels of oil-sand crude a day to the U.S. “There’s enough carbon there to create a totally different planet,” says James Hansen, a NASA climatologist and activist.

Jan. 31, 2014: Report Raises No Major Climate Objections to Keystone Pipeline, But the Choice Is Obama’s

After the President’s initial rejection of the pipeline proposal due to insufficient information, the State Department spent the next few years putting together an assessment of its potential environmental impact. The finding, released early this year, was disappointing to environmentalists: that whether or not the pipeline was built, about the same amount of oil would be produced.

A lot has changed since Keystone was first proposed back in 2005. U.S. domestic oil production has soared, last year hitting the highest level in two decades—a fact that has weakened the case for the international pipeline. At the same, the rapid—and not always safe—growth of oil being shipped by rail in lieu of pipelines has shown just how creative the oil industry can be when it comes to moving their product. Given the overwhelming demand for oil, it’s quite possible that the State Department is right that whether or not the pipeline is built, it will have little impact on the carbon footprint of the oil sands—though that hasn’t stopped the Canadian government from lobbying hard for the project.

The Keystone XL Pipeline: Three Stories to Help You Understand the Debate

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