The hotly contested 1897km Keystone XL cross-border pipeline will take oil from Alberta to Nebraska.

TransCanada pointed out last month that, according to the Canadian Association of Petroleum Producers, oil sands emissions were 55 million tonnes in 2011 – the equivalent to 4.3% of emissions of US coal sector.

“That’s less than the emissions from three coal-fired power plants in the US,” TransCanada said.

“In total, the entire oil sands industry – which employs tens of thousands of people and generates billions of dollars of wealth throughout North America – contributes about 1/630th of global greenhouse gas emissions.

“Keystone XL will help boost US energy security by linking North America’s key oil fields in the northern US and Canada to its state-of-the-art refinery complexes in the Gulf Coast where they are needed to replace higher-priced oil from places like Venezuela, Russia and the Middle East.”

“Despite what you may have heard about the greenhouse gas intensity of Canadian oil sands operations, numerous studies have shown that oil sands crude has a comparable GHG (greenhouse gas) footprint to nearly half of all crude oils currently refined in the US.

“In many cases, oil sands derived crudes have a smaller GHG footprint than oils derived from Venezuela and California (two prominent sources for heavy crude oil). Keystone XL would replace costly, more GHG intensive Venezuelan crude oils with stable, secure oil from Canada and the US.”

It quoted International Energy Agency chief economist Faith Birol as saying: “Canadian oil-sands production, well-to-wheels carbon dioxide emissions are between 0% and 15% higher [than conventional production]. This is really insignificant compared with current worldwide emissions, but it is still important that the industry continues to work at reducing its carbon intensity to reduce Canada’s own emissions.”

Despite their big impact, the oil sands only make up 7.8% of Canada’s total emissions, TransCanada said.

As tens of thousands reportedly gathered in New York City last weekend for what organisers claimed to be the biggest demonstration for climate action, campaigners called for a moratorium on “dangerous, polluting” tar sands expansion projects in North America.

Sierra Club executive director Michael Brune called on US President Barack Obama to reject the Keystone XL project – which has been undergoing environmental reviews for nearly six years – and the Alberta Clipper.

“The Sierra Club stands behind communities and activists coming together at the People's Climate March to say, 'We won't stop fighting tar sands until we stop it at the source, and usher in a new era of clean energy prosperity'," Brune said.

"Tar sands crude is a disaster for the climate, for clean air and water, and for communities at the source, along pipeline routes, and those living next to refineries and export terminals.”

The Centre for Biological Diversity’s Valerie Love called tar sands “exactly the kind of energy that is pushing the planet toward climate catastrophe”

“It's long past time for President Obama to reject tar sands and other fossil fuel projects that only dig us deeper into the climate crisis,” she said. “A healthy, liveable future for people and wildlife depends on us shifting toward safer energy sources – not 20 years from now but today.”

Environmental Defence Canada’s Tim Gray said the country needed to stop giving its biggest polluter (the oil and gas industry) a “free pass”.

“Despite years of federal government promises, there is still no law limiting the soaring greenhouse gas pollution from the tar sands, the fastest growing source of carbon emissions in the country,” he said.

“If industry gets its way and triples tar sands production over the next few decades, greenhouse gas emissions from the tar sands will soar by over 250%. Canada needs to stop sacrificing our climate in the name of reckless tar sands development.”

The bottom line, TransCanada said, is that Keystone XL represented “a choice between an investment in North American energy infrastructure, North American labour and North American manufacturing, or an investment in Venezuelan and Middle Eastern economies. For those reasons we believe, like a vast majority of Americans believe, that Keystone XL is in the national interest”