Environmentalist Bill McKibben was among 100 people arrested at the weekend for protesting against the Keystone XL tar sands pipeline. But why are climate campaigners so concerned?

Bill McKibben is leading what may be the largest green civil disobedience campaign in a generation, against the proposed construction of the 1,600-mile long Keystone XL pipeline.  The pipeline would transport oil from the Alberta tar sands in Canada to American refineries at the Gulf of Mexico, and many are concerned about the associated impacts on the climate. 

Digging up new sources of fossil fuels will inevitably increase the amount of CO2 in the atmosphere, and the tar sands result in higher carbon emissions than even conventional oil.  On 15 June 2011, the Energy and Power Subcommittee of the House Energy and Commerce Panel approved a bill to expedite a decision on the pipeline, possibly trying to rush it through before adequate environmental impact assessments are completed.

The project must be approved by President Obama in order to proceed, and the aim of the protest is to convince the president to reject the project.  If the Keystone pipeline is not approved, the tar sands oil may be stuck in place.  As McKibben noted,"Alberta is remote, and its only other possible pipeline route — to the Pacific and hence Asia — is tangled in litigation."

McKibben is among those who have already been arrested for this display of civil obedience.  We felt that this would be a good time examine the climate impact of the tar sands and proposed pipeline.

Background and Politics
Tar sands (a.k.a. oil sands) are an unconventional deposits of petroleum containing bitumen, which is a very viscous form of petroleum generally known as tar or very heavy crude oil.  Alberta, Canada contains the largest deposits of crude bitumen in the world, the biggest of which is the Athabasca tar sands.

There is political pressure in the USA to utilize oil from the tar sands, because although it's not quite a domestic energy source, obtaining oil from our friendly neighbors to the north is considered preferable to relying on sources in the less politically stable and friendly Middle East.

Additionally, gas prices have increased in recent years, and there has been pressure on politicians to take action to counteract the rising costs in the USA.  Republicans in particular have frequently called for increasing domestic oil drilling, even though research has universally concluded that this action will have virtually no effect on gas prices. 

In fact, in the rise in gas prices coincided with increased domestic oil drilling in the USA.  But of course, certain American politicians don't seem to care that their claims have no factual or scientific basis.

Environmental Impacts
Before we examine the climate impacts of the tar sands, it's worth noting that they result in substantial adverse impacts to the environment in general, as is clear in aerial photographs from Google of the region (Figure 1).

Tar sands mining operations involves clearing trees and brush from a site and removing the overburden soil that sits atop the deposit.  As you can see in Figure 1, in Alberta this results in significant destruction of the boreal forest.  The mining process also requires vast amounts of water, although much of it is recycled. 

However, Environment Canada found in 2010 that water quality monitoring in the region was lacking. Some scientists have raised concerns that the tar sands may be causing aquatic life deformities downstream.  Kelly et al. (2010) found a number of pollutants downstream of the tar sands.

"Canada's or Alberta's guidelines for the protection of aquatic life were exceeded for seven [priority pollutants]—cadmium, copper, lead, mercury, nickel, silver, and zinc—in melted snow and/or water collected near or downstream of development."

Additionally, there are always concerns about environmental impacts related to potential oil spills and leaks.  On a similar pipeline, Keystone I, there were 12 spills over a period of less than a year, and a team of University of Nebraska hydrologists expressed concern over the associated risks to drinking and irrigation water supplies in the US Midwest, though which the pipeline would run.

Greenhouse Gas Emissions
Making liquid fuels from bitumen requires energy for steam injection and refining.  Currently the energy is produced from natural gas. This process generates more greenhouse gas emissions per barrel of final product than the production of conventional oil.

There is a slight challenge in quantifying the climate impact of tar sands oil as compared to conventional oil, because there are different ways to make this comparison. Approximately 80% of the carbon from any barrel of crude is emitted when it's burned. Therefore, evaluating well-to-wheel (extraction to combustion) emissions, tar sands emit approximately 10 to 45% more greenhouse gases than combustion of conventional oil. 

However, if we exclude combustion and evaluate well-to-tank emissions, tar sands emissions are approximately twice those of conventional oil.  According to a recent US Environmental Protection Agency (EPA) assessment, tar sands well-to-tank emissions are approximately 82% higher than conventional oil.

Keystone Pipeline Emissions
The EPA also evaluated the greenhouse gas emissions specifically associated with the proposed Keystone pipeline which McKibben's group is protesting.

"recognizing the proposed Project 's lifetime is expected to be at least fifty years, we believe it is important to be clear that under at least one scenario, the extra GHG emissions associated with this proposed Project may range from 600 million to 1.15 billion tons CO2-e, assuming the lifecycle analysis holds over time"

Over 1 billion tons of equivalent CO2 emissions is a substantial chunk of emissions.  We recently discussed The Critical Decade report produced by the Climate Commission established by the Australian government.  Their report concluded that humanity can emit not more than 1 trillion tonnes of CO2 between 2000 and 2050 to have a probability of about 75% of limiting temperature rise to 2°C or less. 

According to the latest data, between 2000 and 2010 we emitted approximately 300 billion tons of CO2, so after 20% of the allotted timeframe, we're already over 30% of the way through the allotted emissions.

Climate Concerns
In addition to being more emissions-intensive than conventional oil, the main concern is that exploiting the tar sands is conceptually backwards.  As The Critical Decade report made clear, we need to be looking for ways to leave fossil fuels in the ground, not trying to find more unconventional sources of carbon for combustion. 

The USA in particular has taken very few concrete steps to minimize its greenhouse gas emissions to this point. Building the Keystone pipeline to exploit an unconventional source of fossil fuels is a step in the wrong direction, and will encourage other countries to follow suit.  

If we're to have any hope of achieving sufficient global greenhouse gas emissions cuts, the USA needs to start leading the way in finding ways to reduce fossil fuel consumption, not lead the way in finding ways to burn new unconventional sources, especially when they're more emissions-intensive than conventional sources.

(By Dana Nuccitelli, Skeptical Science / Guardian.co.uk, 23/08/2011)