RealClimate on the Keystone XL ‘carbon bomb’

by Milan on November 7, 2011

in Climate change, Climate science, Oil sands

I am personally a bit uncomfortable with the James Hansen’s much-repeated claim that approving the Keystone XL pipeline would be ‘game over’ for the climate. While the amount of greenhouse gas pollution facilitated by the pipeline is large, I am not sure if it is large enough to justify that particular piece of rhetoric.

As such, I was glad to see a new post on the RealClimate blog that fleshes out and evaluates this claim. In it, the author crunches the numbers and basically concludes that Hansen’s argument is defensible. The huge amount of carbon in the oil sands is cause enough to be concerned about their extraction:

Are the oil sands really the “biggest carbon bomb on the planet”? As a point of reference, let’s compare its net carbon content with the Gillette Coalfield in the Powder river basin, one of the largest coal deposits in the world. There are 150 billion metric tons left in this deposit, according to the USGS. How much of that is economically recoverable depends on price and technology. The USGS estimates that about half can be economically mined if coal fetches $60 per ton on the market, but let’s assume that all of the Gillette coal can be eventually recovered. Powder River coal is sub-bituminous, and contains only 45% carbon by weight. (Don’t take that as good news, because it has correspondingly lower energy content so you burn more of it as compared to higher carbon coal like Anthracite; Powder River coal is mined largely because of its low sulfur content). Thus, the carbon in the Powder River coal amounts to 67.5 gigatonnes, far below the carbon content of the Athabasca Oil Sands. So yes, the Keystone XL pipeline does tap into a very big carbon bomb indeed.

But comparison of the Athabaska Oil Sands to an individual coal deposit isn’t really fair, since there are only two major oil sands deposits (the other being in Venezuela) while coal deposits are widespread. Nehring (2009) estimates that world economically recoverable coal amounts to 846 gigatonnes, based on 2005 prices and technology. Using a mean carbon ratio of .75 (again from Table 6 here), that’s 634 gigatonnes of carbon, which all by itself is more than enough to bring us well past “game-over.” The accessible carbon pool in coal is sure to rise as prices increase and extraction technology advances, but the real imponderable is how much coal remains to be discovered. But any way you slice it, coal is still the 800-gigatonne gorilla at the carbon party..

Commentators who argue that the Keystone XL pipeline is no big deal tend to focus on the rate at which the pipeline delivers oil to users (and thence as CO2 to the atmosphere). To an extent, they have a point. The pipeline would carry 500,000 barrels per day, and assuming that we’re talking about lighter crude by the time it gets in the pipeline that adds up to a piddling 2 gigatonnes carbon in a hundred years (exercise: Work this out for yourself given the numbers I stated earlier in this post). However, building Keystone XL lets the camel’s nose in the tent. It is more than a little disingenuous to say the carbon in the Athabasca Oil Sands mostly has to be left in the ground, but before we’ll do this, we’ll just use a bit of it. It’s like an alcoholic who says he’ll leave the vodka in the kitchen cupboard, but first just take “one little sip.”.

So the pipeline itself is really just a skirmish in the battle to protect climate, and if the pipeline gets built despite Bill McKibben’s dedicated army of protesters, that does not mean in and of itself that it’s “game over” for holding warming to 2C. Further, if we do hit a trillion tonnes, it may be “game-over” for holding warming to 2C (apart from praying for low climate sensitivity), but it’s not “game-over” for avoiding the second trillion tonnes, which would bring the likely warming up to 4C. The fight over Keystone XL may be only a skirmish, but for those (like the fellow in this arresting photo ) who seek to limit global warming, it is an important one. It may be too late to halt existing oil sands projects, but the exploitation of this carbon pool has just barely begun. If the Keystone XL pipeline is built, it surely smooths the way for further expansions of the market for oil sands crude. Turning down XL, in contrast, draws a line in the oil sands, and affirms the principle that this carbon shall not pass into the atmosphere.

I find this analysis convincing. If approved, Keystone XL would certainly feed the process of oil sands development. Being able to export and process more bitumen would justify digging up more of the stuff. It would also justify continued investment in research and development of oil sands technologies.

By exploiting the oil sands, we are riding the last desperate coat-tails of fossil fuel dependence. Instead, we should be investing our wealth and energy and intelligence into developing truly sustainable sources of energy that are compatible with a stable climate.

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. November 17, 2011 at 9:36 pm

Coal exports are a bigger threat than the tar-sands pipeline

The planned Keystone XL oil pipeline has earned major national attention for the damage it would do to the climate. At the same time, another climate drama is playing out with much less attention as coal companies make plans to export huge quantities to Asia by way of Pacific Northwest ports. It’s pretty clear that both projects are environmental horror stories, but I’ve been wondering: Which one is worse?

The result surprised me: Coal exports look to be an even bigger climate disaster than the pipeline. There are, in fact, quite a bit more direct emissions from burning the coal than from the oil. That’s true even when one counts the energy-intensive tar-sands extraction and processing — and, of course, there are plenty of upstream emissions associated with coal mining that I’ve left out of the equation here. (In order to make a roughly direct comparison, I also omitted emissions associated with both products’ mining, refining, transportation, and so forth.) Clearly we can ill afford either one of these projects, but until we have a clear energy policy that respects climate science we’ll be wrestling with these kind of killer projects one at a time.

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