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Is Gas Just as Bad as Coal?

by Michael Levi
November 18, 2010

I’m part of an online debate at Slate this week over the future of climate policy. My initial contribution covers a lot of territory, but the editors (who got to pick the title) zeroed in on my exhortation not to screw up shale gas. The upshot is that there’s been some interesting pushback.

In particular, some commenters (responding to a reprint of the piece over at Mother Jones) have raised the question of whether, once you include emissions not only from power generation but also from production and distribution, gas might actually be just as bad as coal. They point to an analysis (just updated earlier this week) by Cornell professor Robert Howarth claiming that when you account for the whole “lifecycle” of natural gas – particularly the release of methane into the atmosphere – it’s actually worse than coal.

It’s important to account for the full lifecycle, but I’m skeptical, for two pretty simple reasons. (I’m actually skeptical for a third – Howarth doesn’t distinguish between domestic production and LNG – but that’s more complicated.) As someone at Worldwatch pointed out when Howarth released his preliminary analysis earlier this year, he’s comparing apples and oranges. In particular, Howarth completely ignores the fact that coal mining generates greenhouse gas emissions too. When those are included, natural gas is clearly better than coal, as this CMU analysis (PDF) shows.

The CMU analysis also makes another important technical decision that clarifies the advantage of gas over coal: it uses what’s called a 100-year global warming potential for methane, rather than the 20-year potential that Howarth uses. (The paper isn’t explicit about that choice, but if you dig into the references, you can find it.) What does this mean in something vaguely resembling English? Methane doesn’t stay in the atmosphere for as long as carbon dioxide does. What Howarth is doing is largely ignoring that. The result is a three-fold increase in the calculated impact of methane leaks. One can make a case for that choice if you’re trying to get greenhouse gas concentrations down very quickly. But as far as long-term concentrations (which are the primary focus for policy) go, that’s the wrong choice.

To be sure, there are plenty of opportunities to reduce methane emissions from natural gas production and distribution, and we should be pursuing whichever ones are cost-effective. And there are other, I think bigger, challenges associated with natural gas, including local  impacts in particular. I’ll leave those for another post.

Post a Comment 2 Comments

  • Posted by Jonathan Koomey

    One point about the 20 year vs. 100 year potentials for warming potential from natural gas: The 20 year potentials are actually relevant if we’re in a race to halt warming in the near term, which I think we are if we’re to have any chance of keeping the temperature from climbing more than 2 degrees from pre-industrial times. I feel strongly that both numbers are relevant, just for different purposes. And of course, we need to do all of our life cycle analyses consistently across fuels if we’re to draw any conclusions at all, as you correctly point out.

  • Posted by Jack Rivkin

    The CMU PHD Thesis published in 2007 was based on emission data from 1993 for the most part and really doesn’t address specifically fracked shale gas. Even this thesis says the following: “Looking at the life cycle also allowed us to identify that in a future where emissions from the power plant are reduced, the benefits of natural gas over coal are not very significant…” It would be useful if the industry would provide data to make the case for shale gas, using research as opposed to attacking the researcher. The industry has this data. They should provide it. Of course, this doesnt address the local impacts as you imply. The industry runs the risk of killing a big step toward energy independence if they frack without considering the consequences of not addressing the local issues, spending more time understanding the geology, chemistry of these shale formations, and making sure that the GHG footprint is in fact better than competing carbon sources. Gas will be fracked in the rest of the world. If it is not fracked here because of short-sightedness on the part of the industry, we lose a real opportunity to move toward energy independence, much less toward reduced GHG emissions. Looking forward to your comments on the “local” issues.

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