Natural Gas: Worse Than Coal?

| Tue Apr. 12, 2011 6:00 AM EDT

Natural gas is often touted as a climate-friendly alternative to traditional fossil fuels like coal or oil, and as a bridge fuel that will lead the country to a clean-energy future. But it turns out the overall greenhouse gas emissions related to natural gas extracted from shale formations are actually far greater than coal.

A new study in Climatic Change from Robert Howarth, a professor in the department of ecology and evolutionary biology at Cornell University, finds that shale gas is responsible for 20 percent more greenhouse gases than coal. While burning natural gas may emit less carbon dioxide, its extraction releases quite a bit of methane, a more potent greenhouse gas. Gas from shale—a fine-grained layer of rock below the earth's surface—is also responsible for 30 percent more greenhouse gas emissions than conventional natural gas. The study found that up to 7.9 percent of the methane escapes directly from the wells, leaks from pipelines, or is released in venting and flaring. While the leaks may be relatively small, methane is such a potent greenhouse gas that those leaks have a major impact, Howarth tells Mother Jones.

This is the first peer-reviewed study to look at the overall emissions from this type of gas. It was slated for publication later this week, but The Hill obtained a leaked copy over the weekend that has been generating a stir, as it would undermine the claims of the natural gas industry—and their boosters in Washington—that the gas is a boon for the planet. And major discoveries of shale gas in particular have made it a more appealing fuel source, with increased production and lower costs. The Department of Energy estimates that natural gas production in the US is going to grow 20 percent by 2035. Shale gas accounts for 16 percent of total production right now but is expected to increase its share to 45 percent by 2035.

Howarth is the first to admit that the numbers they had to rely on to write the paper are "not terribly good." That's because industry isn't currently required to report their emissions—and in fact are one of several industries suing the Environmental Protection Agency to keep it that way. Getting the data proved to be "amazingly frustrating," he says. The numbers he and his coauthors used in the study were drawn from a combination of industry reports, presentations, and dated EPA estimates.

While it may be true that burning natural gas produces 40 percent less emissions than burning coal, says Howarth, "what they don't tell you is that's not the whole story." Whether there will be a closer look at the whole story before the US moves forward in developing shale gas is the big question. "I do find it surprising that the nation would rush ahead on developing this a transitional fuel without doing a better job of looking at its greenhouse gas emissions," says Howarth.

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