Tuesday, April 12, 2011

Could Natural Gas Be as Dirty as Coal?

The New York Times reports that a study by Cornell professor Robert Howarth, not yet published, argues that natural gas may not be better for the climate than coal.
The problem, the studies suggest, is that planet-warming methane, the chief component of natural gas, is escaping into the atmosphere in far larger quantities than previously thought, with as much as 7.9 percent of it puffing out from shale gas wells, intentionally vented or flared, or seeping from loose pipe fittings along gas distribution lines. This offsets natural gas’s most important advantage as an energy source: it burns cleaner than other fossil fuels and releases lower carbon dioxide emissions.
Methane is a potent greenhouse gas, though it does not last as long in the atmosphere as carbon dioxide. An industry executive disputes the numbers:
Mark D. Whitley, a senior vice president for engineering and technology with Range Resources, a gas drilling company with operations in several regions of the country, said the losses suggested by Mr. Howarth’s study were simply too high.

“These are huge numbers,” he said. “That the industry would let what amounts to trillions of cubic feet of gas get away from us doesn’t make any sense. That’s not the business that we’re in.”
Just how much gas is escaping is not well known, which is in itself a problem. What the study doesn't dispute is that natural gas burns cleaner than coal, so much so that burning landfill gas is considered far cleaner for the air and the climate than letting it escape. It's the fugitive emissions that worry Howarth:
The GHG footprint of shale gas is significantly larger than that from conventional gas, due to methane emissions with flow-back fluids and from drill out of wells during well completion. Routine production and downstream methane emissions are also large, but are the same for conventional and shale gas. Our estimates for these routine and downstream methane emission sources are within the range of those reported by most other peer-reviewed publications inventories (Hayhoe et al. 2002; Lelieveld et al. 2005).

Despite this broad agreement, the uncertainty in the magnitude of fugitive emissions is large. Given the importance of methane in global warming, these emissions deserve far greater study than has occurred in the past. We urge both more direct measurements and refined accounting to better quantify lost and unaccounted for gas.
An advance copy of the study is available online via The Hill.

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