Is Natural Gas Cleaner Than Coal? It Depends on Leaks---and There's a Huge One in the North Sea

80beatsBy Sarah ZhangApr 12, 2012 2:52 AM


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http://youtu.be/C3VkkCdPCas A news report from the first week of the leak.  Since March 25, the Elgin gas platform off the coast of Scotland has been leaking 7 million cubic feet of gas a day. The natural gas, mostly methane, doesn't have the dark stain of oil and it hasn't inspired the news coverage of Deepwater Horizon. But that doesn't mean it can be ignored. Like carbon dioxide, methane is a greenhouse gas that traps heat in the Earth's atmosphere. But methane is much worse: the same amount of methane will have 25 times the warming effect of carbon dioxide over a 100-year period. In the six months that it will take to stop the leak, enough methane would have escaped into the atmosphere to equal the annual global warning impact as 300,000 new cars, according to a recent TIME article. The Elgin gas leakage is an extreme example of how natural gas exploration and processing is always beset by leaks. After all, the stuff is gas that wants to float away. The TIME piece dissects a recent paper in the Proceedings of the National Academy of Sciences evaluating whether natural gas really is more environmentally friendly than coal. Their answer? It depends, and it partially depends on leaks.

The redline for power plants seems to be a leakage rate of 3.2%. As long as the share of methane that escapes remains below that level, natural gas beats coal. And since a 2009 estimate from the Environmental Protection Agency (EPA) pegs the average leakage rate at 2.4%, natural gas does seem to come out comfortably ahead — especially when you factor in the much lower levels of mercury and other traditional air pollutants emitted when power plants burn gas as compared with coal. But if we replace gasoline cars with ones powered by natural gas in an effort to reduce oil consumption — as some like natural-gas tycoon T. Boone Pickens have urged — methane leakage would need to be kept below 1.6% to provide a meaningful climate benefit. For heavy-duty trucks run on diesel — a fuel that has a smaller carbon footprint than gasoline — methane leakage would have to be reduced by two-thirds below the EPA estimate of 2.4% to provide a climate benefit. "It's a much steeper hill to climb," says Hamburg.

The full TIME article goes through a more detailed explanation and possible caveats for some of these numbers. Indeed it is frustrating that we don't have better information about natural gas, and one reason to use caution in ramping up domestic natural gas exploration with fracking. Natural gas may or may not be a solution, but it's almost certainly not a permanent, one-size-fits-all solution.

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