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April 8th, 2016

Coal vs. natural gas in the climate ring: Calling this fight is tricky

Part of the argument over natural gas-generated electricity is whether it is less damaging to the climate than coal-powered electricity.  Burning coal puts more carbon dioxide, a greenhouse gas, into the atmosphere than does burning natural gas.  But there is good agreement that this immediate benefit only comes into play if the natural gas process doesn’t leak much methane, a greenhouse gas at least 25 times more potent than carbon dioxide.  In 2012, Alvarez, et al. calculated a 3.2% limit on total methane leakage as the point where switching to natural gas ceases to be a climate benefit.  A 2014 study by Howarth, et al. used new figures from the 2013 IPCC report, changing the number to a range of 2.4%–3.2%.  Many of the climate benefits of switching to natural gas may be seen 100 years out, but many scientists are concerned that permanent negative changes will occur in the next 15 to 35 years (Howarth, et al., 2014).

The EPA and many independent research teams have shown widely varying rates of methane leakage: anywhere from under 1% to over 7% nationally (summarized in Howarth, et al., 2014).  Regional studies also show variation: for example, a 2013 study led by scientists from NOAA and CIRES (Karion, et al.) found leakage rates of 7–11% at the Uintah Basin in Utah.  We need to understand much more clearly what leakage rates really are.  If methane leakage is well over the threshold point, then switching from coal power to natural gas will actually increase greenhouse gas emissions for the foreseeable future.

The 2012 paper by Alvarez, et al. gets deep into exactly where natural gas benefits and costs occur depending on time scale, leakage rates, and what kind of thing gets converted to natural gas—grab a copy from your local university library if you want a super-detailed understanding of this complex issue.  (p.s. This is a very well-written science paper—it gets technical, but it is clearly written and conclusions are clearly stated.  You won’t regret reading it!)