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Susan Kieffer can be contacted at s1kieffer at gmail.com

Wednesday, August 9, 2017

The "natural gas for clean energy" flaw

(If this contains garbage in the last paragraph, please note that I have tried to correct it and can't seem to do it in Blogger.)

Bill McKibben has an interesting op-ed in The Seattle Times today debunking the argument that switching from coal to natural gas will "save the planet."  The argument goes like this: Replacing coal with natural gas does indeed cut down CO2 emissions, and this has been observed to happen as America's power plants have replaced coal with natural gas.  However, natural gas is methane, CH4 and it is 80 times more powerful at trapping heat in the atmosphere on a molecule by molecule basis.  Methane leaks during the drilling process and, McKibben asserts, if as little as 3% of natural gas leaks during fracking then it is WORSE for the atmosphere than coal.
      For perspective, the methane budget in the atmosphere is complicated because there are both natural and human sources. Natural sources include wetlands, termites, and oceans. Human-related sources include fossil fuels, livestock farming, landfills, biomass burning, rice agriculture and biofuels. The attached figure (from Bousquet, P. et al. Nature 443(7110), pp. 439-443, 2006) illustrates details.
From this reference based on the Bousquet article cited in the text.

     A 2016 paper by Turner et al. in Geophysical Research Letters (DOI 10.1002/2016GL067987) examined methane emissions over a ~ a decade (2002-2014) from satellite data and surface observations. They found that global emissions increased by 17-22 Tg/a and that the U.S. methane emissions accounted for  30-60% of this increase. The emissions were primarily in the central part of the country but could not be attributed to definite sources, e.g., relative amounts from livestock and oil and gas sectors. McKibben's argument appears to be based on the 30% number and thus is probably conservative.
     Leakage rates may be higher than 3%: An aerial survey of a natural gas and oil production field in Uintah County, Utah on one day found emission rates between 6.2-11.7% of average hourly natural gas production for the month of February. Obviously more data are needed but rates are clearly above 3% in this case. The authors (Karion et al., JGR, doi: 10.1002/grl.50811) stated that "this high leak rate probably negates any immediate climate benefits of using natural gas instead of coal or oil and represents a possible air pollution hazard."
    On the other hand, some studies point to lower leakage rates, e.g., Peischl et al. (JGR, doi:10.1002/2014JD022697) found leak rates from <1 1.5="" 10.1002="" 2.1="" 6.3="" a="" agency="" al.="" and="" are="" be="" between="" ch4="" doi:="" emission="" environmental="" et="" fayetteville="" found="" from="" haynesville="" higher="" in="" inventory.="" leak="" marcellus="" northeastern="" northern="" of="" p="" pennsylvania="" protection="" rates="" regions.="" ren="" shale="" significantly="" southwestern="" study="" than="" the="" these="" to="" u.s.="" virginia="" west="">less than 1 percent to over 6 percent.  It is possible that because of the reduction of coal and increase in natural gas use that the U.S. greenhouse gas emissions may have actually gone up during the Obama years. McKibben points out that "at least the Obama administration required drillers to keep track of how much methane they were leaking--one of the first acts of the Trump EPA was to scrap that requirement, apparently on the grounds that what you don't know can't hurt you." He then argues that the illusion that we are doing something to reduce climate change by switching to natural gas is hurting us because it is making it harder and slower to switch to solar power which emits no carbon at all (I guess that's if you don't count the fact that it probably takes carbon to produce solar panels at the this time.)