In North Carolina, much opposition to fracking has reflected concern over air, water, and soil contamination. At the national level, debate has also swirled around the potential impact of natural gas extraction on the global climate. A recent PhD dissertation from Princeton University attaches numbers to a concern that has largely escaped notice until now: the potential impact of methane leaking, not from active wells, but from old wells that have ceased production.
Methane is, behind carbon dioxide, the second most important greenhouse gas; each emitted unit packs roughly 23 times the climate forcing impact of an equivalent unit of carbon dioxide. Most atmospheric methane decays into carbon dioxide within a decade or so, so emitting methane front-loads the impact on global climate, just at the time - the present - when it is vital to curb emissions to avoid irreversible climate thresholds.
At the national level, some have argued that burning natural gas for energy is less destructive than burning coal. Critics of fracking make two arguments in response. First, it would not take a significant rate of methane leakage in our natural gas production and delivery infrastructure to wipe out the benefits of gas relative to coal. Second, when it comes to avoiding dangerous climate tipping points, what matters is not the relative benefit of natural gas, but the absolute reductions it offers -- and it doesn't offer enough.
In an effort to get a better read on how bad the problem of leakage is, Environmental Defense Fund has partnered with industry and universities to conduct a suite of 16 studies to measure emissions from various parts of the natural gas production process. In March, the White House released its Strategy to Reduce Methane Emissions, seeking white papers and advice on how to address methane. A comment period on the strategy closed yesterday; with respect to the oil and gas sector, the strategy says "in the fall of 2014, EPA will determine how best to pursue further reductions from these sources."
The concern raised by the Princeton dissertation raises a new concern: what happens after production has ended and wells are closed and abandoned.
Mary Kang, the author, measured direct methane fluxes at 19 abandoned oil and gas wells in Pennsylvania - apparently the first time this has been done. Five of the wells were plugged, but Kang found "methane fluxes at plugged wells were not necessarily lower than methane fluxes at plugged wells" [at 69]. Equally significant, when Kang extrapolated from her data to the estimated number of abandoned wells across the state, she found that the total annual emissions of methane from abandoned wells could be roughly equivalent to the estimated leakage from ongoing production. Moreover, "[i]n contrast to oil and gas production activities that are finite in time, methane emissions from abandoned wells are likely to occur indefi nitely with cumulative emissions likely being significantly larger than the rates of leakage associated with production"[at 77].
It's worth noting that Kang does not identify any of her 19 wells as tapping shale gas or other unconventional sources, and given the design or her research - investigating abandoned wells - it is likely they were are conventional. The rapid decline curves of shale gas wells in comparison to conventional wells may mean that methane leakage from closed fracked wells is smaller - because gas migrates poorly through the shale once the initial volume of fractured rock is emptied - but there isn't any empirical data on that yet.
Also worth noting: EPA's proposed carbon rules do not (yet) propose to establish any sort of overarching state budget for greenhouse gas emissions from all sources. But, it's not hard to imagine a day when some states, at least, will want that - and it is the way regulation of conventional pollutants is handled under the Clean Air Act. If that were to happen for greenhouse gases, leakage from abandoned wells would count against the state cap. It's not the main reason to oppose fracking in North Carolina, but it does reinforce one of the basic questions about efforts to bring fracking here: why recruit this industry when there are so many others that would co-exist better with the industries that already drive the state's economy and employ our citizens?
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