I’ve been reading a lot lately about the controversy over fracking—fracturing layers of shale, deep underground, using a concoction of pressurized water, sand, and chemicals, to release pockets of natural gas trapped in the rocks. Traditional fracking methods have been around for decades, but almost always involved drilling vertically before cracking a roughly columnar piece of shale. Newer methods drill just as deep into the shale layer, but then turn ninety degrees and extend several thousand feet horizontally through that layer. A single mine may drop several such horizontal bores, and may crack the same layer of shale repeatedly.
The process has garnered a lot of press from both sides of the issue. (See pieces from the New York Times here and here, as well as good references from Scientific American and ScienceDaily, and from the opposite perspective: Yahoo! News and the American Petroleum Institute’s completely and utterly unbiased viewpoint here.) Most of this press hits a few key points: concerns over methane leaking into groundwater reservoirs (which, according to some reports, has resulted in tap water bursting into flame), concerns over potential carcinogens in the chemical portion of the fracking cocktail, and the sheer abundance of domestically available, clean-burning natural gas waiting just beneath our feet.
The first point certainly warrants further exploration. Indeed, testing is underway nationwide to locate weak points in the fracking process and to determine if gas is making its way into drinking water supplies. The second point is also valid—some of the chemicals used, by some drilling companies, may be carcinogens. This point is addressable by research and by regulations, or—this might be a stretch—by responsible corporate environmental stewardship. But the last point may be only half true.
By some estimates there are hundreds of trillions of cubic feet of natural gas trapped in shale formations about a mile down—enough to meet American energy demands for decades. One of the points routinely made by organizations on both sides of the issue is that natural gas is a cleaner solution to our energy consumption problems than dirty-burning coal. Coal presently provides about half the electricity generated in the US, and coal-fired electrical plants spew millions of tons of carbon dioxide (CO2) into the atmosphere every month, which traps heat and accelerates global warming. Natural gas, on the other hand, emits about half as much CO2 as coal when burned. Seems great, no?
No. As with most topics, the equation is more complicated than that. Tom Wigley, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, recently released a study showing just how complicated that equation is. According to Wigley and others researching the issue, somewhere between two and ten percent of all natural gas mined—from fracking, yes, but also during traditional mining and during transportation, processing, and storage—leaks into the atmosphere; and methane, the primary ingredient in natural gas, is a heat-trapper “significantly more powerful” than CO2—ten to forty times as powerful, according to Wigley.
Also a factor in the natural-gas equation is sulfur dioxide. SO2 is another pollutant released when burning coal, but it has the opposite effect of CO2: instead of trapping heat near Earth’s surface, it reflects it away, both because the individual particles of SO2 are reflective and because they act as moisture condensers, increasing the cloud layer, which acts like a giant mirror reflecting sunlight back out into space. (By the way, this isn’t necessarily a good thing. Before anyone suggests we just dump massive quantities of SO2 into the atmosphere, those clouds that form around SO2 particles, while they do reflect heat away from us, also have a nasty tendency to drop acid rain.)
The end result of all this is that if we were to replace a significant percentage of our coal-sourced electricity with electricity generated by burning natural gas, we would be doing two things: putting more methane in the atmosphere, and less SO2. Less SO2 means more heat makes its way to Earth’s surface; more methane means more of that heat gets trapped here.
Methane does dissipate faster than CO2, but we’re still working on timelines decades long. Wigley estimates that replacing coal with natural gas will result in more global warming over the coming few decades, not less, and just slightly less warming thereafter. In any case, we’re talking about fractions of a degree, plus or minus—certainly not enough to justify the argument that natural gas is an unassailably greener fuel than coal.
I’m not a foreign policy expert, but the argument that increased natural gas production could aid national energy security and decrease dependence on foreign oil seems sound. The arguments about carcinogenic chemicals and tainted groundwater supplies may also be true—further study is required. But justifying increased drilling because natural gas is a “greener” fossil fuel than coal is myopic.
The For frack’s sake, stop calling natural gas “green” by PLOS Blogs Network, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 4.0 International License.