Natural gas obtained by hydraulic fracturing will contribute more to global warming than coal over its life cycle according to a new Cornell University study. “Methane and the Greenhouse-Gas Footprint of Natural Gas from Shale Formations“, by Robert W. Howarth, Renee Santoro, and Anthony Ingraffea will be published soon in Climate Change and shatters beliefs held by the White House that domestic natural gas burns cleaner.
Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.
The industry is already pushing back against these findings but the study steps taken using known technology to reduce the emissions would not be adequate and notes that the, “Industry has shown little interest in making the investments needed to reduce these emission sources, however (Percival 2010).”
Considering the 20-year horizon, the GHG footprint for shale gas is at least 20% greater than and perhaps more than twice as great as that for coal when expressed per quantity of energy available during combustion (Fig. 1-a; see Electronic Supplemental Materials for derivation of the estimates for diesel oil and coal). Over the 100-year frame, the GHG footprint is comparable to that for coal: the low-end shale-gas emissions are 18% lower than deep-mined coal, and the high-end shale-gas emissions are 15% greater than surface-mined coal emissions (Fig. 1-b). For the 20 year horizon, the GHG footprint of shale gas is at least 50% greater than for oil, and perhaps 2.5-times greater. At the 100-year time scale, the footprint for shale gas is similar to or 35% greater than for oil.
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