|A natural gas drilling rig|
in the Marcellus shale region.
Natural gas has long been touted as a "cleaner" fuel than oil, simply because less carbon dioxide is released into the atmosphere upon burning. However, the principal component of natural gas is methane, which is a much more potent global warming gas than carbon dioxide. During natural gas production a small percentage of methane is released into the atmosphere, either intentionally through venting, or inadvertently through leaks in the pipeline. While methane does not last nearly as long in the atmosphere as carbon dioxide, over the short term (20 years as opposed to 100 years), its global warming potential is estimated to be 72 times greater than that of carbon dioxide.
The researchers looked at the overall life-cycle of natural gas production and compared methane emissions at each stage of production using industry reported data. They also compared emissions between shale gas production and conventional gas. They found that 3.6% to 7.9% of methane from shale-gas production escaped into the atmosphere during venting and leaks, almost two times greater than the emissions from conventional gas. These increased emissions in shale-gas production occured during the hydraulic fracturing of a well and during the drill out following fracturing. Their findings are in conjunction with a November 2010 Environmental Protection Agency report that found that emissions, particularly for shale gas, are larger than previously believed.
As many countries consider the adoption of shale-gas production as an alternative to oil-based energy sources, more research, similar to this study, will become gravely important to asess the true consequences to climate change.
These briefs are part of a weekly series of updates to the publication: Climate Change: Past, Present, and Future. The entire series can be found here.