Fracking for natural gas has been regarded as a relatively low emission source of energy due to lower emissions levels from the burning of the gas compared to coal. However, leakage of methane from some natural gas fields, largely caused by fracking practices, has recently been measured at levels that eradicate these emissions benefits.
Natural gas is mostly comprised of methane, which has a global warming potential of up to 100 times that of carbon dioxide over two decades, but due to the shorter lifespan of methane in the atmosphere the global warming potential over a 100 year period is around 25 times that of carbon dioxide. As a result, leakage of methane could more than triple the stated global warming effects of natural gas from fracking sites, making it considerably worse for climate change than coal.
A study in 2011 by the US National Center for Atmospheric Research concluded that "unless leakage rates for new methane can be kept below 2%, substituting gas for coal is not an effective means for reducing the magnitude of future climate change." Estimates of leakage rates from shale gas wells were previously around 1.9%, but recent research over several fields has shown actual rates to be considerably higher.
Industry has downplayed the issue of leakage from natural gas fields, so when the National Oceanic and Atmospheric Administration (NOAA) measured rates equivalent to around 4% of total production over a natural gas field in Colorado in 2012, it sparked concern about the fracking industry. A new independent study by the NOAA of a gas field in the Uinta Basin in Utah not only confirmed a high rate of leakage, but showed it to be considerably higher than all previous estimates at an astonishing 9%.
A similar survey in Queensland, Australia in 2012 captured readings of methane above the Tara gas field at over three times the natural level; the Australian Production and Exploration Association reacted by disputing the findings and labeling them as premature. The implications are ominous, as leaks from infrastructure such as well heads are comparatively easy to fix compared with leakage through the soil of gas fields after fracking practices have been deployed.
If these surveys provide an indication of what can be expected from other natural gas fields around the world, the idea of using natural gas to replace "dirtier" forms of generation, and as a bridge to a lower emissions scenario, may be deeply flawed. If this research is taken seriously - and further study is clearly needed - the implications could be far-reaching. The emissions cost of natural gas when viewed across its whole lifecycle may be considerably higher than current prices indicate, and any expansion of fracking - which was recently given the green light in the UK - may need further review.