How leaky is shale gas production?

The boom in US natural gas production made possible by fracking techniques has raised an awkward question: how much is leaking to the atmosphere before reaching a power plant turbine or your furnace? Natural gas power plants are more efficient than coal-burning plants and emit much less CO₂. But methane is a potent, though short-lived, greenhouse gas, so the exact benefit of that trade off depends on the level of leaks from wells and pipelines.

The EPA produces estimates of leakage calculated using limited measurements of typical equipment and production practices. Those estimates put natural gas leakage in the neighborhood of one percent of production— low enough to ensure that the shale gas (fracking) boom is a net positive in terms of climate-changing emissions. A major study sampling new shale gas wells showed that the EPA estimates for well leakage did a pretty good job—at least for those newer wells.

Much has been made, however, of several studies that took a different approach and got very different results. Those studies used methane measurements made from a NOAA airplane upwind and downwind of shale gas fields. At a field outside Denver, that yielded an estimate of 3.1 to 5.3 percent leakage. At a Utah field, leakage was estimated at between 6.2 and 11.7 percent. Near Los Angeles, a leakage rate of 12-22 percent was calculated.