The New York Times has an article today reporting the results of a study by an acknowledged opponent of shale gas extraction, noting that methane released during production and distribution may obviate to some degree it's advantage as a cleaner carbon fuel than coal.
The point is that methane is a potent contributor to climate change: it dissipates more quickly into the atmosphere and traps more heat than carbon dioxide, so leaks are damaging. (No one is disputing that natural gas is at least twice as clean as coal when it is burned.)
The natural gas industry of course argues with the estimates of fuel losses throughout the production and delivery system, and whether the losses are higher for shale extraction compared to traditional wells. The utility industry ought to be able to state with a large degree of accuracy losses in distribution. (I know we accurately account for leakage at the water district where I serve on the board.)
This isn't a tempest in a tea cup, but it does point out that all types of energy production and delivery should be evaluated on an end-to-end supply chain perspective. All fuels require energy for processing and delivery (in some parts of the world natural gas is simply flared off as a waste product because the LNG market can't handle the load), and environmental impacts should properly be accounted for.
The issue raised by the report reminds me of the perception of utilities that I found in the information technology industry when I first started getting engaged on energy efficiency. Smart, bright engineers were saying that utilities lost as much as seventy percent of power generation to transmission and distribution losses.
Simply not true. Utilities lose as much as seventy percent of the energy from source fuel (for coal, natural gas, and biomass) in the power plant, but only four to seven percent in line losses. There is also a small band of over-production to provide gris stability (typically three to five percent), but being very clear about where these losses occur is crucial to understanding efficiency and environmental opportunities for improvement.