Mother Nature Network: Critics of the natural gas extraction technique known as fracking have long criticized it for leaking too much methane a potent greenhouse gas into the atmosphere during the extraction process. The Environmental Protection Agency recently estimated that natural gas operations emitted about 145 million metric tons of methane in 2011, making it the biggest source of these emissions in the country. Now a new study, sponsored by the Environmental Defense Fund (EDF) and nine energy petroleum companies,...