The environmental impact of "fracking," the drilling technology largely responsible for America's boom in oil and gas production, are hotly contested. Consequences like water contamination have been established, but often it is not clear if they were directly caused by fracking or the result of sloppy drilling practices.
*China has seen little commercial shale production so far. BEIJING, March 11- China's plans to unlock what could be the world's biggest shale gas reserves risk running further off track after 16 firms awarded exploration rights in the latest auction lacked one core skill- not one has drilled a gas well before.