Forbes: Shale gas has upended U.S. energy markets, cutting oil imports to their lowest level in two decades. Can China pull off the same feat? It has already passed the U.S. as the biggest buyer of oil cargoes and by far the largest burner of coal, which explains the noxious air pollution that cloaks its northern cities. Hydraulic fracturing, or fracking, of underground reserves offers a way to cut emissions while feeding heating systems and power plants. It now accounts for around 40% of U.S. natural gas...