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 production. The topic was certainly on the agenda of visiting U.S. Secretary of Energy Ernest Moniz, who met with Chinese government officials and oil-industry executives during a three-day visit that ended Wednesday. At a media briefing on Wednesday, Moniz said there was a strong interest in both countries in collaborating on unconventional oil and gas. "We have a lot of practices to share," he said.