On the outskirts of Datong in northern China’s Shanxi Province, a compound that once teemed with noise and activity has fallen silent. Its underground tunnels where thousands of workers toiled has been sealed, and machines that saw busier days lie rusting. Tongjialiang Coal Mine, which employed some 4,000 workers at its peak, closed in 2016 after operating for 67 years. It was one of 25 collieries in the province that were shut down last year as China gradually weans itself away from its traditional energy source.