Workers unload coal from a supply truck at a yard on the outskirts of the western Indian city of Ahmedabad in this April 15, 2015 file photo. Coal futures are trading at $50 a tonne for the first time since 2003 as the commodity downturn deepens, and U.S. investment bank Goldman Sachs says the resource will never gain enough traction again to lift it out of its slump. (Photo by Amit Dave/Reuters)
