President Trump says he is a friend of coal country. He promised to end the "war on coal" and bring back jobs in the coal mines. A year on from his inauguration and he seems to have made good on some of his pledges. Late last year his administration overturned several Obama-era regulations on mining and energy production. But can coal really make a comeback? Coal production remains a source of cheap electricity around the world but it's up against the rising availability of natural gas and increasingly competitive renewable energy. Could clean coal technology help re-brand a dirty fossil fuel? And how will China's move away from coal affect the picture? (Photo: a coal miner in Ukraine. Credit: Getty Images)