As early as 3.5 thousand years ago, residents of the north-western part of China, as the first people in the world, systematically exploited coal as an energy source. Today, China consumes almost as much coal as the rest of the world combined. While looking for traces of bronze casting in the north of China, John Dodson of the Australian Nuclear Science and Technology Organisation in Sydney and his colleagues from China surveyed, among others, ancient slag heaps, where they found pieces of burnt brown coal.