Use of coal in the Bronze Age in China

People in northern and western China were probably the first in the world to use coal as a source of energy in a consistent way. The ages cluster around 1900-2200 BC in modern day Inner Mongolia and Shanxi provinces. These are areas where near-surface coal is abundant today and woody vegetation was scant in the Bronze Age. Since coal is bulky to transport, it was probably not a cost-effective energy source in areas with abundant wood supply. The sites where coal was first used were probably occupied for a century to a few centuries at most and were associated with Bronze Age societies. The earliest age is about 3490 BC from a house site at Xiahe in Shaanxi Province; however, the coal is not securely tied to the radiocarbon ages and is assumed to have been used at this site sometime after 3490 BC. The elemental composition of modern mine and sedimentary coal in nearby archaeological contexts suggests that coal was used from local sources, and that elemental composition of coal may be a useful tool in identifying site origin of coal.