ABSTRACT
Pyrolysis has found broader definition in describing any chemical changes brought about by the application of heat, even with air or other additives. Until the late 1800s, wood carbonization was the major pyrolysis process, and supplied the increasing amounts of charcoal that were required for iron ore smelting in a growing America. The pyrolysis of wood was probably man's first chemical process. Hardwoods are generally preferred to softwoods because they produce higher yields of acetic acid and methanol, and a denser charcoal. Wood must be dried before undergoing pyrolysis in continuous retorts. The charcoal industry had almost exhausted surrounding woodlands in the East, and soon concentrated in Michigan and the South, where supplies of wood were adequate. In the US and more generally the Western Hemisphere, competition from alternate feedstocks has forced out all but a few wood distillation and carbonization plants.
