Teepee burners, or wood burners, were used to burn mill waste up until the mid-70s. And what a lot of waste there was. Even by 1970 it is estimated that only about 50% of every tree cut was utilized. Even less was used in the early days when refuse was often sent down a river or burned in open pits. Mills were tinderboxes just waiting to ignite (and many did)and the flammable sawdust needed to be disposed of.