Wood occurs naturally in trees, which are cut into pieces at a sawmill to produce boards and other lumber. Every part of the tree is used in this process, including the bark and any leftover wood chips or sawdust.
When logs arrive at a sawmill, workers first sort them by size, type and quality. Next, workers remove the bark and gradually cut the logs into smaller sections until they achieve the desired board thickness and length. Some waste accumulates during this process, as the boards must be square and uniform.
These remaining wood scraps, chips and sawdust are usually then processed at a separate facility where they are ground into wood pulp used to make a variety of paper products and wood-pellet fuels. The pulp contains plant fibers known as cellulose, which must be separated from the rest of the matter in a chemical process. In addition to producing paper products, the byproducts of this process also have a wide range of uses, including in medicine, cosmetics and cleaning products.
While the bark from the logs can't be processed into paper, it is often sold for use in landscaping. In addition, some mills actually burn the bark to generate electricity to help run the mill.