Virtually nothing is wasted. This makes good environmental and economic sense. From very early on, animal hides were used for clothing and shelter. Bones and horns were used as tools and weapons. Animals provided the fertilizers used in the early cultivation of crops, the power to harvest them, and the transportation to move them.
Industrial uses have a long history too.
2800 B.C. Soap was made from goat fat, ash and clay. The same basic chemistry, with greater refinement and purification, is used to make soaps today. In fact, up until this century almost all industrial inputs and consumer goods were based on plant and animal products. Although animal products are a natural ingredient in many things, synthetics or imitation substances are sometimes used in their place. However, scientists are finding that in some cases natural products work better than synthetics and may actually help conserve resources.