Animal manure has been used for centuries as a fertilizer and a soil builder because it contains nutrients and organic matter. However, as animal production shifts toward fewer but larger operations, the number of confined animals has increased in some geographical locations, resulting in more manure produced than can be assimilated by the available farmland where the animals are raised.

Biodiesel is a renewable fuel that can be made from vegetable oil, animal fat, and recycled cooking oils. Oils produced from algae, fungi, bacteria, molds, and yeast can also be used to produce biodiesel.