Processing        

Plant fats and oils and oils are obtained by crushing and solvent extraction. Crushing, or pressing is the older, less efficient, but easier process.

In animal and marine life, though, fats and oils are obtained by a process called rendering. Its purpose is to free the fat from the fatty tissue and the cells that it is held in. You begin this process by cutting the fatty tissue (see fig. 3) into small pieces. Then, using large vats, you heat the fatty tissue of the animal with steam or hot water. The fat, freed from its cells, floats to the surface of the water. Next you separate the fat from the aqueous layer. This is usually done by pressing it using a screw press or hydraulic press. The aqueous layer can then be dried and used as animal feed. Once the fat is rendered it is ready for use to make other products.