Rendering is a process that converts waste animal tissue into stable, usable materials. Rendering can refer to any processing of animal products into more useful materials, or, more narrowly, to the rendering of whole animal fatty tissue into purified fats like lard or tallow. Rendering can be carried out on an industrial, farm, or kitchen scale. It can also be applied to non-animal products that are rendered down to pulp. In animal products, the majority of tissue processed comes from slaughterhouses, with the most common animal sources are beef, pork, mutton, and poultry. The rendering process simultaneously dries the material and separates the fat from the bone and protein, yielding a fat commodity and a protein meal. The occupation of renderer has been described as dangerous and dirty. Description A rendering process converts waste animal tissue into stable, usable materials. Rendering can refer to any processing of animal products into more useful materials, or, more narrowly, to the rendering of whole animal fatty tissue into purified fats like lard or tallow. It can also be applied to non-animal products that are rendered down to pulp. The rendering processes simultaneously dry the material and separate the fat from the bone and protein. A rendering process yields a fat commodity (yellow grease, choice white grease, bleachable tallow, etc.) and a protein meal (meat and bone meal, poultry byproduct meal, etc.). Input sources In animal products, the majority of tissue processed comes from slaughterhouses, but also includes restaurant grease, butcher shop trimmings, expired meat from grocery stores. This material can include the fatty tissue, bones, and offal, as well as entire carcasses of animals condemned at slaughterhouses and those that have died on farms, in transit, etc. The most common animal sources are beef, pork, mutton, and poultry. Processes Rendering can be carried out on an industrial, farm, or kitchen scale. It can also be applied to non-animal products that are rendered down to pulp. Rendering plants often also handle other materials, such as slaughterhouse blood, feathers and hair, but do so using processes distinct from true rendering. Process variations The rendering process varies in a number of ways: Whether the end products are used as human or animal food depends on the quality of input material and the processing methods and equipment. The material may be processed by wet or dry means. In wet processing, either boiling water or steam is added