Although often overlooked, industrial rending is an important part of the agricultural industry. These plants turn waste by-products from slaughterhouses into useful items in an attempt to use every part of the animal in a safe way.
Rendering plants get most of their materials from the meat packaging industry, but they also collect used oil from restaurants, expired meat from supermarkets, and carcasses of dead animals from shelters and zoos.
At an industrial rendering plant, workers first separate the fat, bone, and protein. Some plants also use feathers or hides, and some even collect blood from slaughterhouses if it can be kept separate from wastewater. Most of the products created at rendering plants are inedible, though some meat products can be used to create lard or tallow for human consumption.
Workers also separate out the parts of the animal that are fit for animal/pet consumption, which is processed for zoos and pet food companies. Some products go through a wet processing method, which can be used to make canned food. Other products go through a drying process to create meat and bone meal, a dry product that can be added to animal feed to increase protein. In the United States, meat and bone meal can only be used in feed for animals with one stomach (like pigs and horses), since it can spread mad cow disease and other diseases in ruminant animals (those with multiple stomachs like cows).
In addition, materials that cannot be rendered into products edible for humans or even animals can be used in other ways. Some industrial rendering plants make soap, biodiesel, candles, and lubrication for machinery.
Most of the work in an industrial rendering plant involves running machinery, moving materials and ingredients from one station to the next, and packaging the final product for sale to consumers or for sale to another company (like a pet food company) that will use it for a final product. These facilities of course also have inspectors to ensure that the products, especially those for human consumption, are prepared safely.