Waste Not

Whether at home, on the farm or in a large-scale meat processing facility, the basic principle of rendering is the same: to use parts of the cow that would otherwise be discarded. Although many parts of the animal can be rendered, the term usually refers to fat. Exposure to heat, followed by filtering, removes moisture from the fat and turns it into a stable form that can be used for cooking or as an ingredient in other products.

Rendering at Home

The simplest form of rendering takes place in the kitchen. After trimming excess fat from beef, the cook heats it to convert it into usable tallow. This can be done by wet rendering or dry rendering. In wet rendering, the fat is heated in a pan with water; the fat will float to the surface of the water as it melts. In dry rendering, the fat melts in a pan without water until it is liquid. After rendering, the cook strains the fat to remove impurities. The resulting tallow can be used in frying or baking. To produce large quantities of tallow, some people use commercially available suet rather than offcuts from their own cooking to make tallow.

Industrial Rendering

Commercial rendering employs similar processes to kitchen rendering, but on a much larger scale. According to the National Renderers Association, the American rendering industry processes nearly 30 million tons of waste meat products each year. Commercial rendering uses not only fat, but brain, bone and other unused parts of the animal. Products of the rendering industry include important ingredients in livestock feed and pet food, and they are found in products ranging from lubricants to cosmetics and even explosives.

Controversy

Rendered beef products contributed to the spread of bovine spongiform encephalopathy (BSE) in the 1990s. The disease's infectious agent was found in rendered beef products that were being fed to cows, transmitting the disease. FDA regulations now prohibit feeding rendered beef to cows, together with a number of other safety regulations to prevent the infection from recurring. Cattle feed still uses rendered products from other animals, while other types of animal feed contain rendered beef products.