by John C. Stauber and Sheldon Rampton
The U.S. Department of Agriculture calls "rendering" a process of heat-treating fat, bone, offal and related material derived from the carcasses of livestock, poultry, fish and used cooking fats and oils. Renderers call themselves "the invisible industry" and are thankful that most people remain blissfully unaware of their existence.
Each year, at hundreds of plants in the U.S., more than 12.5 million tons of dead animals, fat and meat waste are melted down, most of it to become protein supplements fed to pets, chickens, cows, sheep and other animals, the rest to make products ranging from gelatin to cosmetics.