what would otherwise be waste materials and makes useful products such as fuels, soaps, rubber, plastics, etc. At the same time, rendering reduces what would otherwise be a major disposal problem. As an example, the United States annually recycles more than 21 million metric tons of highly perishable and noxious organic matter. In 2004, U.S. industry produced over 8 million metric tons of products, of which 1.6 million metric tons were exported. Usually, materials used as raw materials in the rendering process are susceptible to spoilage. However, after rendering, the materials are much more resistant to spoiling. This is due to the application of heat either through cooking in the wet rendering process or the extraction of fluid in the dry rendering process. The fat obtained can be used as low-cost raw material in making grease, animal feed, soap, candles, biodiesel, and as a feed-stock for the chemical industry. Tallow, derived from beef waste, is an important raw material in the steel rolling industry, providing lubrication when compressing steel sheets. Meat and bone meal in animal feed was one route for the late-20th century spread of bovine spongiform encephalopathy (mad-cow disease, BSE), which is also fatal to humans. Early in the 21st century, most countries tightened regulations to prevent this. See also Animal slaughter Animal euthanasia Dead Horse Bay Flensing Whale oil References Inline citations General references Lyman, Howard, F. (1998). Mad Cowboy. Simon & Schuster, New York. Render Magazine (April 2005), National Renderer's Association. Meeker, David L. Essential Rendering: All About The Animal By-Products Industry. National Renderer's Association. Burnham, Frank. North American Rendering: The Source of Essential High Quality Products. National Renderer's Association. Clemen, Rudolph (1978). Rendering, The Invisible Industry, Aero Publishers. Young, H.H. (1927). By-Products of the Meat-Packing Industry, University of Chicago Press. Franco, Don and Swanson, Winfield (1996). The Original Recyclers, APPI, FPRF and NRA. Cooking fats Cooking techniques Meat industry Industrial processes