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Article Outline
Recycling, collection, processing, and reuse of materials that would otherwise be thrown away. Materials ranging from precious metals to broken glass, from old newspapers to plastic spoons, can be recycled. The recycling process reclaims the original material and uses it in new products. In general, using recycled materials to make new products costs less and requires less energy than using new materials. Recycling can also reduce pollution, either by reducing the demand for high-pollution alternatives or by minimizing the amount of pollution produced during the manufacturing process. Recycling decreases the amount of land needed for trash dumps by reducing the volume of discarded waste. Recycling can be done internally (within a company) or externally (after a product is sold and used). In the paper industry, for example, internal recycling occurs when leftover stock and trimmings are salvaged to help make more new product. Since the recovered material never left the manufacturing plant, the final product is said to contain preconsumer waste. External recycling occurs when materials used by the customer are returned for processing into new products. Materials ready to be recycled in this manner, such as empty beverage containers, are called postconsumer waste.
Just about any material can be recycled. On an industrial scale, the most commonly recycled materials are those that are used in large quantities—metals such as steel and aluminum, plastics, paper, glass, and certain chemicals.
There are two methods of making steel using recycled material: the basic oxygen furnace (BOF) method and the electric arc furnace (EAF) method. The BOF method involves mixing molten scrap steel in a furnace with new steel. About 28 percent of the new product is recycled steel. Steel made by the BOF method typically is used to make sheet-steel products like cans, automobiles, and appliances. The EAF method normally uses 100 percent recycled steel. Scrap steel is placed in a furnace and melted by electricity that arcs between two carbon electrodes. Limestone and other materials are added to the molten steel to remove impurities. Steel produced by the EAF method usually is formed into beams, reinforcing bars, and thick plate. Approximately 64 percent of all steel is recycled, making it one of the world’s most recycled materials. In 2000 31 billion steel cans, weighing 2.4 million metric tons (2.6 million U.S. tons), were used in the United States, of which 58.4 percent were recycled. In 2000 more than 60 million metric tons (70 million U.S. tons) of scrap steel were recycled in the United States.
Recycling aluminum in the United States provides a stable, domestic aluminum supply amounting to approximately one-third of the industry’s requirement. In contrast, most of the ore required to produce new aluminum must be imported from Jamaica, Australia, Surinam, Guyana, and Guinea. About 2 kg (about 4 lb) of ore, a mixture of aluminum oxides called bauxite, are needed to make 0.5 kg (1 lb) of aluminum. The U.S. aluminum industry has recognized the advantage of a domestic aluminum supply and has established systems for collection, transportation, and processing. For this reason, aluminum cans almost always produce a profit in community recycling programs. A number of states require deposits for beverage containers and have established redemption centers at supermarkets. The overall recycling rate of all forms of aluminum is about 35 percent. Cans brought to collection centers are crushed, baled, and shipped to regional mills or reclamation plants. The cans are then shredded to reduce volume and heated to remove coatings and moisture. Next, they are put into a furnace, melted, and formed into ingots, or bars, weighing 10,000 kg (30,000 lb) or more. The ingots go to another mill to be rolled into sheets. The sheets are sent to a container plant and cut into disks from which new cans are formed. The cans are printed with the beverage makers’ logos and are shipped (with tops separate) to the filling plant. About 100 billion aluminum beverage cans are used each year in the United States and about 55 percent of these are then recycled. The average aluminum can in the United States contains more than 50 percent postconsumer recycled aluminum. About 97 percent of all soft drink cans and 99 percent of all beer cans are made of aluminum.
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