New Life for Shredded Plastic Waste

Advanced recycling processes help return shredded plastic scrap into regenerated plastics with properties nearly equaling those of the original material. Consider the mix of materials that go into household appliances and automobiles. The good news, say researchers at (Argonne), is that over 95% of the over 50 million vehicles scrapped globally each year enter a comprehensive recycling infrastructure. Nearly 75% of the weight of the vehicles is metals and the metals are profitably recycled through direct reuse, component remanufacturing, and scrap processing or shredding. Other components such as batteries, automotive fluids, some windshield glass, starters, alternators, and other dismantled parts are also recycled. The percentage of recycled materials from vehicles is about to go up. Argonne, working with the Vehicle Recycling Partnership (VRP) of the United States Council for Automotive Research (USCAR), a partnership between General Motors, Ford Motor Co. , and the American Chemistry Council-Plastics Div. (ACC-PD), is developing technology for recycling polymeric materials from shredder residue. Scrap processors use giant 3,000 to 8,000-hp hammer mills to shred both vehicles and other obsolete metal-containing products. Household appliances, industrial scrap, and demolition debris are all candidates for being turned into fist-sized chunks as a means of liberating the metals. Processing-unit operations vary but the basic process involves air classification of the “lights” fraction followed by one or more stages of magnetic separation to recover the ferrous metals. Trommels and screens are then used to remove particles smaller than about 5/8 in., followed by one or more stages of eddy-current separations to recover the nonferrous metals. Once the metals are gone, what’s left is called shredder residue. It’s typically a mix of polymers (plastics, rubber, and polyurethane foam), a “fines” fraction that includes metal oxides, glass, and dirt, as well as residual amounts of ferrous and nonferrous metals. For each ton of