The shredding of automobiles and major household appliances is a process where a hammermill acts as a giant tree chipper by grinding the materials fed into it to fist-size pieces. The shredding of automobiles results in a mixture of ferrous metal, non-ferrous metal (e.g. alloys of copper and aluminum) and shredder waste, called automotive shredder residue (ASR). ASR consists of glass, fiber, rubber, automobile liquids, plastics and dirt. ASR is sometimes differentiated into shredder light fraction and dust. ASR often contains hazardous substances such as lead, cadmium, and PCB. Therefore, some countries have classified ASR as hazardous waste and have established legislative controls.
