Overview: Railroads are the backbone of American industry. 170,000 miles of track crisscross the country from coast to coast, moving two quadrillion tons of freight every year. But nothing lasts forever, and that includes a couple of 180-ton locomotives. Their engine technology is inefficient so they're headed for the scrap dealer where they'll be cut down and cannibalised. Any salvageable parts must come out intact for resale, while any leftover metals – like steel and copper – will be cut up, melted down and ultimately reformed into new products. In this business, nothing goes to waste. Take an inside look at the unknown world of scrap, where locomotives go to die and be reborn