Junkyard Planet: Travels in the Billion-Dollar Trash Trade

by Adam Minter

the point of this building isn’t to awe, but rather to separate shredded metal from shredded foam, plastic, and other nonmetallic pieces of a pulverized automobile. The physics of how this happens are deceptively simple. Consider for a moment, a common egg. If you place it in a bowl of fresh water, it sinks. But if you add enough salt to that water, the water becomes heavier than the egg, and the egg floats. In the mid-1960s Ron Dalton, an engineer who first went to work for Leonard Fritz in 1957, wondered what you’d need to add to water to make various metals float. The idea, he told me in an interview, came from reading a book that described how floatation was used to separate minerals in the mining industry. There, miners used “heavy media”—the industrial equivalent of table salt—to increase the weight of water, and thus float away crushed rock from crushed minerals. It seemed logical that the concept could be extended to scrap metal.