There's gold in them thar ... wastewater treatment plants? Yes, researchers think that human waste contains enough gold and other valuable metals to make a mining operation pay off, reports LiveScience. Scientists with the USGS spent eight years analyzing treated solid waste to detect minute metal particles, which come from an array of products, including shampoos and detergents. "The gold we found was at the level of a minimal mineral deposit," says lead researcher Kathleen Smith. They also found silver, platinum, vanadium, and copper, the latter two with potential applications for cellphones and computers.
Extracting metals of all kinds would have a bonus, says the research team at EurekAlert. Not only could valuable metals be sold or put to use, "nuisance metals" could be eliminated from the waste, allowing more of it to be used as fertilizer. One idea is to use the same chemicals that leach metals out of rock to leach them from the waste. The practice is controversial at traditional mining sites because of environmental concerns, but "in the controlled setting of a sewage plant, the chemicals could be used liberally without the ecological risks," notes the Guardian. A previous study found that a city with 1 million people flushes about $13 million worth of metals away every year. (Read more gold stories.)