Stinkin’ rich

Sewage may be a gold mine. Researchers have found that sewage entering municipal wastewater treatment plants teems with 58 valuable elements such as gold and copper.

To dig up the soiled loot, researchers analyzed treated sewage samples from 94 sites around the country. Extracting the goods, however, would be a dirty job.

Editor’s Note: This story was corrected May 4, 2015. The approximate value of elements in a metric ton of sewage sludge is $500, not $500 million.