The planets 1.5 billion cows are (innocently) an environmental scourge thanks to the copious amounts of horrible greenhouse gases they disgorge. Scientists from Michigan State U have flopped that around, however, and figured out how to turn the resulting manure into something good for the planet: fresh water. By running the poop through a so-called anaerobic digester and reverse osmosis system, they got pure H2O out the other side.