AMBER WAVES Each year, Americans produce 31 billion gallons of prime fertilizer: water-soluble nitrogen, phosphorous, and potassium. "We excrete the same quantity of elemental nutrients as we eat, and that's the same amount plants need to grow," says Abraham Noe-Hays, research director at the Rich Earth Institute in Brattleboro, Vermont. The 100 gallons of urine each of us generates annually, he says, could be used to grow more than 300 pounds of wheat—enough to keep a person in bread for a year. This year the institute is conducting a U.S. Department of Agriculture-funded test in which 3,000 gallons of donated urine will be sprayed on a Vermont hay field. In a smaller trial last year, a treated field yielded 5.8 times more hay than an untreated one. "We're creating sustainable fertilizer out of something that pollutes rivers and streams," Noe-Hays says. "We're closing a loop that's been broken."

POWER FROM THE PEE-PLE The stuff we flush is nice and warm—as is the water from showers, washing machines, and dishwashers that joins it down the drain. That warmth is now being recognized as an energy source. "Sewage heat recovery" uses wastewater—the average temperature of which is 65°F to 70°F—to preheat clean water on its way to the tap. "The heat never leaves the building," says Lynn Mueller, president of International Wastewater Systems. The technology is already being used in Chicago, Vancouver, Oslo, and Beijing, and the market is expanding rapidly. "There's sewage in every city," Mueller observes. "Everywhere there's people, you have energy."

TOILET HABITS The rock hyrax is a furry mammal (the closest living relation to the elephant, by the way) that lives in colonies in rock crevices in Africa and the Middle East. Creatures of habit, hyraxes are remarkably faithful to their latrines; one South African colony has been using the same toilet for 55,000 years. The resulting layers of dried urine, called hyraceum, are a boon to paleoclimatologists at the Montpellier, France-based Hyrax Project, who analyze the stable isotopes and pollen trapped within to measure how climate and vegetation have changed over the eons. "Some researchers use ice cores," project leader Brian Chase of Montpellier University says. "We just happen to use urine."