Aarian Marshall is a transportation reporter at WIRED and former CityLab contributor. She lives in San Francisco.
How some urban zoos are turning brown into green, in more ways than one.
Call it the circle of life: By next year, the Detroit Zoological Society says it will have installed facilities to transform animal and human waste into electricity to power its zoo hospital, according to a recent report from the Daily Tribune. The zoo’s forthcoming anaerobic biodigester equipment may sound fancy, but it uses pretty simple (and natural) processes. The zoo will place approved waste (including feces and food waste generated by zoo restaurant patrons) in airtight tanks filled with a special mélange of bacteria. When organic materials are put in the tanks, the bacteria consume it, producing biogases like methane. That methane is then used to power turbines that, in turn, create electricity.
According to Zoological Society Communications Director Patricia Mills Janeway, the $850,000 facility will result in an annual cost savings of $80,000.*
Detroit isn't the only urban zoo that's taking advantage of its biological waste in dollar-smart—and environmentally-friendly—ways. Many zoos use their animal manure to nourish their own garden displays.
Others are selling their poop to the public. The Woodland Park Zoo in Seattle, Washington, holds biannual Fecal Fests every spring and fall, wherein local gardeners are encouraged to enter a lottery for aptly-named Zoo Doo, a compost made of zoo animal manure. As Zoo Compost and Recycling Coordinator Dan Corum explains in the video below, the Woodland Park Zoo used to pay about $60,000 to dispose of zoo residents’ doo in landfills. “Now we make between $15,000 and $20,000 by people ... buying it from us after it's been made into compost,” Corum says. “It's good for the planet because we take something that was going into the landfill and now it goes back into people’s gardens.” (There are some really excellent poop puns in this video, by the way; highly recommended.)
Zoo Doo sold during this fall’s Fecal Fest (going on now) is about $5 a bag, depending on the size. But competition for the stuff is fierce. “[P]eople just get a real kick out of using rhinoceros doo,” a Zoo Doo enthusiast told the New York Times.
Other zoos are performing similar community services. The Kansas City Zoo’s got Zoo Manoo. The Louisville Zoo holds a Zoo Poopy Doo Sale every April, boasting “the most exotic blend of compost in the city!” That includes manure from the Zoo’s hoof stock (like elephants, rhinos, camels and giraffes), hay, straw, and wood shavings.
Why are some animals left out of the mix? Michigan’s Binder Park Zoo’s ZooDoo Days boasts manure that “usually does go quickly,” Jenny Barnett, director of wildlife conservation and education, told MLive.com. But for fear of disease transmission,“we don’t include carnivore or monkey poop,” she said.
*This post has been updated with more current information from the Zoological Society Communications office.