The Detroit Zoo’s Newest Attraction Could Revolutionize The Way Zoos Get Energy

Apr 23, 2015 by



CREDIT: flickr/majorbonnet

If seeing lions and tigers and bears isn’t reason enough to visit the zoo, at the Detroit Zoo there will soon be a new spectacle: a biodigester facility turning animal waste into valuable energy.

The Detroit Zoological Society (DZS) and the Michigan Economic Development Corporation launched a campaign this week to take something the zoo has an endless supply of — animal waste — and turn it into something the public has a never-ending demand for — energy. The supporters are looking to raise enough money to process around 400 tons, or 800,000 pounds, of manure annually into methane-rich biogas using a biodigester. The gas will then be used to power the 18,000-square-foot Ruth Roby Glancy Animal Health Complex, thus saving the zoo around $70,000 to $80,000 in energy costs and another $30,000 to $40,000 in waste disposal fees every year. The compost leftover from the anaerobic digestion process will be used in zoo gardens and other grounds.

The Detroit Zoo has a goal of being zero-waste by 2020, and the addition of a biodigester, which would generate around 7 or 8 percent of the zoo’s annual electricity needs, would be a big step closer to that achievement. It would also set a precedent for other animal zoos and sanctuaries to strive towards.

“We’ll be the first zoo in North America to have a dry biodigester on grounds, turning the dry animal waste into electricity,” said DZS COO Gerry VanAker. There’s also a zoo in Munich, Germany that operates a biodigester, and the Toronto Zoo is in the early phases of developing one, VanAker said.

While the new equipment is not cheap, VanAker said the zoo expects a return on its investment in around a decade. As part of the $1.1 million cost, DZS is trying to raise $55,000 by June 15 through a crowdfunding campaign. Michigan State University’s Anaerobic Digestion Research Education Center will help manage the biodigester for the first year before handing it over to zoo employees.

The Detroit Zoo, which welcomes more than 1.3 million visitors annually, wants to reduce its electricity-related greenhouse gas emissions by 20 percent below 2009 levels by the end of 2015. In 2014 the zoo won the Green Award from the Association of Zoos and Aquariums.

Anaerobic digestion, otherwise known as biogas recovery, is a biological process in which organic wastes, such a livestock manure or food waste, produce biogas primarily composed of methane (CH4) and carbon dioxide (CO2). In the controlled environment of a biodigester, the waste is put in an oxygen-free container with various types of bacteria that break down the manure. According to the California Energy Commission, depending on the waste feedstock, “biogas is typically 55 to 75 percent pure methane,” however “state-of-the-art systems report producing biogas that is more than 95 percent pure methane.”

According to the EPA, if half the U.S.’s annual food waste was anaerobically digested, it would create enough electricity to power 2.5 million homes for a year. As of January 2015, there were around 250 anaerobic digester systems operating at large-scale livestock farms across the country.

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