The Denver Zoo's Poo-Powered Rickshaw

What is a zoo to do with its excess panda poo? Denver's answer is to compress it into pucks and feed them to a syngas-powered hybrid-electric Tuk Tuk.

As anyone who's been to a zoo can attest, those animals truly enjoy a good deuce. They do it constantly, typically producing more waste than the facility can reuse. Zoo's often have to haul the excrement away for disposal in landfills—an expensive and inefficient option. But the Denver Zoo has spent nearly a decade working on an ingenious and local alternative to landfills—a 20-year-old motorized rickshaw, also known as a Tuk Tuk.


The zoo collects all of its animal waste, as well as 90 percent of the garbage generated by guests and staff, and compresses the refuse into small pellets. When these pellets are heated in an anaerobic environment, they produce synthesis gas (syngas) which is burned to drive generators to power the Tuk Tuk's batteries, pumps, and electric motor.

Development of the technology began nearly a decade ago, when the zoo began planning for its new Elephant Passage exhibit. Conservation was a major focus of the exhibit, so the planning committee decided the Tuk Tuk needed a more environmentally-friendly fuel source than its original diesel engine.

The zoo then hired a three-engineer team to develop and deploy an alternative power-source. "These guys spent a lot of time in Dumpsters figuring out what kind of trash we produce," zoo spokeswoman Tiffany Barnhart said. In the end, the team discovered that just about any non-metal, non-glass waste can be compressed and burned on-site at the zoo—about 1.5 million pounds a year in all. The Tuk Tuk could be a model for a syngas generator system that can provide a full 20 percent of the zoo's annual energy requirements, reducing the zoo's waste hauling bill by $150,000. Not bad for material unworthy of even a shoe sole.

The Tuk Tuk, which was purchased in Thailand, is actually the second prototype of the poo-powered generator. The first prototype used to be the zoo's margarita blender.


The rickshaw is expected to make its debut on June 1 when the Toyota Elephant Passage exhibit opens. "(The tuk tuk) can be a place for us to interact with guests about this great technology," the zoo's sustainability manager, Jennifer Hale, told the Denver Post. "It was a good theme with the elephants." [Denver Post, Syngas Wiki via Autoblog - Images: Helen H. Richardson, The Denver Post]


Mike Dunbar works on the tuk tuk while George Pond, left, watches. To the right, Brian Bruggeman and Paul Quick check on electrical components. Image: Helen H. Richardson, The Denver Post


Enrique Tapia De La Torre is underneath, with Quick helping. Images: Helen H. Richardson, The Denver Post


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