Environmentally Friendly 'Poop Mobile' Comes To Palm Desert

The Tuk Tuk with its unique propulsion system on the back | Image courtesy Denver Zoo

We've all had experiences with vehicles that run like crap. Yesterday, the Living Desert Reserve in Palm Desert welcomed a vehicle that runs on the stuff.

The Denver Zoo's "poo-powered" Tuk Tuk, an electric cart that's been making news in tech blogs over the last week, is appearing at the popular Coachella Valley zoo and botanic garden as part of a Association of Zoos and Aquariums meeting this week in Palm Desert. The Tuk Tuk ends its cross-country zoo tour at the Living Desert.

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Zoo animals produce a large amount of solid waste, including not just manure but compostable trash from visitors as well. In this era of increasing disposal costs sending that much waste to the landfill isn't just environmentally unsound, it can also take an elephantine bite out of zoo budgets. A few years ago, the Denver Zoo decided to see whether there might be a way to reduce their waste stream and their carbon footprint at the same time. "We wanted an innovative energy solution that would help us eliminate our landfill waste," said the Denver Zoo's George Pond. "We immediately considered ways to create energy from animal poop and human trash."

A team of engineers hired by the Denver Zoo developed a process in which the manure and other organic waste, dried and compressed into pellets, is heated in the absence of oxygen, creating a gas that can be burned as fuel. An engine burns that fuel and charges a set of batteries, which then provide power through an electric motor.

The first trial of the new technology was used to power a blender at the Denver Zoo, with which Zoo staff made margaritas at a fundraising reception. That proof of concept proving a success, the engineering team turned their sights to larger implementations.

The Tuk Tuk, which had already seen two decades of service in Thailand as one of that country's common motorized rickshaws (earning their name, pronounced "took-took," for the noise made by their small motors), was pressed into service. Its back cargo area was reconfigured to hold the complex propulsion system, at a cost of about $50,000. If this coverage by the Denver Post is any indication, the Tuk Tuk seems to run cleanly and relatively quietly.

While the Tuk Tuk will be staying in the Coachella Valley, Denver Zoo engineers plan to take what they've learned and build a much larger stationary generator to provide electrical power for an upcoming elephant exhibit. Eventually, the zoo hopes to generate a fifth of the electrical power it uses from reclaimed waste.

The Tuk Tuk is admittedly more of a demonstration project than a new model for transportation. It's unlikely that animal waste will become a major American transport fuel any time soon -- no matter how enticing the thought of a Greyhound bus fueled by its own passengers on long trips might be.

But in some developing countries, light vehicles like the Tuk Tuk constitute a significant part of the transportation infrastructure. The light engines used in autorickshaws, some of them of the notoriously polluting two-stroke design, are a significant contributor to air pollution. Governments around the world are struggling to implement emissions controls, and in some places a shift to cleaner-burning Compressed Natural Gas (CNG) is underway.

But most people in the world don't have any way to create CNG in their villages, and so relying on it as fuel locks locals into the global energy economy. Meanwhile animal waste, agricultural waste, and other combustibles can often be found in abundance, especially in rural settings. The Denver Zoo's Tuk Tuk was created as a novel way to demonstrate a technology that will see its first use in an admittedly affluent setting: a zoo in a major US city. But the technology, if it's available and adaptable, could actually to increase the quality of life in some of the world's poorest places.

Chris Clarke is an environmental writer of two decades standing. Author of Walking With Zeke, he writes regularly at his acclaimed blog Coyote Crossing and comments on desert issues here every week. He lives in Palm Springs. Read his previous posts here.

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