You’ve heard of the Popemobile, the pontiff’s modified Mercedes-Benz M-Class SUV that sports bulletproof glass and is powered by traditional fossil fuel. But now there’s the Poop Mobile, developed by the Denver Zoo and designed to run on animal manure. The best part being, of course, that the zoo has no shortage of fuel for it.

When a 20-year-old tuk tuk, or motorized rickshaw, from Thailand ended up at the Denver Zoo, a couple of crafty mechanical engineers on staff decided to power it using animal droppings. The zoo already had a program that collects all of its animal droppings, along with much of its human-generated garbage, and turns them into "gasified pellets."

When the smelly pellets are exposed to extreme heat in a non-oxygen environment, they give off a form of synthetic gas, or "syngas." In a patent-pending process, zoo engineers Mike Dunbar and Paul Quick use the syngas to fuel a generator that in turn charges the batteries of the electric-powered tuk tuk.

The tuk tuk is a part of a prototype program at the zoo, and officials hope to turn 100 percent of its animal waste into syngas that would then produce 20 percent of its overall power needs. As part of the plan, the poo-powered tuk tuk is paving the way for a new Elephants Passage exhibit, opening June 1, powered solely by syngas.

They probably thought it was better to start with the elephants than, say, relying on their star red panda Daisy to deposit enough fuel for the tuk tuk.