The Denver Zoo has to deal with a lot of waste. A good deal of that waste comes from visitors, but the zoo also produces hundreds of thousands of pounds of animal poo each year. Now, zoo engineers have found a positive use for it: They rigged up a poo-powered tuk-tuk. (A tuk-tuk is a motorized rickshaw.)
"We want to show people that we're not crazy for wanting to take elephant poop and turn it into energy," one engineer told the Denver Post.