There is a new prototype of the classic Volkswagen Beetle in the U.K. that gets its fuel from a nearby sewage plant. That’s right: it runs on human waste. As a car that runs on biogas, VW’s Bio-Bug is not really a new concept. But the specific type of biogas it consumes is raising a lot of eyebrows and questions.

Yes, the sewage is treated. And no, if you didn’t know the fuel source, you’d have no way of knowing it was sewage, the company says. In fact, the U.K. biogas plant that introduced the prototype says that it already uses biogas derived from sewage to produce electricity. It said it had a surplus of gas that it wanted to put to a good use and thought automobile fuel was a natural fit. Volkswagen is reportedly considering converting some of its cars to run on biogas, depending on the outcome of the Bio-Bug test run.

Now, before anyone gets too excited – or too offended as the case may be – remember this: Poop-powered cars probably are not coming to a road near you anytime soon. It is estimated that it would take the annual, “output” of 70 households to get one car to produce enough fuel for one car to travel 10,000 miles. Even under the best case scenario, we’re looking at a pretty small niche market.

But at a time when consumers are raising all sorts of objections to less controversial energy sources like wind and solar power, human waste as fuel does bring up some interesting questions. Could it ever fly in the United States? Or, would automobile fuel derived from sewage just make a lot of people uncomfortable? What about you? Would you buy a car that got fuel from the same stuff that gets flushed down the toilet? If not, why not? Would you rather fill up you vehicle on cooking oil?

Tell us what you think.