Bristol airport in the UK has started a four-week trial of a bus that runs on bio-methane, generated by sewerage treatment.
So yep, it runs on poo (and processed food waste, but there's nothing funny about that).
The 40-seat airport transfer service has a range of 300km on a single tank of the (endlessly) renewable fuel.
Bio-methane has cleaner emissions than diesel and also reduces the reliance of fossil fuels.
The bus is expected to carry 10,000 passengers a year on the service from Bath to Bristol airport in southern England.
GENeco, the company behind the bio-methane generation, also operates a Volkswagen Beetle that uses the technology.
There is no word yet on what the exhaust gasses smell like, or if the quieter ones are worse.
And yes, I thought long and hard about that headline - come up with a better one and win a CarAdvice prize pack!