A bus powered entirely by food and human waste will started running in the UK next week. It does 186 miles on a full tank of what’s literally gas.

The bio-bus, which can carry up to 40 passengers, runs on biomethane produced at a local sewage treatment center. The gas comes from both food waste and sewage: in other words, from food that’s been eaten and excreted, and food that has not.

The treatment center turns around 75 million cubic meters of sewage and 35,000 metric tons of food waster a year into 17 million cubic meters of biomethane through anerobic digestion.

The bus will run on a route between Bristol Airport and the nearby city of Bath. (By coincidence, the route runs within a few streets of my house.) The biomethane does require some processing before use in the vehicle, which includes replacing its carbon dioxide content with propane, and removing impurities so that the bus emissions don’t have any unwanted odor. While the bus still generates carbon dioxide, the levels are said to be 30 percent lower than with ordinary diesel-fuelled buses.

The operators of the bus are making a big deal of the idea that many local passengers may have indirectly contributed to the production of the biomethane. They note that an average individual’s food waste and sewage over a year is enough to power the bus for 37 miles.

Sadly the bus doesn’t have bathroom facilities.