A 40-seat bus powered by sewage and food waste is now operating between Bristol and Bath in the UK.

Dubbed the Bio-Bus, the eco-friendly bus can travel up to 186 miles on one tank of biomethane gas. The gas, which is generated through the treatment of human sewage and food waste at Bristol sewage in Avonmout, is pumped through the bus' combustion engine, an engine similar in design to diesel engines for buses.

Bristol sewage treatment works converts about 75 million cubic metres of sewage waste and 35,000 tonnes of food waste each year, though just one passenger's annual sewage and food waste could fuel a Bio-Bus for 37 miles. A bus powered by such waste typically emits 30 per cent less carbon dioxide than conventional buses.

Tour operator Bath Bus Company is using the unique bus to transport about 10,000 passengers each month between Bristol Airport and Bath city centre and claims Bio-Bis was launched at an "appropriate" time, because Bristol is expected to be named the European Green Capital in 2015, according to the BBC.

There's just one question that has to be asked: How does the Bio-Bus smell when driving by on the street? Let's hope Bristol sewage also treated foul odors.