The “Number Two” Bus Runs On–What Else?–Human Waste

Surprisingly, Bristol’s Bio-Bus doesn’t even smell.

The new Bio-Bus in Bristol, England, is nicknamed “the number two” for a reason: It runs on fuel made from human waste. The biogas in the bus’s tank is also made from food waste.


Ironically, powering a bus with poop can actually help a city smell better. The waste treatment plant that produces the fuel is virtually odor free, and as the bus drives, there’s no longer a black cloud of diesel exhaust coming out the tailpipe.

A bus running on diesel pumps out around 40 toxic air contaminants, from benzene, arsenic, and formaldehyde to smog-causing nitrogen oxides. The Bio-Bus, by comparison, reduces those pollutants by 97%.

GENeco, the waste treatment company that produces the fuel, processes millions of cubic meters of sewage waste and 35,000 tons of food waste every year at a nearby plant. Through an anaerobic digestion process they heat up the sludge to create biomethane. A new plant sends some of the gas off to power about 8,500 homes. The rest goes to a new refueling station for buses.

“For many years, we’ve generated gas to create electricity,” says Ian Drury, a spokesperson for Wessex Water, GENeco’s parent company. “But we decided that we also wanted to put gas in the local network to go to homes. We built a gas-to-grid plant, and we also installed a refueling unit at the same time so we could put gas into vehicles like the bus.”

The new system isn’t fully environmentally sustainable, since the fuel still pumps out carbon dioxide. Still, it creates 20%-30% less CO2 than a diesel bus, it’s cheaper than a diesel-electric bus, and the process captures methane from food waste that might otherwise be released in a landfill. It’s also, well, a renewable and local fuel source.

“Gas-powered vehicles have an important role to play in improving air quality in U.K. cities, but the Bio-Bus goes further than that and is actually powered by people living in the local area, including quite possibly those on the bus itself,” GENeco general manager Mohammed Saddiq said in a statement.


A single passenger’s annual food and sewage waste could fuel the Bio-Bus for about 34 miles. A busload of passengers would create enough waste to drive the bus from the southern tip of England all the way to the northern tip of Scotland and back again.

The new bus is plastered with a cartoon of passengers on toilets. “I think it’s safe to say that the graphic has turned heads,” says Drury. “People can clearly see how the bus it’s fueled. There’s a fun side to it, but there’s also a serious message behind the bus–it’s much better for the environment than diesel vehicles.


About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley.