by Liza Farr
In November, GENeco, a subsidiary of a UK utility company, debuted a new bus line that is powered by human and food waste (BBC, Nov 20, 2014). The so-called “poo bus” carries about 10,000 passengers each month between the Bristol airport and the Bath city center. The 40-seat bus can travel up to 186 miles on one tank, which can be produced from the annual waste of about five people. The combustion engine on the bus similar in design to diesel equivalents. The gas is generated through anaerobic digestion, where oxygen starved bacteria breaks down the biodegradable material to produce methane-rich biogas. The gas is processed over 12 to 18 days, where it also undergoes upgrading, where carbon dioxide is removed and propane added, and impurities are removed to produce virtually odour-free emissions (Frangroul, Feb 3, 2015). By the end of processing, the composition of the biogas is the same as natural gas. The compressed gas is stored in dome-like tanks on the roof of the bio bus (BBC, Nov 20, 2014).
The bus produces up to 30 percent less carbon dioxide compared with conventional gasoline engines, and harmful emissions would be reduced by as much as 97 percent if fossil fuels were replaced with this human waste gas (Opelka, Feb 3, 2015). The bus was launched right as Bristol became the European Green Capital of 2015 (BBC, Nov 20, 2014). GENeco hopes the bus serves to educate people about fossil fuel use and using waste productively. However, as of yet there is little discussion of expansion of the bus line to include multiple bio buses. It is unclear as to whether the bus is economically sustainable, or simply a novel reputation piece to bring awareness to the issue of waste and energy. The Bristol sewage plant generates 17 million cubic meters of biomethane annually, which is enough to power 8,300 homes (BBC, Nov 20, 2014). GENeco does sell the biomethane to homes in the area, although it is unclear how many homes they do power. The bio bus and GENeco’s innovative use of human and food waste is still an exciting frontier in renewable energy and in closing the waste loop.
BBC. “UK’s first ‘poo bus’ goes into service between Bristol and Bath.” Nov 20, 2014. [http://www.bbc.com/news/uk-england-bristol-30115137]
Frangoul, Anmar. “Flush with success: The UK’s first poop-powered bus.” Feb 3, 2015. [http://www.cnbc.com/id/102375325#]
Opelka, Mike. “Yup, There’s a ‘Poop-Powered’ Bus Out There…and It Works.” Feb 3, 2015. [http://www.theblaze.com/stories/2015/02/03/yup-theres-a-poop-powered-bus-out-there-and-it-works/]