by Briton Lee
The British company Geneco has begun implementing prominent buses with a cartoon graphic detailing its power source: human waste. The concept of using waste to produce fuel is not novel, and is termed biomethane or renewable natural gas (RNG). It is most commonly used to power vehicles. The biomethane is collected from sewage treatment plants that process human waste while producing methane and carbon dioxide as byproducts. Typically, the resulting gases are simply released into the atmosphere, with plants in Oslo, Norway producing and releasing approximately 17,000 tons of carbon dioxide a year (Demerjian 2009).
The use of RNG in buses allows the reuse of these organic molecules and extracts remaining energy from these sources before releasing carbon dioxide back into the atmosphere. Our carbon footprint is not only mitigated at wastewater plants, as the engines needed to run on RNG are more efficient than traditional diesel engines, eking more mileage for the same amount of carbon emissions (Chappell 2014). In fact, the Bio-Bus’ engine allows it to cover 186 miles on a full tank, which is equivalent to the annual waste of five people. There are further avenues for pursuing sustainability with the production of RNG, which can be obtained from decomposing food waste. Food waste and food not suitable for human consumption can be recycled via anaerobic digestion into an alternative energy source, instead of being wasted in landfills and incinerators that squander the untapped methane. The methane can also come from other sources of feces, such as livestock. RNG is usually locally sourced, and there is potential to turn rural communities into alternative fuel producers. In California, proponents of biomethane claim that collecting the methane from the state’s 1.7 million cows would potentially produce 8 million pounds of methane a year, rivaling approximately 150 gallons of gasoline (Demerjian 2009). Regardless, there are multiple sources available for biomethane, and implementing RNG is quite feasible with 60% of Sweden’s natural gas vehicles running on RNG (U.S. Dept. of Energy).
Chappell, Bill. 2014. “Poo Power: New British Bus Runs On Human Waste.” NPR. (http://www.npr.org/blogs/thetwo-way/2014/11/21/365761662/poo-power-new-british-bus-runs-on-human-waste)
Demerjian, Dave. 2009. “Norway or the Highway: Poo Powers Oslo Buses.” Wired. (http://www.wired.com/2009/01/oslos-buses-to/)
U.S. Dept. of Energy. “Renewable Natural Gas (Biomethane).” (http://www.afdc.energy.gov/fuels/emerging_biogas.html)