In the UK, the government participated strive to reduce fuel consumption. In fact, they recently launched its first environmentally friendly buses that use fuel from human faeces.
The bus was going to go and serve the passengers who want to travel between Bristol to Bath. The bus is actually completely using fuels from bio methane produced from waste processing and human waste in Bristol. By doing so, these buses can reduce the rate of fuel use in the local area.
The purpose of making this an environmentally friendly bus itself is to reduce the level of pollution in the city center. By using bio-methane fuel, these buses produce greenhouse gases 30 percent less than diesel buses. If you are concerned with the odor generated, just take it. The gas used was purified so odorless.