Oslo will introduce buses that run on biofuels generated from fermented sludge as of 2010. This type of biofuel is “carbon neutral, hardly pollutes the environment, less noisy and endlessly renewable”, claim the city officials. The cost of the fuel is less expensive than other biofuels, but building and maintaining new buses to run with it is 15% higher than for traditional buses. Nevertheless, environmentalists are delighted about using this new source of energy. Compared to diesel, biomethane emits 78% less nitrogen oxide, 98% fewer fine particles and is 92% less noisy.