A biogas powered double-decker bus is being trialled on the Guided busway between Huntingdon and Cambridge.
It's hoped the bus can cut emissions by up-to 84 per-cent.
Biogas is created from waste products such as household food waste, farm waste and sewage.
The six-week trial of a 'greener' Enviro 400 Scania double-decker began on November 1st.
The Scania model has been specifically developed for the UK bus market.