Electric and biomethane-fuelled urban buses: comparison of environmental performance of different powertrains

Purpose: The paper aims to promote the transition to low/zero emission of the local public transport, particularly, urban buses are taken into account. Method: The life cycle assessment of electric and biomethane-fuelled urban buses is performed by exploiting SimaPro commercial software (v.9.1.1.). Attention is focused on powertrains. Both midpoint and endpoint analyses are performed. Referring to environmental impact, the best compressed biomethane gas (CBG) powertrain was compared to the best electric one. Additionally, the worst-case scenario has been considered for both CBG and electric powertrains. Results: CBG powertrain outperforms the electric one if overall greenhouse gas emissions are considered. However, the electric powertrain seems promising for human health and ecosystem. Conclusions: The environmental performance of the two powertrains is good. Both of the two technologies have strength and weak points that anyhow make them good candidates for a clean local public transport of the future. The analysis performed in the paper suggests a future investigation on hybrid electric-CBG powertrain. Actually, such a solution could benefit from both the strengths of the biomethane and the electric powertrain.