Multi-Criteria Life-Cycle Assessment of bus fleet renewal: A methodology with a case study from Italy

To decarbonize the transport sector, national and local government have introduced policies to incentivize the replacement of old diesel-powered vehicles with new clean-fuel ones (e.g., battery electric, hydrogen fuel-cells). This paper focuses on both the economic and ecological transition of local public transit (LPT) bus fleets. A methodology based on a Life-Cycle Assessment (LCA) approach of both costs and environmental impacts is proposed to identify suitable pathways for the renewal of the existing buses: these are compared using a multicriteria decision matrix. The application to the Italian basin of the provinces of Como, Lecco and Varese (with about 860 operating buses almost all equipped with diesel engines) has allowed to validate the approach for both the urban and the ex-urban context. In the urban context, the study has shown that the full-electric scenario has the lowest environmental impact since there are zero tailpipe emissions and greenhouse gases (GHG) are lower than all the other scenarios. For the ex-urban service, that is characterized by medium and long-distance routes, a "full-electric" scenario is not yet feasible, considering that long-range BEBs having sufficient battery autonomy to guarantee efficient operations on medium-long distance routes are not yet widely marketed. Liquefied natural gas-powered buses could be a suitable solution in these contexts, however it was found that they have even worse environmental performances compared to diesel buses (+14% GHG emissions and more than doubled direct emissions). Hybrid electric vehicles would be an option for decarbonising ex-urban LPT, but the costs of the transition in such direction should be considered with care.