Energy use and carbon dioxide emissions assessment in the lifecycle of passenger rail systems: the case of the Rio de Janeiro Metro

Passenger rail systems have been considered, from an operational perspective, as a means of transport that can contribute to meeting the carbon dioxide emission goals established by many governments worldwide. However, the impact produced by these systems can only be fully assessed by a lifecycle approach. This article assesses the energy used and the emissions produced and avoided in the lifecycle of a new line of the metro network in Rio de Janeiro, built as a requirement for hosting the Olympic Games in 2016. Infrastructure construction, train manufacture, maintenance, infrastructure operation and train operation were considered in the 60-year lifecycle. The study shows emission of 13.90 g of carbon dioxide per passenger kilometer traveled during lifecycle and that non-operational emissions will be compensated 14 years after the inauguration of the system. Infrastructure construction and train operation represent most of the emissions produced and energy used. Renewable energy represents 53.27% of total energy used. Electricity consumption has the greatest share of emissions, with 46.66%, followed by cement and concrete, with 30.53%, and steel, with 12.43%. The conclusion is that the system, over the horizon analyzed, can help to reduce emissions by the city's transport system. The increase in the renewable energy share in electricity generation and the improvements in the production of cement and steel, are the key factors in reducing emissions produced during the lifecycle.