Uncovering the Carbon Emission Intensity and Reduction Potentials of the Metro Operation Phase: A Case Study in Shenzhen Megacity.

The huge energy consumption of metro operations has become a significant challenge faced by the urban public transportation sector to achieve low-carbon development. Using Shenzhen as an example, this study has made efforts to quantify the metro's energy consumption and carbon emission intensity during the operation phase by using the Life Cycle Assessment approach. Furthermore, this study evaluates the actions that can be taken to reduce energy consumption and emissions. A comparative analysis between metros and other public transportation modes has also been conducted. The results show that the annual carbon emissions from the metro's operation phase in Shenzhen city increased from 63,000 t COe in 2005 to 1.3 Mt COe in 2021, and the historically accumulated carbon emissions are 9.5 Mt COe. The unit operating mileage, the unit station area, and the per capita carbon emission intensity were 2.1 kg COe/km, 132.5 kg COe/m, and 0.6 kg COe per capita (13th Five-Year Plan Period), respectively. By continually promoting the low-carbon operation of the subway, the cumulative carbon savings could reach 0.1 Mt COe (2022-2035).