Embodied energy evaluation for the Hong Kong MTR South Island Line

Over the past two decades, research on embodied energy has been associated with construction projects in an effort to tackle sustainability issues. In this study, the embodied energy of two types of tunnels of the South Island Line (East) contract 904 in Hong Kong were evaluated. The results show that the cut-and-cover tunnel has a higher embodied energy than the drill-and-blast tunnel, at 243 and 157 GJ/m, respectively. By breaking down the analysis of embodied energy consumption into different categories (i.e. materials, transportation and construction), it is shown that, in both tunnels, materials dominate approximately 63% of the total embodied energy, as steel has the highest embodied energy intensity among all construction materials. Tunnels require direct energy-intensive construction, as transportation and construction can collectively account for as much as 37% of the total embodied energy. The total embodied energy of both tunnels is equivalent to approximately 4700 per-capita annual energy consumption and almost one 40-storey residential building of embodied energy in Hong Kong.