Uncovering the lifecycle GHG emissions and its reduction opportunities from the urban buildings: A case study of Macau

The building sector has become the main source of implicit greenhouse gas(GHG)emissions worldwide, and Macau is no exception. However, as yet, there is a lack of work to quantify the GHG emissions and guide cities on how best to reduce emissions. By using the life cycle assessment method, this study is therefore designed to estimate the GHG emissions from urban buildings during the period of 1999-2016, to figure out the major contributors, and finally, to propose potential effective measures for GHG emissions reduction in Macau. The results show that total GHG emissions from buildings have grown quickly from 1.52 million metric tons (Mt) CO(2)e in 1999 to 5.91 Mt CO(2)e in 2016. The use phase contributes to most GHG emissions during the whole life stage, accounting for 65.75% of the total GHG emissions, followed by construction stage (33.72%). The unit GHG emissions in the construction stage is 1.47 (0.84-3.82) tons CO(2)e/m(2), while for the use stage, unit GHG emissions from resident and non-resident buildings in 2016 are up to 65.33 and 3316.37 CO(2)e/m(2)/year, respectively. It is noted that EoL stage has 'negative value', indicating that it could generally bring some environmental benefits due to materials recycling. e.g. In 2016, the environmental impacts and benefits in the EoL stage are 21.12 and 85.94 Kt CO(2)e, respectively. The gaming industry and clean electricity should be the key points of building GHG emission reduction in Macau. Further scenario analysis shows that the enforceable policies can slow down the growth rate of GHG emissions.