**3.1 Carbon emission impact of life cycle stages of demolished waste material**

According to the analytical assessment model, the total carbon emission of different stages in the lifecycle of the waste materials was calculated (see **Table 4**). The value of the treatment stage was the largest representing about 81% of the total endof-life carbon emission. This includes the environmental impact of input/output of treating and recycling demolished waste, carbon emission reduction of waste replacement as well as landfilling unrecyclable waste. The carbon emission values of demolition and transportation stages accounted for 18% and 1% respectively. The carbon emission of the treatment stage is influenced by different carbon emission values compared to the demolition stage (see **Table 2**). Despite being the major carbon emission contributor, if recycling is selected, where possible, for waste treatment, the reuse of recycled materials could result in environmental benefits. This suggests that the choice of waste material treatment option should be given priority in order to reduce carbon embodied in them.


#### **Table 3.**

*End-of-life options for common building elements.*


**Table 4.**

*Carbon emission of life cycle stages of demolished waste materials.*

**Table 4** indicates that transportation is by far the least carbon emission end-of-life stage. This is because the distance of transporting waste materials to the processing plant or disposal site is located locally. This result emphasises the need for selecting local processing facilities as long distance defeats the goal of carbon emission reduction.
