**5. Conclusion**

Building demolition waste represents a huge environmental challenge worldwide. The environmental implications are not only associated with volume, but also with

### *Life Cycle Assessment of Buildings: An End-of-Life Perspective DOI: http://dx.doi.org/10.5772/intechopen.110402*

carbon embodied in the waste. These adverse environmental impacts associated with the generated waste can be minimised through appropriate waste treatment strategies. This chapter evaluates the various stages of the life cycle of demolished waste materials, the potential carbon emission reduction associated with different demolished wastes and waste treatment strategy options. This was exemplified by a case study of a supermarket building. The analytical framework and the detailed method of quantifying the environmental impact have the potential to be adopted in other building demolition projects.

The results of this study show that the processing or treatment stage might generate the largest amount of carbon emission (81%) in the life cycle of demolished waste materials. In contrast, the transportation of stage contributed the least (1%) to the total life cycle of carbon emission.

Likewise, this study revealed that carbon emission reduction can be achieved through the substitution effects of reusing recycled waste materials. The analysis indicates there are environmental benefits to substituting virgin resources with recycled building-demolished waste, which compensates for the environmental impacts associated with the processing of waste materials. The environmental gain differs considerably from one waste material to another. For example, despite representing only 10% of the total mass of generated waste materials, steel has a carbon emission reduction potential of more than 90% of the case building. The recycling of metal (steel and aluminium) and timber-based materials should be given priority in terms of material potential to reduce carbon emissions during end-of-life.

Additionally, this study revealed that landfilling generated the largest amount of carbon and the largest contributor to life cycle carbon emission during the end-of-life phase. On the other hand, recycling demolished waste materials can lead to significant environmental, particularly for materials with a high-value recyclable potential such as steel, aluminium and timber. For instance, the results indicate that recycling over 80% of the total mass of generated waste materials could achieve an overall 7% environmental benefit.

This study offers some useful implications and guidance for designers, engineers and other stakeholders regarding the treatment of construction and demolition waste. For instance, where reuse is less viable, recycling waste should be considered an integral part of the demolished waste treatment strategy for each building's end-of-life project. The development of the waste treatment strategy should give major priority to metal waste such as steel and aluminium as well as wood-based materials because of their positive environmental performance during end-of-life treatment. Also, the findings reported in this study can contribute to mitigating the environmental impact of building demolition projects. Furthermore, the detailed assessment approach provides theoretical and methodological guidance which can be adopted to guide the quantitative analysis of other types of demolition projects globally. Finally, the findings complement the existing literature, which mainly addresses the environmental performances of demolished waste by means of the life cycle assessment methodology.
