Moving towards sustainable construction in Malaysia: A holistic model for construction and demolition (c&d) waste management

Sustainable construction has become part of the national agenda in Malaysia in an effort to preserve the environment for a better future. The management of construction and demolition (C&D) wastes is considered an essential element in achieving the sustainability goal in Malaysia. In this light, the high rate of waste generation will put pressure on the limited space for landfill, deplete the natural resources, and create more illegal dumping issues, which will directly harm the environment. The pressures to reduce wastes have significantly contributed to the shift in mindset among construction actors to elude the linear-based practices of the construction industry. A holistic model is required to manage waste generation more efficiently, and the concept of circular economy (CE) has been identified as a potential approach to handle waste generation by putting forward the idea of turning waste into wealth, by maximising the available resources as long as possible, throughout the construction cycle. This research was undertaken to develop a holistic model for C&D waste management that is applicable throughout the construction cycle (planning and designing stage, procurement stage and construction and demolition stage) in Malaysia. The methodological approach taken in this study is a mixed methodology approach, which is based on systematic literature review, a combination of the Delphi method and Analytical Hierarchy Process (AHP), the distribution of questionnaires and a simulation process using system dynamics. The relevant previous studies were reviewed to develop the preliminary model, based on the three layer approaches of micro, meso and macro of CE. The developed model was then validated using the combination of the Delphi method and AHP to scrutinise the suitability of the model to be adopted in the Malaysian construction industry. An enhanced model of C&D waste management was then introduced; based on the twenty experts' opinions. The experts are comprised of personnel from government agencies, developers, consultants and contractors in Malaysia. A causal loop diagram (CLD) was developed as an initial step towards the simulation process, which is designed based on the feedback gathered from 167 respondents. These respondents comprise the construction actors in Malaysia who answered and returned the questionnaires that are circulated. Finally, the C&D waste management system was simulated using the system dynamics modelling software, to evaluate and analyse the suitability of the model in the real-case scenario. The findings emphasised the significance of defining the right 3R principles of 'reduce, reuse and recycle', the suitable waste minimisation strategies, and the organisations responsible to ensure the implementation of C&D waste management at different stages of the construction cycle. The results revealed that the 3R principles should be integrated throughout the entire construction cycle, and the 'reduce' principle should be prioritised as early as possible. Moreover, the adoption of a modern construction method and the application of a waste management plan are necessary at the planning and designing stages to minimise waste generation. At the procurement stage, regulatory enhancement is required to ensure attention is given towards managing waste generation more effectively. Government agencies play a vital role in these stages to ensure the implementation of C&D waste management, especially in promoting the application of 3R principles. The contractors are responsible for planning an effective site management that includes proper material storage and monitoring workers' behaviours at the construction and demolition stage. Furthermore, the findings also pointed out that the main influencing factor to waste generation is the lack of on-site materials and waste management plans. Meanwhile, there is an increasing motivation to develop a better C&D waste management commitment to environmental sustainability. Lastly, the simulation modelling in this study enhanced the result and provided a clear view on understanding the dynamics and relationships of the selected variables in the model. This study extends the current literature that frequently covers the C&D waste management strategy after waste generation, by presenting the knowledge and awareness of managing the C&D wastes throughout the construction cycle. It provides guidance and serves as a platform for construction actors to hone their focus on the management of C&D waste generation as as early as possible. It can also promote the involvement of all construction actors to play their role in prioritizing the management of C&D wastes in a more sustainable and efficient way.