Waste Generation and Recycling: Comparison of Conventional and Industrialized Building Systems

Problem statement: In the Malaysian construction industry, there is a pressing issue of minimizing construction waste, which cause signific ant impacts on the environment. With the increasing demand for major infrastructure projects , ommercial buildings and housing development programmers, a large amount of construction waste i s be ng produced. Adoption of prefabrication and industrialized building systems is now a priority i n the industry and also an important means of reducing waste. Approach: Discussion of the prefabrication adoption were bas ed on a comprehensive review of literatures and studies that contained da ta, information, findings and evidences related to prefabrication and industrial building systems in M alaysia. This study also highlighted a comparative study of material wastage and recycling based on tw o project sites e.g., conventional and prefabrication construction. Results: In the Malaysia construction industry, adoption of prefabrication and IBS is strongly encouraged to reduce constructi on time as well as the industry’s dependency on foreign workers. In addition, this study confirms t ha a huge amount of material wastage can be reduced by the adoption of prefabrication. This stu dy also revealed that the rates of reused and recycled waste materials are relatively higher in p rojects that adopt prefabrication. Conclusion: Thus, the adoption of prefabrication and IBS has potentia l in the reduction of huge waste generation and management problems in the construction sector of M alaysia although there are some challenges in the adoption of prefabrication.


INTRODUCTION
The issue of minimizing construction waste which cause significant impacts on the environment is pressing for the Malaysian construction industry. With increasing demand for major infrastructure projects, commercial buildings and housing development programmers, large amounts of construction waste are being produced (Begum et al., 2009). Alshammari et al. (2008) expressed that the current environmental concerns have forced developed and developing countries to reduce air, water and land pollution for sustainable growth. Awomeso et al. (2010) also emphasized to be introduced and utilized of appropriate technologies and efficient facilities that are suitable for environmental protection. Therefore, government efforts to promote usage of Industrialized Building Systems (IBS) have been an alternative to the conventional, labor intensive and wasteful construction method. The Construction Industry Development Board of Malaysia (CIDB) has redesigned its strategies and formulated a roadmap known as the "Industrialized Building Systems (IBS) Roadmap 2003Roadmap -2010 According to the IBS Roadmap 2003-2010, IBS is a construction process that utilizes techniques, products, components or building systems which involve prefabricated components and on-site installation. Normally, this method would involve the assembly of precast elements such as floor slabs, in-filled walls, bathrooms and staircases into place for incorporation into the main units, columns and beams that reduced the amount of site lab our involved in building operations and increased the productivity of the industry. Precast building systems can reduce the duration of a project if certain conditions are met (Kadir et al., 2005). In the conventional construction method (reinforced concrete frames and brick as infill), the beam, column, wall and roof are cast in situ using timber formworks while steel reinforcement is fabricated on site. This method of construction is labor intensive and involves three separate trades, namely, steel bending, formwork fabrication and concreting (Badir et al., 2002). Adoption of prefabrication and IBS is now a priority in the industry and also an important means of reducing waste. This study provides an overview of adoption of prefabrication including its advantages and difficulties. It also highlights a comparative study of material wastage and recycling in conventional and prefabrication construction.

MATERIALS AND METHODS
Discussion of the prefabrication adoption are based on a comprehensive review of literatures and studies that contained data, information, findings and evidences related to prefabrication and industrial building systems in Malaysia. This study also highlighted a comparative study of material wastage and recycling based on two project sites e.g., conventional and prefabrication construction. The conventional project site (Kamsis H) is a non-residential/institutional building (completed in 2004) located in University Kebangsaan Malaysia (UKM), Bangi and Selangor (Fig. 1). Begum et al. (2006) demonstrated a detailed study on waste characterization and economic feasibility based on this site. Figure 2 shows a location of the prefabrication/IBS construction project site of the residential building in Parcel 7, Presint 9, Putrajaya (completed in 2008). Both the project sites were selected because they involved conventional and prefabrication building and construction activities. Information and data were collected through interviews (using questionnaire) with 2-3 years of monitoring throughout the project duration, in conjunction with the developer, contractor, subcontractor, project manager, quantity surveyor and site supervisor. It should be noted that this study takes into account only on-site waste generation, composition and recycling. The study has a limitation. For the prefabricated construction project site, it did not include data from off-site or the precast plant. The study is based on a conservative method of estimation using gross waste generation in tonnage. Nevertheless, the study is useful as it shows a comparison of material wastage and recycling from a conventional and an IBS or fully prefabricated project site. Table 1 shows the composition and amount of waste generated from the IBS and conventional project sites. The composition of the waste is similar while its proportion differs. The largest components of waste materials are concrete and aggregate, soil and sand and brick and blocks. The total waste generated is very much higher in the conventional project i.e., 54.6 tones 100 m −2 compared to the prefabricated/IBS project of 1.5 tones 100 m −2 . The huge difference in waste generation is similar to findings from other studies such as Tam et al. (2007) and Poon et al. (2001). Table 2 shows the amount of reused and recycled waste materials from the IBS and conventional project sites. Based on the total waste generated at each site, it is observed that 94% of waste generated at the IBS site is reused and recycled compared to only 73% at the conventional project site. For the both sites, the most frequently reused and recycled materials are concrete and aggregate, soil and sand, wood as well as brick and blocks. It was noticed that a majority of the metal waste generated was removed to another project site and this is not accounted for this analysis. The study shows that there is good practice in reusing and recycling of construction waste materials on the IBS site compared to the conventional. Tam et al. (2007) also demonstrated that the adoption of prefabricated building components can effectively reduce waste generation and improve the environmental performance for overall site conditions.       The transformation of the construction sector is crucial in ensuring the successful achievement of Vision 2020 (IBS DIGEST, 2007).
In the Malaysian construction industry, the use of IBS as a method of construction is evolving (Kamar et al., 2007). With the advancement of technology and innovation, various prefabricated materials have entered the market including gypsum, wood wool, polymer, fiberglass, glass and aluminum-based IBS components. Currently a total of 128 IBS companies have registered with CIDB Malaysia (IBS DIGEST, 2007). More local manufacturers have established themselves in the market. As a result pre-cast, steel frame and other IBS were used as hybrid construction methods to build national landmarks such as the Bukit Jalil Sport Complex, Light Rail Transit System (LRT), Petronas Twin Towers, Putrajaya, Kuala Lumpur Central and Kuala Lumpur International Airport. It was reported that at least 21 manufactures and suppliers of IBS are actively promoting their systems in Malaysia (Kamar et al., 2007). The establishment of the IBS Centre at Jalan Chan Sow Lin, Cheras, Kuala Lumpur has also provided an impetus to the IBS agenda.
However, it appears that the usage of IBS or fully prefabrication in Malaysia is still low compared to that of other developed countries such as Japan, United Kingdom, Australia and United States of America (CIDB, 2003b). It seems a loss for the local industry players as IBS offers solutions to various issues which would definitely exert a major impact on the industry's productivity, quality, health and safety, as well as the environment. The adoption of prefabrication assures valuable advantages and difficulties to implement IBS in the construction industry of Malaysia. The following advantages have been identified of applying prefabrication in the building and construction activities (IBS DIGEST, 2007;Tam et al., 2007;CIDB, 2003b;Badir et al., 2002;Ho, 2001;Hassim et al., 2009): • Reduction of unskilled workers • Less waste generation • Reduction of foreign workers employed in the construction sector that will also reduce the amount of remittance by the foreign workers (for the case of Malaysia) • Reduce construction cost effectively by adopting prefabrication and mass production of building components • Frozen or fixed design at the early stage of design for the adoption of prefabrication • Better supervision on improving the quality of prefabricated products • Reduce overall construction costs e.g., material and labor cost savings • Promote safer and more organized construction site • Improve environmental performance through waste minimization • Enhance integrity on the building design and construction The advantages of adopting prefabrication are accompanied by several challenges (IBS DIGEST, 2007;Tam et al., 2007;CIDB, 2003b;Badir et al., 2002;Ho, 2001;Hassim et al., 2009). These are as follows: • Inflexible for changes of design-sometimes consultants and clients are reluctant to adopt prefabrication for the previous projects, since the design has not frozen in the development stage, which will affect adoption of prefabrication and environmental awareness for various construction parties • Highly capital intensive or higher initial construction cost • Lack of information based on research • Time consuming for the initial design development • Limited site space for placing prefabricated building components • Leakage problems that will occur while joining the prefabrication • Lack of contractors or labor experience on the prefabrication • Lack of demand for prefabricated building components • Need for expert labor and also need for training the semiskilled labor force for highly skilled jobs • Lack of awareness among architects, engineers, developers and contractors

CONCLUSION
Adoption of prefabrication and many prefabricated building components is not new in the construction sector of Malaysia. The application of floor and roof slab, wall panel, staircase, load bearing block, sandwich panel, timber and steel frame are the most common practices for construction activities which can effectively reduce waste generation and improve environmental performance of the construction site.
However, it appears that the usage of IBS in buildings is still low. A survey conducted by CIDB (2003b) shows that the usage level of IBS in the local construction industry stands at only 15%.
In the Malaysia construction industry, adoption of prefabrication and IBS is strongly encouraged to reduce construction time as well as the industry's dependency on foreign workers. In addition, this study confirms that a huge amount of material wastage can be reduced by the adoption of prefabrication. This study also reveals that the rates of reused and recycled waste materials are relatively higher in projects that adopt prefabrication. Thus, the adoption of prefabrication and IBS has potential in the reduction of huge waste generation and management problems in the construction sector of Malaysia although there are some challenges in the adoption of prefabrication.

ACKNOWLEDGEMENT
This study is part of the research project entitled "Materials Security and Waste Management for Industrialized Building Systems (IBS)" funded by the Construction Research Institute of Malaysia. We are grateful to Mr. Suresh Kumar Lachimpadi from Putra Jaya Holdings Sdn Bhd for helping during data collection and also wish to thank the contractors and their staff for providing information and data. An earlier version of this article was presented at the 2nd Construction Industry Research Achievement International Conference (CIRAIC), Kuala Lumpur, 3-5 November 2009.