Application of the lean philosophy to reduce carbon emissions in the precast concrete industry of Singapore

Climate change has emerged as one of the most pressing environmental issues in recent years. The construction industry contributes to the increase in the level of carbon dioxide (CO2) in many aspects. For example, the cement sector alone accounts for 5% of global man-made CO2 emissions. Manufacturing of raw materials (e.g. cement and steel) and chemicals have considerable impact on CO2 emissions. The lean concept has proven to be effective in increasing environmental benefits by eliminating waste, preventing pollution and maximizing value to owners. However, an in-depth investigation of the lean concept's role in reducing carbon emissions should be conducted before any recommendations can be made. Prefabrication systems are believed to have the potential for better environmental performance and have been adopted by the construction industry to meet the challenges posed by sustainable development. However, there remains many areas in the prefabrication systems that can be improved in order to achieve sustainability, such as site layout, work flow and inventory control. This research therefore aims to identify the non-value adding activities in precast concrete production and installation to reduce carbon emissions. The non-value adding activities identified in this research can be used to help guide the precasters' and contractors' decision-making process to meet the challenges of global climate change. Four stages in the precast concrete production cycle are investigated, which are site layout management, supply chain management, production management and stock management. In addition, four stages in the precast concrete erection cycle are investigated, which are site layout management, transportation management, stock management and erection management. The importance of the non-value adding activities identified in this research is rated by a weighted factor model using both the non-parametric tests (for precasters) and the parametric tests (for contractors). The results suggest that many lean principles can be applied in precast concrete factories and in the construction sites to reduce carbon emissions, e.g. the pull system, total quality control and benchmarking. In addition to the data collected from the survey work, four case studies (one precaster and three contractors) are presented in this study. Various theoretical and practical implications and conclusions of this research are provided for precasters, contractors and regulatory authorities. It is argued that the lean production philosophy can be used to achieve low-carbon production and low-carbon installation in terms of eliminating non-value adding activities from waste of raw materials, waste of finished products as well as inappropriate production/erection arrangements. The lean improvements will enable precasters and contractors to perform better in many sustainability-related rating systems, such as the Singapore Green Labelling Scheme, and the Building and Construction Authority (BCA) Green Mark Scheme provided for under the Building Control Act. It also suggests that the practitioners should pay special attention to the 'continuous improvement' characteristics of the lean concept to focus on long-term improvement.