System Dynamic Analysis of Impacts of Government Charges on Disposal of Construction and Demolition Waste: A Hong Kong Case Study

With the purpose of reducing the amount of construction and demolition (C&D) waste disposed to landfills, many countries and municipalities have introduced increasingly stringent C&D waste disposal charges (CDWDC) but the level of CDWDC is often determined without a clear understanding of its broad and complex impacts. Against this background, this paper aims to propose a system dynamics (SD) model that can help predict CDWDC's environmental implications as well as its financial implications. Specifically, the proposed model explains complex causal relationships between variables such as the level of CDWDC, the amount of C&D waste disposed to landfills, the government's revenues from CDWDC as well as the costs of supplying and operating landfills over time. For a case study, the developed model is customized and calibrated with actual data from Hong Kong, where the remaining capacities of existing landfills are limited and the need for supplying more landfills is imminent. The simulation analysis with the model predicts that the current charging levels may not be high enough to effectively control the amount of C&D waste disposed to landfills or to compensate for the costs to the government of supplying additional landfills. The analysis also predicts how much illegal dumping may increase as the level of CDWDC increases. This case study illustrates that the proposed SD model can help policy makers to see the potential impacts of increased CDWDC on the amount of C&D waste disposed to landfills, government costs and the amount of illegal dumping of C&D waste; and can therefore help them to determine the most appropriate level of CDWDC.