A system dynamics model for assessing impacts of policies on supply and demand of recycled aggregate

It has become urgent for virgin aggregate to be replaced with recycled aggregate, because acquiring virgin aggregate involves considerable amount of energy and carbon dioxide emissions. In recent decades, governments worldwide have formulated policies to develop the market for recycled aggregate, while introduction of these policies could cause uncertainties in its supply and demand, potentially hindering its market acceptance. This study develops a system dynamics model to assess impacts of five policies (i.e., enhanced supervision on illegal dumping, landfill charge, subsidies for recycling activities, development of recycling centers, and restriction on mining) on the supply and demand of recycled aggregate. The model is described through Vensim PLE software, and Chongqing, China is selected as a case study. Single policies, including enhanced supervision, development of recycling centers and landfill charge are observed to have limited impacts on supply and demand of recycled aggregate. When the subsidy equals to 50 yuan/ton (or US $7.41/ton), the subsidy policy could suppress the increase in illegal dumping percentage and increase the supply of recycled aggregate. Restriction on mining could contribute to the growth of demand. However, single policies are found to have limitations and combination of policies should be considered. Impacts of three different combination policies are discussed in this study. Findings of this study could contribute to practice of C & D waste management and present possible stimulus to use recycled aggregate.

Automated summary

It is urgent to replace virgin aggregate with recycled aggregate due to the high energy consumption and carbon dioxide emissions involved in acquiring virgin aggregate. Government policies worldwide have been developed to promote the market for recycled aggregate, but these policies may create uncertainties in supply and demand, potentially hindering its market acceptance. This study uses a system dynamics model to assess the impacts of five policies on the supply and demand of recycled aggregate and concludes that a combination of policies should be considered.