Co-benefits of urban concrete recycling on the mitigation of greenhouse gas emissions and land use change: A case in Chongqing metropolis, China

Abstract

Rapid urbanization drives massive construction, which, in return, leads to ever increasing urban metabolism challenges on the provision of raw materials, as well as the disposal of construction and demolition waste. Due to its large volume, the transporting and processing of these materials cause considerable greenhouse gas emissions and land use change. With this circumstance, shortening the supply chains of urban construction by efficient recycling of construction and demolition waste becomes a frontier field for the circular transition of cities. It is particularly important in current China, where the concrete recycling is still rare. This paper aims to map the opportunities and potentials of concrete recycling on the mitigation of greenhouse gas emissions and land use change, with an integrated material flow analysis and life cycle assessment for the case study city e Chongqing, China. For the baseline year 2015, four scenarios representing various recycling routes in Chongqing have been explored: (1) improving brick manufacturing; (2) recycling on-site for road base filling; (3) recycling aggregate for prefabricated concrete component and (4) recycling concrete aggregate for structure use. Results highlighted that different technological routes have different potentials to increase recycling rates but all generate co-benefits on greenhouse gases mitigation and land transformation reduction. Recycling of stony construction and demolition waste for high value concrete aggregate has the biggest potential to bring the co-benefits on greenhouse gases mitigation and land use reduction. Besides, on-site recycling for road-base aggregates also presents a high performance, especially on greenhouse gases mitigation in transport. Based on the sensitivity analysis, policy implications were discussed, highlighting the necessity of to develop the recycling routes that substitute primary gravel with aggregates recycled from the stony waste; unlocking the existing recycling capacity and restricting landfilling.

The State of the Art of Material Flow Analysis Research Based on Construction and Demolition Waste Recycling and Disposal

“…Therefore, many scholars combine MFA and other methods to achieve an accurate economic and environmental assessment, which further extends the MFA applications. One of typical combination applications is the integration of MFA and LCA methods [2,11,18,53]. Zhang et al illustrated through the integration between MFA and LCA that the recycling of C&D waste can generate the co-benefits of land use reduction and greenhouse gases mitigation [18].…”

“…In the new emerging economies, the new environmental policies and taxation could be proposed based on evidence from MFA [17]. In recent years, MFA has had some new developments and extensions to provide dynamic, robust, and multifaceted assessment results [18][19][20]. Material flow usually contains certain time and space scales.…”

“…Additionally, the integration between MFA and its spatial distribution can describe a broader scale of materials social usage and is beneficial for sustainable strategic planning [25] because this integration provides a basis for the formulation of a sustainable development strategy [26]. Furthermore, MFA has been deeply regarding the processing and management of C&D waste from a single waste material [27] and mixed wastes [28], and at regional [18,29], national [28,30], and global scales [31]. For a multifaceted assessment, MFA is combined with other analytical tools and optimal methods.…”

“…For a multifaceted assessment, MFA is combined with other analytical tools and optimal methods. The combination of MFA and Life Cycle Assessment (LCA) can accurately calculate embodied carbon or carbon emissions, and track material flows, which is helpful for estimating the potential impacts of the changes of urban metabolism [2,18,32,33]. An integration framework of MFA and LCA is presented to assess the potential impacts of concrete recycling and metabolism [18].…”

“…The combination of MFA and Life Cycle Assessment (LCA) can accurately calculate embodied carbon or carbon emissions, and track material flows, which is helpful for estimating the potential impacts of the changes of urban metabolism [2,18,32,33]. An integration framework of MFA and LCA is presented to assess the potential impacts of concrete recycling and metabolism [18]. In some studies, the cost of recycling and reuse of building materials is also considered as an important factor [11,34].…”