Study on benefits of concrete recycling on transport carbon emissions and land use reduction, with case in Chongqing, China

Cities are the main source of global greenhouse gas (GHG) emissions. As to China, it is particularly true, due to its on-going urbanization and the related infrastructure construction. In the past decades, massive construction... [ view full abstract ]

Cities are the main source of global greenhouse gas (GHG) emissions. As to China, it is particularly true, due to its on-going urbanization and the related infrastructure construction. In the past decades, massive construction in China led to ever increasing Construction and Demolition Waste (CDW) and caused threefold problems: GHG emissions from bulk material transportation, land occupation for CDW landfilling and land transformation for quarrying. From a life cycle perspective, the development of circular construction lays an innovative pathway to low-carbon construction. As concrete is the most used construction material, and waste concrete makes the largest fraction of CDW, urban concrete recycling can be an effective way for urban GHG mitigation. However in China, the concrete recycling is at its initial stage; only 5% CDW is recycled and the single dominate route is to make low-value bricks not concrete for structure use. With this circumstance, in order to map the opportunities and potentials, the study applied an improved Material Flows Analysis (MFA) on the urban concrete recycling system in one of the mega cities in China, named Chongqing. It first established the baseline situation in the year of 2015, using data of Chongqing concrete production and consumption that were gained via on-site surveys and reviews of industrial reports and sectoral statistics. Upon the baseline situation, four scenarios were constructed to investigate what-if certain technological route would be developed for further concrete recycling, including: (1) improving brick manufacturing (BM+); (2) recycling on-site for road base filling (RB); (3) recycling aggregate (RA) for prefabricated concrete component (PFC) and (4) recycling concrete aggregate for structure use (RCA). The results show, different technological routes have different potentials to increase recycling rates and all of them generate co-benefits on transport GHGs mitigation and land transformation reduction. But for land occupation, trade-offs exist between the land use for recycling centres and the space saving for landfilling. Although it is the most demanding route, recycling stony CDW for high value RCA is technically has the potential to bring the biggest co-benefits on GHGs mitigation and land use. It should be a further direction for Chinese cities to explore their circular construction and low-carbon economy development.