Assessing environmental impacts of utilizing recycled concrete waste from the technosphere: a case study of a cement industry in West Java, Indonesia

Cement industries generate massive amounts of greenhouse gas (GHG) emissions. As a fast-growing economy in Southeast Asia, Indonesia consumed more than 62 Mtons of cement in 2020. To cut down the impacts from extensive resource extraction and GHG emissions from cement industries, utilizing secondary raw materials such as concrete is an option to simultaneously reduce the limestone requirement at cement plants. This study aims to estimate yearly concrete waste flow from residential building stocks and the environmental impacts of utilizing those concrete waste in a cement-producing region in West Java, Indonesia by combining dynamic material flow analysis, stock modeling, and life cycle assessment (LCA). We found Cirebon Regency’s residential buildings would accumulate 46.2 Mtons concrete stocks by 2050. The estimated concrete waste from demolished residential buildings in Cirebon would reach up to 2 Mtons by 2050 depending on building lifetimes. At the baseline scenario, environmental impacts per ton cement are 647.35 kg CO₂ eq. of Global Warming Potential (GWP), 90.25 kg C deficit of Land Use (LU), and 4,707.24 MJ of Cumulative Energy Demand (CED). By utilizing 1 Mtons of recycled concrete, the cement production facility would decrease those values by up to 5.42 kg CO₂ eq./ton cement, 0.09 kg C deficit/ton cement, and 0.43 MJ/ton cement, respectively. Our results help inform decision-makers to formulate policy options on utilizing concrete waste to reduce cement production environmental impacts.