Sustainable Materials Management (SMM)

Sustainable materials management (SMM) is an approach that encourages the sustainable use of materials. The vision of SMM is much broader than that of conventional waste management, encompassing economy-wide resource-consuming activities and the environmental impact they entail. One major assessment method in SMM is material flow analysis (MFA), which can be used to identify hot spots of environmental impact caused by the use of materials and resources or the emission of pollutants. The basis of MFA is the law of conservation of mass—in any given system, the mass remains constant over time. Therefore, the mass entering a system must equal the system’s accumulated mass minus the amount that leaves the system. Through MFA, the sources, pathways, and intermediate and final sinks of a target material can be clearly and comprehensively identified. MFA can be divided into three major steps: (1) problem definition and system definition; (2) determination of flows and stocks; and (3) illustration and interpretation of results. MFA-based management indicators can reflect whether consumption of a target substance in a specific area has achieved a sustainable level. At the national scale, the main MFA indicators are input, consumption, balance, and output indicators. The information represented by the indicators is related and complementary. These basic indicators can be combined with economic output indicators, such as GDP or added value, to establish efficiency indicators. Urban mining, a process that reuses and recycles materials as secondary resources, has the potential to reduce resource consumption and improve resource recycling; thus, estimating the amount of reusable resources in a city is a priority task. Sustainable manufacturing refers to minimizing the environmental impact, energy consumption, and natural resource consumption during the product manufacturing process, including during the input, manufacturing, final product, and disposal stages. SMM-based indicators can serve as crucial references for decision makers and stakeholders at national, municipal, and corporate levels.