Studying construction materials flows and stock: A review
Thirty-one scientific publications on the joint study of construction materials flows and stock with a focus on non-metallic minerals are reviewed. These studies serve different purposes: forecasting and comparing future input and output flows, studying the influence of several parameters on future flows, estimating the present or future stock as well as its evolution, studying urban metabolism and analysing the interaction between flows and stock. They are carried out at national, regional or urban level and their time scale range from a century to a single year. Six main methodological approaches can be distinguished: static bottom-up or top-down flow analysis; bottom-up stock analysis; dynamic retrospective or prospective flow analysis using flow-driven or stock-driven models; and top-down prospective or retrospective stock analysis using a flow-driven model. Approaches are often combined, which is a way to accounting for uncertainty. They rely on assumptions such as homogeneity of material composition and lifetime within groups of built works, whereas quality and coverage of data used are very variable. Most of the case studied show that stock accumulation is still ongoing and that non-metallic mineral secondary resources would be insufficient to totally meet future demand. They also point out infrastructures as the major part of the stock. Reviewed studies contributed to the development of a methodological framework for the joint study of flows and stock, as well as a conceptual framework for analysing the metabolism of a socioeconomic system. Further research could develop these frameworks and support the implementation of industrial ecology policies.