Urbanisation processes as key for analysing construction materials flows and stocks: Paris Region case study
Urbanisation processes generate various urban structures (Steadman, 1994) which have a significant effect on urban metabolism, as shown for instance for residential heat-energy demand by Rode and colleagues (2014). Those processes have yet received little attention in studies on construction materials flows and stocks. Indeed, analysis is often based on criteria such as population size or gross domestic product and forecasting on the assumption of homogeneity across national or regional areas (Augiseau and Barles, 2017). Whereas some studies assume different urban structures to forecast inflows (Schiller, 2007), future outflows are generally estimated through average lifetimes or survival functions which do not consider urbanisation processes. Yet statistics show that buildings demolition strongly differs within a country, between rural or urban areas, as well as between urban areas according to their development dynamics (Huuhka and Lahdensivu, 2016). Miatto and colleagues (2017) also show that the survival functions generally used in dynamic materials flows analysis are not adapted to cities like Salford (Greater Manchester, UK) where a significant urban renewal occurred. Considering urbanisation processes would improve forecasting by adapting the parameters used in dynamic models. This would also bring a better understanding of past and present flows dynamics in terms of total mass and distribution between built works, and especially between buildings and networks. Indeed, while debris from building demolition are mainly recycled in road construction in countries like Japan, road networks development declines and may lead to an imbalance between the supply and demand of recycled crushed stone (Hashimoto et al., 2007). Anticipating such changes is important to implement appropriate recycling and dematerialisation policies. Moreover, taking into account urbanisation processes enables a better comparison of flows and stocks in different areas.