Urban renewal and metabolism optimisation: A complex equation

In the context of a socio-ecological transition to reduce pressures on natural and environmental resources, construction flows appear to be a major lever of public action. Encouraging compactness and density of urban forms therefore appears as a virtuous policy, likely to reduce the consumption of natural soils and material withdrawals.On the contrary, the article highlights a contradictory dynamic between the materials flows that tend to become the majority in the extension of the city’s footprint on its environment and the urban renewal doctrine that aims to limit urban extension. Therefore, it seems essential to consider the impact of planning scenarios or flows management scenarios with regard to the recovery rate, CO2 emissions, but also to the consumption of space associated with the management of these flows.The methodological framework implemented thus demonstrates the antagonistic impact of the same scenario: a particular attention to the recovery is thus associated with an increase of the distances and thus of the emissions, while an ambition of modal shift contributes to the urban extension.