Assessing the impact of implementing circular economy strategies in the construction industry: A case study in the Ruhr Area in Germany.

Mineral construction and demolition waste accounts for the largest waste stream in the European Union. In Germany, for instance, 220 million tonnes of this waste are produced annually. In this study an implementation of the 9R Circular Economy framework is proposed for the construction sector to improve the circularity of the mineral construction and demolition waste stream, using the Ruhr Area as a case study. A data-driven, scenario-based material flow analysis is conducted using the software STAN, complemented by CO2 accounting for the reference year 2023. The system boundary comprises construction material production, building construction, demolition, and waste management within the Ruhr Area. Three scenarios were analysed: a status quo, a circularity and an ambitious circularity scenario. The 9R-strategies considered in the scenarios were adaptive reuse, selective deconstruction, recycling and carbonation of recycled aggregates. The findings show a 40% reduction in primary raw material use in the ambitious circularity scenario, particularly a decrease in sand and gravel by 1.05 million tonnes. CO2 emissions were reduced by 25% in both the circularity and ambitious circularity scenarios. These results highlight how regional resource efficiency can improve through circular construction and how this localized approach serves as an effective model for urban regions.