Buildings and the circular economy: Estimating urban mining, recovery and reuse potential of building components

Continuous accumulation of materials in cities have led to the prospects of urban mining for secondary resources. Several commodities and/or products have been assessed in recent years for urban mining and reuse potential viz. automobiles, electronic waste etc. Urban mining for buildings, the largest material sinks globally, however require considerations which differ from the product-centric urban mining approaches. This study proposes a methodological framework for estimating city-wide urban mining, recovery and reuse potential of building materials and components. First, it extends the material stock and flow assessment to urban mining potentials so that recoverable and reusable flows can be highlighted. Secondly, it expands potential applications of recoverable flows to provide an impactful representation to stakeholders such as policy makers, consumers, designers and practitioners. The proposed framework has been applied to the public residential buildings of Singapore, a city state in Southeast Asia, for assessing building components such as windows, doors, tiles, light fixtures, toilet and kitchen fittings. As a case study, construction of low-cost houses in neighbouring Indonesia was explored to receive building component flows. Results highlight that the reuse of building components could have supported construction in the range of 830–1910 houses in 2016 with more than 30,000 households getting benefit over the six years assessed in this study. Overall, outflows from the Singapore city can partly support the construction of 2200–6030 houses annually to resource-constrained housing sector in the surrounding developing region. Realization of such a circular economy practice will contribute towards sustainable development goals and climate change mitigation efforts.