Material Flow Analysis for a Circular Economy Development: A Material Stock Quantification Method of Urban Civil Infrastructures with a Case Study of PVC in an Amsterdam Neighbourhood
Massive material flows that are mostly originating from the lithosphere are entering the cities, adding to and shaping the stock of the built environment. Due to concerns with material resource scarcity and the finiteness of virgin materials, resources will have to be measured and tracked. As a result of insufficient data on (average) civil infrastructure material usage and a lack of appropriate means for its determination, a four step methodology, termed Citymass, was created to fill this gap. By analysing the urban tissue, the quantity of different civil infrastructure typologies (buildings, water networks etc.) and their material composition and amounts can be assessed (with technical drawings, if necessary). Thereby, it enables the quantification and localisation of built environment stocks with a bottom-up model. The methodology was applied for a first validation or more so an illustration of its application to polyvinyl chloride (PVC) stock as a building material in Merkelbach, an Amsterdam neighbourhood of 0.013 km². It showed that the assessable stock consisted of underground water pipes and data cable protection pipes and totalled in 3,618 kg PVC, or 0.28 kg/m². In order to address the resource scarcity issue, it was further examined if the PVC outflows could be predicted, applied in the three circular economy loops and eventually connected with the inflows in the Amsterdam Metropolitan Area (AMA). It was concluded that PVC outflows can be predicted with a calculation method based on the (material) lifetime of the object or with an estimation from the share of PVC of C&D waste. Based on best practices and the principles of the circular economy (CE) it was found that even though the material can be reused and recycled within the AMA, PVC products in their current state do not have a place in the circular economy. By analysing the stock and predicting the outflows, the material flow analysis (MFA) is complemented and provided with a smart way of data generation. This method is facilitated over time as more case studies and validations aid in building up a database for average material usages per typologies. Moreover, it creates a bridge between MFA and CE where the latter provides a sense of purpose and direction to the analysis, which in turn generates transformational knowledge for a transition to a restorative future.