Residential buildings have become a priority product category for the circular economy agenda in the Netherlands due the large amount of materials that their construction requires, the environmental impact of this demand, and the fact that increasingly more houses are needing to be built in response to the housing crisis. To guide and monitor the circularity transition for housing, a quantitative understanding of material stocks and flows is needed, together with insight into the potential impact that different circular options could have. This study begins by quantifying the material stocks and flows for residential buildings in the Netherlands in 2019, including material origins and waste treatment flows, by combining data from past studies into an accounting material flow analysis (MFA) model. The environmental impact of the 2019 material demand is also calculated. This quantification of the current state creates a baseline from which circularity and environmental performance for housing can be improved. Desk research is used to create an inventory of options for increasing circularity in the Dutch housing sector, including estimates of the potential and environmental impact of each as can be found in the literature. Modular construction is often mentioned as a circular option for housing due to its industrialized and demountable construction method, which allows for module, component, and material reuse and facilitates building repair, adaptability, and recycling. However, the impact that more modular construction would have on national material flows and circularity has not yet been quantified. Therefore, this study performs a dynamic MFA to investigate how the large-scale adoption of modular construction could influence the material flows for residential buildings in the Netherlands towards 2100. Primary data from two Dutch modular building companies was used as input for the model. The results illustrate that modular construction is an effective narrowing the loop strategy, capable of reducing material demand by 33% in 2030, 40% in 2050, and 60% in 2100, though its reusability benefits remain limited toward 2100 due to the long lifespan of buildings. Ultimately, this study concludes that modular construction, house splitting, transforming existing non-residential buildings into housing, and adding floors on top of existing buildings appear to be the most impactful options for reducing the material input required for residential buildings in the Netherlands and the associated environmental impact.

This thesis explores the relatively large contribution of the product category ‘chemicals n.e.c.’ (chemicals not elsewhere classified) to the Dutch healthcare sector’s carbon and material footprint observed in previous studies. For this, an input-output study using SNAC-EXIOBASE data was performed. SNAC-EXIOBASE uses national statistics for the Dutch part of the multi-regional input-output table. It also distinguishes a separate chemical and pharmaceutical industry in the Dutch part. This can help identify possible aggregation problems in the EXIOBASE category ‘chemicals n.e.c.’ which is an aggregate of the chemical and pharmaceutical industry sectors. Comparing the carbon and material footprint of pharmaceuticals used in the Dutch health care sector as calculated with (default) EXIOBASE and SNAC-EXIOBASE shows that there is an aggregation problem in the ‘chemicals n.e.c.’ category. This means that grouping the pharmaceutical industry with the chemical industry greatly influences the carbon and material footprint of pharmaceuticals. The carbon footprint decreases by 11% and the material footprint by 61% when using SNAC-EXIOBASE compared to EXIOBASE data. The multiplier analysis showed that in all cases the Dutch pharmaceutical industry has a lower carbon, mineral and metal intensity (footprint per euro) compared to the Dutch chemical industry or ‘chemicals n.e.c.’ confirming the aggregation problem. The LCA literature review showed that the range of carbon intensities of individual pharmaceuticals matches the carbon intensity of the ‘pharmaceutical industry’ in SNAC-EXIOBASE. This study also showed that the material footprint of the Dutch healthcare sector is uncertain and should be used with care. Future research should focus on using MRIOs that better depict the pharmaceutical industry like the ICIO which is based on the ISIC Rev. 4 classification and, therefore, includes a separate pharmaceutical industry. Before performing analyses with the ICIO is possible, higher sectoral resolution and environmental extensions are needed.