Recycling residential building materials: opportunities and limitations

This study models the opportunities for urban mining in the Netherlands under practical constraints, up to the year 2050. The researchers find a limited potential for recycled materials to meet demand and reduce emissions. They highlight priority areas that could improve possible outcomes.

Waste materials from construction and demolition activities make up over a third¹ of all waste in the EU. Reuse of materials from existing buildings to supply new construction and renovation activities, sometimes called ‘urban mining’, has the potential to reduce demolition waste, as well as demand for primary (non-recycled) materials and greenhouse gas emissions. However, previous efforts to evaluate this potential have generally focused on total volumes of materials generated and used without accounting for logistical and economic constraints in collecting, reprocessing and redistribution.

The construction industry in the Netherlands is responsible for 50% of the country’s raw material use, 40% of waste generation and over one third of greenhouse gas emissions. The government has set targets to halve the use of primary materials in construction by 2030 and create a circular economy with net-zero carbon emissions for the sector by 2050. This study uses detailed information on buildings across the Netherlands, combined with realistic collection and recycling rates, to assess the potential benefits of urban mining between 2020 and 2050.

The researchers used a model to project the potential use of 25 construction materials reclaimed from renovation and demolition sites and used in construction and renovation works. They considered material inflow and outflow at the city scale, recognising that these materials are typically high volume and low value, and hence unprofitable to transport. They based the demolition rate on a building lifetime of 130 years². They also estimated greenhouse gas emissions based on two scenarios projecting the carbon intensity of the electricity mix for decarbonisation pathways at the higher and lower ends of the moderate range (representative concentration pathway (RCP) 6 and RCP 4.5).

The researchers report that reclaimed materials can only make a limited contribution to satisfy overall materials demand, in part due to the net expansion of housing required for an increasing urban population. They note that the main waste materials generated over the period, by weight, are concrete (60%) and clay bricks (24%), with the latter rarely used in new building construction. Many secondary materials can only contain up to a certain maximum level of recycled content, they say, so collected amounts can exceed demand even when a significant volume of new material is still required. They project that this would be the case for concrete – one of the materials in highest demand – by 2035, and for some lower-demand materials even earlier. Other materials with significant demand, such as sand and mineral wool (production of which leads to high greenhouse gas emissions) are not generated as waste materials in significant volumes they say, either because they were not used in the original building or because they cannot be reclaimed from the waste material.

The potential reduction in greenhouse gas emissions achieved by urban mining, according to the researchers, is less than that achieved by following the more ambitious green energy pathway. They report that the reduction in emissions from using available quantities of recycled materials is limited by the absence of mineral wool in construction waste from older buildings and the requirement to use at least 50% new material in concrete production. However, they report that a combination of accelerated decarbonisation and urban mining could lead to a 40% reduction in greenhouse gas emissions by 2050.

The researchers highlight the mismatch between the materials available from urban mining and those required for construction and renovation. They also note that recyclable materials may originate in different areas from where they are required for re-use, and they suggest that neighbouring urban areas could co-ordinate recycling strategies to optimise waste management.  They note that their model uses current levels of collection and recycling, and that improvements in these areas could enable greater use of materials from reclaimed sources in the future. Increasing the potential for use of recycled concrete and finding low-emissions alternatives to mineral wool are critical for reducing greenhouse gas contributions from the sector, they argue. It is likely that extensive renovation would also entail reduced greenhouse gas emissions relative to demolition and rebuilding in many cases.

Footnotes

1. See latest Eurostat figures: https://ec.europa.eu/eurostat/databrowser/view/ENV_WASGEN__custom_2884925/default/table?lang=en
2. The researchers have used the life-time figure of 130 years because building lifetimes vary widely. In addition, they say that the number of annually demolished buildings would be too great (almost impossible) if a lifetime figure of 50 is used. They have taken the 130-year figure from the supporting study: Deetman, S. et al. Modelling global material stocks and flows for residential and service sector buildings towards 2050. J. Clean. Prod. 245, 118658 (2020).

Source

Yang, X., Hu, M., Zhang, C., and Steubing, B. (2022) Urban mining potential to reduce primary material use and carbon emissions in the Dutch residential building sector. Resources, Conservation and Recycling 180: 106215. Available from: https://doi.org/10.1016/j.resconrec.2022.106215

To cite this article/service:

“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.