Closing the material cycle in construction

The building stock as a raw material storage

 

The National Circular Economy Strategy, (NCES), adopted in December 2024, aims to achieve a sustainable, cycle-oriented economy. The transformation it seeks to bring about is a key prerequisite for achieving legally enshrined goals such as climate protection and sustainable development in Germany.

This transformation poses enormous challenges for the construction sector, as it is one of the areas that consumes large amounts of land, raw materials, and energy. At the same time, the building materials contained in existing buildings form an unexpected storage of materials – valuable reserves that need to be used in the cycle.

Digitale Landkarte Deutschlands. Als Säulen (dritte Dimension) sind die in den einzelnen Gebieten verbauten Massen an Baumaterialien der Gebäude gezeigt. Je höher die aus der Karte ragende Säule, desto mehr Materialien (in Tonnen pro Quadratkilometer) wurden verbaut. Besonders hohe Ausschläge ergeben sich somit zum Beispiel für Berlin oder das Ruhrgebiet.
Spatial distribution of building materials in Germany. (Graphic: R. Schinke/ IOER)
Drei Kreisdiagramme im Dreieck angeordnet, die 1) Menge der in Gebäuden in Deutschland verbauten Baumaterialien, 2) die Materialinduzierten CO-2 Emissionen und 3) die Materialinduzierte CO-2-Speicherung darstellt. Rechts daneben eine Legende – verschiedene Farben zeigen verschiedene Baumaterialien an (z.B. Beton, Ziegel, Holz). 1) Das erste Kreisdiagramm zeigt, dass insgesamt etwa 20,8 Gigatonnen Material in Gebäuden verbaut sind. Den größten Teil nimmt dabei Beton ein. 2) Das zweite Kreisdiagramm zeigt, wie groß der Anteil der einzelnen Materialien an CO-2 Emissionen ist. Der größte Anteil entfällt hierbei auf Metalle. 3) Ein Kreisdiagramm zeigt die Menge in Baumaterialien gespeicherten CO-2. Da nur Holz als einziges hier aufgeführtes Baumaterial CO-2 speichern kann, ist nur ein Kreisabschnitt farbig. Gezeigt wird, dass durch verbautes Holz (in Deutschland) 0,32 Gigatonnen CO-2 gespeichert werden.
Material quantities and material-induced emissions for the building stock in Germany in gigatonnes (Gt) (1 Gt = 1 billion tonnes) (Graphic: R. Schinke/IOER)

21 billion tonnes of building materials and 2.8 billion tonnes of CO₂ emissions

Knowledge about the materials used in buildings is essential for achieving a circular economy. This is why the IOER has compiled a Germany-wide material cadastre and calculated that the 52 million buildings contain around 20.8 billion tonnes (20.8 gigatonnes) of building materials. The majority of these are concrete (46 %), followed by sand-lime bricks and fired bricks (10 % each). The production of these materials would release approximately 3.2 billion tonnes of CO₂ equivalents today. Only about ten percent of the CO₂ emissions (0.32 Gt) are fixed within the existing buildings by renewable building materials, meaning that all in all 2.8 billion tonnes of CO₂ are attributed to the building stock.

The detailed data of the material cadastre with its 44 building material groups closes a central information gap for the recyclable and resource-efficient development of the construction and building sector. This makes an important contribution to achieve the goals of the National Circular Economy Strategy.

The IOER Material Cadastre for Germany can be used to estimate the potential for circular construction.

The basis for the development of the material cadastre is formed by the 3D building models provided by the Federal Agency for Cartography and Geodesy (Bundesamt für Kartographie und Geodäsie, BKG). This data set was processed at the IOER and enriched with additional data in order to classify the building stock and to link the material indicators.

The material indicators used for this purpose are the result of many years of research at the IOER. To this end, numerous buildings and their components were analysed in detail, particularly with regard to the building materials used and their quantities. This work provides the basis for deriving the building type-related material indicators.

The result is a detailed picture of the German building stock. It describes which materials are used in buildings and in what quantities. The German Material Cadastre thus offers −for the first time at the federal level− a comprehensive information on the materiality of buildings, which can be used for a wide range of new applications in circular construction.

All interested parties, especially local authorities, companies and researchers, are welcome to download the research data free of charge from the IOER repository, called ioerDATA.

Zu sehen sind drei Karten Deutschlands und drei Kartenausschnitte in verschiedenen Auflösungsgraden – angefangen bei Bundesländern, über einzelne Gemeinde bzw. Kreise bis hin zu einzelnen Gebäuden.
Options for visualising the provided data sets – from buildings to grid cells to administrative units (such as municipalities, districts, and federal states).

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Publications

G Schiller, K Gruhler, N Zhang and A Blum: 2024: From Material Cadastres to a Materiality Informed City Information Modelling“ in: IOP Conference Series: Earth and Environmental Science 1363 (2024) 1: 012084, https://doi.org/10.1088/1755-1315/1363/1/012084

G Schiller, K Gruhler (2024): “Strengthening Circular Urbanization Based on Regional Material Cadastres“ in Proceedings of the 7th International Conference on Geotechnics, Civil Engineering and Structures, CIGOS 2024, 4-5 April, Ho Chi Minh City, Vietnam https://doi.org/10.1007/978-981-97-1972-3_141

 

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