Energy and material flows from production to the consumption site of secondary materials from the building sector for the construction sector

The recycling of construction waste is an important stepping stone towards the goal of resource conservation and the reduction of environmental impacts of construction. Within the multi-stage German resource efficiency programme, an energetic perspective to the use of natural material resources is added in order to develop synergies as well as to reveal possible goal conflicts. This also applies to the consideration of secondary materials. However, it has not yet been clarified how such a combined analysis should be implemented.

The aim of the research was to expand material-orientated investigations into resource conservation potential to include energy considerations and to develop an investigation approach that enables the energy consumption of recycling processes to be calculated and evaluated and provides the basis for comparisons of the recycling of different construction products.

In terms of methodology, a uniform balance sheet approach was developed that enables an equivalent analysis of the recycling of different building products. The approach was tested using the example of eight building products: Concrete, bricks, sand-lime bricks, plaster, flat glass, rock wool, PVC window profiles and PVC floor coverings. For each building product, instructive examples in the form of "continuous" recycling process chains from the demolition material to the use of the recycled material in a new product were analysed and examined in three steps with regard to energy consumption: (1) from demolition material to secondary material, (2) from secondary material to substitute and (3) comparison of the energy consumption of substitute and primary material.

The results show that recycled building products can often be manufactured with less energy, in some cases even significantly less (plastics). This statement cannot be made with the same clarity for mineral materials. Depending on the area of application, recycled products are energetically advantageous (bricks, sand-lime bricks), are of a similar order of magnitude (concrete, flat glass) or require a higher energy input during production (plasterboard, rock wool).

The assessment of the energy benefits of recycled building products is only reliable if the recycling process chains are considered as a whole, from the demolition material to the recycled material in its new application. Only by taking into account the differences (in recipes, processing steps, transports) between the standard production of building products without recycled material and the production of building products with recycled material can statements be made about the energy advantages and disadvantages.

The results show that it makes sense to promote recycling. They provide important information for developing cycle-orientated recycling business models in such a way that the potential for conserving raw materials and protecting the climate is consistently used in an integrated manner.


Gruhler, Karin; Schiller, Georg (2023): Grey energy impact of building material recycling – a new assessment method based on process chains. In: Resources, Conservation and Recycling 18 (Online First): 200139. (Online First 2023)

Gruhler, Karin; Schiller, Georg (2022): Energy flows along the production and use of secondary materials with a special focus on concrete. In: Acta Polytechnica 33 (2022), S.193-199,

Gruhler, Karin; Reichenbach, Jan; Steinmetzer, Sonja; Schiller, Georg (2021): Wo steht das Recycling von Bauprodukten energetisch? In: Bauen+ 7 (2021) 2, S.10-16

Bimesmeier, Tamara; Gruhler, Karin; Deilmann, Clemens; Reichenbach, Jan; Steinmetzer, Sonja (2020): Sekundärstoffe aus dem Hochbau – Energie- und Materialflüsse entlang der Herstellung und des Einsatzortes von Sekundärstoffen aus dem Hochbau für den Baubereich. Abschlussbericht SEROBAU. Stuttgart: Fraunhofer IRB Verlag, 2020, S.1-161 (Forschungsinitiative Zukunft Bau; Band F 3184),

The Leibniz Institute of Ecological Urban and Regional Development is jointly funded by the federal government and the federal states.

FS Sachsen

This measure is co-financed by tax funds on the basis of the budget approved by the Saxon State Parliament.