If you want to build, you need raw materials. Their occurrences are limited. In order to conserve resources and the environment, experts are calling for more recycling of construction and demolition waste.

Kassel/Wiesbaden (dpa/lhe) – Bricks, concrete, wood, glass, plastics: A lot of waste is produced during construction and demolition work. According to figures from the State Statistical Office, around 14 million tonnes of construction and demolition waste was disposed of in Hesse in 2018. Of this, around 5.7 million tons were recycled in treatment plants. Burkhard Siebert, general manager of the construction industry association Hesse-Thuringia, is not enough. “If we continue as we have been up to now, we will no longer be able to realize all projects. It is becoming more and more expensive and we are increasingly polluting our environment.”

“Around 40 percent of the CO2 emissions worldwide come from the construction sector,” adds Helena Fischer, Managing Director of the regional group North Hesse of the association. Sustainable construction and the highest possible recycling rate for raw materials are important levers for reducing carbon dioxide emissions and conserving resources. At the moment, most of the construction and demolition waste ends up in the substructure of roads or directly in landfills.

“There are still too many obstacles to recycling construction waste,” says Siebert. He demands that recycled building materials be taken into account in tenders. At best, the idea of ​​recycling should already be included in the planning, says Fischer: “What materials do you use? How long is their service life? How can you recycle them after demolition?”

Intelligent approaches are needed in which the focus is not on disposal but on recycling. After all, raw materials such as building sand, which is used, among other things, as an additive for concrete and mortar, are not an infinite resource, explains Siebert.

This is also emphasized by Volker Thome, Head of the Mineral Materials and Building Material Recycling department at the Fraunhofer Institute for Building Physics. “Around 50 billion tons of construction sand are used every year worldwide,” he explains. “There are already countries that lack it.” The raw material must therefore be extracted from where it occurs, namely in building rubble. So far, however, there has been no process for recovering it on a large industrial scale.

In the “Favre” project (fragmentation plant for composite material recycling), Thome and his team are working on such a process. With ultra-short electrical impulses, they break down old concrete into its components and prepare it in such a way that the components are available as climate-friendly and resource-saving substitutes for cement production. “The process promotes resource efficiency and has the same energy consumption as established processing methods.”

The new plant can also fragment composite materials that are difficult to process, such as reinforced concrete, which cannot be completely broken down using today’s mechanical processing methods. If financing is secured, the patented process can be brought to market in three years.

Reusing as many raw materials as possible in order to conserve resources and reduce waste is also the goal of a pilot project by Nassauische Heimstätte Wohnungs- und Entwicklungsgesellschaft (NHW). “The building materials industry is responsible for 40 percent of all waste,” says department head Robert Lotz. Quality products with a long service life that are not yet at the end of their life cycle are disposed of.

When adding stories to two residential buildings in Kelsterbach in the Groß-Gerau district, NHW has now reused such recyclable materials. “Among other things, we processed roof rafters from demolitions into timber frame construction walls and processed and reinstalled windows and interior doors,” reports Lotz. Façade panels, downpipes, window sills and switches were also reused, as was a roof foil. All materials were examined for suitability and reused in the same building class. “We made no compromises when it came to safety,” emphasizes the architect. The recyclables that are used in Germany are so safe that they can be reused without any problems.

According to Lotz, the costs have even remained below those of a new building. In addition, CO2 emissions have been reduced and primary energy saved. The project shows: “The possibilities are there, we just have to have the courage.”