Kassel / Wiesbaden (dpa / lhe) – Brick, concrete, wood, glass, plastic: A lot of waste is generated during construction and demolition work. According to the data of the State Statistics Office, in 2018 approximately 14 million tonnes of construction and demolition waste were exported in Hesse. Of these, approximately 5.7 million tonnes were recycled in treatment plants. Burkhard Siebert, CEO of the Hesse-Thuringia construction industry association, is not enough. “If we continue as we have done so far, we will not be able to complete all the projects anymore. It is becoming more and more expensive and we are polluting our environment more and more. ‘
“About 40 percent of CO2 emissions worldwide come from the construction sector,” adds Helena Fischer, managing director of the North Hesse regional group. Sustainable construction and the highest possible recycling rate of raw materials are important levers for reducing carbon emissions and conserving resources. Currently, most of the construction and demolition waste goes to the base of roads or directly to landfills.
“There are still too many obstacles to recycling construction waste,” says Siebert. Calls for recycled building materials to be included in tenders. At best, the idea of recycling should already be in the planning, says Fischer: “What materials are you using? How long is their service life? How can you recycle them after demolition? “
Smart approaches are needed where the emphasis is not on disposal but on recycling. After all, raw materials such as construction sand, which is used as an additive to concrete and mortar, among other things, are not an infinite resource, explains Siebert.
This is also underlined by Volker Thome, head of the department of mineral materials and recycling of building materials at the Institute of Building Physics. Fraunhofer. “About 50 billion tonnes of construction sand are used every year around the world,” he explains. “There are already countries that lack it.” The raw material therefore has to be extracted where it occurs, namely from construction waste. Until now, however, there was no way to recover it on a large industrial scale.
In the Favre project (a fragmentation plant for recycling composite materials), Thome and his team are working on this process. Using ultra-short electrical pulses, they break down old concrete into elements and prepare it in such a way that these elements 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 facility can also grind difficult-to-process composite materials such as reinforced concrete that cannot be completely broken down using today’s machining methods. If financing is provided, the patented process can be brought to market within three years.
Reusing as many raw materials as possible to conserve resources and reduce waste is also the aim of the pilot project led by the Nassauische Heimstätte Wohnungs- und Entwicklungsgesellschaft (NHW). “The building materials industry is responsible for 40 percent of all waste,” says department manager Robert Lotz. High-quality products with a long service life that have not yet reached the end of their life cycle are disposed of.
By adding storeys to two residential buildings in Kelsterbach in the Groß-Gerau district, NHW has reused such recyclable materials. “Among other things, we worked on rafters from demolition to timber-framed walls, and reworked and reassembled internal windows and doors,” reports Lotz. The façade panels, downspouts, window sills and switches were also reused, as was the roofing foil. All materials have been tested for suitability and reused in the same construction class. “We did not make any compromises when it comes to security,” emphasizes the architect. The recyclable materials that are used in Germany are so safe that they can be reused without any problems.
According to Lotz, the costs remained even below the costs of the new building. In addition, CO2 emissions have been reduced and primary energy saved. The project shows: “There are opportunities, just have the courage.”
© dpa-infocom, dpa: 220526-99-437601 / 2