Building with garbage | Economy | DW

The construction industry has been short of materials for some time and prices have been skyrocketing. Recycling of building materials can alleviate the bottleneck and reduce energy consumption and CO2 emissions.

The house has a colorful mix of windows. Small, large, elongated, square, framed in white, brown and black, it seems that nothing fits together. “We bought them together on eBay and as second-hand goods from manufacturers and designed the facade accordingly,” says Elena Boerman.

View of the Solar Decathlon plant in Wuppertal

She researches secondary building materials at the Karlsruhe Institute of Technology (KIT) and helped build the RoofKIT student project. RoofKIT was the contribution of the Karlsruhe team to this year’s Solar Decathlon Europe in Wuppertal, the largest international university competition for the most sustainable building, and won first place there.

RoofKIT has taken the round idea to the extreme: the paving stones of the house are made of rubble, the facade is from an old barn that can be looked at. Metal stairs leading to the second floor are also used. The interior is also great for furnishing with discarded items and recycled materials.

According to Boerman, white plastic kitchen fronts with splashes of color used to be yogurt pots. The shower cubicle is made of melted glass bottles. “Normal path from the earth’s crust to landfill that has to stop,” confirms the project employee. Visitors to the sunny village in Wuppertal were able to obtain information on component replacement and leftovers that turn used items into high-quality items.

Raw material or waste?

Virtually all Solar Decathlon participants are committed to recycling, recycling and use. Old wooden walls were proudly displayed, and the insulation consisted of frayed jeans, wool felt and waste paper. There were few composite materials, and screwing and hammering nails instead of gluing and gluing was used for better future recycling. While the circular economy is now an important topic in the studies of architects and civil engineers, there is almost no trace of it on construction sites.

Recycled material construction

Donor Building in Cottbus – the concrete slabs have been reused

When a building is demolished, 45 percent of the building materials end up in landfill and another 45 percent is thermally recycled. Only 10 percent of this is processed into road surfaces in road construction, says Prof. Natalie Eßig, who teaches architecture at the Munich University of Applied Sciences. “We can easily increase recycling and reuse to 70 to 80 percent. Unfortunately, the legal regulations in particular still hold us back, ”says a sustainable building expert. First, documentation of the (harmful) substances used is needed. Second, “whatever leaves the site must be declared as waste”.

Concrete recycling pioneer

And which building owner wants ‘waste’ in his building, which contractor is responsible for any problems with old things? To avoid personal risk, the use of recycled building materials is often prohibited, and the recycling rate is thereby unreasonably reduced, said Peter Hübner, president of the Central Construction Industry Association, during the May trade day. “We often fail because of ordinances and regulations that then take 20 years to verify.”

Recycled material construction

Shell construction from used parts

Angelika Mettke has been traveling in Germany and Europe for decades to convince builders to rebuild used concrete slabs. Associate professor at the Brandenburg Technical University in Cottbus-Senftenberg (BTU) is a pioneer in concrete recycling: in the GDR, concrete was scarce. After reunification, there were one million vacant apartments, mostly in unpopular prefab buildings. In structurally weak regions, many are still being dismantled. A structural engineer believes that massive ceilings and walls are too good to break. “My heart bleeds when these undamaged pieces are taken and crushed,” although almost all of them may have a second life.

Sand, gravel and gravel are becoming less and less

The production and grinding of concrete consumes enormous amounts of energy and is therefore considered a climate killer. Prof. Mettke calculated that consistent reuse of the panel will result in up to 95 percent less CO2 emissions. In addition, sand, gravel and gravel are finite raw materials that are gradually running out of stock. “Thanks to our high standard of living, we extract over 500 million tonnes of aggregate annually and produce up to 60 million tonnes of rubble at the same time.”

Recycled material construction

Make new from old: Ready-made club in Kolkwitz

The professor checked with his students the condition and contamination of many ingredients and found them good. With the help of Mettke, 30 to 40 objects were built from old panels. These include clubs, youth centers, showrooms and single-family houses, the technical center of the New Value Management Institute, but also, for example, dike reinforcements. “In the finished state you see nothing, zero that whatever is needed!” The service life of concrete is over 120 years. A building made of used panels does not have to be gray and boring.

Online exchange of used components

The ReCreate research project studies panel disassembly and reuse in six European countries by 2025. While this makes ecological and economic sense, there are several issues with reuse. First of all, this is only possible with assembled, prefabricated elements. According to prof. Mettke buildings with easily detachable connections could be dismantled several times, like Lego, and made something new out of them. Therefore, it calls for a change in construction and building processes. Industry digitization would also help to fully document the internal workings of the various components.

“Something only becomes waste when I have no use for it,” says a professor at Cottbus. Ideally, when the ‘donor building’ is demolished, you already know where parts are needed in the area.

For her objects, Mettke marks out what is appropriate as soon as the wallpaper is left. However, demolition and new construction rarely coincide in terms of time and space: temporary storage is needed – and this costs money. The engineer sees a possible solution in component replacements and in online markets such as Concular and Restado. “They sell windows, doors and radiators that have been removed, for example. It can be extended to walls and ceilings, and everything can be saved digitally. “

Also, operators of stationary recycling plants with large storage areas could receive such large-format components and offer them to customers. “Anything that doesn’t find a buyer after a certain period of time, say five years, can still be chipped up and used in concrete or road construction.”

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