Otto Dörner turns demolition waste into valuable aggregates with STEINERT sorters

Otto Dörner Recyclinganlage, a family-owned company from Northern Germany, operates the Otto Dörner recycling plant (ORCA), a wet processing plant for mineral construction and demolition waste. The name comes from plant manager Simon Gühlstorf's idea that the company's work should be direct and dependable. The words "Nassklassierungsanlage" (wet classification plant) and "Baustoffwaschanlage" (aggregate washing plant) seemed like a mouthful for everyday use, so it became ORCA. 

Otto Dörner turns demolition waste into gravel-pit products

The material processed at ORCA comes from demolition contractors and construction firms. When C&D waste arrives at the facility, the truck tips its load, and the wheel loader checks the material before feeding it into the plant. During the pre-treatment step, the maximum particle size limit is set, while steel, plastic film, and light materials are removed.

Water is used to separate two-millimetre grains of sand from coarser aggregates. A density separator removes light material, and the water washes the grains. The wash water removes materials like chemicals used in operations and building products. The sand is continually washed in the closed water circuit before being sent to a screen to be sorted by size. 

How STEINERT sorting units create a customized solution

After the washing step, two STEINERT MSort AP units separate materials by size — one for particles sized 8 to 16 millimetres and one for 16 to 32 millimetres. The ranges are deliberately narrow so that size and other material properties overlap less during detection. Dörner was familiar with the technology from its sister facility operating commercial waste sorting. As materials move down the conveyor belt, the camera detects the surface colour, then compressed air nozzles direct each grain into the stream that matches in colour. Because the grains have just been washed, the camera sees differences that are invisible under a layer of soil. The MSort AP is also built for moist material that does not need artificial drying. 

For example, ORCA targeted basalt and ran it on both particle size ranges. Alongside the dark material, the stream contained red brick, glass, asphalt, and concrete, which need to be removed from the final product. The camera detects each item by colour, the compressed air separates them, and then a wheel loader moves the basalt. The separated stream is not necessarily waste — the streams are sorted depending on the input and the sorting program. Changing the program produces a different material mix, with properties that suit other uses better. This system makes it possible to remove red brick, produce black aggregate, or separate glass and asphalt. 

What comes out can be used in construction as a primary raw material, for example as an aggregate for concrete. The quantity is enough to supply a concrete plant continuously, so that it does not receive material one day and none the next.

For Gühlstorf, quality of the output is what counts; he ensures that materials meet the facility's high standards. For red brick in grey or black material, ORCA achieves an impurity content of less than 10 percent. For glass, the share of impurities in the product is even below one percent. 

Before the first machine was brought in, Dörner and his team tested the plant's main sorting tasks at the STEINERT Test Center in Wedel. The MSort units were determined to meet Dörner's needs. Gühlstorf notes that assembly went smoothly and all installation deadlines were met. 

The plant continues to learn alongside new material streams 

Gühlstorf saw the system move from a theoretical idea to a working system. Basic sorting tasks deliver exactly what he had in mind. Now, he's tasked with fine-tuning the system with technicians from STEINERT, including belt transfers, bearings, and points where dirt collects or wear is too high. Performance is measured by throughput, product quality, and the final product. 

Gühlstorf assumes that recycling will replace conventional gravel deposits as the pressure on landfills increases. In his view, the era of the 1960s and 1970s, when large areas near major cities could be bought cheaply and an opencast operation could be started, is over. His advice to others facing a similar project is to simply get started.