Building rubble: a circular economy instead of landfilling

Building rubble
© Shutterstock / Vasin Lee

The building materials industry processes many millions of tons of valuable primary raw materials every year - instead of using recovered or recycled materials. This is particularly the case where buildings are concerned. One reason for this is the complex challenge of separating heterogeneous residue streams - such as building rubble - into cleanly-sorted, homogeneous secondary raw materials. So that building rubble can be fully processed and recycled the future, our experts have already developed several innovative technologies - and it goes without saying that we continue our research work every day.

Electrodynamic Fragmentation: Selectively separating concrete

Building rubble consists mainly of heterogeneous composites, especially concrete, brick, gypsum and sand-lime brick. While conventional mechanical processing methods do not selectively separate these composites into their constituents, electrodynamic fragmentation (EDF) makes it possible to cleanly sort the various materials. In the case of concrete, for example, sand and gravel can be completely freed from any adhering residues of cement paste without impairing their quality and can be re-used to make fresh concrete. Our researchers have already developed a similar process for masonry rubble.

BauCycle: Sorting fine-granded building rubble

While large fragments of concrete, brick, mortar or plasterboard can be easily separated from each other, sorting fine-grained building rubble a few centimeters or millimeters in size is quite a challenge. In a joint project with the Fraunhofer Institutes for Material Flow and Logistics IML, for Optotronics, System Technologies and Image Exploitation IOSB and for Environment, Safety and Energy Technology UMSICHT, we have succeeded in developing a fully-automated sorting process that is capable of this.

Our method makes it possible to sort fine fractions (< 2mm) by color as well as by their chemical-mineralogical composition. This means: not only can red brick be separated from gray concrete, but also concrete from sand-lime brick, gypsum or aerated concrete. The process is also “adaptive” and can be extended to include other materials - such as special types of ceramic or glass.

ENSUBA: Desulfating building rubble

An often unknown consequence of the “coal phase-out” in Germany is the anticipated - and significant - deficit of gypsum. More than five million metric tons of FGD gypsum are currently processed each year, which is recovered from residues from flue gas desulfurization (FGD) plants. At the same time, residual materials containing gypsum - such as crushed and screened sands or other fine fractions obtained when building rubble is processed - invariably have to be disposed of at high cost because of their high landfill class.

With our ENSUBA process, we have found an innovative way to solve this “dilemma” and to create synergies between processing companies and the gypsum industry. The wet chemical process is capable of selectively removing sulfate from heterogeneous mixtures and also of recovering it in the form of pure gypsum.   

Finding solutions to new challenges

Processing building rubble is a comprehensive and complex topic which extends beyond the above-mentioned aspects of separation, sorting and desulfation. That's why we like to take on new challenges every day. For example, we are currently developing a method for rapidly detecting asbestos. If you are faced with these or similar issues or challenges associated with processing building rubble, please feel free to contact us - we will find a solution!