RESycling – Reduced process emissions in steel and cement production: preparation and utilisation of hot metal desulphurisation slag (RES)

Unused raw material potentials are to be made available through a novel processing strategy. The focus here is on the processing of hot metal desulphurisation slag (RES) from iron and steel production. The recyclable materials obtained in this way are to replace primary materials in the steel, cement and fertiliser industries and also reduce climate-relevant process emissions.


RES is produced during the desulphurisation of molten pig iron in steel production. In Germany, about 450,000 t of RES are made available in this way every year, the most of RES is stored in landfills. The complete treatment and use of the previously unused RES components, such as iron, minerals and sulphur, can reduce climate-relevant process emissions.


In concrete terms, the treatment of the RES with high-voltage pulses is intended to first separate the iron contained in it and thus make it usable again as a high-quality raw material for the steel industry. In a subsequent wet chemical process, raw materials for the fertiliser and cement industries are to be selectively produced. To this end, the process will first be optimised in an application-oriented manner and evaluated in a pilot plant in the later course of the project. Parallel to development, an ecological and economic hot-spot analysis will be carried out for further process optimisation. In addition, the effects of substituting primary materials and the savings in climate-relevant process emissions will be quantified in order to derive ecological potentials. In addition, based on the comparison of running costs and revenues, an economic feasibility study for the novel reprocessing strategy will be prepared.


CBP's task is to scale up the wet chemical process and to support the planning, construction and commissioning of the subsequent pilot plant at Fraunhofer IBP. Furthermore, the know-how generated from the project is to be made accessible to the public through publications, for example.

Project information

Project title

RESycling – Preparation of hot metal desulphurisation slag to recover secondary raw materials and reduce climate-relevant process emissions.


Project duration

January 2022 – December 2025


Project partner  

  • Fraunhofer-Institut für Bauphysik (Gesamtkoordinator)
  • thyssenkrupp MillServices & Systems GmbH 
  • Hochschule Weihenstephan-Triesdorf 
  • Südbayerisches Portland-Zementwerk Gebr. Wiesböck & Co. GmbH (Rohr-dorfer Zement) 


We would like to thank the German Federal Ministry of Education and Research (BMBF) for funding the project "RESycling", promotional reference 01LJ2101A. 

Federal Ministry of Education and Research.