Experimental Development of Material Recovery and Recycling Processes to Enhance Recycling Rates along the Value Chain of Mixed Commercial Waste

To meet the ambitious recycling targets of the European Union, reduce dependence on raw material imports, and preserve the planet's limited resources, it is essential to unlock the currently untapped recycling potential in mixed waste streams. Currently, only metals are separated as recyclable fractions from mixed commercial waste (MCW), resulting in a recycling rate of merely 3 ¿ 5%. The aim of this Doctoral Thesis is therefore to develop and implement innovative approaches to increase this rate significantly. To explore the untapped recycling potential as MCW in Austria is primarily processed into solid recovered fuels (SRF), a comprehensive material characterization of a representative sample of MCW was conducted, identifying polyolefins, particularly polypropylene (PP), as the most promising fraction for mechanical recycling. Based on these findings, three process concepts for PP recovery were designed and experimentally validated, enabling the production of high-quality granules. These granulates were used to produce the first marketable PP products from MCW. Building on the processing results, it was hypothesized that the use of a ballistic separator could enhance both the efficiency and quality of the PP material recovered for mechanical recycling. To test this hypothesis, a comprehensive parameter study was conducted to determine the optimal operating conditions of a ballistic separator. Subsequent trials confirmed that its application significantly improves the processing performance of previously extracted PP pre-concentrates for mechanical recycling. Next, the recovery of recyclable fractions alters the composition and calorific value of the remaining output, i.e. SRF. To assess these impacts, an idealized model of a waste treatment plant was developed. The simulation results show that, under ideal recovery conditions of recyclable plastics, the calorific value of the resulting SRF decreases significantly. Nevertheless, their use in the cement industry remains feasible. As the ash from these fuels remains in the clinker during co-processing, it constitutes a secondary raw material that contributes to increasing the recycled content of the cement. To quantify this contribution, a gen-erally applicable methodology for determining the recycling rate in cement was developed and applied exemplarily at two Austrian cement plants. The results indicate that approximately 37% of the cement composition originates from secondary sources, with around 1.2% attributable to the ash of the utilized SRF. With its systemic approach, this Doctoral Thesis makes a significant contribution to transforming linear waste streams into closed material cycles, thereby promoting the transition toward a sustainable circular economy.