Upgrading and Characterization of Glass Recovered from MSWI Bottom Ashes from Fluidized Bed Combustion

Glass in mixed municipal solid waste (MSW) is often lost for recycling. Glass recovery from incineration bottom ash (IBA) after MSW incineration (MSWI) is technically feasible by sensor-based sorting, but rarely applied. Especially IBAs from fluidized bed combustion contain high recoverable glass amounts, but upgrading this glass is required for recycling in the packaging glass industry. This study examines different upgrading setups based on sensor-based sorting to improve the glass quality from two Austrian fluidized bed IBAs. Sensor-based sorting removed extraneous material like ceramic, stones, porcelain, metals, and lead glass. The fractions produced were characterized by manual sorting and X-ray fluorescence analysis. The glass fractions before upgrading contained 85–89% glass, of which 67% and 83% could be recovered after four sorting steps. Previous sieving caused high glass losses and is therefore not recommended. By sensor-based sorting, the extraneous material contents were lowered from 13% and 9% in the two IBAs to below 2.2%. Four-step upgrading could even ensure extraneous material contents <0.11% and Pb contents <200 mg/kg. Although limit values for packaging glass recycling were still exceeded, this study shows that upgrading of glass recovered from fluidized bed IBAs suggests a novel opportunity to enhance closed-loop glass recycling, thereby reducing the amount of landfilled glass.