Landfill mining approach for resource recovery from glass dumps into the circular economy

Abstract: Landfills and open dumps have been the most cost-effective waste disposal option, resulting in over 500,000 landfills and dumps in the EU alone. They pose significant environmental and health threats due to emission of toxic gases and release of persistent contaminants to soil and groundwater, triggering a considerable global economic impact annually. Contrariwise, since they have been the ultimate end-of-life sink for materials over time, dumpsites are potential secondary resource reservoirs whose recovery could offset their impacts. However, resource recovery is impeded by the heterogeneous nature and contamination of the wastes, and thus uncertainty about availability and efficiency of recovery techniques. This thesis, therefore, proposes techniques that could improve excavated material quality and enhance their recovery as potential secondary resources for the circular economy.Waste from glass dumps in south-eastern Sweden was characterised to evaluate safe handling, pre-recycling storage requirements, and suitability for resource recovery or disposal. The dumps were mapped with Electrical Resistivity Tomography (ERT) before excavation to detect glass locations and enhance recovery. Furthermore, metal extraction from the recovered glass was assessed using a combination of mechanical activation of the glass and leaching with acids and biodegradable chelating agents. The waste required safe pre-recycling storage in hazardous waste class ‘bank account’ cells due to hazardous concentrations of leachable As, Cd, Pb, Sb and Zn. The waste obtained was also highly heterogeneous, although its recycling could not pose any radiological risks. However, application of ERT as a pre-excavation tool improved excavated material composition and secured a more homogeneous, recyclable fraction (>87% glass). Subsequently, leaching of the homogeneous glass fraction achieved Pb extraction efficiency of 78%, 64% and 42% for HNO3, EDDS and NTA respectively, at low leachant concentrations. The extraction was enhanced by the mechanical activation step, as comparison between activated and inactivated samples showed a 1200% difference in extraction.The findings in this thesis highlight dumped waste as a resource whose recovery requires integrating the landfill mining approach with techniques that enhance material quality and extraction efficiency to ensure a resource-secure circular economy and decontaminated ecosystems.