Value Added Abstract
William Hogland, Richard Mutaf
Abstract
Landfills and dumpsites have been the ultimate end-of-life sinks for various materials. Since the mid-1990s, the Environmental Science and Engineering Group at Linnaeus University has established research in Landfill mining in cooperation waste management companies in Sweden, the Baltic Sea region and Europe. In the ‘Kingdom of Crystal’ in southeastern Sweden, centuries of crystal glass production have resulted in over 50 contaminated glass dumps with heavy metals leaching to soil, surface and ground water. Unlike re-landfilling of materials in the on-going remedial excavations of the dumps, excavated materials could instead be re-directed into the circular economy. To achieve this, Electrical Resistivity Imaging (ERI) is used before excavations to identify buried glass ‘hotspots’ for careful excavation to avoid material mixing and ultimate sorting needs. Thereafter, excavated materials are sieved, hand-sorted, scanned with X-ray Fluorescence (XRF) and leached to generate waste composition, particle size distribution, metal contents and leaching potential, which are vital parameters for material handling and metal recovery processes. ERI has successfully identified glass ‘hotspots’ with waste composition around 90% glass and 30–40% fine fractions (>11.3 mm). The materials are around neutral pH with hazardous concentrations of As (13,000 mg/kg), Cd (400 mg/kg) and Pb (200,000 mg/kg), but with non-hazardous concentrations in leachate (<0.1 mg/l for As and Cd and 8 mg/l for Pb). However, careful handling and storage is recommended to avoid environmental contamination and health hazards. Lastly, metal extraction through reduction-melting has shown high potential for recovery of As (99%), Cd (100%) and Pb (99.9%). The methodologies developed so far in glass mining could achieve landscape restoration, environmental contaminants minimization and contribution to circular economy through provision of potential secondary resources (extracted metals and decontaminated glass) for use in other industrial applications.