Rare earth elements and critical metal content of extracted landfilled material and potential recovery opportunities

• Samples from multiple core drills were obtained from 4× landfill sites in the UK.
• Each sample analysed for rare earth elements, critical metals and valuable metals.
• Two stage microwave digestion method ensuring high yield.
• High quantities of copper and aluminium were observed in the soil layers of landfill.
• Across 4× landfills aluminium and copper present has a value of around $400 million.

Rare earth elements (REEs), Platinum group metals (PGMs) and other critical metals currently attract significant interest due to the high risks of supply shortage and substantial impact on the economy. Their uses in many applications have made them present in municipal solid waste (MSW) and in commercial and industrial waste (C&I), since several industrial processes produce by-products with high content of these metals. With over 4000 landfills in the UK alone, the aim of this study was to assess the existence of these critical metals within landfills. Samples collected from four closed landfills in UK were subjected to a two-step acid digestion to extract 27 metals of interest. Concentrations across the four landfill sites were 58 ± 6 mg kg−1 for REEs comprising 44 ± 8 mg kg−1 for light REEs, 11 ± 2 mg kg−1 for heavy REEs and 3 ± 1 mg kg−1 for Scandium (Sc) and 3 ± 1.0 mg kg−1 of PGMs. Compared to the typical concentration in ores, these concentrations are too low to achieve a commercially viable extraction. However, content of other highly valuable metals (Al and Cu) was found in concentrations equating to a combined value across the four landfills of around $400 million, which increases the economic viability of landfill mining. Presence of critical metals will mainly depend on the type of waste that was buried but the recovery of these metals through landfill mining is possible and is economically feasible only if additional materials (plastics, paper, metallic items and other) are also recovered for reprocessing.