Comparative Characterisation of Closed and Active Landfill Composites Using EDX, FTIR and Proximate Techniques.

The elemental and chemical constituents of an active and a closed landfill were compared using Fourier transform - infrared (FTIR) spectroscopy, scanning electron microscope / energy-dispersive X-ray (SEM/EDX) spectroscopy, and proximate analysis. The two landfills had similar major elemental constituents representing 96.5% and 98.4% of elemental composition for the closed (O > C > Si> Fe > Ca >Al) and active(C > O > Si > Al > Ca > Fe) landfill samples respectively. The average concentration of Al was significantly higher (p=0.024) in the active landfill, while Ca was significantly higher (p=0.023) in the closed landfill. Cluster analysis revealed that similarities were more influenced by the level of composite degradation (more degraded / less degraded) than by depth or seasonal variations. Samples from both landfills showed FTIR absorption peaks that indicated mineralisation and stability of waste constituent. Active landfill samples showed distinguishing peaks at 3690 and 3619 cm-1 attributed to O-H vibration of clayey mineral (kaolin), while closed landfill samples were characterised by a carbonates peak at 873 cm-1. For both landfills, the average ash content (>51%) of the waste was above the level considered suitable for energy recovery from waste. These findings inform strategic decisions in management of the landfills and in the determination of possible alternative uses for landfill waste.