Leachate and gaseous emissions from initial phases of landfilling mechanically and mechanically–biologically treated municipal solid waste residuals

In this study, the behaviour, and leachate and gaseous emissions during the initial phases of landfilling mechanically (M) and mechanically–biologically (MB) treated municipal solid waste residuals in northern climatic conditions was compared using two landfill lysimeters (112 m3). The results demonstrate that the strong acid phase of M residuals degradation lasts at least 2 years, while in the MB residuals the acid phase lasts only a few months. The SCOD and NH4–N concentrations varied 20–100 g/l and 600–1800 mg/l in M leachate and 1–4 g/l and 100–400 mg/l in MB leachate, respectively. The leaching of SCOD was approximately 40-fold (24.2 and 0.6 kg/t TS) and leaching of NH4–N approximately 5-fold (356 and 60 g/t TS) from the M than MB residuals; thus the effect of biological stabilisation was more marked on the leaching of SCOD than of NH4–N. Moreover gas (methane, carbon dioxide and nitrous oxide) emissions were several-fold higher from the M than MB residuals.