MODELLING OF BIOGAS EXTRACTION AT AN ITALIAN LANDFILL ACCEPTING MECHANICALLY AND BIOLOGICALLY TREATED MUNICIPAL SOLID WASTE

This paper presents the results of the modelling of the biogas extraction in a full scale Italian landfill by respectively the USEPA LandGEM model and the Andreottola-Cossu approach. The landfill chosen for this research (“Il Fossetto” plant, Monsummano Terme, Italy) had accepted for about fifteen years mixed municipal raw waste, then in the year 2003 a mechanical biological treatment (MBT) has been implemented and starting from the end of the year 2006, the recirculation in the landfill of the concentrated leachate coming from the internal membrane leachate treatment plant has been put into being. USEPA LandGEM model and the Andreottola-Cossu approach have been chosen since they require only input data routinely acquired during landfill management (waste amount and composition) and allow a simplified calibration, therefore they are potentially useful for practical purposes such as landfill gas management. The results given by the models are compared with measured data and analysed in order to verify the impact of MBT on biogas production; moreover, the possible effects of the recirculation of the concentrated leachate are discussed. The results clearly show how both models can adequately fit measured data even after MBT implementation. Model performance is instead significantly reduced for the period after the beginning of recirculation of concentrated leachate when the probable inhibition of the methane production, due to the competition between methanogens and sulphate reducing bacteria, significantly influences biogas production and composition.