Abstract This work presents a new version of the landfill dynamic simulation program “MODUELO”. Based on landfill characterization data, the program calculates the daily leachate flow and organic pollution and the generation and composition of biogas. The models that constitute the principal body of the program have been improved in the new version, called “MODUELO 2”. The mathematical expressions for the calculation of the surface water balance and the saturated flow between the landfill's model cells have been corrected. The runoff effect on the leachate flow and a model for the variation of the waste hydraulic conductivity with depth have now been included, as well as an improved biodegradation model. As a first verification of the new version, the model has been applied to the Meruelo I landfill (Spain). The hydrologic model results are compared to the available data and other models, MODUELO 1 and HELP. The biodegradation model is then evaluated by contrasting its results with the available data and the emission trends found by other authors in different facilities. The simulation results are close to the available data, indicating that the models presented here can constitute an adequate basis for the development of future models representing other landfill phenomena.