Extensive simulations have been carried out to study generation of landfill gases by biodegradation of wastes and their transport in a model landfill, using a comprehensive three-dimensional model developed in Part I of this series. The model has been developed for a four-component gas mixture, and takes into account the effect of heterogeneity in the landfill's morphology, as well as that of the surrounding soil. It accounts for the presence of gas extraction wells with an arbitrary spatial distribution. The model is utilized for investigating the dynamic behavior of a landfill, and in particular pressure build-up, under a variety of conditions. These include, for example, the cases in which some of the extraction wells are shut down, or new wells are drilled. It is shown that the spatial distribution of the permeability has a very strong effect on the dynamic behavior of a landfill, whereas mechanical dispersion, manifested by effective dispersion coefficients that depend on the flow velocities, has virtually no effect. Thus, development of an accurate data base for the spatial distributions of the permeability, porosity, and other morphological characteristics of a landfill, in addition to its transport and reaction properties, is essential for accurate forecasting of the landfill's behavior, including identifying the areas with large amounts of methane and a potential for explosion. Limited comparison of the model's predictions with experimental data for a particular landfill indicates the potential of the model for predicting the dynamic behavior of large landfills. (c) 2006 Elsevier Ltd. All rights reserved.