In a densily populated industrialized country, waste disposal must be compatible with the requirements of the environment. This is one of the indispensable requirements to guarantee an effective protection of the environment. While in the past, waste disposal performance was more or less evaluated in terms of short-term costs, there is at present a reorientation in the direction of a science-based waste disposal industry. These new tendencies are taking into account ecological factors as well as the long-term consequences of waste disposal methods. This field confronts science with an urgent challenge and calls for close collaboration between many different specialized disciplines. In this light, an overview of the geochemical processes taking place in landfills is presented in this paper.