Organic covers may be used to prevent diffusion of oxygen into reactive sulphide wastes and subsequently to eliminate sulphide compounds oxidation and generation of acidic waters. The main advantages over other types of covers are related with their low hydraulic permeability, high cation exchange capacity and high alkalinity. In addition, the establishment of organic covers, which is considered as a low cost solution for the prevention of acid mine drainage generation, does not disturb the natural environment, since they consist of industrial wastes rather than natural materials and allow the development of vegetation which improves the aesthetics of the reclaimed areas. However, treatment of municipal sewage sludge is necessary prior to discharge, in order to minimize potential health and environmental risks, resulting from the presence of toxic elements. In the present paper all processes associated with the function of an an organic cover are described and discussed, including potential health and environmental risks resulting from land application of municipal sewage sludge. In addition, preliminary laboratory data derived from the application of organic coves over reactive sulphidic concentrates are presented and discussed, in order to evaluate the performance of the covers and to determine the critical factors affecting their performance. The final aim of this research work is the development of an experimental model, that predicts the performance of an organic cover, by taking into account critical parameters such as annual rainfall rate, organic material height, initial moisture and moisture under saturation conditions. (C) 2000