Coal mining and processing activities in Russia result in the generation of huge quantities of wastes containing elevated concentrations of residual S (S-t(d) = 2.1-9%), C (C-o(d) > 12%), heavy metals and other hazardous elements. These wastes which are usually piled or dumped without specific care close to mining sites and processing plants are subjected to adverse climatic conditions and in most cases cause severe impacts to various receptors. The worst impacts, in Russian mining and disposal areas, are due to the oxidation of the residual sulfide phases and the generation of coal mine drainage, with pH often ranging between 2.5 and 4. These acidic leachates contaminate severely soils, surface- and groundwater; therefore the risk for humans and ecosystems in these sites is considered as extremely high. The present paper examines the feasibility of thermal treatment of high sulfur coal wastes, in particular those containing elevated content of carbon, kaolin and iron, in order to reduce environmental risk at the disposal sites and produce saleable by-products. Carbon reduces substantially fuel consumption while kaolin and iron assist the formation of secondary products. Parameters studied include temperature and air excess ratios, up to 1400 degreesC and 1.4 respectively. Coal wastes were subjected to thermal treatment (a) as such, in order to study the removal of sulfur and the production of saleable products (sulfuric acid, various construction materials, products with high magnetic susceptibility, aluminum sulfate) and (b) after mixing with calcium carbonate in order to study the fixation of sulfur in multi-mineral phases possessing binding properties. Prior to implementation of laboratory experiments in order to assess the potential of thermal treatment, thermodynamic calculations were performed to determine optimum operating parameters and possible phase transformations. (C) 2003 Elsevier Ltd. All rights reserved.