Fossil fuels as black coal, crude oil and natural gas are at present still the main sources of energy production. Thermal energy is the second most important source in Slovakia (after electricity), representing almost 13.6% of total energy production. One Slovak power plant, Vojany Power Plant (EVO), sees an undesirable by-product of coal combustion as ash, which is deposited on the tailing ponds and a stabilizer deposited on a landfill. The aim of our paper is to formulate conclusions from laboratory testing and testing field results of combinations of stabilizer as a by-product, waste from combustion, and from EVO desulphurization technology in combustion processes. The reinforcement of the stabilizers with cement and lime was realised for forming the sealing respectively water-permeable layer. The reason for testing was the use of stabilizer for tailing pond reclamation as a component of the underlying impermeable part. This can attain an environmental as well as economical solution for the use of stabilizer and waste from thermal power plants.