Majority of solid emissions into the atmosphere originate in the Czech Republic from combustion of brown coals in power and heating plants and households. There are three factors influencing the amount and composition of emissions from the combustion processes: composition of coal and additives, combustion regime and efficiency of filtrating and separating devices. To contribute to resolving the problem of decreasing of emissions, the proposed project will be aimed to study of influence of brown coal minerals, additives, and inorganic elements of fly ashes from fluidized bed combustion. The project has two parts. In the first part of the project composition of brown coal inclusive mineralogical composition and mode of occurrence of the elements will be studied. In the second part of the project the effect of additives on the reactivity of brown coal as well as the composition of ashes (bottom ash from combustor, fly ash from cyclone and fly ash remaining in the flue gas. Special attention will be paid to the study of the effect of additives on the distribution of choice elements (esp. S, As, cd, Hg, Ni, Pb, Se, V, Zn) in emitted particles. The stability of fly ash will be investigated by leaching of toxic elements in responsible environment.