A complex analysis of the influence of various atmospheres on SO2 emission is presented by comparing two types of coal under the following conditions: combusted alone and mixed with biomass. The results are correlated with the content of pyrite, sulfate and organic sulfur in both coal types. SO2 emission in different atmospheres was compared separately for each coal type, reporting it in percentage of emission in the air for the same mass of coal sample. We found a strong dependence of SO2 emission on the combustion atmosphere in case of bituminous coal, whereas we found a weak dependence in case of lignite. Combustion of bituminous coal in oxygen enhanced atmosphere resulted in a high increase in SO2 emission. A significant reduction in the emission of SO2 was obtained by combusting either bituminous coal alone in O-2/CO2 atmosphere or in a blend with biomass in O-2/N-2 or O-2/CO2 atmospheres.