The results of experimental studies of thermal decomposition processes of mixed fuels based on 2B and 3B brow coals with addition of dispersed wood were conducted. Ratio of wood biomass (pine sawdust) varied from 10% to 50%. It was established that wood displaces the combustion process of mixed fuels in the region of low temperatures (relative to homogeneous coal). It was also determined that the presence of biomass leads to a significant reduction (up to 60% for coal/wood ratio of 50/50%) of the concentration of sulfur and nitrogen oxides in the gaseous products of 3B coal combustion. It also leads to changes in the content of these anthropogenic oxides in combustion products of fuel based on 2B coal (up to 40%). It was established by the results of technical analysis of the initial components and the group of researched mixed fuels that the yield of solid combustion products of the latter does not correspond to the numerical value of the ash content obtained as a result of calculations under the assumption that there is no mutual influence of combustion products of coal and wood on each other. A hypothesis was formulated on the mechanism of nitrogen and sulfur oxides suppression during combustion of such mixed fuels due to the effect of charcoal formed in low-temperature stages of thermal decomposition of wood in the absence of oxygen, which adsorbs a significant part of the sulfur and nitrogen compounds during combustion stage of the initial fuel.