The thermolysis of D-grade (long-flame) coal, refinery waste, coal-processing waste, and biomass was studied by thermogravimetry in order to increase the total efficiency of the thermal processing of organic carbon-containing products and the selectivity of formation of particular by-products (solid, gaseous, or liquid). The deconvolution of the resulting thermogravimetric curves was performed using SCIENTIST 3.0 software. In accordance with published concepts, it was proposed to separate the thermal degradation of complex multicomponent solid or liquid starting products into individual components and to relate them to the thermolysis of particular structural fragments of the starting carbon-containing materials. Quantitative (yield/temperature) and qualitative (composition/nature) data were obtained for the conversion of individual structural fragments in complex multicomponent organic materials. In addition, the effect of alkali metal carbonate additives on the thermolysis of the individual structural fragments of the test products was analyzed.