The results of field and laboratory studies of the component and fractional composition of solid municipal waste (MSW), humidity and ash content of MSW components, which made it possible to evaluate the properties of individual fractions and waste in general, are presented. The fractional composition of MSW was determined by the method of separating waste into five fractions of different sizes: more than 250 mm, 100-250 mm, 50–100 mm, 15–50 mm and less than 15 mm. An assessment of the energy and biological potentials of MSW of various sizes has been carried out. In each fraction, the main biogenic components have been identified, which form the biological potential. The calculation of thermal properties (moisture content, ash, combustible substances, as well as the heat of combustion) for the fractions under consideration has been performed. The dependence of the heat of combustion of MSW on the particle size has been established.