According to calculations, about 90% of the organic carbon in the soil is concentrated in structural aggregates of various sizes. Agronomically worthless structural aggregates (>10 mm and <0.25 mm) are characterized by minimal organic carbon content. Depending on the share in organic carbon sequestration, the agronomically valuable aggregates (10-0.25 mm) are divided into 3 groups: a) with moderate sequestration capacity – 10-5 mm; b) with good capacity – 5-1 mm; c) with high capacity – 1-0.25 mm. Aggregates with dimensions >5 mm are totally devoid of hydrostability and as a result are characterized by extremely low capacity to stabilize organic carbon in the soil. The 5-3 mm aggregates are characterized by low capacity and the 3-1 mm ones with good capacity. Aggregates with a diameter of 1-0.25 mm are characterized by a high capacity to stabilize organic carbon. The obtained results imply the conclusion that for the reduction of CO2 emissions from arable chernozems, measures are needed to optimize the composition of the aggregate system of the soils and the aggregate stability of the structure through the differentiated practice of biologization measures of the practiced agricultural systems.