Creating biodegradable polymer compositions is an urgent problem. In this research, the processing parameters and physicomechanical properties of materials based on secondary polypropylene and secondary polyethylene filled with plant-based fillers are studied. It is estimated that the introduction of a filler leads to an increase in the maximal torsion torque; the lowest resistance against filler introduction is observed in the use of secondary polyethylene. Similar regularities are observed during the study of the minimal torsion torque; however, in this case, the lowest resistance is observed for the sample of secondary polypropylene. It is shown that the introduction of 10–15 parts by the mass of the filler leads to an increase in the elastic modulus and an insignificant decrease in the values of rupture stress and elongation upon breaking.