Rigid polyurethane-polyisocyanurate foams were synthesized by reacting the corn. propyloxylated sorbitol with techn. (OCNC(6)H(4))(2)CH(2) in presence of KOAc and (EtNHCH(2))(2) and filled with corn. wood dusts (grain size 40-300 mu m) and/or solid residues (slopes) from alc. fermn. of corn starch. The resulting foams were studied for d., compression strength, brittlness, flammability, shape stability, mass loss at elevated temp., thermal resistance and ability to alcoholysis. The foams were alcoholyzed with (HOC(2)H(4))(2)O in presence of NH(2)C(2)H(4)OH and Zn stearate at 150-250 degrees C for 3.5-4 h to check the possibility for their recycling. The glycolyzates showed the OH nos. 377-543 mgKOH/g. The addn. of wood dust resulted in decreasing the thermal stability of the foams. The filling of the foams resulted in decreasing their brittlness, compression strength and softening temp.