Polyurethanes (PUs) such as flexible (cushioning material and sponge) and rigid (different insulators) forms and elastomers (flexible tube and smartphone case) were thermally decomposed at 500 degrees C. The useless decomposition products were converted into H-2-rich syngas and the toxic HCN in it was removed by Ni/Mg/Al catalysts at 800 degrees C under 50 vol% steam/He flow. The resultant total gas production was 1411-1623 mL/g (H-2: 794-967 mL/g), which was almost 30 times larger than that obtained from simple pyrolysis of PUs where no H-2 was produced. Meanwhile, there was a drastic reduction of HCN concentration in the product gas from a maximum at 2.8 to 0.2-0.6 vol%. The excellent performance on the removal of HCN and the enhanced H-2-rich syngas production is due to the synergy between Ni, Mg, and Al in the catalysts. This approach has great promise for treating a variety of PU wastes that cannot be recycled effectively otherwise.