One-pot syntheses of the value-added heterocyclic compounds 3-methylpyridine and pyridine using a renewable chemical, glycerol, were achieved in acidic medium by thermal conversion reactions. Condensation/cyclization reactions of the thermal degradation products of glycerol were investigated in situ using different ammonia and acidic moiety producing inorganic ammonium salts under pyrolysis or microwave heating conditions. The reaction parameters were studied in detail and satisfying product yields up to 72% were obtained under optimized conditions. Structural identification of all compounds was accomplished by spectroscopic methods.