Glycerol is a major by-product in biodiesel manufacturing, which surplus raises a critical need to transform it into high added-value products. In particular, glycerol carbonate is an important glycerol derivative being the most valuable intermediate for the production of glycidol, which is an added-value product of major industrial interest used, for example, as a precursor for the synthesis of a large number of polymers. Solvent-free conventional thermal activation, ultrasound-activation and microwave-activation in the liquid phase are able to selectively transform glycerol carbonate into glycidol under mild conditions using a ZSM-5 zeolite catalyst and a zinc oxide-supported nanoscaled cobalt oxide catalyst with short reaction times and in the absence of solvent. To the best of our knowledge, we report the highest selectivity to glycidol (>99%) from glycerol carbonate at high conversion values (71%).