Polyester polyols are low molecular weight polymers characterized by hydroxyl terminal groups useful for the preparation of flexible and rigid polyurethanes (PUs). Normally, these polyesters are highly crystalline compared with their polyether equivalents. For this reason, they impart peculiar characteristics to PUs such as the resistance to solvents, hydrolysis, weather condition, fire etc. The Polyester polyols are used for the production of elastomers, flexible foams, coatings, adhesives, rigid foams, synthetic leather, sealants, etc. They are rapidly biodegradables and can proceed from renewable source so lowering the carbon footprint of PUs.