Based on the present research, i.e., experimental biodiesel yield of 19.2%from dry primary sludge basis,the annual biodiesel potential,theoretically produced from primary sludge generated at WWTP of Reus (1922 t/year of dry primary sludge generation), was estimated to be 369 t. Speculating the biodiesel production from wastewater produced from all Spanish population, 6 h m3/day, the annual biodiesel potential was estimated at 88,664 t. This value may replace approximately 15% of current biodiesel production in Spain