The biodiesel yield regarding MgSO4·H2O method showed a decrease in all methods, −17% for oven at 105 °C, −53% for oven at 70 °C, −65% for freeze-dryer, −71% for fume hood and −73% for sun drying. On the other hand, the values of biodiesel obtained from primary sludge dried by oven at 70 °C (8.8%) and fume hood (5.5%) compares well to those reported elsewhere [3,6].