New sources of biomass for biofuels production had been studied in recent years. Microalgae as oil donors for biodiesel production are a very attractive alternative due to their several benefits but it still is a process that must overcome several technological barriers. Oil composition and the amount of free fatty acid (FFA) makes the microalgae oil a difficult yet promising alternative. In this paper, sequential stages of esterification and then transesterification were studied to convert the microalgae oil (MAO) in biodiesel, glycerol, and water mostly. A more realistic microalgae oil composition was simulated using 9 triglycerides (TG) and 9 FFA's in contrast with other studies were 1-5 components are used to represent the oil. A sensitivity analysis was performed to determine the temperature effect on the glycerol and water concentration. Finally, energy integration alternatives were analyzed to find a cost-effective way to produce biodiesel from MAO. (C) 2011 Elsevier B.V. All rights reserved.