In this work, the optimization of microalgae oil (MO) based biodiesel production process is carried out by waste heat recovery and process integration. The exergy analysis of each heat exchanger presented an efficient heat coupling between hot and cold streams, thus minimizing the total exergy destruction. Simulation results showed that the unit production cost of optimized process is 0.592 $/L biodiesel, and approximately 0.172 $/L biodiesel can be avoided by heat integration. Although the capital cost of the optimized biodiesel production process increased 32.5 % and 23.5 % compared to the reference cases, the operational cost can be reduced by approximately 22.5 % and 41.6 %. (C) 2015 Elsevier Ltd. All rights reserved.