Abstract-The aim of this work was to perform life cycle analyses (LCA) based on detailed process mass and energy balances for the production of biodiesel from microalgae in order to compare the conventional transesterification with in situ transesterification. GaBi software was used to perform the LCA. The material balances revealed that a slightly lower biodiesel yield was obtained for in situ transesterification process (5.06 kg/day) when compared to the conventional one (5.5 kg/day). GaBi results showed that the global warming potential (GWP) of the conventional transesterification process was higher than in situ transesterification by 140 kg CO 2 equivalent (per tonne of biodiesel produced). No substantial difference was noted however, for acidification (4.15 vs. 4.34 kg SO 2 equivalent), eutrophication (0.641 to 0.666 kg PO4-equivalent) and human toxicity potential (72.3 vs. 77 kg dichlorobenzene equivalent) between the two processes per kg of biodiesel produced. The results of the LCA analysis also show that electricity production was the major contributor for all the environmental impacts. When both the global warming potential and biodiesel yield were taken into account, it could be concluded that biodiesel production via in situ transesterification was a better option.