The kinetics of alkali-catalysed reactive extraction ("in situ transesterification") of Chlorella vulgaris with methanol to produce biodiesel were investigated. Both the experiment and the model showed that a maximum 96% biodiesel yield can be obtained in 10 min before saponification FAME losses become significant. This high FAME yield was achieved despite high levels of free fatty acid (6% lipid) in C. vulgaris. The process shows higher level of water tolerance than a two-step transesterification. At 600:1 methanol to oil molar ratio, the process was not adversely affected by up to 20% moisture in the microalgae. A derived numerical model fitted with experimental data from this study showed that other side reactions including FAME and triglyceride saponification; free fatty acid neutralisation occur alongside the desired biodiesel synthesis in a NaOH-catalysed reactive extraction. (C) 2016 Elsevier B.V. All rights reserved.