Biodiesel production offers a promising route towards achieving net-zero emissions by 2050. However, the move away from crop-based feedstocks towards a variable waste base feed oil presents several challenges. This study addresses these challenges by using waste cooking oil (WCO) as a renewable feedstock for transesterification in a microreactor. Kinetic analysis was performed using both pseudo-homogeneous and biphasic second-order models to evaluate their suitability for describing the reaction.