As seen, biodiesel yield increased with reaction time at the beginning, reached at a yield of 99.3% in
the first 40 sec and was also the best conversion efficiency, and then decreased dramatically with
increasing reaction time. Due to longer reaction times led the hydrolysis of esters and caused more fatty
acids to produce soap [23]. According to experiment results, reaction time had a significant effect on the
conversion of the triglycerides up to 40 sec, but increasing further the reaction time had decreased the
biodiesel yield. Due to reaching the maximum biodiesel yield as 99.3 %, 40 sec was selected as the
optimal reaction time for cooking oil transesterification in the present conditions.