As seen, the stoichiometric ratio (3:1) was the lowest biodiesel conversion efficiency as
48.34%.During the experimental study, the best biodiesel conversion efficiency was 6:1methanol: oil
molar ratio. This result was similar with previous studies [24, 25]. Nevertheless, increasing the molar
ratio more than 6:1 reduced the biodiesel conversion efficiency. Due to excess methanol increased the
solubility of glycerol; this caused the interference of a little amount of glycerol with the ester phase. The
diluted glycerol in ester phase leaded more foam formation with the lower product [26].