The procedure used in the esterification/transesterification reactions was: the oil sample was
transferred into a stirred tank reactor equipped with a reflux condenser and immersed in a
temperature‐controlled water bath and heated until the desired temperature (usually 63°C). Then a
mixture of methanol and catalyst was added to the oil. Sulphuric acid was used as the esterification
catalyst, whereas KOH was used to catalyze the transesterification reaction. In the end of the
esterification reaction period (1h), the acid value was measured and the transesterification reactionwas carried out for 1 h with addition of KOH dissolved in methanol. After separation of the glycerol
phase and methanol recovery by distillation, the biodiesel phase was washed with water, with a
0.1M HCl solution and once again with water and dried.