In this study, fresh vegetable oils, used frying oil and the mixtures of fresh vegetable oil and used frying oil were used as feedstocks for alkali-catalyzed methanolysis. The used frying oil-to-fresh vegetable oil ratios were 0.03, 0.05, 0.10, 0.15, and 0.20 v/v. The averages of the methyl ester contents in the biodiesel products are shown in Table.
It was found that the methyl ester contents reached the maximum values when the fresh vegetable oils were used as feedstocks. These results were in accordance with the results found by other researchers. On the other hand, used frying oil provided the lowest methyl ester content for all reaction conditions.