Effect of Alcohol to Oil Ratio: Four different concentrations of methanol (20, 30, 40 and 50 vol.%) were used to produce biodiesel from UVO. Other parameters such as reaction time, temperature, type of oil and amount of catalyst were kept constants. After remixing of biodiesel and glycerol products, the position of the interface between sediment (glycerol) and supernatant liquid (biodiesel) as a function of time is illustrated in Figure 3.