Production of biodiesel via methyl and ethyl routes from Nile tilapia and hybrid Sorubim crude oils

•Biodiesels were obtained from Nile tilapia and hybrid Sorubim fish crude oils.•KOH (0.5, 1 and 1.5%) and alcohols in the molar ratios of 1:6 and 1:9 were studied.•The use of 0.5% of catalyst proportioned the best results for all experiments.•Best yield was found above 92% (methanol 1:6, 0.5% KOH) for Nile tilapia biodiesel.

Fish oils are presented as an alternative for biodiesel production due their adequacy for transesterification. In the present work, transesterification reactions for Nile tilapia and hybrid Sorubim oils were carried out with potassium hydroxide (KOH) as catalyst in the concentrations of 0.5, 1.0 and 1.5% and with anhydrous ethanol and methanol in the molar ratios of 1:6 and 1:9 (oil:alcohol molar ratio). The best yields were found above 92% for the reactions with methanol in the molar ratio of 1:6 (oil:methanol) and 0.5% of KOH for both Nile tilapia and hybrid Sorubim. The same reaction with ethanol also yielded satisfactory results (yields higher than 84%). Regarding biodiesel quality, it was detected that the different molar ratios did not affect the chemical parameters acidity and peroxide index, iodine value, moisture content and density for most of the reactions carried out.