Biodiesel production from three mixes of oils with high free fatty content: quality evaluation and variable analysis

Due to the excessive use of fossil fuels around the world, more environmentally friendly alternatives have been studied. Technologies for the production of ethanol, biogas and biodiesel are focusing on the importance of improving costs and efficiency. Biodiesel can be used in automotive internal combustion, is biodegradable and has no presence of metals, however, it lacks competitiveness versus petrodiesel mainly by the high cost of the pure oils used for its production. The aim of this study was to obtain biodiesel from oil samples with high content of free fatty acids (>1 %) obtained from three fast food restaurants using their molecular weight and acidity index values in order to neutralize the free fatty acids in a one-step reaction and perform a screening for optimal conditions for transesterification. The experimental design consisted of two reaction times (60 and 90 min); four methanol–oil molar ratios—6:1, 10:1, 15:1 and 20:1; and two catalysts (NaOH and KOH) at three concentrations 0.5, 1 and 1.5 % with a constant temperature of 60 °C and 500 rpm. The optimum conditions for the different waste cooking oil feedstocks were established reaching a final yield up to 85.53 % of biodiesel, concluding that there is viability of production through the use of this raw material and free fatty acids neutralization technique, obtaining a biofuel that meets international quality standards.