Physicochemical study of used frying oil as feedstock for the production of biodiesel

Abstract

A diagnosis was made of the availability and quality of the used frying oil of the establishments dedicated to chicken fry in the city of San José de Cúcuta, to evaluate its technical feasibility as a feedstock in the biodiesel production. A survey was applied to 21 restaurants, evidencing that they reuse the oil less times when having a high monthly consumption (i.e. more than 80 liters, contrary to those consuming less than 60 liters, which reuse the oil more than 3 times. As a final disposition, 86% of establishments sell the used frying oil at $750/liter and 14% deliver it to be used by external persons. The physicochemical properties of used frying oil were analyzed as: fatty acid profile, density, moisture content, refractive index, acidity index, peroxide index and saponification index. The used frying oil presented high content of oleic acid (42.45%) and palmitic acid (33.52%), converting it into a potential feedstock by presenting fatty acids characteristics from palm oil, which is the main source for the production of biodiesel in Colombia. To improve the organoleptic characteristics of the used frying oil (dark colour, strong odour, emulsions), it was subjected to heating and filtering to remove the particles that affect the yield of biodiesel production.