Glycerolysis of two high free fatty acid waste materials for biodiesel production

Abstract

Biodiesel is generally produced from edible vegetable oils; however, some waste materials with high free fatty acids (FFA) content might be used if an adequate pretreatment technology is employed. The present study evaluated the use of glycerolysis for the pre-treatment of two high FFA waste materials, for further biodiesel production. The raw-materials were sludges, one from an urban wastewater treatment (sample one - acid value around 140 mg KOH g1) and one from a wastewater treatment of the dairy industry (sample two - acid value around 4.5 mg KOH g1). Biodiesel was further produced by alkaline transesterification. The glycerolysis (1:2 glycerol:oil (w/w), 200C, 100 rpm, 2 h) allowed to decrease between 85% to 96% the FFA content of the raw-materials. The best results were obtained for sample two; however, although with effective pretreatment, transesterification led to a maximum product purity of 67% and relatively low product yields. (c) 2015 Taylor & Francis Group, London.