The aim of this work was to obtain biodiesel from animal fats, an inedible feedstock. Three different types of fats were used to produce biodiesel; their main characteristic was high free fatty acid content. Animal fats were transesterified with acid catalyst and basic catalyst with and without pre-esterification. Biodiesel of 89.0 wt.% ester content was obtained by acid-transesterification (9 wt.% H(2)SO(4), 6:1 methanol:fats molar ratio, 60 C, 48 h). Pre-esterification conditions were studied for different fats and acid catalysts: 0.5 wt.% H(2)SO(4) or 1.0 wt.% p-TsOH, 6:1 methanol:fats molar ratio, 65 degrees C and 4 h made it possible to obtain fats with acid value less than 0.5% FFA. Pre-treatment was effective for fats with different FFA content. Alkali transesterification of esterified fats resulted in a product with 97.3 wt.% ester content. Biodiesel quality was evaluated and most of properties were well within EN 14214. (C) 2011 Elsevier Ltd. All rights reserved.