Synthesis and characterization of ethylic biodiesel from animal fat wastes

Abstract

This study optimized the conversion of animal fat wastes into ethylic biodiesel by alkali-catalyzed process under mild conditions. A mix of chicken and swine fat residues was used as feedstock for biodiesel production. A full 3³ factorial design was used to optimize process parameters for maximum fatty acid ethyl esters yield. Factors were evaluated at three different levels: temperature (30; 50; 70 °C), ethanol:fat molar ratio (6:1; 7:1; 8:1) and catalyst concentration (0.44; 0.88; 1.32 wt.%). Effects of the process variables were analyzed using response surface methodology. Moreover, optimum conditions were applied in a bench-scale reactor and biofuel produced was characterized. It was observed that at high temperatures (50 and 70 °C), phase separation between biodiesel and glycerol was impaired. Although high conversion was achieved (96.2%) at 70 °C, this condition is not recommended because no spontaneous phase separation was verified. On the other hand, 30 °C was identified as the best temperature for biodiesel ethanolysis, using 0.96 wt.% catalyst and 7:1 ethanol:fat molar ratio. With these conditions, it is possible to achieve around 83% conversion. Despite the oxidative stability and total glycerin, biodiesel measured properties agreed with quality requirements established by Official Regulations (ASTM 6751 and EN 14214).