Synthesis and characterization of ethylic biodiesel from animal fat wastes

► Ethylic biodiesel was produced from animal fat wastes under mild conditions. ► Waste-derived biofuel showed most properties in agreement with the standards. ► Mixed swine and chicken fat are a source of biomass to produce biofuel. 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).