After two stage pretreatment reactions applied to chicken fat, the FFA level was reduced to 0.97% on average. In the transesterification reactions, reaction parameters were chosen considering the results in the previous study (Alptekin and Canakci, 2011). The ingredient amounts used in the transesterification reactions for the chicken fat were shown in Table 4a. The transesterification were performed with the alkaline catalyst amount of 1% weight of the initial triglyceride weight in the chicken fat at 6:1 M ratio between methanol and fat-ester mixture. Mean molecular weight of the chicken fat was calculated to be about 865 g mol1. After transesterification and purification process, the ester yield was found to be about 81% on average. The transesterification results were given in Table 4c. Fuel properties of the chicken fat methyl esters were very close to each other.
3.4. Comparison of the fuel properties
After transesterification reactions, two different methyl esters were obtained for fleshing oil and chicken fat. Hence, these methyl esters were mixed separately. Then, the fuel properties of all produced methyl esters were determined and compared to each other. The fuel properties of the methyl esters produced in the pilot plant and laboratory scale and related fuel specifications in European biodiesel standards (EN 14214) and American biodiesel standards (ASTM D6751) were summarized in Table 5.
Density of a fuel is an important fuel characteristic and it directly affects the engine performance. Many performance parameters such as cetane number and heating value are related with the density (Tat and Van Gerpen, 2000; Ryan et al., 1984; Guru et al., 2010). The densities of produced methyl esters were close to each other and in the range of 876.7–889.7 kg m3 which were suitable