Biodiesel fuel: The transesterification of beef tallow

More beef cattle are slaughtered in Nebraska each year than in any other state. Beef tallow, beef fat, is the by-product of this industry. The objectives of this project were to utilize this by-product by converting it into biodiesel, methyl esters, and to optimize this conversion process. Transesterification of beef tallow was investigated. The solubility of ethanol in beef tallow was much greater than that of methanol. At 68°C the solubility of methanol was 13% w/w, while the solubility of ethanol was 100% w/w at 68°C. The percentage of total methanol in the glycerol phase was higher than that in the beef tallow methyl ester (BTME) phase in a 90:10 blend of BTME and glycerol at room temperature. However, the percentage of total methanol in BTME (60% w/w) was higher than that in glycerol (40% w/w) in the same blend ratio at above 65°C. After the reaction, the products were distilled to recover as much of the unreacted methanol as possible, which also made the subsequent phase separation of esters and glycerol quicker and easier. At neutral pH, the phase separation and water washing were easier because the emulsion was substantially reduced. A simple BTME quantitation. method was developed, by which fatty acid methyl esters in the product can be calibrated with a standard curve of oleic acid methyl ester. Sodium hydroxide (NaOH) was more effective than sodium methoxide at catalyzing the transesterification. NaOH reached its maximum activity at 0.3% w/w of the beef tallow. The content of free fatty acids should be kept below 0.5% w/w and water content below 0.4% w/w. The transesterification of beef tallow was complete after 15 min. For the transesterification of beef tallow and methanol, stiffing was very important to make the reaction occur Adding the NaOH-methanol solution to melted beef tallow after stirring was better than adding before stiffing. Lower stirring speeds and shorter stirring times lowered the energy requirements without sacrificing conversion efficiency