## 3 Transesterification for Producing Biodiesel from Animal Fats
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Fatty Acid**} & \multicolumn{2}{c}{**Pork Lard**} & **Beef Tallow** & **Mutton Tallow** & **Poultry Fat** \\ \cline{2-5}  & \multicolumn{1}{c}{[37]} & \multicolumn{1}{c}{[38]} & \multicolumn{1}{c}{[39]} & \multicolumn{1}{c}{[40]} \\ \hline Myrsitic & C14:0 & 1.6 & 1.6 & 2.2 & 0.4 \\ Palmitic & C16:0 & 25.1 & 21.6 & 21.1 & 21.6 \\ Stearic & C18:0 & 12.6 & 17.7 & 11.6 & 6.3 \\ Palmitoleic & C16:1 & 2.8 & 2.5 & 2.1 & 3.2 \\ Oleic & C18:1 & 36.5 & 31.5 & 38.7 & 30.0 \\ Linoleic & C18:2 & 16.5 & 3.3 & 10.2 & 28.4 \\ Linolenic & C18:3 & 1.1 & 1.3 & 0.6 & 2.4 \\ Arachidic & C20:4 & 0.3 & - & - & 3.4 \\ Docosapentenoic & C22:5 & 0.2 & - & - & 0.3 \\ Docosahexenoic & C22:6 & - & - & - & 0.8 \\ Total saturated & SFA & 39.4 & 49.1 & 40.4 & 29.1 \\ Total monounsaturated & MUFA & 39.7 & 41.0 & 47.1 & 33.2 \\ Total polyunsaturated & PUFA & 20.9 & 10.0 & 12.5 & 37.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Typical composition in major fatty acids (as % of total fatty acids) of pork, beef, mutton and chicken fats. catalyst, either sodium hydroxide or potassium hydroxide, to generate 100 kg of biodiesel and 10 kg of glycerin [55]. Examples of operating conditions during the transesterification step for production of biodiesel from animal fats are shown in Table 2. The optimum alcohol to oil molar ratio to get a biodiesel yield higher than 90% in alkaline catalyzed transesterification is reported to be around 6:1 which gives enough alcohol the capability to break the fatty acid-glycerol linkages. The use of a ratio greater than 6:1 gives a better yield in some cases but could hinder the glycerol separation process [56]. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Animal Fat**} & \multirow{2}{*}{**Catalyst**} & **Weight** & **Reaction** & **Alcohol:OII** & **Operating** & \multirow{2}{*}{**References**} \\ \cline{3-4}  & & **(\% to Fat)** & **Yield (\%)** & **Ratio** & **Conditions** & \\ \hline Beef tallow & KOH & 0.8 & 90.8 & 6:1 & 60 °C, 2 h & [57; 58] \\ Pork Lard & KOH & 0.8 & 91.4 & 6:1 & 60 °C, 2 h & [57; 58] \\ Poutry fat & KOH & 0.8 & 76.8 & 6:1 & 60 °C, 2 h & [57; 58] \\ Chicken & KOH & 1 & - & 6:1 & 60 °C, 2 h & [59] \\ waste & KOH & 1 & 97.1 & 3:1 & 65 °C, 3 h & [60] \\ Duck tallow & KOH & 0.5 & 97.3 & 6:1 & 65 °C, 2 h & [61] \\ Pork fat & KOH & 0.8 & 92.7 & 6:1 & 50 °C, 0.75 h & [62] \\ Chicken fat & KOH & 0.8 & 82.0 & 8:1 & 60 °C, 1 h & [63] \\ Swine lard & KOH & 1.1 & 98.0 & 7:41 & 65 °C, 3 h & [64] \\ Mutton fat & MgO-KOH & 20 & 98.0 & 22:1 & 65 °C, 2 min & [65] \\ Chicken fat & H\({}_{2}\)SO\({}_{4}\) & 1.25 & 99.0 & 1:30 & 50 °C, 24 h, & [24] \\ Mutton & H\({}_{2}\)SO\({}_{4}\) & 1.25 & 93.2 & 1:30 & 60 °C, 24 h & [24] \\ tallow & \multicolumn{1}{l}{} & \multicolumn{1}{l}{} & \multicolumn{1}{l}{} & \multicolumn{1}{l}{} & \multicolumn{1}{l}{} & \\ Chicken fat & NaOAc & 1 & 88.5 & 6:1 & 60 °C, 4 h & [66] \\ Chicken fat & Nano CaO & 1 & 88.5 & 9:1 & 60 °C, 5 h & [67] \\ Chicken fat & Composite membrane \& NaOAc & 1 & 98.1 & 1:1 & 70 °C, 3 h & [68] \\ Chicken fat & CaO/CuFe\({}_{2}\)O\({}_{4}\) & 3 & 94.5 & 15:1 & 70 °C, 4 h & [69] \\ Lard & 35\%/CaO/2 coile & 8 & 90.9 & 30:1 & 65 °C, 1.25 h & [15] \\ Chicken fat & AC/CuFe\({}_{2}\)O\({}_{4}\) encapsulated with & 3 & 95.6 & 12:1 & 65 °C, 4 h & [70] \\ Brown & Mesoporous silica & & & & & \\ grease & diphenylammonium triflate & & & & & \\ grease & ZnO/ZrO2 & 0.8 & 78.0 & 1:1.5 & 200 °C, 2 h & [72] \\ Lard & Supercritical methanol & - & 89.9 & 45:1 & 335 °C, 20 MPa, 15 min & [73] \\ Waste lard & Immobilized lipase from _Candidata_ & & & & & & \\ _antarctica_ & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Examples of operating conditions during the transesterification step for the production of biodiesel from animal fat waste. Figure 1: Major steps in the production of biodiesel from animal fat waste. Adapted from [46; 47; 53].