| Methods | Catalyst | Advantages | Disadvantages | References |
| Alkali homogenous catalyst | (1) NaOH (2) KOH (3) Sodium methoxide (4) Potassium methoxide | (1) Fastest reaction (2) Higher yield (3) Mild reaction condition (4) Low cost | (1) Formation of soap (2) Difficult to separate it from the final product, water interferes with reaction | [10, 14–26] |
| Alkali heterogeneous catalyst | CaO, CaTiO3, CaZrO3, CaO–CeO2, CaMnO3, Ca2Fe2O5, Al2O3/KI, ETS-10 zeolite, alumina/silica-supported K2CO3 | (1) Separation of catalyst from product is easy (2) Formation of soap is avoided (3) Less corrosive, less toxicity, less environmental problem | (1) High methanol to oil ratio is required to reach the highest possible conversion | [10, 14, 19, 27–29] |
| Acid homogenous | Concentrated H2SO4, sulfonic acid | (1) Suitable for high free fatty acid feed stock (2) Yield is high | (1) Slow reaction (2) Need extreme pressure and temperature conditions (3) Difficult to separate (4) More corrosive | [10, 14, 18, 21, 30] |
| Acid heterogeneous | ZnO/I2, ZrO2=SO2, Sr/ZrO2TiO2=SO2, carbon-based solid acid catalyst, carbohydrate-derived catalyst, Vanadyl phosphate, niobic acid, sulphated zirconia, Amberlyst-15, Nafion-NR50 | (1) Less corrosive (2) Less toxicity (3) Less environmental problem | (1) Low acid concentration (2) High cost (3) Diffusion limitation | [10, 17, 27, 31] |
| Enzyme | Candida antarctica fraction B lipase, Rhizomucor mieher lipase, E. aerogenes lipase, lipase immobilized on hydrotalcite and zeolites | (1) By product of process can be easily removed (2) Free fatty acid can be completely converted into methyl esters, regeneration and reuse of immobilized enzyme catalyst are possible | (1) High reaction time required (2) Expansive, activity loss, agglomeration of enzyme | [10, 16, 20, 21, 32–38] |
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