Biodiesel Production Technologies

Commercially, biodiesel is produced by transesterification, also known as alcoholysis, which is a chemical reaction between triglycerides and alcohols (Fan and 

Burton, 2009 Helwani et al., 2009). A typical form of this reaction is shown in Chapter 2. The fatty acid chains present in the feedstock usually range from 12 to 22 carbon atoms. In these types of reactions, the triglycerides are transformed into straight-chain molecules by exchanging the alcohol from an ester with another alcohol in a process similar to hydrolysis, except that an alcohol is used instead of water. The final product is always similar in size to the molecules of the species present in the diesel fuel (Rajan and Senthilkumar, 2009 Sinha et al., 2008). Therefore, such products can be used in normal engines without any modification. By transesterification, oil molecular weight can be reduced to approximately one-third and the viscosity to about one-seventh, and the flash point and in some cases the volatility can be reduced as well (Demirbas, 2009b). 

Typically, triglyceride and short-chain alcohols are immiscible, resulting in two phases with poor surface contact, which yields relatively slow reactions. However, these rates can be significantly increased by introducing a catalyst or carrying the reaction at a supercritical state (Fjerbaek et al., 2009 Lin et al., 2009). The catalytic reaction can be carried out using a catalyst, where by the end of the reaction, the biodiesel produced and the glycerol can be separated and purified to remove by-products and the catalyst. Catalyst selection depends on various factors. The most important of which is the free fatty acids (FFAs) and moisture contents of the feedstock. 

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Gerpen, Van J., Shanks, B., Praszko, R., Clements D. and Knothe, G., Biodiesel Production Technology. NREL/SR-510-36244 (2004). 

Harten, B. 2006. Westfalia Separator, Food Tec GmbH, Germany. Westfalia biodiesel production technology. Lecture on Practical Short Course on Biodiesel Market Trends, Chemistry and Production, 14-16 August 2006. Istanbul, Turkey. 

Bacovsky, D., Korbitz, W., Mittelbach, M. and Worgetter, M. (July, 2007) Biodiesel production technologies and European providers. A Report to lEA Bioenergy Task 39, Report T39-B6. 

J. Van Gerpen, B. Shanks, R. Pruszko, D. Clements and G. Knothe, Biodiesel Production Technology, Subcontractor Report NREL/SR-510-36244, Golden, 2004. 

Abbaszaadeh, A., Ghobadian, B., Qmidkhah, M.R., Najafi, G., 2012. Current biodiesel production technologies a comparative review. Energy Conversion and Managemeivt 63,138-148. 

Ha, V.T.T., Chuc, M.N., Pham, T.T., Ngoc, L.H., Nguyen, T.T.T., Le Minh, V., Le Anh, T., et al., 2009a. Final Report of a National Project on Assessment of Current Biodiesel Production Technology and Conducting Field Tests for Biodiesel Fuel Based Cat-Fished Oil, Contrihution to Process of Completion of Biodiesel Standard in Vietnam. Vietnamese Institute of Industrial Chemistry. 

Van Gerpen J, Shanks B, Pruszko R, Qements D, Knothe G. Biodiesel Production Technology. Golden, Colorado 80401 National Renewable Energy Laboratory 2004. NREL Subcontractor Report NREL/SR-510—36244. 

There is a real opportunity to reduce biodiesel production costs and environmental impact by applying modem catalyst technology, which will allow increased process flexibility to incorporate the use of low-cost high-FFA feedstock, and reduce water and energy requirement. Solid catalysts such as synthetic polymeric catalysts, zeolites and superacids like sulfated zirconia and niobic acid have the strong potential to replace liquid acids, eliminating separation, corrosion and environmental problems. Lotero et al. recently published a review that elaborates the importance of solid acids for biodiesel production. ... 

Zhang Y, Dube MA, Mclean DD, Kates M (2003) Biodiesel production from waste cooking oil 1 Process design and technological assessment. Biores Tech 89 1-16... 

Warabi, Y., Kusdiana, D., Saka, S., Reactivity of triglycerides and fatty adds of rapeseed oil in supercritical alcohols, Bioresource Technology, 91, 283-287, 2004 Xie, W., U, H., Alumina-supported potassium iodide as heterogeneous catalyst for biodiesel production from soybean oil, J. Molec. Catal. A Chemical, 205,1-9,... 

One impediment to the cultivation of jatropha for the production of bio-fuel is that it would threaten the growing of food crops and the technology of commercial biodiesel production plant is not yet readily available on the market. However, the area of land that would be brought under jatropha cultivation during the initial years would not yield adequate quantities of seeds for a trans-esterification unit to operate economically. Farmers, on the other hand, would not go in for jatropha cultivation on a commercial basis without being assured of a reliable market. Clearly, it is necessary to find alternative uses for the oil in its natural form (i.e., without trans-esterification), for which a large quantity of the oil can be used for soap making. 

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