Progress in Vegetable Oils Enzymatic Transesterification to Biodiesel - Case Study

Abstract

These days the interest of fuels preparing from sustainable natural resources is continuously increasing due to the rising prices of the fossil fuels and the political instability in the oil producing countries. The fuels manufacturing from local vegetal resources can sustain the every country’ prosperity, including rural, agricultural, economically disadvantaged regions. Nowadays only the bioethanol and the biodiesel are already produced at industrial level from sustainable raw materials. The biodiesel is manufactured by the chemically catalysed transesterification of the triglycerides from the vegetable oils, rapeseed oil in Europe and soya oil in USA. As the methanol is often used as alcohol reagent, the reaction is consequently named methanolysis. The most applied catalysts are alkalines (especially NaOH) or mineral acids. So the biodiesel represents the methyl esters of the fatty acids from the vegetable oils. The present diesel engines can normally use a mixture of diesel with 5% v/v biodiesel. Biodiesel contains virtually no sulfur or aromatics, and use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide and particulate matter. The production and use of biodiesel, compared to petroleum diesel, resulted in a 78.5% reduction in carbon dioxide emissions. Moreover, biodiesel has a positive energy balance. The chemical transesterification applied at industrial level has important advantages, but also limitations: in spite of the high conversion yields and the short reaction duration, the global transformation is energetically intensive, the glycerol recovery is difficult, the alkaline catalyst must be separated, the wastewaters are to be treated by a rather complex procedure, and both the free fatty acids and water can badly influence the reaction. These unfavourable situations can be diminished by performing the enzymatic transesterification on conditions that: (a) the immobilised lipase used as biocatalyst must be as cheap as possible; (b) one can obtain the economic efficiency of the whole biotransformation process similar to that characteristic to the chemical process, these objectives being presented function of the research methodology and results. The comparison between the chemical way and the enzymatic way is presented in the Table 1.