HETEROTROPHIC PRODUCTION OF LIPID BY MICROALGAE AND ITS CHARACTERIZATION AND PERFORMANCE EVALUATION IN CI ENGINE

Abstract

The problem of fuel depletion and the increase of carbon emissions increased the concern of researchers towards biodiesel. The algae species-rich in oil content were considered to be a potential feedstock for biodiesel which can easily replace diesel. But the biodiesel production from microalgae is still in its development phase and requires cost-effective biodiesel production and extraction techniques in order to commercialize it. Thus, in the present work, advanced biodiesel production techniques were investigated. The transesterification is a long and complicated process, which usually require different stages to complete the reaction. To simplify the above complex phenomena direct transesterification method of wet algae was also investigated. There is a lack of awareness on the techniques for algae oil methyl ester production, and its combustion effect and its performance analysis in CI engine, which are addressed in the present work. Firstly, the microalgae species Neochloris oleoabundans was selected, and its growth conditions were optimized using statistical software Design expert. It is very vital to optimize cultivation conditions in order to minimize the cost. It was observed that microalgae biomass growth depends upon the glucose and sodium nitrate concentration in the media as well as on the temperature of the surrounding. Different experiments were performed according to the number of experiments suggested by design of expert (DOE). DOE has provided two solutions according to the condition applied, in one solution predicted biomass yield was 1.97 g, while in other method biomass yield was 1.59 g. Based on the above solution, validation test was conducted and biomass yield 1.79 g and 1.42 g was obtained. Further, best harvesting technique was analyzed. It was obtained that among all the harvesting techniques chemical flocculation method is the best method of harvesting. v

The solvent extraction method was used for lipid extraction, and then the oil was trans esterified, and biodiesel yield was optimized by varying the molar ratio of oil to alcohol and catalyst concentration. To reduce the production cost of biodiesel, optimization is essential. The optimum yield was obtained at 6:1 molar ratio and 1% catalyst concentration, and maximum yield was obtained within 20 minutes for ultrasonic reactor and 80 minutes for mechanical stirrer method. It was concluded that using advance technique like ultrasonic assisted transesterification; the yield was increased to higher extent. Fuel properties highly depends upon the fatty acid composition, so its composition must be determined and make sure that it should meet the international standards. Therefore, microalgae biodiesel physiochemical properties were analyzed. It was found that major fatty acids in algal oil were palmitic acid, oleic acid, and linoleic acid. GC-MS data shows the fatty acid methyl ester composition lies in the range of C14-C18, it has 31% saturated fatty acid 67.9% unsaturated fatty acid. Different fuel properties were tested, for example, viscosity, pour point and calorific value. All of these are within the prescribed limit of different standards. The knowledge of microalgae oil methyl ester properties increases our knowledge about algae oil and its potential to fulfill the demand of world. A significant amount of literature is available on vegetable oil biodiesel but very few on microalgae. Thus, this work increases the knowledge about the microalgae biodiesel production and its performance in the engine. Finally, different blends of microalgae oil were prepared and tested. The examination of microalgae oil methyl ester in CI engine reveals that algae oil is appropriate for the engine. It is the best fuel for the engine because utilizing this fuel all the emissions were reduced to a great extent except NOx emission.