Optimization and Kinetic Studies on Production of Biodiesel form Industrial Waste

Abstract

Fuels derived from petroleum have been used as the major source of world’s energy requirements in the last few decades. However, it is estimated that fossil oil will deplete in the near future. There is the need to search for new sources for replacing the conventional hydrocarbon based fuels and for preserving the global environment. Future projections indicate that economics and energy needs will increase the focus on the production of biodiesel derived from renewable sources. Currently, researchers are interested in finding a low cost as well as an efficient source for the continuous expansion of biodiesel. The search for a suitable low cost feedstock has resulted in the use of industrial bio wastes, which are generated from leather, dairy, fish and food processing industries. In the present research work, tannery scum, dairy sludge, fish waste and microalgae are taken as low cost feedstock for biodiesel production. The feedstocks obtained from processing industries contain more amount of water, which was removed by drying operation. Bio-oil extracted from the biomass and subjected to suitable pretreatment process to make them fit for biodiesel production. The fatty acid profile of bio-oil used to predict the physicochemical properties of the biodiesel. Biodiesels derived from four industrial bio wastes are having proper blending of saturated and unsaturated fatty acids. Due to which the cetane value of fuel will increase. The predominant level of saturated fatty acids in the tannery scum and fish waste oil suggests that the biodiesel produced from these bio-oils will affect the performance in cold climate. According to the quality of bio-oil, the pretreatment methods are selected for refining. Degumming and dewaxing is required for dairy sludge oil, due to its higher contamination like phospholipids, mineral oils, waxy esters, etc. Here, both contaminants and free fatty acids are removed. Whereas, tannery scum oil refined only by crystallization process to remove impurities of wax, heavy mineral oil, greases of high molecular weight compounds, etc. Algae and fish oil contains high free fatty acid and free from other impurities. Based on the free fatty acid content, the catalyst required for the process is selected. So, alkali catalyst is used for transesterification of dairy sludge bio-oil and acid catalyst is used for esterification and transesterification of tannery, algae and fish oils. The process parameters such as catalyst concentration, reaction temperature, reaction time, oil to methanol molar ratio and stirring rate is optimized to increase the yield of biodiesel. Each parameter is optimized to get maximum yield. At optimized condition, tannery, dairy, fish and microalgae bio-oils yielded above 98% of biodiesel. Kinetic, thermodynamic and activation data are needed to scale up the process are determined. The kinetic study reveals that, all the biodiesel follows first order reaction and the rate constants are increased linearly with increase in temperature which is independent of bio-oil. The activation energy, change in enthalpy and Arrhenius constant are determined for the four biodiesel. Both change in enthalpy (ΔH) and change in entropy (ΔS) yielded positive values, whereas ΔG was negative at 60°C, indicating that this process is endothermic, irreversible and spontaneous. Physicochemical properties of all biodiesels are determined as per ASTM methods and their results are compared with ASTM D6751 specifications. Based on the bio-oil characteristics, all the biodiesel properties vary each other. Even though, all the properties are within the standard limit. So, the product biodiesel obtained from industrial bio wastes can be used as a fuel in exist engine without any modification. Also, it proves that industrial bio wastes are reduced by converting into useful fuel.