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Calcium oxide (CaO) itself, as cheap, highly active and easily available, is one of the most used solid catalysts for transesterification reaction of different oils and fats to biodiesel. A way to improve its catalytic activity is to increase its specific surface by preparing it in the nano-form. This paper gives an overview of the preparation of nano-sized CaO-based catalysts and their application in the biodiesel production. Various forms of nano-sized CaO-based catalysts have been employed in the biodiesel production like neat, doped and loaded CaO as well as waste material containing CaO. The modern technology based on the use of nano CaO-based catalysts aiming at high biodiesel yields will have further positive implications like simplicity, safety, economy and efficiency of biodiesel production. This overview proves the promising potentiality of nano CaO-based catalysts as solid catalysts in biodiesel production. [ABSTRACT FROM AUTHOR]

Abstract: Biodiesel, an alternate and ecologically acceptable substitute for the conventional fuel, is usually produced from a wide range of edible vegetable oils, which are normally used for human consumption and whose prices are expected to increase in the future. In this regard, reliable and low-cost raw materials have increasingly drawn interest for biodiesel production, such as by-products of the meat-processing industries or waste animal fats. This paper provides a review of the different methods employed for biodiesel production from waste animal fats employing transesterification reaction. The aim of this paper is to present the exploitation possibilities of waste animal fats as low-cost feedstocks for biodiesel production. Also, the various methods for treatment of waste animal fats such as chemical (homogeneous and heterogeneous) and enzyme catalysis as well as non-catalytic processes were considered with emphasis on the influence of the operating and reaction conditions on the process rate and the ester yield. In depth discussions were given to the process optimization, kinetics and possibilities for improvement of biodiesel production from waste animal. [Copyright &y& Elsevier]