Academic Journal of Chemistry ISSN(e): 2519-7045, ISSN(p): 2521-0211 Vol. 6, Issue. 1, pp: 20-27, 2021 URL: https://arpgweb.com/journal/journal/20 DOI: https://doi.org/10.32861/ajc.61.20.27 Academic Research Publishing Group 20 Original Research Open Access Evaluation of Shell-Derived Calcium Oxide Catalysts for the Production of Biodiesel Esters from Cooking Oils Ngee Sing Chong (Corresponding Author) Department of Chemistry, Middle Tennessee State University, Murfreesboro, Tennessee 37132, USA Email: Ngee.Chong@mtsu.edu Francis Uchenna Okejiri Department of Chemistry, University of Tennessee Knoxville, Tennessee 37916, USA Saidi Abdulramoni Catalent Biologics, 1300 S Patterson Drive, Bloomington, Indiana 47403, USA Shruthi Perna Department of Chemistry, Middle Tennessee State University, Murfreesboro, Tennessee 37132, USA Beng Guat Ooi Department of Chemistry, Middle Tennessee State University, Murfreesboro, Tennessee 37132, USA Email: Beng.Ooi@mtsu.edu Article History Received: February 2, 2021 Revised: February 27, 2021 Accepted: March 24, 2021 Published: March 29, 2021 Copyright © 2021 ARPG & Author This work is licensed under the Creative Commons Attribution International CC BY: Creative Commons Attribution License 4.0 Abstract Due to the high cost of feedstock and catalyst in biodiesel production, the viability of the biodiesel industry has been dependent on government subsidies or tax incentives. In order to reduce the cost of production, food wastes including eggshells and oyster shells have been used to prepare calcium oxide (CaO) catalysts for the transesterification reaction of biodiesel synthesis. The shells were calcined at 1000 °C for 4 hours to obtain CaO powders which were investigated as catalysts for the transesterification of waste cooking oil. The catalysts were characterized by Fourier Transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD) and X-ray fluorescence (XRF) spectroscopy. Reaction parameters such as methanol-to-oil molar ratio, CaO catalyst concentration, and reaction time were evaluated and optimized for the percentage conversion of cooking oil to biodiesel esters. The oyster-based CaO showed better catalytic activity when compared to the eggshell-based CaO under the same set of reaction conditions. Keywords: Biodiesel production; Calcium oxide; Calcination of oyster and egg shells; Catalyst characterization; Transesterification; biodiesel composition; Catalytic conversion of triglycerides into fatty acid methyl esters. 1. Introduction The increase in global energy demand, diminishing fossil fuel reserves, awareness of climate change issues, and environmental pollution resulting from the excessive use of fossil fuels, have in the recent past triggered serious interest among researchers in investigating alternative energy sources which can supplement or substitute fossil fuels. Vegetable oils are mainly esters of fatty acids and glycerol, which can be converted to fatty acid methyl esters (FAME), also known as biodiesel [1]. Much attention has been focused in the last few decades on utilizing heterogeneous catalysts for biodiesel production instead of the homogenously catalyzed transesterification of vegetable oil. The pure CaO or CaO mixed with some other metal oxides, with its low solubility in methanol, FAME and glycerol, low cost and availability, is one of the most promising among the proposed heterogeneous catalysts [2]. Biodiesel has been identified as a suitable alternative to petroleum diesel due to its advantages including biodegradability, renewability, negligible toxicity, higher flash point, higher cetane number, and higher combustion efficiency [3, 4]. Although biodiesel has many advantages over the traditional petroleum diesel, the commercial acceptance of biodiesel has been limited due partly to the high production cost and the dependence on government subsidies to make biodiesel cost-competitive with petroleum diesel [5, 6]. The high cost of production is mainly attributed to the high cost of feedstocks and catalyst consumption. Approximately 70 – 95% of the overall production cost of biodiesel is expended on raw material purchase [7]. Effective ways to reduce the cost of production involve the use animal fats or waste cooking oil (WCO) as feedstocks. The use of WCO as biodiesel feedstock is of interest to researchers because it utilizes waste products thereby eliminating the need for their disposal. Using alternative feedstock like WCO can effectively reduce the cost of raw material by 60 – 70 % [8]. Transesterification is the most advanced and the commonest technique used in biodiesel production. This process is often reliant on a catalyst to improve the surface contact between the alcohol and the triglyceride. Currently, biodiesel synthesized for commercial purpose via transesterification of triglycerides generally makes use of inexpensive homogeneous base catalyst like potassium hydroxide or sodium hydroxide. However, the application of homogeneous catalyst in biodiesel synthesis is usually accompanied with some purification and separation processes that require more equipment which ultimately add to the overall production cost. Also, large amounts of