 Corresponding author: Davidson Chukwudi Onwumelu Department of Chemical Engineering, Federal University of Technology, P.M.B 1526, Owerri, Nigeria. Copyright © 2022 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Determination of optimum conditions for maximum bioethanol yield from the Nigerian sweet potato (Ipomoea Batatas (L.) Lam) Tobechukwu Charles Okoro 1 , Davidson Chukwudi Onwumelu 1, * , Etinosa Peter Igbinidu-Uwuigbe 1 , Daniel Chukwuebuka Ofoegbu 2 , Michael Kelechi Onwuka 1 and Stanley Ebuka Nnebeana 1 1 Department of Chemical Engineering, Federal University of Technology, P.M.B 1526, Owerri, Nigeria. 2 Department of Petroleum Engineering, Federal University of Technology, P.M.B 1526, Owerri, Nigeria. World Journal of Advanced Engineering Technology and Sciences, 2022, 07(01), 075–085 Publication history: Received on 03 August 2022; revised on 06 October 2022; accepted on 09 October 2022 Article DOI: https://doi.org/10.30574/wjaets.2022.7.1.0099 Abstract Bioethanol is an important biofuel produced from biomass and is generally regarded as the future of fuels. This research was carried out for the main purpose of determining the optimum process conditions required for maximum bioethanol yield from the pulp of local sweet potato. The variety of potato used in this research is the Nigerian sweet potato (Ipomoea Batatas (L.) Lam) containing high amount of starch and the experiment was carried out with the use of Baker’s Yeast (Saccharomyces cerevisae) as the biocatalyst. In this study, the effect of acid concentration for hydrolysis, pH and fermentation period was examined. The sweet potato pulp was hydrolyzed using dilute sulphuric acid solutions of 0.5M, 1.5M and 2.5M and heated for 30 minutes at 100 ℃ yielding 0.9% (v/v) reducing sugar for fermentation. The hydrolysates were then subjected to fermentation at different pH values for different fermentation periods of 2, 3.5 and 5 days respectively. The pH values ranged from 4.5 to 6.5, an increment of 1.0 was used during the examination of pH with 1.0 M sodium hydroxide solution (NaOH) used for adjustment. The rate of bioethanol production was seen to increase as the pH and fermentation periods increased with the exception of the fermenting cultures of pH of 6.5. The maximum bioethanol yield of 13.40 ml, equivalent to 3.350% (v/v), was gotten from the hydrolysate obtained using the dilute acid of concentration 0.5M and left to ferment for 5 days at a pH of 5.5. Keywords: Sweet potato; Bioethanol; Biofuel; Fermentation; Hydrolysis; Saccharomyces cerevisae 1. Introduction Global energy demands for everyday use in industry, transportation, power generation, heating and other aspects of human life is on a steady rise [1]. Every country needs energy to keep up with the pace of rapid development going on in other parts of the world. This is also not unconnected to the rise in the world’s population [2]. Thankfully, fuels from fossil sources have been there for humans and contributed immensely to economic and infrastructural development of many nations especially since the turn of the twentieth century [3]. The United States Department of Energy, DOE, defines fossil fuels as fuels that are obtained from non-renewable sources which accumulated in the earth crust as a result of decomposition of plants and animals buried in the ground long ago [DOE Portal, https:// www. energy. gov/ science- innovation/ energy sources/fossil#:~:text=Fossil%20energy%20sources%2C%@)including%20oil,buried%20by%20layers%20of%20ro ck, Last accessed 04/07/2022]. Examples of fossil fuels are crude oil, natural gas and coal. As it stands today, crude oil account for more than 37% of the world’s energy needs [4]. The National Academy of Sciences also attributes 81% of the energy used in the United States of America to be from crude oil, coal and natural gas [National Geographic Portal: https://education.nationalgeographic.org/resource/fossil-fuels/, Last accessed 04/07/2022]. Between the three, coal is largest domestically produced energy source in the US and is used extensively to produce electricity in the country.