Effect of Organic Loading Rate (OLR) on Biogas Yield Using a Single and Three-Stages Continuous Anaerobic Digestion Reactors Ejiroghene Kelly Orhorhoro 1,a* , Patrick Okechukwu Ebunilo 1,b , Godwin Ejuvwedia Sadjere 1c 1 Department of Mechanical Engineering, Igbinedion University, Okada, Nigeria 2 Department of Mechanical Engineering, University of Benin, Benin City, Nigeria a ejiroghene.orhorhoro@iuokada.edu.ng, b patrick.ebunilo@uniben.edu, c godwin.sadjere@uniben.edu *Ejiroghene Kelly Orhorhoro (ejiroghene.orhorhoro@iuokada.edu.ng) Keywords: Anaerobic Digestion, Co-Digestion, Feedstock, Biogas Yield, Anaerobic Digestion Reactors, Organic Loading Rate Abstract. The rate at which feedstock is added to the anaerobic digester (AD) reactor has to be adjusted for the growth rate of methanogens bacteria. Increase in biogas yield is as a result of improved mathanogens forming bacteria. Under loading and over loading of feedstock in the AD reactor has effect on methanogens forming bacteria. If more feedstock is added than the bacteria are able to degrade, the process will become acidic. Feedstock has to been fed to the reactor at a uniform rate and volume. If feeding pattern has to change, this must be done gradually so that bacteria can adapt to the new conditions. For optimum biogas yield, required amount of feedstock must be added to the AD reactor. The aim of this research work is to determine the effect of organic loading rate (OLR) on biogas yield from food waste, water hyacinth, cow dung, waste water from abattoir, poultry dropping and pig dung. The experimental set up comprises of single stage and three-stage continuous AD reactors. The same quantity and composition of feedstock were used and this was subjected to a variation of OLR 0.5 kg/m 3 (1.5 kg/m 3 , 2 kg/m 3 , 2.5 kg/m 3 , and 3 kg/m 3 ). The experiment was conducted within a mesophilic temperature range of 36 0 C-37 0 C, percentage total solid (%TS) of 9.98% and percentage volatile solid (%VS) of 78%. pH meter was used to monitored the daily pH reading of the slurry. It was observed that the quantity of biogas yield from the feedstock increases with increasing organic load rate to the optimum value of 1.5 kg/m 3 and started decreasing above the optimum value for a single stage AD reactor but this was not the case for the three-stages continuous AD reactors that experienced continuous increase in biogas yield with a successive increase in OLR from 1-5 kg/m 3 -3.0 kg/m 3 . Introduction Due to unavailability and rapidly increase in costs of energy supply couple with waste disposal and increasing public concerns with eco-friendly environmental, conversion of biodegradable organic waste such as household food solid waste to energy is becoming a more economically viable practice [1,2]. The anaerobic digestion (AD) process has become an increasingly important industrial process. The production of biogas from AD process is of growing interest across the world [3,4,5] and this is due to decline in wood and fossil fuel resources and their resulting effect on the ozone layer [6,7,8]. Worldwide greenhouse gas (GHG) emissions from biomass have doubled since the 1960s and could further increase by 30% if nothing is done about it [9]. In Africa, poor air quality resulting from indoor cooking with wood fuel has huge negative health impacts on the entire populace, such as increased stroke, lung disease and chronic pulmonary problems [10]. Renewable energy remains the vital options that can reduce GHGs [11, 12]. The development of highly efficient renewable energy processes and their optimization is on the increase across the world especially from the year 2000 to 2015. There was an increase in the share of renewable International Journal of Engineering Research in Africa Submitted: 2017-12-21 ISSN: 1663-4144, Vol. 39, pp 147-155 Revised: 2018-09-03 doi:10.4028/www.scientific.net/JERA.39.147 Accepted: 2018-09-05 © 2018 Trans Tech Publications, Switzerland Online: 2018-11-05 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.scientific.net. (#110421149, University of Benin, Benin City, Nigeria-05/11/18,15:46:07)