World Journal of Engineering Research and Technology

Omonigho B. Otanocha* and Benson O. Oduh

ABSTRACT

Biodigesters are crucial for optimizing biogas production from organic waste, contributing to the generation of clean, low-cost renewable energy. This study focuses on the design, fabrication, and testing of an automated slurry mixer equipped with an electronically controlled stirring system, tailored for small-scale biogas production. Locally sourced materials were used to construct the mixer, with cow dung from an abattoir along Effurun-Sapele road serving as the feedstock. The mixer was engineered to achieve a homogeneous mixture by blending a calculated amount of cow dung through anaerobic digestion. The system is composed of four primary components: aconical sewage tank, stirrer, hopper, and electric motor. The tank, with a capacity of approximately 250 liters, was fabricated from Mild Steel (ASTM A36) and measures 830mm in height and 600mm in diameter. The galvanized steel (ASTM A653) stirrer extends to the full height of the tank, while the hopper and 2Hp (approximately 2800rpm) electric motor measure 220mm in height. Experimental tests revealed a direct proportional relationship between critical parameters, including operation time, feed content mass rate, mixing volume, and output slurry. The results demonstrated that mixing 50 kg of cow dung with 50 liters of water produced 74 liters of slurry, while increasing the input to 150 kg of organic matter with 150 liters of water yielded 221 liters of slurry. The total cost for designing and fabricating the automated mixer was estimated at NGN281,000. Additionally, the mixer was found to be environmentally sustainable. To enhance the design's quality and performance, future iterations could incorporate features such as a flushing system, wheels for mobility, and a mechanical pump for transferring the slurry to the biodigester.

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