Turning Waste into Calcium Source: Design, Fabrication, and Performance Evaluation of a Motorized Oyster Shell Crushing Machine at Different Speeds

Abstract

A motorized oyster shell crusher machine was designed and fabricated in the study to turn waste shells into lime for agricultural application. The study evaluated the performance of the machine at different speeds (348rpm, 290rpm, and 249rpm) in terms of crushing efficiency, crushing capacity and power consumption in crushing oyster shell for layer’s feed; establish the optimum speed (rpm) of two rollers in crushing; and perform a simple cost analysis of the machine. Results showed that the rollers speed significantly affected the crushing efficiency, crushing capacity and power consumption. The highest efficiency was attained at 290rpm (90.32%) and lowest at 348rpm (84.76%). On the other hand, the highest capacity was attained at 348rpm with 54.99kg/hr and lowest at 249rpm with 40.78kg/hr. The power consumption of the machine increases as the rollers speed decreases, from 20.10 W-hr to 31.16 W-hr with a speed of 348 to 249rpm, respectively. The optimum speed of the machine is at 290rpm with a crushing efficiency of 90.32% and has a crushing capacity of 53.11kg/hr. After a simple cost analysis of the machine, the computed initial cost of the machine is Php 46, 267.50. The computed payback period is 0.3 years with 115.37% return on investment, annual net income of Php160, 707.11, and break-even point of 2,459.23kg of dried oyster shells per year.