Efficient onion sorting and grading systems for small scale farmers

Onion cultivation plays a key role in Philippine agriculture, contributing significantly to the national economy and rural employment. However, small-scale onion farmers face several challenges in sorting and grading, including dependence on manual labor, limited access to mechanized equipment, and postharvest losses caused by manual handling.

This paper reviews and analyzes existing onion grading technologies, both mechanical and automated, to identify the most efficient and cost-effective solutions for small-scale farmers in the Philippines. Automated graders equipped with advanced sensors can achieve high accuracy levels, up to 99%, in size classification and defect detection. In contrast, mechanical graders such as rotating cylindrical systems and divergent roller designs can reach up to 95% grading efficiency, reduce labor requirements, and offer a practical and affordable option for farmers dealing with high postharvest losses.

For the conceptual design of a mechanical grader suitable for small-scale farmers, parameters such as roller speed (13–15 rpm) and inclination (8°–13°), as well as drum speed (10–15 rpm) and inclination (3°–4°), must be optimized to ensure high efficiency and minimal damage. Furthermore, finite element analysis and discrete event modeling are necessary to evaluate the effects of drum inclination, rotational speed, and feed rate on throughput capacity and grading accuracy.

Source

Bernabe, M. L., J. A. Lavarias, J. V. Fabula, and C. G. S. Almerol. 2026. The development of onion sorting and
grading machine. Agricultural Engineering International: CIGR Journal, 28(1):189-201