Evaluating Small-Scale Grain Dyer for Developing Countries

Jaden Tatum
Graduate (PhD)
Ajay Shah
Food, Agricultural and Biological Engineering

Inadequate grain drying and storage infrastructure in developing countries leads to post-harvest losses of over 40%. Corn is the most important grain crop in sub-Saharan Africa and is subject to the highest losses. These are mainly due to microbial degradation and aflatoxin development because of inadequate moisture removal during drying. Smallholder farmers – who make up 80% of farmers in sub-Saharan Africa - are the most vulnerable to these losses, and small-scale technological solutions are lacking to improve access to drying infrastructure In this study, 55-gallon drums - widely available in sub-Saharan Africa - were adapted into a small-scale grain dryer and evaluated in drying dent corn. The objectives of this study were to 1 - Create and validate a thin-layer drying model for a grain dryer adapted from a 55-gallon drum; and 2 - Construct and experimentally evaluate the novel grain drying system to determine impacts on grain quality. A time-step differential system of equations to model thin-layer drying was developed in MATLAB with a time-step of 10 minutes and a thin layer, dX, of one inch. Replications of the dryer were constructed, and three batches of corn were dried with initial dry-basis moisture contents of 17.01, 17.08, and 18.70. The temperature and relative humidity of the ambient air, drying air, and exiting air were monitored continuously, and every 12 hours moisture content samples were taken using a probe to capture an average of the whole grain bed. The drying trials revealed a drying time under 30 hours and 15 kWh of energy use to dry grain to a safe storage moisture content of 12%. The moisture profile samples showed that the grain at different points in the bed dried evenly. The model accuracy was low, likely due to diurnal temperature variations and large amounts of fines in the grain. This system shows potential as an affordable and low-energy grain dryer designed for small-scale farmers. Further research will include developing a time-step model to account for diurnal temperature variations in sub-Saharan Africa, and evaluate the renewable energy options for powering the system.