Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Agricultural and Biosystems Engineering

First Advisor

Carl J Bern


Significant grain and seed losses occur during maize storage in East Africa. This is due to high ambient relative humidity, and the fact that storage ecosystems and the stored maize equilibrate with ambient moisture and temperature. The result is rapid pest multiplication and mold formation in the stored maize, leading to a high spoilage rate. This is particularly important considering that a large number of farmers store their maize in open-air storage that utilizes little or no chemical preservatives. Of these pests, the most economically important are the maize weevils, and to reduce losses, a non-chemical system that naturally eliminates them was developed.

Three studies aimed at "Testing time to complete adult weevil mortality in hermetic storage", testing the "effect of hermetic storage on maize seed germination", and "using recycled edible oil containers for hermetic maize storage" were conducted to solve these problems.

The first study found significant (p<0.0001) treatment effects. A laboratory-scale study found mean adult weevil mortality and standard error of 94.2±10.77% for hermetic treatments versus 3.1 ±4.69% for non-hermetic treatments, while a field-scale study found 96.8±3.43% mean mortality and standard error for hermetic treatments versus 3.4±3.71%, for non-hermetic treatments. In the second study, hermetically stored (sealed) maize seeds had 98.7 to 99.5% germination rates versus 35.0 to 72.9% for non-hermetic (open-air) storage, over the 12-month seed storage period. The conclusion is that hermetic storage preserves seed viability, even when seeds are stored under ambient (atmospheric) conditions, and with weevils. In the third study, market surveys found edible oil containers available for sale and reuse as hermetic storage containers, in East African markets, and a comparison of three cleaning methods showed that oil-drain plus water at 90 to100°C plus soap is the most effective, as well as the only one that met our cleaning objectives. Leftover oils following cleaning with oil-drain plus water at 45°C, oil-drain plus water at 90 to100°C, and oil-drain plus water at 90 to100°C plus soap were 0.249g, 0.142g, and 0.004g, respectively. The 0.004g from the oil-drain plus water at 90 to100°C plus soap treatment compares favorably with 0.005 to 0.006 from the control (unused experimental units (20-L HDPE containers), which had no oil contaminants. Research results, therefore, indicate that using 3g of 99.44% pure Ivory soap and hot water per gram of soybean oil contaminant is enough to clean and sanitize soybean oil contaminated 20-L HDPE containers, for safe hermetic maize storage.


Copyright Owner

Ali Yakubu



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269 pages