Abstract

The use of ozone as a non-chemical alternative in stored grain protection was studied by conducting scale-up demonstrations using a fixed bed ozonation system and developing a semi-continuous counterflow and a continuous flow ozonation treatment system. The objectives of this research were to determine the efficacy of ozonation to control insect pests without affecting end-use quality; to prove the concept of the semi-continuous counterflow ozonation system to ozonate grain at a faster rate and quantify its effect on mold growth reduction; to evaluate the efficacy of a modified screw conveyor for pest control by treating grain in a continuous-flow ozonation treatment system; and to determine technically feasible scale-up configurations of each ozonation treatment system including which is most cost-effective. Ozonation treatment in fixed bed systems resulted in 100% insect mortality for adults of maize weevil (MW) and red flour beetle (RFB) with no end-use quality effect on grain. The semi-continuous counterflow system was proven as an effective system to treat grain based on control of three key variables: airflow, ozone mass flow, and exposure time. Mold in stored grain was reduced by more than 50% for ozone cumulative CTP between 340 to 565 ppm-h. The continuous flow system proved to be effective resulting in 100% insect mortality for adult MW and RFB with an average grain retention time of 1.8 minutes and ozone concentration of 47,800 ppm. The scale-up and economic analysis showed that continuous flow ozonation was predicted to have the lowest treatment cost of 1.21 $/MT compared to fixed bed ozonation (1.33 $/MT) and semi-continuous counterflow ozonation (2.72 $/MT) when treating 1,272 MT of grain. Also, continuous flow ozonation was 55% more expensive than contract fumigation, but 29 and 43% less expensive than ambient aeration and grain chilling, respectively. Two comparative case studies for eradication of adult insects in stored grain on-farm (i.e., food grade maize and HRW) showed that traditional pest control (i.e., phosphine fumigation and ambient aeration plus phosphine fumigation) had a lower treatment cost per metric tonne of 35 and 25%, respectively, compared to the alternative techniques (i.e., continuous flow ozonation in Indiana and grain chilling plus continuous flow ozonation in Kansas). A comparison of blending odor-damaged sorghum from a hopper car at a grain export facility versus continuous flow ozonation showed that blending was more economically feasible as long as the discount price is below 1.21 $/MT. Despite the higher treatment cost of ozonation, fixed bed, semi-continuous counterflow and continuous flow treatment systems can be scaled up in a technically feasible and economically viable manner within the limits of available generator capacities. Thus, ozonation can be used commercially by farmers, grain processors and seed producers as a non-chemical alternative for stored grain protection.

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Agricultural and Biological Engineering

Committee Chair

Richard Stroshine

Date of Award

Fall 2013

First Advisor

Richard Stroshine

Committee Member 1

Dirk Maier

Committee Member 2

Charles P. Woloshuk

Committee Member 3

Linda Mason

Committee Member 4

Michael Langemeier

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