Date of Award

Fall 2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Agricultural and Biological Engineering

First Advisor

Richard Stroshine

Committee Chair

Richard Stroshine

Committee Member 1

Dirk Maier

Committee Member 2

Charles P. Woloshuk

Committee Member 3

Linda Mason

Committee Member 4

Michael Langemeier

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.

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