Ozonation Systems as a Non-Chemical Alternative for Stored Grain Protection

Campabadal, Carlos A. Ph. D., Purdue University, December 2013. Ozonation Systems as a Non-Chemical Alternative for Stored Grain Protection. Major Professors: Dirk E. Maier and Richard L. Stroshine. 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 semicontinuous 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