Phosphine distribution and insect mortality in commercial metal shipping containers using wireless sensors and CFD modeling

Abstract

In the present work, the distribution of phosphine gas in metal shipping containers was modeled and compared with available data from phosphine sensors. Two different sizes of containers, 20 and 40 ft, were used in the experiments with different doses for each treatment. In each container, sensors were placed to monitor the distribution of phosphine, along with vials with phosphine –susceptible and –resistant insect populations. The insects used in the experiments were the Rhyzopertha dominica (F.) and Oryzaephilus surinamensis (L.), which are two of the most common species found in stored products. A Computational Fluid Dynamic (CFD) model was developed using the OpenFoam software and combined with phosphine sensors for precision fumigation practices. Gas transport and sorption effects of phosphine into empty and filled containers were considered in the CFD model. In light of our findings, in an empty container, the phosphine concentration was approximately similar for all locations, while in the filled container there were noticeable variations inside the fumigated area. Moreover, there was a time delay for phosphine to reach the sensors that were submerged inside the fumigated commodity, at the rear side of the containers. Regarding the simulations, the predictions of the computational model were in accordance with the phosphine concentration as recorded by the sensors. Concerning insect mortality data, in most of the cases, for both species, complete control was noted, regardless of the resistance level of the population tested. These results indicated that the CFD correlated well with the phosphine concentration and insect mortality and thus, a methodology for precision fumigation in containers can be further established. © 2021 Elsevier B.V.