Sorption characteristics of various fumigants depending on the loading ratio of wood pellets

Abstract

Wood pellets, an eco-friendly alternative to fossil fuels, have experienced significant market growth. However, the detection of stored-grain pests in processed wood pellets during quarantine in Korea has led to using methyl bromide (MB) and phosphine (PH₃). Due to MB's ozone-depleting effects and PH3-resistant pests, alternative fumigants and treatment methods must be explored. This study investigates the sorption characteristics of alternative fumigants—sulfuryl fluoride (SF), ethyl formate (EF), ethanedinitrile (EDN), and methyl iodide (MI)— along with PH₃ on wood pellets at varying loading ratios (10, 30, and 50 % w/v). The results indicate a declining trend in fumigant concentrations due to sorption onto the wood pellets. This trend was quantified using equations derived from regression analysis to model concentration decline over time (P < 0.05 in all cases except for SF). All fumigants, except SF, showed increased sorption with higher loading ratios of wood pellets. The order of sorption characteristics from the lowest to highest was as follows: SF, PH₃, EDN, MI, and EF, with residual rates at the highest loading ratio (50 %) recorded as 111.1, 24.6, 15.8, 8.9, and 1.5 %, respectively. The concentration-time (Ct) products were calculated for each fumigant at various loading ratios to evaluate the maximum loading ratio that could achieve the target Ct value required for effective pest control. The residual rates of fumigants, following fumigation, along with the equations detailing concentration decline, will provide essential data for determining the optimal dosage and loading ratios for disinfecting insects in wood pellets through confirmation tests.