Mealworms and superworms fail to biodegrade PVC despite consumption

Abstract

Polyvinyl chloride (PVC) is a prevalent plastic material that presents significant environmental concerns due to its resistance to degradation and plasticizer content. While insects like mealworms and superworms have been suggested as potential biodegraders of PVC, several critical questions remain unexplored: Can mealworms and superworms utilize plasticized PVC as a carbon source, and how do varying dioctyl phthalate (DOP) concentrations affect consumption, survival, and polymer degradation mechanisms? This study addresses these questions by feeding PVC formulations containing 50–100 % PVC with varying DOP concentrations to individually housed mealworms and superworms. Growth, survival, and metamorphosis patterns were monitored, while gel permeation chromatography (GPC) was used to study polymer changes. Our results reveal a fundamental disconnect between physical consumption and biochemical utilization. While both species consumed PVC, with consumption rates increasing proportionally with DOP content (reaching 0.20 mg/day in superworms at 50 % DOP), this mechanical processing failed to translate into metabolic benefit. Instead, PVC exposure proved actively toxic, with survival rates falling below starvation controls, indicating that consumed PVC disrupts normal physiological processes rather than serving as a carbon source. Importantly, GPC analysis revealed no molecular weight changes in consumed PVC, confirming the absence of biochemical depolymerization despite enhanced consumption of plasticized formulations. These findings demonstrate that while plasticizers facilitate mechanical breakdown through polymer softening, the organisms cannot achieve the biochemical transformation necessary for PVC utilization. These findings provide the first systematic evidence that neither mealworms nor superworms can effectively utilize PVC or its plasticizers as carbon sources for metabolism, challenging previous assumptions about insects' capacity for PVC biodegradation. Future research should focus on alternative approaches for addressing PVC waste accumulation.