Biodegradation of polyethylene, biodegradable-polyethylene bags and corn residues using Tenebrio molitor larvae

Abstract

The degradation capacity of different types of plastic from its ingestion by mealworms (the larvae of Tenebrio molitor), as well as its survival, was studied. Bags build from plastic nominally known as low-density polyethylene (LDPE); compostableplastic, made from corn waste (CPE); and polyethylene with d2w technology (d2wPE) plastic, were used. T. molitor larvae were subjected to a 7-day starvation period and then only fed with the different types of plastics for 56 days. Two groups of samples were prepared with the different plastics. On the one hand, the plastics were exposed to a UV photodegradation pretreatment from 260 to 285 nm and then used as the only source of food for the larvae. On the other hand, the same experiment was carried out without the UV pretreatment. The objective was to compare the possible effects of UV radiation on the plastics and their subsequent degradation by the larvae. The maximum degradation rates with UV pretreatment were 98%, 77% and 4% for CPE, LDPE, and d2wPE samples, respectively. Degradation rates without pretreatment were 79%, 54%, and 3%, and were obtained in the same order. In both scenarios, larval survival was significantly affected just for the d2wPE samples, reaching an average mortality rate of 98%. For the rest of the samples, the average mortality rate was only 12%.