Composting with mealworms for plastics degradation

Recycling plastics is an energy intensive process, but entomoremediation (the use of insects to transform environmental contaminants), and insect-driven plastics degradation (plastivory) may offer a natural, low energy, cost effective approach to plastics waste reduction. Polystyrene and some polyethylene materials are amenable to degradation by darkling ground beetle (Tenebrionidae) adults and larvae, and a wide range of polyethylene can be degraded by waxworm moth larvae. Mandibular activity of the insects chewing on plastics serves to increase the surface area of the polymers that can be attacked by insect digestive enzymes and gut bacteria that can degrade the polymers into individual monomers and other low molecular weight compounds. The objective of this work was to determine the feasibility of an innovative solution to the plastics waste problem using a holistic, low technology, low cost, and low maintenance technique. Plastivory by ground beetle mealworm larvae was tested using small batch, mixed food and plastics waste compost bins. Different combinations of food waste and plastics were assessed and ultimately modeled through a continuum model of mealworm population dynamics. Our idealized, coarse-grained continuum population model suggests that a modestly-sized compost bin, can support a steady population of ~1100 mealworms that can degrade plastic at a rate of ~2 g of polystyrene foam per week. It is anticipated that this model will allow for assessing the extrapolation of empirically derived plastics degradation rates at various scales such as individuals and households, to industrial scales that would comply with municipal regulations.