Humans produce much plastic waste that contains useful nutrients and energy but must be landfilled as waste. Some waste problems could be solved by finding uses for the waste plastic or inexpensive methods to reduce the plastic into biowaste that could reenter the ecosystem.
Wax moths are probably not the answer because they are pests of honey bees. Wax moths enter bee nests and feed on the beeswax comb. A large population of plastic-munching wax moths would also be a source of honey bee pests. Other moth species may be capable of consuming plastic and those non-pest species might be better options. One potential stumbling block: What would confine a plastic-eating insect to waste plastic only and prevent consumption of plastic that is in use?