Decomposition of plastics

Fighting plastics waste with mealworms

Press release / 10.5.2017

At present, environmental pollution due to plastics is higher than ever before. Fraunhofer UMSICHT performs research on environmentally friendly processes for the decomposition of plastics and is using small biological helpers for this: mealworm larvae that utilize the plastics and secrete them again as organic substances.

decomposing polystyrene
© Fraunhofer UMSICHT

The larvae decompose the polystyrene and secrete it again as organic substances.

mealworm larvae
© Fraunhofer UMSICHT

Mealworm larvae in measuring cups with polystyrene.

Be it plastic bottles or plastic bags: a lot of industrially utilized plastics are not decomposable in the environment and pollute landscapes and bodies of water worldwide. Due to this development, the decomposition of plastics in an environmentally friendly manner currently constitutes a relevant research topic. In the fight against plastics waste, researchers are therefore – in addition to microorganisms, fungi, or isolated enzymes – increasingly also utilizing insect: as such, a Spanish researcher was recently able to show that the larvae of the greater wax moth can decompose polyethylene (PE) plastics in relatively short time – at least faster than bacteria in past tests. The combination of a mechanical disintegration by the insect's chewing tools and a subsequent microbial disintegration in the intestine is apparently particularly powerful.

The research of biology student Elma Mehovic, who – for her thesis – is investigating the decomposition of polystyrene by mealworms at the Fraunhofer Institute for Environmental, Safety, and Energy Technology UMSICHT in Oberhausen (Germany) also shows similar results. The plastics that are generated via the polymerization of styrene find varied use in the context of not only the thermal refurbishment of old buildings through thermal insulation, but also in the packaging industry. “Mealworm larvae have different bacteria on their biofilm in the intestine that decompose the polystyrene”, Elma Mehovic explains. This way, the mealworms can consume polystyrene without a lot of effort and in the process decompose the plastics in a natural way at the same time.

Plastics become fish food

In the context of her thesis, Elma Mehovic is now trying to find out under which framework conditions the mealworm larvae optimally utilize the polystyrene. In this, the young researcher is, in particular, investigating the impact of ambient temperature and humidity on the feeding behavior of the larvae. In a next step it is then to be checked whether the results from polystyrene can also be applied to other mass plastics. In a last step, Elma Mehovic will finally inspect and check the intestinal bacteria of the mealworm larvae to see to what extent it is possible to multiply them subsequent to an extraction and to utilize them in decomposition processes in the industry, in landfills, or in sewage treatment plants.

By the way, the impact of mealworm larvae is not limited to just the biological decomposition of plastics: “The larvae convert the polystyrene into biomass for their own organism. The mealworms can then, for example, subsequently be utilized further as high-quality fish food,” says Elma Mehovic. Even if there are still numerous unanswered questions regarding the overall environmental balance or regarding a conceivable technical implementation, insects therefore appear to outline a promising new path in dealing with plastics waste.