Plastic-eating worms and bugs: Are they a real fix for our waste?

The larvae of some insects have developed a taste for waste. Is it enough?

The dietary cravings of a handful of creepy crawlers have caught the eyes of researchers around the globe. In recent years, scientists have discovered polymer-munching critters that look like plastic-eating worms. More specifically, they’ve found that certain insect larvae can break down materials like polyethylene and polystyrene—the fossil fuel-derived polymers used to make ubiquitous products like water bottles, food packaging, disposable bags, and car parts. 

After we use and discard these items, very little of it ends up being recycled into new products. Instead, millions of tons make their way to oceans and soil around the world. But sustainable solutions for all this waste may be around us.

Insects may offer a distinct advantage over other forms of nature-powered deterioration. While researchers have found that degrading plastic with bacteria and fungi works better when the material is pretreated with techniques like UV light and heat, insect larvae work well without any work beforehand. 

Which worms can eat plastic?

The larvae poised to munch on plastic aren’t actually worms—but they sure do look like ‘em, and confusingly have “worm” in their names.

Wax worms: Galleria mellonella

Wax worms refer to the larvae of the wax moth. These creatures naturally feed on beeswax inside beehives, which has a somewhat similar texture to plastic. Scientist and beekeeper Federica Bertocchini discovered their plastic-crushing powers by accident: She was cleaning out a beehive and placed some worm-infested bits in a plastic bag, which she soon observed was covered in holes.

So Bertocchini, a molecular biologist at the Spanish National Research Council, decided to take the discovery to the lab. She and her team noted that the larvae began to poke holes in films of polyethylene (PE) after only 40 minutes, as reported in a 2017 study.1 After leaving the larvae with a commercial shopping bag, the team observed that it broke it down faster than the better-known plastic-eating bacteria Ideonella sakaiensis

These larvae aren’t actually eating and deriving energy from plastic. Rather, enzymes in their saliva can oxidize plastic polymers—or penetrate the molecules with oxygen. This is a critical step in turning these materials from polymers (the long chains of atoms that make up plastics) into their monomer building blocks. In nature, this process can take years to go down. 

Right now, wax worms are the speediest known creature to break down PE polymers into smaller molecules, faster than additives and acids.2 Plus, the wax worm larvae work at room temperature, while many of the plastic-eating microbes studied by scientists require temps of at least 68 degrees Fahrenheit.

Right now, wax worms are the speediest known creature to break down polyethylene polymers into smaller molecules.

Certain enzymes in the larval saliva may work well to aid in the biodegradation of plastics, or the process of turning them into relatively harmless products like water, carbon dioxide, and compost. Of course, carbon dioxide isn’t great to release into the environment, the emissions are far lower than in a landfill

The goal now is to recreate these naturally occurring enzymes in the lab at a large scale and test them on tough products like mixed plastics, which are harder to repurpose than more-common plastics and appear in lots of items, including recycled bottles and certain food packaging pouches.

Lifespan of a wax worm

The other challenge with studying these particular larvae is that wax worms are only wax worms for so long. It takes between 28 days and 6 months before they turn into pupae, the stage that precedes full-blown wax moth adulthood.3 This short timespan can limit how long researchers can glean insights from them. But that may not matter in the future once biologists figure out how to harness the enzymes they create and roll them out in industrial facilities.

How much plastic can wax worm larvae degrade?

We don’t know yet how much plastic we can count on wax worm larvae to break down, Bertocchini says. It’s easier to decipher this with organisms that actually feed on plastic, since scientists can measure the amount of carbon dioxide released over time during the munching process.4 But in the future, she and her colleagues hope to eventually measure the tiny compounds left over by the larvae.

Mealworms: Tenebrio molitor

These larvae grow into a beetle species called Tenebrio molitor, or the mealworm beetle. Unlike wax worm larvae, these critters do actually eat plastic. They likely accomplish this thanks to microbes in their gut that can break down polymers, making them natural plastic-degrading factories.5 

In fact, these baby beetles can survive solely on styrofoam for a month, according to a study published in 2015.6 In this experiment, the mealworms turned around half of the plastic into carbon dioxide and the rest showed up as broken-down bits in the starch released at the end of digestion. Later in 2020, a master’s student at Washington State University built on these findings by adding chicken feed to the mealworm meals. This recipe change made the “worms” more efficient at polystyrene munching and consume more of the plastic.

Superworms: Zophobas morio

These larvae, which eventually grow into the darkling beetle, have also been shown to eat through polystyrene with the help of their own gut bacteria. In one experiment, a group of these so-called “superworms” lived on a polystyrene diet for three weeks, as reported in a 2022 study from a team at the University of Queensland in Australia.7 The Zophobas morio superworms break down the long-chained polymers into their monomer building blocks, then send these to their cells to use as a carbon and energy source. Ultimately, the research team found, the critters converted around half of the plastic into carbon dioxide—they pooped out the rest in small amounts.

“This is the beginning of the story. There’s something to explore there.”

Federica Bertocchini, molecular biologist, Spanish national research council

Superworms use both physical and chemical tactics to deteriorate plastics: They shred them up with their “oral appendages” before going to work on them in their guts. “It’s not the superworms alone doing the work, but the symbiosis of superworms and their gut bacteria that makes the plastic breakdown possible,” says study author Chris Rinke, a senior lecturer at the University of Queensland’s Australian Centre for Ecogenomics. “Working together, as a team, that’s the secret here.”

Next up, Rinke says he and his colleagues need to pinpoint exactly how these bacteria break down plastic. The researchers are currently working on recovering them from the superworm gut and growing them in his lab so they can study them more closely.

Can worms be the future of plastic recycling?

It is possible that worms could enable a new type of plastic recycling. Rinke envisions a recycling machine that mimics what superworms do naturally: shredding the plastic waste into small pieces before unleashing bacteria or enzymes to turn plastics back into their building blocks which can be turned into a material that is chemically identical to brand-new virgin plastic.

The enzymes from wax worms, meanwhile, could help prep plastic for further degradation by other naturally occurring methods like microbes. 

What would need to happen for this to become part of the recycling process? 

While insect-aided recycling sounds pretty cute, it would likely be more efficient and cost-effective to replicate their skills with machinery and lab-created enzymes. This probably won’t come anytime soon, and could be far costlier than common waste processing methods today like burning, landfilling, and grinding and compounding used plastics to make new products (aka, mechanical recycling). Ultimately, these enzymes would work best on huge volumes of plastic if they’re paired with techniques like mechanical recycling, Bertocchini says. 

To start, it may be easier to launch small-scale enzyme-aided operations in individual municipal plants or even with home kits to send to consumers. They could then send the leftover compounds for companies to make new products. Scientists have only touched the surface when it comes to all of the goodies that insects can extract from plastics. “This is the beginning of the story,” Bertocchini says. “There’s something to explore there.”

  1. Polyethylene bio-degradation by caterpillars of the wax moth Galleria mellonella, Current Biology, Apr. 2017
  2. Wax worm saliva and the enzymes therein are the key to polyethylene degradation by Galleria mellonella, Nature Communication, Oct. 2022 ↩︎
  3. The biology and control of the greater wax moth, Galleria mellonella, Insects, Jun. 2017
  4. Microbial degradation of plastic in aqueous solutions demonstrated by CO2 evolution and quantification, International Journal of Molecular Science, Feb. 2020 ↩︎
  5. Biodegradation of polyethylene and plastic mixtures in mealworms (larvae of Tenebrio molitor) and effects on the gut microbiome, Environmental Science & Technology, May 2018 ↩︎
  6. Biodegradation and mineralization of oolystyrene by plastic-eating mealworms: Part 1. Chemical and physical characterization and isotopic tests, Environmental Science & Technology, Sep. 2015 ↩︎
  7. Insights into plastic biodegradation: community composition and functional capabilities of the superworm (Zophobas morio) microbiome in styrofoam feeding trials, Microbial Genomics, Jun. 2020 ↩︎