In a paper released last week in the journal of Microbial Genomics, scientists from the University of Queensland in Brisbane, Australia, showed that the larvae of a darkling beetle, called zophobas morio, can survive solely on polystyrene, commonly called plastic foam.
The findings come amid a flurry of research on ways bacteria and other organisms can consume plastic materials, like plastic foam and drinking bottles.
Now, the researchers will study the enzymes that allow the superworm to digest plastic foam, as they look to find a way to transform the finding into a commercial product. Industrial adoption offers a tantalizing scenario for waste managers: A natural way to dispose and recycle the plastic foam trash that accounts for as much as 30 percent of landfill space worldwide.
“You cannot really escape plastic anymore — plastic waste is everywhere,” said Christian Rinke, the study’s co-author. “This is definitely a new, arguably, better, environmentally friendly way to break [it] down.”
The world is facing a plastic crisis. Each year, half of all plastic designed for single use — things like bottles, plastic foam cups and shopping bags — become trash, clogging up landfills and decomposing slowly while releasing noxious greenhouse gases, according to the U.N. Environment Program. More than 14 million tons end up in the water every year, data shows, killing animals and degrading underwater habitats.
Among plastics, foam is particularly troublesome. The material is dense and takes up a lot of space, making it expensive to store at waste management facilities, industry experts said. The cups, plates and other materials made from it are also often contaminated with food and drink, making it hard to recycle. Polystyrene fills landfills, where it can often take 500 years to break down and decompose, researchers have found.
As the garbage crisis escalates, scientists across the world are trying to find bacteria and other living organisms that naturally dispose of plastic waste.
In 2015, researchers from Stanford University revealed that mealworms could also survive on plastic foam. The next year, Japanese scientists found bacteria that could eat plastic bottles. In April, researchers from the University of Texas found an enzyme which could digest polyethylene terephthalate, a plastic resin found in clothes, liquid and food containers.
Wei-min Wu, a senior researcher at Stanford University who led its mealworm study, said there has been a growing chorus of researchers looking for natural solutions to recycle plastic because of the environmental risks.
He said many researchers in this field, including the ones from Australia, will face several challenges in the years ahead. It will take time to study the gut enzymes of things like mealworms and superworms, and when they do, it is not guaranteed they can digest plastics at large levels at a very quick and efficient rate.
Rinke said he was excited by his research results but noted it will take time to develop into an industrial solution, estimating somewhere between five to 10 years.
To conduct the study, his research team in Australia fed the superworms three separate diets. One group was given a “healthy” solution of bran. The second was given polystyrene. The third was put on a starvation diet.
Ninety percent of the larvae that ate bran became beetles, compared with roughly 66 percent from the group given polystyrene and 10 percent from those forced to starve. This indicated to researchers that superworms have enzymes in their gut that can effectively digest plastic foam.
Next, the scientists will study those enzymes to see how well they can digest polystyrene on a large scale — modifying them if necessary to become more effective. “We want to not have gigantic superworm farms,” he said. “Rather, we want to focus on the enzyme.”
If the research proves successful, Rinke said waste managers could collect and grind plastic foam materials and put them into a liquid solution made with the superworm enzyme. The solution would ideally dispose of the plastic foam or digest it in a way that allows new plastic products to be created, thereby reducing the need for new plastic materials, Rinke said.
“If you can go all the way to the end,” he said, “the idea is to use the system and come up with a biological solution to recycle plastic.”
Despite the findings from Rinke and others, there are reasons that none have successfully translated into industry applications over the past decade, researchers said. Andrew Ellington, a professor of molecular biosciences at the University of Texas at Austin, said it has been difficult to find a plastic-digesting organism or enzyme that can operate in industrial conditions, which often process trash in very hot environments or through the use of organic solvents.
“When you find something on a beach or you find something in a worm gut, that’s great, but all the enzymes in that thing work pretty much under the conditions where you found it,” he said. “And those may not be industrial conditions.”
He added that even if researchers decided not to extract enzymes and simply flood landfills with plastic foam-eating worms, problems would occur. Landfills combine all types of plastics together, and separating plastic foam from other trash to let worms eat the pile would be cumbersome and costly. He suggested an alternative solution.
“I believe that we will be able to offer up, in the not-so-distant future, worm-based composting kits so that individuals can do this themselves,” he said.
Jeremy O’Brien, the director of applied research at the Solid Waste Association of North America, said there are other business challenges in putting this type of solution into use.
As envisioned, the solution would require waste managers to collect plastic foam separately from other trash, he said, which makes it cost-prohibitive.
O’Brien also said it remains unclear what kind of organic waste the enzyme process would generate, and he worries it could harm the microorganisms landfills already use to process trash and reduce odors. He added that a more desirable and cost-effective solution would be to take plastic foam in landfills and condense them enough so that they can be turned into new plastics.
“That’s a lot simpler solution,” he said.
