“In no small part because of the amount of plastic we pollute the whole planet, in almost every type of environment, microorganisms are starting to interact with plastic more and more,” says Anja Brandon, an expert of plastic by the Ocean Conservancy, a nonprofit group. “We’ve found some that are starting to develop and be able to handle this material or, in fact, we can start to break it down.”
The research is still in the early stages, and it remains unclear how much plastic microorganisms can break down. But given the magnitude of plastic pollution, some experts say, different strategies need to be explored.
There are more than 170 trillion pieces of plastic in the world’s oceans – an amount that doubles every six years, according to a major study released in March.
The most obvious way to curb plastic pollution, advocates say, is to stop making the material. But that’s challenging for a number of reasons, including that it’s hard to find plastic substitutes that are as cheap and effective.
The countries of the world have moved to create a global agreement on plastic pollution, but they are struggling to agree on how to solve the problem.
Bacteria and fungi capable of breaking down plastics help support traditional recycling efforts — if scientists can figure out a way for microorganisms to do it at scale.
“To even make a small dent in the management of our plastic waste, we must be able to scale and accelerate these systems, which comes with its own potential complications,” said Brandon. “Scaling up is never as simple as, ‘Oh, I’m just going to improve it.'”
There’s a strong incentive for microorganisms to evolve to eat the plastics, said Brandon, who studies biodegradation using mealworms.
Research suggests that some of these organisms seem to think that plastics can be a valuable food source. In 2015, researchers from Stanford University found that mealworms can survive on polystyrene, or what is widely known as plastic foam. Shortly thereafter, Japanese scientists documented bacteria that could eat plastic bottles. Recently, a team from the University of Texas developed an enzyme that can digest polyethylene terephthalate, a common plastic resin found in clothing, liquids and food containers. Meanwhile, Australian researchers have shown that the larvae of a black beetle can only survive in plastic foam.
How these organisms degrade solid material can lead to different outcomes. Most bacteria, for example, release certain enzymes that allow them to break down large molecules into smaller ones, Brandon said. In some cases, these enzymes can break down a large molecule into its building blocks. Those simple monomers can be extracted and used to make new plastic, effectively recycling the material, he said.
It can be done too for microorganisms to break down plastics into water, carbon dioxide and organic material known as biomass, say other experts.
But many of the known life forms that like to eat plastics are selective about what they eat. Most of the microorganisms identified by researchers eat only certain types of plastic, experts said. That means that if recycling centers want to use this method, they will still have to sort waste by material, a complicated process that limits the types of plastic they can currently recycle.
“There are so many different types of plastic resins, thousands of different chemical additives and different colorants,” said Judith Enck, a former senior official at the Environmental Protection Agency under President Barack Obama. now heads the Beyond Plastics advocacy organization. “One size does not fit all.”
These organisms also need time to break down plastics. Brandon’s research on mealworms that eat polystyrene shows that on average, 100 of the critters consume 20 to 30 milligrams of plastic per day. That means it takes 3,000 to 4,000 mealworms to process one Styrofoam coffee cup. At this rate, more than a quadrillion mealworms are needed to eat a day’s worth of plastic production in the world.
“Even the fastest microorganisms we’ve found pale in comparison to the amount of plastic we make and use in a day,” says Brandon.
Researchers at Harvard’s Wyss Institute for Biologically Inspired Engineering say they have developed a solution to these obstacles by not only identifying organisms that naturally degrade plastic, but also using genetic engineering to develop their ability to effectively destroy material.
The Harvard team started by looking for these plastic-eating microorganisms, said Sukanya Punthambaker, one of the project’s lead researchers. Then, they plan to isolate the enzymes and work on ways to speed up their functions.
“It’s a natural solution, so we’re just trying to work with what nature already knew millions of years ago and we’re trying to speed up the process,” Punthambaker said.
Most research on the ability of microorganisms to biodegrade plastics remains at the laboratory stage. But some experts say if the method is scaled up and made more efficient, it could be used in the real world.
The organisms can help supplement existing recycling systems, Brandon said, especially for waste that is extracted from the environment. These plastics often degrade and don’t fit through most recycling facilities, so they often end up in landfills.
However, Brandon and other experts emphasize that there is a way to go before these types of solutions can be easily deployed.
Bacteria and enzymes are “incredibly cool and very new, and I can see value for them in the future,” he said. “But in terms of being a solution or a get out of jail free card from our plastic pollution crisis, this is not the case.”
Pranshu Verma contributed to this report.