Plastic-Munching Bacteria Could Save the Planet
Plastic-chomping bacteria could save landfill space, oil and energy consumed in manufacturing.
Every year, we churn out 56 million tons of plastics to protect our food, water and consumer products from contamination, but less than 14 percent of these cans, bottles and wrappers are recycled. Now, researchers in Japan have discovered a new kind of bacteria that can break down one common form of plastic into its chemical building blocks, a discovery that could save landfill space, oil and energy consumed in plastics manufacturing.
"We have shared the possibility of biological recycling of plastic," said Shosuke Yoshida, an author on the new paper coming out today in the journal Science. "We want to develop this discovery into the application. This is the very first step."
Polyethylene terephthalate (PET) is a widely used, clear plastic made from two simple compounds, however until now, nobody has found an organism that can break it down.
Right now, when you recycle a PET bottle, it usually has bits of food or other contaminants that are difficult to remove. The PET is taken to a recycling facility, shredded and then turned into a lower-grade material, such as carpets, for example.
But using a plastic-munching bacteria instead could save energy and the environment, according to Yoshida, a professor of applied biology at Kyoto Institute of Technology.
For five years, a team of Japanese researchers collected 250 PET debris–contaminated environmental samples including sediment, soil, wastewater, and activated sludge from a PET bottle recycling facility.
Using these samples, researchers screened for microorganisms that used PET film as their food source. The team initially found a whole ecosystem of bacteria living on the PET, but only one species that could actually break down the surface of the plastic using two unique enzymes. The end product are two environmentally benign chemicals that make up PET -- ethylene glycol and terephthalic acid.
The bug-driven biologically recycling is slow, it takes six weeks, but Yoshida believes the process can be sped up with a bit of industrial engineering. Bacteria are often harnessed to ferment alcoholic products, for example, while yeast is harnessed to bake bread.
Uwe T. Bornscheuer, professor at the Institute of Biochemistry in Griefswald University in Germany, says this breakdown has never been done before. Other teams have found worms that can munch Styrofoam, but it's not clear how fast they work and whether they have other food sources at the same time.
This new bacteria, Ideonella sakaiensis, does the entire job, Bornscheuer explained.
"This one can do it from the beginning to end," he said via Skype.
PET was invented in the late 1940s and became a widespread consumer item in the decades that followed. Somehow, this bacteria quickly evolved to use it as a food source in a relatively short time.
"This gives us hope that there are other microbes that can eat up other plastics as well," he said.
Out To Sea
Our oceans have a pollution problem. Over a decade ago, the North Pacific Gyre was discovered harboring untold tons of plastic trash, and quickly became known as the "Great Pacific Garbage Patch." It was a shocking wake-up call to the world which showed that even the most remote corners of the global were not immune to our throw-away culture. There are five main gyres in Earth's oceans. In January, members of the ocean advocacy group 5 Gyres set out to chart the North Atlantic Gyre. They're suspicion: that the world's water was more polluted than anyone knew, and that a "Great Atlantic Garbage Patch" was lurking somewhere between the U.S. Virgin Islands and Bermuda. But no one had ever looked for it before.
No sooner had the first trawling net been raised from the water than the crew's worst fears were confirmed: plastic. The material's pervasiveness struck Stiv Wilson who, as he says, "began the cruise an independent journalist, and ended it a board member of 5 Gyres." "If you look for it, you will find plastic everywhere, in or out of the gyres," Wilson said. "If you go two miles off the coast of San Francisco and trawl you will find it. It's denser in the gyres, but it's everywhere."
Sampling by Hand
Most of the brown gunk in this image is natural. It's sargassum algae, which gives the North Atlantic Gyre its other name: Sargasso Sea. But the white flecks researchers are reaching for are chunks of plastic floating near the surface. Contrary to what many people think, ocean "garbage patches" are really more like thin stews of pollution. All shapes and sizes of plastic trash hang in the water column, sometimes very spread out, sometimes arranged by wind patterns into dense lines that extend to the horizon.
The Big Stuff
During nearly 40 trawls of the North Atlantic Gyre taken throughout the trip, the net never came up empty. "We got plastic every single time," Wilson said. This pile of garbage was hauled out of the water by hand over the course of about 40 minutes. "This was just two people using crappy pool nets to scoop stuff up," Wilson said. "We got 10 percent of all the stuff in the water, maybe."
The Little Stuff
In amongst small-fry lanternfish are blue flecks of plastic, and even a few BB-sized pellets of "nurdles" -- bits of virgin plastic that fell off a freighter or were washed down a river and into the ocean before they were ever made into a product. "As I like to say, 'shit rolls downhill, and at the very bottom of the hill are the oceans,'" Wilson said. Major rivers like the Columbia and the Mississippi can carry huge amounts of plastics into the oceans, where they remain permanently. Once in the open ocean, plastic may be mistaken for food by fish like the lanternfish. Scientists don't know how often this happens, but they worry that chemicals trapped in plastic could leach into animal tissues and begin a slow march up the food web. Sea birds, large ocean predators -- even people -- may be having this stuff for lunch without even knowing it.
Along for the ride was Dutch artist Maarten vanden Eynde (left), who is collecting material to build a reef 40 meters long by 10 meters wide (131 x 33 feet) out of plastic removed from the ocean. He was not disappointed. The expedition collected 876 pounds of plastic, some of it from beaches in the Virgin Islands and Bermuda, but mostly from the open ocean. That included what Stiv Wilson called "his favorite piece of plastic" (right) -- a small fleck with the word "from" still visible, looking like a fractured message from whoever discarded it.
A Losing Battle?
Hauling plastic out of the oceans by hand is never going to work. Wilson said that for the time it takes to fill a freighter with junk, several times that much will be dumped into the sea through everyday human activity. "It's growing at an alarming rate," he said, though he admitted that no one's really sure how much plastic is dumped every year, or how much makes its way to the gyres.
Like the name says, the goal of 5 Gyres is to explore all five of Earth's main ocean gyres. So far the North Atlantic and Pacific gyres are the only ones to have been extensively surveyed. But Wilson said that his colleagues have found plastic in the Indian Ocean gyre during a recent preliminary cruise. "The problem is growing at an alarming rate," he said. The only way to stop it is a dramatic reduction of the plastic we use today, especially single-use items like coffe cup lids, grogery bags, and soda straws. "You're not seeing car bumpers out there," Wilson said. "It sounds trite, but really what's needed is a grassroots effort to reduce our addiction to single-use plastics."