Why compostable plastic is not a silver bullet for eliminating plastic waste

Modern society has has a big problem when it comes to plastic -- and it's contributing heavily to pollution and climate change.

Globally, 400 million metric tons of plastic are produced each year -- and that number is on track to double by 2050, according to the United Nations Environment Programme.

In addition, the U.S. makes more plastic than any other country. In 2016 alone, the U.S. produced 42 million metric tons of plastic, equating to about 286 pounds per person, according to a paper published in Science Advances in 2020 -- nearly more than the amount produced in China and all of the European Union countries combined.

But how is the world supposed to deal with all this plastic? The easiest way to prevent further production and pollution of plastic is to simply avoid using it whenever possible, according to ABC News Chief Meteorologist and Chief Climate Correspondent Ginger Zee.

"The biggest solution is: Don't use it," Zee said.

That's not always possible, though.

Modern humans rely on plastic in their everyday lives. They eat off plastic and use plastic for packaging and transport, Ramani Narayan, a university distinguished professor of chemical engineering and materials science at Michigan State University, told ABC News.

What to know about compostable plastics?

Composting has been identified as a possible solution to managing plastic waste. But that solution isn't always viable, as it requires a high heat commercial composter -- infrastructure that is not easily available at every waste management facility.

"It's possible to have plastic this way, but it isn't easy," Zee said.

Composting shouldn't be thought of as the silver bullet solution to managing plastic waste as a whole but rather separating biodegradable plastic from landfills to reduce the amount of methane entering the atmosphere during the decomposition process, Narayan said.

"Compostable plastics is what I call the enabler technology," he said. "It is not the end-all, but it is an enabler to ensure that the composting of food, paper [and other materials] is done the right way."

Compostable plastic products contain a certification label from the U.S. Composting Council, typically the number "7" inside a recycling symbol along with the letters "PLA" underneath, which stand for Polylactic Acid -- a plastic derived from plant material rather than synthetic materials that are not biodegradable and over time will break down to microplastics.

If the plastic is marked No. 7 with an “O” or “Other" -- instead of "PLA" -- do not throw it in a regular household compost bin.

What to know about microplastics

The worldwide plastics problem is so pervasive that microplastics -- tiny pieces of plastics that could linger for thousands of years -- have infiltrated our daily lives, Zee said.

Discarded plastic -- usually made from hydrocarbon plastics like polyethylene and polypropylene -- will likely wash into a drain, where it will then be taken to the ocean, Zee said. There, as it sits in the sun and salt water, the plastic will take decades, hundreds or even thousands of years to break down, Zee said.

In addition, every time humans throw polyester clothing into the washing machine, it sends microplastics directly into drinking water systems and oceans before they are eventually ingested back into the human body, Zee said.

Humans are likely consuming about 5 grams of plastic per week -- the size of a credit card, according to a 2019 analysis by the World Wildlife Fund.

With compostable plastics, even if they leak into the environment, they won't persist or accumulate, unlike carbon-based plastics, Narayan said.

But humans have proved in decades past that they could live without single-use plastics, Zee said, adding that it's time to stop the use and production of plastics that will only be used one time, even if they are technically compostable.

"We don't need single-use plastics," Zee said. "We survived the 1970s or 1950s without it. So stop buying it and demand that the companies use something else."