Scientists have dispelled the myth about bioplastic packaging

Plant-based plastics are often promoted as an environmentally friendly alternative to conventional plastics. However, many so-called “bioplastic” products do not biodegrade after more than a year in water or land, a new study shows.

Given the growing popularity of bioplastics, researchers from the American non-profit organization 5Gyres decided to find out how these products would behave if they were thrown into the ocean or left on the side of the road.

They left bioplastic products in several places on land and sea, next to regular plastic, as well as objects made of wood or paper. Almost none of these products wore out completely after 64 weeks, and some were virtually unchanged. Those that wore out tended to break into smaller pieces rather than decompose.

The bioplastics industry is valued at approximately $11.6 billion worldwide and is expected to grow at around 19% per year.

Products left on land decomposed more slowly than those left in water, but even after 64 weeks, 78% of bioplastic products remained in their original form.

“Bioplastics” is a category that includes both bio-based plastics made from renewable sources (vegetable fats, corn starch, straw, sawdust or recycled food waste) and so-called “biopolymers” (plastics produced by such microorganisms like bacteria or yeast).

The study mainly looked at PHA (polyhydroxyalkanoate) and PLA (polylactic acid) products, which are biopolymers.

The researchers placed 22 different products at 6 locations in California, Maine and Florida—one on land and one in the sea in each state. Seventeen products were bioplastics. For comparison, they included three polyethylene, one bamboo and one paper products.

The researchers removed the items at regular intervals to track their degree of decomposition. As expected, none of the polyethylene products experienced degradation after 64 weeks. Bamboo forks didn’t do this either.

Paper straws exposed to water disintegrated after 32 weeks. And only the tubes remaining on land in the American state of Maine completely disappeared after 64 weeks.

Bioplastics followed a similar pattern: Of those that did degrade, most ended up in water. Overall, about 78 of the 102 bioplastic items remained intact.

One of the main findings of the study is that consumers need to know the difference between “compostable” products and “biodegradable” ones. All compostable products are biodegradable, but that doesn’t mean they decompose while floating in the ocean or sitting in the dirt.

Part of the problem is that while the products may begin life as natural ingredients (like corn), chemical processing produces a chemical structure almost identical to conventional plastics made from petroleum products.

Most products require high-temperature composting facilities, and most will never make it there. They are more likely to end up in a regular incinerator along with other waste.

Previous research has shown that bioplastics are rarely disposed of properly, making them potentially more of a global warming risk than regular plastics. Environmental groups have called them a “false solution” to the plastic waste problem.