US researchers claim to discover world’s fastest degrading bioplastic

US researchers at Woods Hole Oceanographic Institution (WHOI), Massachusetts, say they have discovered that a new version of cellulose diacetate (CDA) — a plastic-like polymer derived from wood pulp — is the fastest-degrading bioplastic in seawater. The study authors have partnered with scientists from packaging technology company Eastman, which is providing funding and resources for the research.

The study is published in ACS Sustainable Chemistry and Engineering.

Collin Ward, associate scientist for chemistry and marine chemistry at WHOI, tells Packaging Insights that by perforating products, the team managed to massively increase the material’s breakdown speed.

“What surprised us most is how sensitive CDA degradation rates are to foaming or adding small pores of air to plastic articles. It’s remarkable that a seemingly simple modification like foaming can increase CDA degradation rates by up to 15-fold compared to a solid counterpart,” he says.

“Adopting CDA for packaging applications improves the beginning and end-of-life compared to conventional plastics commonly used now for packaging. CDA is mostly made from plants instead of fossil fuels. Moreover, CDA can be composted in home and industrial systems.”

Water degradation rates

A side-by-side microscopic image of polystyrene before and after 36 weeks in seawater. The research team found this material did not show any signs of degradation during this time frame. (Image credit: Bryan James, Woods Hole Oceanographic Institution)The study monitored both foamed and solid CDA in a tank of continuously flowing seawater at a specially designed lab at WHOI. In the lab, researchers were able to control the temperature, light exposure and other environmental variables to mimic the natural marine environment.

“We translated the foundational knowledge into the design of a new material that simultaneously meets consumer needs and degrades in the ocean faster than any other plastic material we know of, even faster than paper,” Ward explains.

“It’s a great success story in a field that often focuses on the negative aspects of plastic pollution rather than working toward solutions to the problem.”

“Using continuous flowing seawater tanks enables us to bring the dynamics of the microbially active ocean into the lab. The ocean is continually changing, and it was important that we replicated this environment by replenishing microbes and nutrients, making for a much more environmentally realistic experiment,” co-author Bryan James adds.

After 36 weeks, the team found that the CDA foams lost 65–70% of their original mass.

Packaging applications

In a previous study using the seawater tank, the researchers tested straws made of standard plastic, paper, solid CDA and foamed CDA, and found that the solid CDA and paper straws reduced in mass the quickest.

They then compared two straws made from CDA, one made from solid CDA and one from a foam CDA and found that the degradation rate of the foam straw was 190% faster than its solid counterpart.

“As our findings have shown, CDA foam does not persist in the environment if leaked, so it does not contribute to persistent plastic pollution,” Ward tells us. 

He says that the use of CDA for packaging applications is already happening at scale.

“There are currently CDA foam trays being used to package protein, like chicken or fish, at grocery stores. These CDA foam trays are replacing the fossil fuel-based and persistent polystyrene foam trays that most people use today. Application to other foam packaging types is in the works and will be rolled out over time.”

“There are lots of different research directions we are headed. One path forward is the ability to predict CDA foam degradation rates based on the characteristics of the pores, such as pore size, shape and wall thickness. If we can accomplish this, we can more readily adopt this technology for different packaging applications,” he concludes.