Biodegradable Plastic: How Can Biodegradation Solve Plastic Pollution

Researchers from the University of California, Berkeley looked at biologically available options for allowing single-use plastic to biodegrade in readily attainable conditions.

Popular Science said plastic waste and microplastics are nearly everywhere globally. These items can be found from the air to the sea since too many various plastics penetrate the waterways and take hundreds of years to decompose.

Compostable plastics, such as corn-based plastic cups and straws, are often promoted as a suitable alternative. Columbia Climate School said that plastics can end up in a landfill without the facilities to adequately compost them.

How Biodegradation Could Help Solve Plastic Pollution

Ting Xu, professor of materials science and engineering and chemistry at UC Berkeley, and her team explain how they used a novel polymer coating on enzymes that can be built into bioplastics to make them easy to compost at home in a new report.

They published their study, "Near-Complete Depolymerization of Polyesters With Nano-Dispersed Enzymes," in the journal Nature.

"So I always believed that biology [has] taught us everything ... we just have to adapt [to] that," Xu told Popular Science.

Enzymes wrapped in random heteropolymers are woven into a fresh, easily biodegradable plastic as it is manufactured. The enzymes are encased in these polymers, such as RHPs, so they don't break apart and become worthless. Previous efforts to bury enzymes without the aid of RHPs, according to Xu, resulted in big clumps in the rubber, rendering it "looking like feta cheese."

The polymer wrapping breaks off as the plastic gets warm, allowing the enzymes to begin "eating" the plastics. Polycaprolactone and polylactic acid, two forms of polyester polymers used in biodegradable plastics, were used in this analysis to test this technique. The addition of enzymes encased in RHPs had little effect on the plastics' properties, but it did enable them to degrade rapidly as they reached the end of their useful product life cycle.

Within a week of sitting in a vat of room temperature water, 80% of the polylactic acid fibers had deteriorated. The polycaprolactone deteriorated in two days at the higher industrial composting temperature of 104 degrees Fahrenheit.

Certain Enzymes Might Stop Functioning

While this study used two different enzymes on two different forms of polyester polymers, Ramani Narayan, a Michigan State University chemical engineering and materials science professor who was not involved in the research, points out that certain enzymes stop functioning at high enough temperatures, so this process might not be practical.

According to Xu, these enzymes also seem to perform well in high-temperature plastic processing environments. However, the researchers intend to test other plastics manufactured at much higher temperatures to see how well the enzymes tolerate them.

These enzymes will be incorporated into new plastics in the future; enzymes thrown on top of existing plastics would have no impact. Enzymes would have a small surface area to operate on if they only stood on top of the plastic. Plastics are therefore impossible to break down due to their structure. "Biodegradable plastics are semi-crystalline," explains Xu, making it difficult for enzymes to penetrate and disassemble the structure. Enzymes gain entry to these more ordered chains by including the enzyme in the plastic structure itself.

It's crucial, according to Narayan, to understand that plastic breakdown is influenced by the circumstances of the world in which it ends up. It's important to think of both the plastic and the world where it'll end up, rather than treating "polymer modifications outside of the receiving biological system."

This suggests that biodegradable plastic research would provide not only an evaluation of the material's deterioration but also the characteristics of the ecosystem in which it is intended to degrade. Plastic intended to decompose in an industrial compost plant, for example, would not decompose the same way when discarded in freshwater, although it does not mean it is not biodegradable. After all, even the best recipes can fail if they aren't baked at the proper temperature.

Fortunately, the enzymes that make this plastic so degradable aren't prohibitively costly, according to Xu. One of her former students has already started a business to devote more effort to producing biodegradable plastics so that industry partners and even customers can participate in a more competitive formula for single-use plastics in the near future.

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