Study finds bio-based polylactic acid poses no microplastic risks

01 Jul 2024 --- A new meta-study report has found that unlike non-biodegradable polymers, which will persist and permanently accumulate as nano- or microplastics in the environment, polylactic acid (PLA) will hydrolyze into molecules of ever-smaller size, becoming soluble in water and eventually fully biodegraded.

The fundamental characteristics of PLA, a bio-based polymer made entirely from fermented plant sugars, and its hydrolysis process indicate that PLA does not produce persistent microplastics. 

“This study is particularly important because it is a meta-study evaluating primary research conducted by many different institutions,” Erwin Vink, board member of Holland Bioplastics, tells Packaging Insights. 

“It isn’t just one study with one set of boundary conditions or tests. Hydra Marine Sciences drew its conclusions from peer-reviewed research published in over 500 papers. It is reassuring that such a significant body of research underscores these conclusions and helps guide us as we continue to develop products that will have lower impacts on our ecosystems and our climate.”

The research was commissioned by Holland Bioplastics, an association advancing bioplastics knowledge worldwide, and completed by Hydra Marine Sciences, a research laboratory.

Building robust infrastructure 
The research confirmed that the environmental degradation of PLA is mainly driven by hydrolysis, an abiotic process that occurs in the presence of moisture or humidity. 

As long as these conditions prevail, the molecular weight and size of any PLA objects or fragments will continually decrease via hydrolysis, at a rate determined by temperature, until the polymer chains are so short that the material becomes soluble in water. 

These soluble substances, oligomers and lactic acid monomers, will subsequently be biodegraded by microorganisms into biomass, water and carbon dioxide.

The packaging industry has material options that will not leave a lasting negative impact on the environment, says Vink.The environmental degradation of PLA is mainly driven by hydrolysis, an abiotic process that occurs in the presence of moisture or humidity. 

“We know that leakage or littering is the worst-case scenario for any product. Therefore, we ensure that we are always working on growing the reach of robust waste collection infrastructure.”

“However, with non-biodegradable, fossil-based plastics, any littering or leakage leading to microplastics will persistently impact the environment. Because these microplastics won’t degrade, they will continually accumulate and never allow our ecosystems to recover,” he adds. 

“In contrast, any microplastics of PLA are transient and will safely degrade or biodegrade, reducing their impact and allowing ecosystems to recover.”

Circular packaging 
PLA is widely recognized as a non-toxic substance. Lactic acid, the monomer building block of PLA, is classified as Generally Recognized as Safe by the US Food and Drug Administration and EU. 

“PLA’s applicability and ability to substitute for fossil-based plastics has grown tremendously. Brands and material suppliers are collaborating more than ever to bring biobased and compostable materials like PLA to market for applications ranging from food packaging and serviceware to tea bags and 3D printing filaments,” explains Vink.

Producing PLA starts with plants as they sequester atmospheric carbon dioxide in sugar molecules through the process of photosynthesis. 

Plant sugars are then fermented using microorganisms to produce the monomer lactic acid, a safe, non-toxic substance that is also used to preserve foods and is produced by our bodies during physical exertion. 

This lactic acid is then polymerized into the PLA biopolymer used to make a wide range of products like cups, cutlery, bin liners or flexible food packaging. 

Because PLA is made from plants that absorb CO2 and water found in nature, when it is composted, hydrolyzed or biodegraded, the CO2 and water will return back to nature, making the process circular. 

By Natalie Schwertheim