Cellulose-based bioplastic disintegrates in ocean much faster than assumed, study finds

09 Dec 2021 --- Cellulose diacetate (CDA), a bio-based plastic used in food packaging, disintegrates and degrades in the ocean far quicker than previously assumed, according to a new study published in Environmental Science & Technology Letters.

“These findings challenge the paradigm set by governmental agencies and advocacy groups that CDA-based materials persist in the ocean for decades,” according to the paper, “Rapid Degradation of Cellulose Diacetate by Marine Microbes.”

“While no one plastic type will likely meet all of the diverse and growing needs of consumers, these initial findings on the fate of CDA-based materials in the ocean, combined with previous reports in terrestrial and wastewater systems, represent a positive step toward identifying high utility, bio-based plastics with low environmental persistence.”

CDA is derived mainly from wood pulp, making it a “bio-based” plastic. It is commonly used in consumer goods, including cigarette filters, textiles, coatings, films, food packaging, and other products such as eyeglass frames and tool handles.

Disintegration in months
Researchers incubated nearly 350 CDA and control samples in a custom-built seawater mesocosm in the study. They equipped the experimental system with a continuous seawater flow from Vineyard Sound, Massachusetts, US.

The seawater flowed over the samples, and the researchers examined their degradation over time using an assortment of techniques. Time-lapse photographs and mass loss measurements documented the disintegration of these materials, indicating the CDA materials disintegrated in seawater on timescales of months.WHOI postdoctoral investigator Michael Mazzotta cuts plastic samples to measure respiration signals of microbial communities respiring cellulose diacetate (Credit: Collin Ward / Woods Hole Oceanographic Institution).

The CDA’s rapid disintegration was marked with increasing esterase and cellulose enzymatic activity, suggesting the native microbial community compositions “are evolving with a metabolic capacity to degrade the CDA materials,” the paper states.

The researchers confirmed this finding using specialized equipment at the National Ocean Sciences Accelerator Mass Spectrometry facility, where they determined the chemical signatures of carbon dioxide respired by the native seawater microbes matched that of CDA.

“Our collective findings demonstrate CDA-based materials disintegrate and biodegrade in the ocean orders of magnitude faster (months) than previously reported (decades),” the study reads.

A marine environment first
Although scientists have previously found CDA appears to be easily broken down by microbes in soil and wastewater environments, no peer-reviewed, environmentally relevant study had assessed the persistence of CDA-based materials in marine environments before this research.

“This is the first paper to try to put a number on how long CDA-based materials last in the ocean,” explains co-author Collin Ward, assistant scientist in the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution (WHOI).

“We attacked this question from so many different angles using a wide range of tools, from pictures all the way up to multimillion-dollar mass spectrometers. Every single line of evidence converged to the same answer: These materials are breaking down on timescales of months. This [finding] challenges the perception they persist for decades.”

Data-driven science
The paper notes that the timeline for CDA biodegradation is subject to variation depending on several factors not included in this study, such as different particle shapes and sizes, times of the year, and location.

“It is very good news that some materials seem not to persist as long as we thought,” adds Ward. The collective goal of the research community should be to survey different types of plastics and try to identify those plastics “that are simultaneously useful, do not persist in the environment, and consist of sustainably sourced materials.”Cellulose diacetate is derived mainly from wood pulp, making it a “bio-based” plastic. It is used in food packaging and consumer goods.

Ward and lead author Michael Mazzotta hope the findings encourage people, including legislators, to rely more on data-driven science when discussing the fate of plastics.

“Environmental persistence of organic contaminants is a key component of risk assessment and regulatory frameworks, with some arguing high persistence alone is sufficient for establishing regulations.”

“However, applying this persistence-based regulatory framework to plastics remains a challenge due to incomplete understanding of the fates of these materials, particularly in the ocean,” the paper states.

No license to pollute
Mazzotta, a postdoctoral investigator in WHOI’s Marine Chemistry and Geochemistry Department, adds that “while this research is a positive step in the right direction, this does not condone pollution. Just because cellulose diacetate degrades faster than what we expected, this is not a license to pollute.”

“It would be foolish to work in our own little silo and not interact with the manufacturers of the exact materials we are trying to track in the environment,” concludes Mazzotta. “They are the experts in producing these materials. We are the experts in understanding what happens to them in the environment. It’s a synergistic relationship.”

Eastman Chemical Company and WHOI funded the study.

European Bioplastics recently revealed global bioplastics production will more than triple over the next five years (2021-2026), according to market data compiled in cooperation with the nova-Institute. Notably, Asia is predicted to surpass 70% market share by 2026.

Edited by Joshua Poole