It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Wednesday, January 31, 2024
Lifetime of ‘biodegradable’ straws in the ocean is 8-20 months, study finds
Plastic drinking straws that get into marine ecosystems make beaches unsightly and pose problems for turtles and seabirds. So, people increasingly favor alternatives marketed as biodegradable or compostable. But do marine microorganisms break apart those straws? Researchers conducted experiments with seawater and report in ACS Sustainable Chemistry & Engineering that some commercial bioplastic or paper straws might disintegrate within eight to 20 months in coastal ocean systems and switching to foam makes a major difference.
To combat plastic pollution, some regions in the U.S. have restricted traditional polymers, such as polypropylene (PP), in drinking straws. These policies have led to a growing market for single-use items made from paper or bioplastics. However, replacement materials need to retain functionality so they don’t flop over after the first sip but will fall apart later if they end up in soil, fresh water or salt water. While the next generation of bioplastics, such as cellulose diacetate (CDA) and polyhydroxyalkanoates (PHA), may be able to meet both requirements, little is known about how long products made of these materials last in the ocean before fully degrading compared to other materials. So, Bryan James, Collin Ward and colleagues conducted experiments using real seawater to investigate the environmental lifetimes of different straws and to find a way to accelerate the breakdown of next-generation bioplastics.
In initial tests, the researchers cut inch-long pieces from commercially available straws made from either coated or uncoated paper, PP polymer, or CDA, PHA or polylactic acid (PLA) bioplastics. Then the pieces were suspended on wires in large tanks with room temperature seawater flowing through them. The team found that after 16 weeks, paper, CDA and PHA straws lost 25-50% of their initial weights. The researchers projected that these degradable straws should fully disintegrate in coastal oceans within 10 months for paper, 15 months for PHA and 20 months for CDA. Additionally, the biofilms on the disintegrating samples contained microbes known to metabolize diverse polymers. Conversely, PP and PLA straws didn’t have measurable weight changes, which suggests they could persist for years in ocean water.
Using the same experimental conditions, the researchers next examined how changing the CDA material’s structure, from solid to a foam, impacted the bioplastic’s environmental lifetime. They observed that the CDA foam broke down at least twice as fast as the solid version, and they estimated that a straw made from the prototype foam would disintegrate in seawater in eight months — the shortest lifetime of any material tested. Having demonstrated that some bioplastic straws are unlikely to remain intact over a long period, the researchers recommend that simple changes, such as switching to foam materials, could further reduce that time frame.
The authors acknowledge funding from Eastman. Some authors are employees of Eastman, a manufacturer of biodegradable plastics.
Some authors have patents in the field of biodegradable plastics.
###
The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.
To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.
Note: ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.
Strategies to Reduce the Environmental Lifetimes of Drinking Straws in the Coastal Ocean
ARTICLE PUBLICATION DATE
30-Jan-2024
Some plastic straws degrade quicker than others, new study shows
WHOI researchers determine lifetimes of commercial drinking straws in the coastal ocean and develop a prototype bioplastic straw that degrades even faster than paper
STRAWS ARE ONE OF THE MOST COMMONLY FOUND SOURCES OF MARINE LITTER. RESEARCHERS SAY WE LACK A FIRM UNDERSTANDING OF HOW LONG PLASTICS LAST IN THE OCEAN, BUT THAT SCIENCE SUPPORTS MOVING AWAY FROM USING THE MATERIAL.
Woods Hole, Mass. (January 30, 2024) — Straws are one of the most common plastic waste products found on coastlines. As more and more plastic products are being produced, consumed, and disposed of, scientists and manufacturers are developing alternative materials that work equally as well, and don’t contribute to persistent plastic pollution in the environment.
But not all plastics are created the same—different manufacturers have different formulations of base polymers—such as polylactic acid (PLA) and polypropylene (PP)—and chemical additives. That means different plastic formulations behave differently in the environment and break down in the ocean at different rates. There are new materials out in the market that move away from petroleum-derived products—like cellulose diacetate (CDA), a polymer derived from wood pulp that is widely used in consumer goods—and Woods Hole Oceanographic Institution (WHOI) scientists have been working to quantify the environmental lifetimes of a wide range of plastic goods to answer the unresolved question, how long do straws last in the ocean?
In a new paper published in ACS Sustainable Chemistry & Engineering, WHOI scientists Collin Ward, Bryan James, Chris Reddy, and Yanchen Sun put different types of plastics and paper drinking straws head-to-head to see which degrade the fastest in the coastal ocean. They partnered with scientists from bioplastic manufacturing company Eastman, who provided funding, contributed as coauthors, and supplied materials for the study.
“We lack a firm understanding of how long plastics last in the ocean, so we've been designing methods to measure how fast these materials degrade,” Ward said. “It turns out, in this case, there are some bioplastic straws that actually degrade fairly quickly, which is good news.”
Their approach involved suspending eight different types of straws in a tank of continuously flowing seawater from Martha’s Vineyard Sound, Massachusetts. This method also controlled the temperature, light exposure, and other environmental variables to mimic the natural marine environment. All straws were monitored for signs of degradation over 16 weeks, and the microbial communities growing on the straws were characterized.
“My interest has been to understand the fate, persistence, and toxicity of plastic and how we can use that information to design next-generation materials that are better for people and the planet,” James said. “We have the unique capability where we can bring the environment of the ocean on land in our tanks at the environmental systems laboratory. It gives us a very controlled environment with natural seawater.”
They tested straws made of CDA, polyhydroxyalkanoates (PHA), paper, PLA, and PP. In the weeks the straws were submerged in the tanks, the CDA, PHA, and paper straws degraded by up to 50%, projecting environmental lifetimes of 10-20 months in the coastal ocean. The PLA and PP straws showed no measurable signs of degradation.
The scientists then compared two straws made from CDA—one a solid and the other a foam, both provided by Eastman. The straw made from foamed CDA was a prototype to see if increasing the surface area would accelerate break down. They found that the degradation rate of the foam straw was 184% faster than its solid counterpart, resulting in a shorter projected environmental lifetime than the paper straws.
“The unique aspects of this foam straw are that it's able to have a shorter expected lifetime than the paper straws but retain the properties that you enjoy of a plastic or a bioplastic straw,” James said, making it a promising alternative to conventional plastic straws compared to paper straws, which degrade quickly in the ocean but sour user experience by getting soggy, according to the authors.
“This study can be immensely valuable for straw manufacturers by providing informed and transparent data when selecting a material for straws. Even more, it provides reassurance that CDA-based straws won’t add to the persistent plastic pollution, while also demonstrating straw manufacturers’ commitment to offering a sustainable product that reduces risk to marine life,” said Jeff Carbeck, Eastman’s Vice President of Corporate Innovation.
Science supports a push away from conventional plastic material. Plastic pollution causes harm to humans and ecosystems and the plastic industry is a large-scale contributor to climate change, accounting for roughly 4 to 5% of all greenhouse gas emissions across their lifecycle. With plastic waste becoming ubiquitous in the global ocean and marine food chain over the past 50 years, it’s important to identify new materials that are sustainably sourced, contribute to the shift from a linear to a circular economy, and break down if they incidentally leak into the environment.
“While some push to shift away from plastics, the reality is that plastics are here to stay. We're trying to accept the fact that these materials are going to be used by consumers, and then we can work with companies to minimize the impacts of them should they leak into the environment,” Ward said.
“We recognize the importance of testing, validating and understanding the marine degradation of our CDA based products, but lacked the necessary resources,” Carbeck said. “Knowing that WHOI possessed the expertise and facilities, we engaged in a collaborative effort to address this challenge. This partnership showcases the power of industry-academia collaboration in advancing shared goals and making a positive impact.”
The research team also found that the microbial communities of the straws that degraded were unique to each straw material. However, the microbial communities on both non-degrading straws were the same despite having vastly different chemical structures. This provided further evidence that the native microbes were degrading the biodegradable straws, whereas the non-biodegradable straws likely persist in the ocean.
“Our understanding of the impacts of plastic pollution on ocean health are really uncertain, and a lot of this boils down to not know the long-term fates of these materials,” Ward said. He and the rest of the research team plan to continue measuring the degradability of plastic materials, with the hope of guiding where the industry goes next.
“There are a lot of advantages of partnering with material manufacturers, including access to analytical facilities, and knowledge about and access to their materials that you don't get if you work in your own silo,” Ward said. “We’re trying to optimize their products for degradation in the environment and ultimately the good of the planet.”
Degradation of straws made from different types of materials were observed for 16 weeks at WHOI's Environmental Systems Lab. The tanks the straws were kept in had a continuous flow of ocean water from Martha's Vineyard Sound.
Not all plastics are created the same, and some last longer in the ocean than others. WHOI scientists have been working for years to quantify the environmental lifetimes of a wide range of plastic goods to see which have the shortest and longest lifespans in the ocean. To determine what plastics persist in the ocean, the team tests different products in large tanks that recreate the natural ocean environment. They focused on drinking straws first, as they are one of the most prevalent forms of plastic waste found in beach cleanups.
The authors found that straws made from cellulose diacetate (CDA), polyhydroxyalkanoates (PHA), and paper degraded by up to 50% in 16 weeks. They all had unique microbial communities that helped break down the material.
A prototype straw from Eastman, made of foamed CDA, degraded more quickly than the solid, meaning that altering the surface area of the straw can speed up the degradation process.
Science supports a shift away from persistent plastics—making it even more important to ensure new materials break down if they leak into the environment and don’t further pollute the ocean.
Authors:
Bryan D. James,*,1 Yanchen Sun,1 Mounir Izallalen,2 Sharmistha Mazumder,2 Steve T. Perri,2 Brian Edwards,2 Jos de Wit,2 Christopher M. Reddy,1 Collin P. Ward*,1
Affiliations:
1 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA 02543
2 Eastman, Kingsport, TN, USA 37662
About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu.
No comments:
Post a Comment