TAGS: Sustainability and Bioplastics
Researchers from ACS Sustainable Chemistry & Engineering report that some commercial bioplastic or paper straws might disintegrate within 8 to 20 months in coastal ocean systems and switching to foam makes a major difference.
PP and PLA Straws Show No Significant Degradation
To combat plastic pollution, some regions in the U.S. have restricted the use of 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. This is to ensure that 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.
The next generation of bioplastics, such as cellulose diacetate (CDA) and
polyhydroxyalkanoates (PHAs), may be able to meet both requirements. However, 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. They investigated the environmental lifespans 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. These straws were 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. The timeline is 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 showed no 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. They estimated that a straw made from the prototype foam would disintegrate in seawater in eight months. It is the shortest lifespan 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 this time frame.
Source: ACS
