NEW DELHI: New research has found that the lifetime of 'biodegradable' straws could be between eight and 20 months.
Plastic drinking straws are known to get into marine ecosystems making beaches unsightly and posing problems for ocean life.
Researchers said that measures like restricting traditional polymers such as polypropylene in drinking straws have led to a growing market for single-use items made from paper or bioplastics, with people increasingly favouring such alternatives.
However, the researchers at Woods Hole Oceanographic Institution, Massachusetts, US, said that little is known about how long products made of bioplastics, such as cellulose diacetate (CDA) and polyhydroxyalkanoates (PHA), last in the ocean before fully degrading compared to other materials. Their findings are published in the journal ACS Sustainable Chemistry & Engineering.
Therefore, the researchers conducted experiments using seawater to investigate the environmental lifetimes of different straws and to find a way to accelerate the breakdown of next-generation bioplastics.
In the initial experiments, the team cut inch-long pieces from commercially available straws and suspended them on wires in large tanks with room temperature seawater flowing through them. The straws were made from either coated or uncoated paper, PP polymer, or CDA, PHA or polylactic acid (PLA) bioplastics.
After 16 weeks (4 months), the researchers found that paper, CDA and PHA straws lost 25-50 per cent of their initial weights. They projected that these degradable straws should fully disintegrate in coastal oceans within 10 months for paper, 15 and 20 months for the bioplastics PHA and CDA, respectively.
Further, the team found that bioplastic straws of PLA did not lose weight measurably, which they said suggested that such straws could persist in ocean water for years.
The researchers next examined how changing the bioplastic CDA material's structure - from solid to a foam - impacted its 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 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 recommended that simple changes, such as switching to foam materials, could further reduce that time frame.