Different types of straws after being continuously run over by ocean water for 16 weeks. Credit: Rachel Mann/© Woods Hole Oceanographic Institution
Have you ever been frustrated by a paper straw becoming soggy and unusable before you could finish your drink? I have, but I always talk myself out of it because of how much better for the environment a paper straw is compared with a plastic straw.
While that remains true, new research from scientists at Woods Hole Oceanographic Institution (WHOI) shows not only do paper straws take longer to degrade than initially thought, but there is also a stronger, faster-to-degrade alternative that manufacturers should consider.
Some manufacturers have already begun to phase out plastic straws made with polylactic acid (PLA) and polypropylene (PP) due to government policies and/or corporate sustainability initiatives. This has led to a growing market for single-use items made from paper or bioplastics, such as polyhydroxyalkanoates (PHA) and cellulose diacetate (CDA), which is a polymer derived from wood pulp. Still, with the market being so new, little is known about how long products made of these alternative materials last in the ocean before fully degrading.
To test that, WHOI researchers used their unique environmental systems laboratory to precisely mimic the environment of natural seawater, including temperature, flow rate, light exposure and more.
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. They then suspending the pieces in a tank of continuously flowing seawater from Martha’s Vineyard Sound, Massachusetts.
According to the study results, published in ACS Sustainable Chemistry & Engineering, over the course of 16 weeks, the paper, CDA and PHA straws lost 25 to 50% of their initial weights. The researchers calculated that out to be 10 months for paper, 15 months for PHA and 20 months for CDA straws to fully disintegrate in coastal oceans. Meanwhile, the PLA and PP straws showed no measurable signs of degradation.
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. Testing a foam CDA prototype straw, the team found that the degradation rate was 184% faster than its solid counterpart. A foam CDA straw, for example, would degrade in seawater in only 8 months—even quicker that 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,” said WHOI scientist and study author Bryan James.
That means no more soggy straws.
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.
“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,” said corresponding author and WHOI scientist Collin Ward.