Plastic pollution represents a huge environmental problem, and drinking straws are a major component of such pollution. It is estimated that 8.3 billion plastic straws contaminate the world’s beaches. Fortunately, there is a burgeoning market for biodegradable polymers that may ultimately reduce marine plastic pollution. Relatedly, light blue Phade drinking straws made of biodegradable polyhydroxyalkanoate (PHA) are now commonly found in restaurants and bars. PHA is one of only two biopolymers that degrade well in the marine environment.
Researchers at NSU and the Reef Discovery Center (RDC) have completed a groundbreaking assessment of PHA drinking straws submerged offshore at the Navy station, near the Oceanographic Center. This project has now been published in the Journal of Environmental Chemical Engineering as the paper “Degradation of Polyhydroxyalkanoate Drinking Straws at an Ocean Shoreline.” This is the first biophysical characterization of degradation of any 3D object made of PHA.
The fifteen-week experiment had two intertwined components: microbial analyses and mass loss assessments. PHA degrades because some types of bacteria eat away at the plastic’s exposed surfaces. These favorable bacterial strains do not exist in all marine environments, so identifying them is key to establishing the efficacy of PHA degradation at any given physical location.
Additionally, precise mathematical modeling of the geometry changes during mass loss is critical for defining the lifetime of PHA straws in the marine environment. Factors like the amount of degradation inside vs outside of the straws can play a major role in the predicted degradation rate. The paper addresses all of these critical issues.
NSU professor Jose Lopez and Master of Science student Emma Gellman conducted the novel microbial analyses to define the key bacterial strains and their abundance as a function of time. NSU Masters student Kyle Pisano and Kirk Dotson, founder of the RDC, addressed mass loss as a function of time and developed a unique model of degradation for hollow cylinders, such as drinking straws. Patrick Roman, a professor at Florida International University, conducted scanning electron microscopy, to create images of the microbes on the degrading straws and associated pitting of the plastic surface. This pivotal study of temporal and spatial variability of microbes and geometry is the first of its kind in the literature.
Ironically, the ability of PHA to degrade quickly in the marine environment also benefits coral reef restoration. A patent-pending biodegradable structure, called the Coral Fort, has been devised that prevents parrotfish, and other predators, from biting and often killing juvenile corals and coral fragments that have been transplanted from laboratories to the ocean floor in reef restoration efforts. Unlike steel cages that have been deployed to combat this problem, the Coral Fort disintegrates prior to the accumulation of algae, which would otherwise necessitate recurrent cleaning by SCUBA divers. This coral predation problem for coral outplants is acute in Broward and Miami/Dade counties, and represents a major bottleneck for restoration in the Florida Coral Reef Tract.
Coral Forts are composed of a cement disc, on which the coral is mounted. PHA straws surround the coral to keep out predators. This pioneering technology has the potential to revolutionize coral reef restoration in Florida and around the world. Proof of concept for “Coral Forts” was provided by Kyle Pisano in his MS thesis.
