Degradation Of Polyhydroxyalkanoate (PHA) Straws In Tampa Bay Marine  Environment 

 Our Team

Abstract

Microplastic contamination is a growing concern for Tampa Bay. In late 2018, St. Petersburg, Florida enacted a plastic straw “ban”, including bioplastic straws made of polylactic acid (PLA), under the City Ordinance 365-H. This ordinance was crafted to promote the general welfare of St. Petersburg by protecting vital marine environments from plastic waste pollution. However, a company has recently developed and marketed the first biodegradable plastic straw made of polyhydroxyalkanoate (PHA) and claims their straws can degrade in as little as 58 days in a marine environment and are 100% marine biodegradable. This straw is heavily marketed in St. Petersburg because of a loophole in the straw ban. We sought to test the extent of the straws' biodegradability and asked three questions: can PHA straws decompose in Tampa Bay conditions, how long does it take for complete degradation to occur, and how do bacterial communities change during degradation? To test this, PHA straws were submerged in jars of seawater, and kept in pools of water in the greenhouse. The surrounding water was maintained at 30°C replicating Tampa Bay’s summer conditions. Samples were weighed, imaged, and processed for microplastics and bacteria biweekly over 70 days. We found little to no degradation of the straws, bringing the efficacy of PHA straws biodegradation claims under question. Regardless of the biodegradability of these straws, they are still present and impacting organisms in the Tampa Bay area. Our work will hopefully influence local policy about the implications of using PHA-based straws.