Strategies to reduce the environmental lifetimes of drinking straws in the coastal ocean

Degradability in natural environments is a growing design requirement for consumer plastics. However, data on their biodegradation rates and environmental lifetimes in the coastal ocean are lacking, limiting informed engineering and regulatory decisions. Single-use drinking straws, a common marine litter relevant to key stakeholders, exemplify this. To fill this knowledge gap, commercial drinking straws made of cellulose diacetate (CDA), polyhydroxyalkanoates (PHA), paper, polylactic acid (PLA), and polypropylene (PP) were incubated for 16 weeks in a flow-through seawater mesocosm and monitored for degradation and microbial community composition. CDA, PHA, and paper straws reduced in mass by up to 50%, projecting environmental lifetimes of 7-15 months in the coastal ocean. PP and PLA showed no measurable mass loss. Lifetimes depended on the material and dimensions of the straw, demonstrating the need to balance function and degradation properties. The materials that biodegraded exhibited unique microbial communities driven by chemical structure, whereas those materials that were persistent exhibited similar communities despite substantial differences in chemical structure. To reduce the persistence of drinking straws, we hypothesized that changing product form (i.e., surface area), not just material, can reduce their environmental lifetimes. To test our hypothesis, we evaluated the biodegradation of a prototype foamed CDA straw. Its specific surface degradation rate was 190% faster than its solid counterpart, resulting in a shorter projected environmental lifetime than the paper straws. Our findings provide the initial constraints of the environmental lifetimes of several commercial drinking straws and identify strategies to design next-generation bioplastic consumer products with reduced persistence.