Biodegradation of drinking straws in the coastal ocean

Single-use drinking straws are a common, polarizing, visible marine litter relevant to key stakeholder groups. Data on their environmental lifetimes in the coastal ocean are lacking, limiting informed regulatory decisions (e.g., straw bans). To fill this knowledge gap, single-use drinking straws made from cellulose diacetate (CDA), polyhydroxyalkanoates (PHA), paper, polylactic acid (PLA), and polypropylene (PP) were incubated for 16 weeks in a flow-through seawater mesocosm. CDA, PHA, and paper straws reduced in mass by up to 50%, projecting lifetimes of 6-14 months, depending on the material type and dimensions of the straw. PP and PLA showed no measurable mass loss. For the CDA, PHA, and paper straws, microbial community composition reflected material type. In contrast, the PP and PLA straws shared similar community structures despite substantial differences in material type. While material type often dominates consideration in designing more environmentally friendly straws, we hypothesized that changing product form (i.e., surface area), not just material can reduce environmental lifetimes. We evaluated the marine degradation of a prototyped foamed CDA straw with closed-cell porosity to test our hypothesis. The degradation rate of the foamed CDA straw was 273% faster than its solid counterpart and yielded a shorter projected lifetime than the paper straws. Our findings provide the first constraints of the environmental lifetimes of several commercial drinking straws and identify strategies to design next-generation bioplastic consumer products with reduced persistence.