Paper straws are wound from paper with a food-safe adhesive and, often, a water-repellent treatment to stop them going soggy. They became the default after the EU, UK, Canada, India and Australian bans on plastic straws.
They replace single-use plastic straws, which weigh about 0.4 g each. As a single-use paper item, they are compostable or recyclable in principle.
The caveat is chemical: a 2023 Belgian study in Food Additives and Contaminants tested 39 straw brands and detected per- and polyfluoroalkyl substances (PFAS) in 90 percent of paper brands, most bamboo and plastic brands, and some glass brands, with none found in stainless steel. PFAS are persistent, mobile and linked to health harms, so a PFAS-treated paper straw is not plastic-free in any meaningful sense and can contaminate compost.
Rule for the swap finder: prefer no straw, then reusable stainless steel, then paper or PHA straws with a written PFAS-free declaration or Biodegradable Products Institute (BPI) certification, which now includes a total-fluorine limit. Cost data were not found; paper straws are a small premium over plastic.