The new version of the cup is still made from paper, and should look and feel the same as a traditional Starbucks cup. But inside, the vessel is coated with a compostable liner, rather than the plastic one used in Starbucks' regular paper cups. That means the new cup can be composted in industrial composters, unlike the cups Starbucks uses today. It's a hard problem to solve: Plastic-lined paper cups are light, stackable and effectively keep liquid from seeping out. Starbucks is intentionally testing the new cups out in cities with recycling facilities that can do so.