It’s official: Your reusable mug has been tainted — with suspicion. Reusing goods and packaging as many times as possible, instead of disposing of them and then buying new ones, is one of the greenest practices there is. It prevents energy and resources from being spent on manufacturing and shipping new stuff. It diverts old stuff from landfills and oceans. These facts are at the heart of the so-called zero-waste movement, which has spawned books, blogs, and package-free stores in recent years.