Generally, reusing items is one of the greenest things you can do. But when it comes to plastic disposable utensils like forks, knives and spoons, it's best to use them only once. While it's tempting to rinse plastic utensils and reuse them, they really aren't designed to be used more than once. When you wash plastic utensils, microscopic spaces are created that can harbor food particles that will turn into bacterial growth. So, if you must use plastic utensils, don't reuse -- but try to opt for reusable silverware whenever possible.