If you are an
environmentalist (like me), then you probably wouldn't be caught dead using a
styrofoam cup. Nope, like any
good-thinking American, you prefer
paper cups. But what if, in fact, paper is actually worse for the environment?
Styrofoam is made out of polystyrene, which is a plastic derived from petroleum. Styrofoam has gotten a bad rap mainly because it is not particularly biodegradable, which means that it does not decompose in landfills. Due to this factor, environmentalists have long fought to have restaurants replace styrofoam with paper, and they scored a high-profile victory in 1990 when McDonald's made the switch. Since then, there has been little debate on the subject -- everybody just knows that styrofoam sucks.
So you can imagine my surprise when I took an Environmental Law class, taught by a bona fide environmentalist, and learned that things are not so simple. It turns out that in pretty much every category other than biodegradability, styrofoam beats the pants off paper. The main reason is that paper-making is not an environmentally friendly industry, due to the pulping and bleaching. Moreover, it requires significantly more energy to create and transport paper cups to their ultimate destination. And while petroleum is non-renewable (unlike forests), the fact remains that much paper comes from the destruction of old-growth forests.
In the end, though, the biggest difference between paper and styrofoam is the price. If you go to your local supermarket, you'll find that paper cups cost 2-5 times more than styrofoam. Pricing is often an indication of environmental impact; higher prices indicate higher input costs, which shows that more "stuff" went into the production. Of course, if a company has to use two paper cups (instead of one styrofoam cup) to avoid burning its customers, this problem is exacerbated.
So what does this all mean to you? If you prefer styrofoam, then don't feel guilty when using or buying it. On the other hand, the best thing of all would be to carry a reusable ceramic mug (just don't wash it!)