Which is the more environmentally friendly bag: paper or plastic?

When your weekly grocery shopping is over and you get in line at the supermarket, it's time for yet another difficult choice. The cashier mechanically asks you, "Paper or plastic?" referring to what kind of bag you'd prefer. For some people, it's a stressful time. When you think of convenience you are pulled towards plastic, but thinking green might automatically pull you toward pa­per. However, if it’s rainy time, your paper bags may break, it could ruin your purchases.