"Paper or plastic?" It seems like it should be an easy choice, but from durability and reusability to life cycle costs, there's a lot more to each bag than meets the eye.
Paper comes from trees -- lots and lots of trees. The trees are found, marked and felled in a process that all too often involves clear-cutting, resulting in massive habitat destruction and long-term ecological damage. It takes approximately three tons of wood chips to make one ton of pulp. The pulp is washed and bleached, and both stages require thousands of gallons of clean water.
If you throw them away, they'll eventually break down over many, many years. But if you choose to recycle the paper bags, then things get a little tricky. The paper must first be re-pulped, which usually requires a chemical process involving compounds like hydrogen peroxide, sodium silicate and sodium hydroxide, which bleach and separate the pulp fibers.
Unlike paper bags, plastic bags are typically made from oil, a non-renewable resource. Plastics are a by-product of the oil-refining process, accounting for about four percent of oil production around the globe. Like paper, plastic can be recycled, but it isn't simple or easy. Recycling involves essentially re-melting the bags and re-casting the plastic.
According to a life cycle analysis, plastic bags create fewer airborne emissions and require less energy per 10,000 equivalent uses. But paper bags can hold more stuff per bag -- anywhere from 50 percent to 400 percent more, depending on how they're packed, since they hold more volume and are sturdier.
Ultimately, neither paper nor plastic bags are the best choice; choosing reusable canvas bags instead is the way to go. From an energy standpoint, canvas bags are 14 times better than plastic bags and 39 times better than paper bags!