“I would wager that the process to create a single plastic bag is more harmful to the environment start to finish than a single paper bag.”
According to the NY Times, quoting the Britain’s Environment Agency:
“You’d have to reuse a paper bag at least three times before its environmental impact equaled that of a high-density polyethylene plastic bag used only once. And if plastic bags were reused repeatedly, they looked even better.”
“The study found that an avid shopper would have to reuse his or her cotton bag 131 times before it had a smaller global warming impact than a lightweight plastic bag used only once.”