Plastic grocery bags have been banned or taxed to discourage their use in other countries, and recently San Francisco approved similar measures. While reusable bags are touted as an obvious alternative to disposable bags, paper bags are also seeing a resurgence, and are the standard bags at upscale grocers like Trader Joe’s. Paper bags are often assumed to be more environmentally friendly, which begs the question: what is the true cost of both bag varieties?

Numerous reports have been published on this topic, with the Washington Post and Environmental Literacy Council providing particularly good comparisons. On most counts, plastic bags come out ahead, even after comparing the true cost of two plastic bags against one paper bag (to make up for differences in bag size). Plastic bags require 50% less energy to produce and cause significantly less pollution during manufacturing. Paper bags are recycled more often, but over 85% of paper and 97% of plastic bags end up in landfills, where neither biodegrades, and where plastic bags take 90% less space. Plastic bags are criticized for endangering certain marine animals, and because they often end up as litter since are easily blown about.

Another good measure of cost is the price of the two items, since neither is heavily subsidized, and since the price that stores pay for bags represents the direct cost involved in production. Plastic bags cost 50% less than paper bags in the US (2 cents for two plastic bags versus 3-4 cents for one paper bag). Advantage plastic.

On most counts plastic is the clear winner for the consumer, the environment, and businesses. In fact, after weighing the costs and benefits, the Natural Resources Defense Council recommends plastic bags to everyone unable to use a reusable bag, and recommends paper bags only for those living on the coasts (to protect marine wildlife). Perhaps, as with ethanol, paper bags have just become another easy way for politicians to score points for being green, rather than taking more beneficial (and difficult) steps to protect the environment.