Paper bags hold more stuff, but plastic bags use less energy during production and recycling. Photo: Getty Images
Paper or plastic: A look at the facts and numbers
Further insight into the implications of using and recycling each kind of bag can be gained from looking at overall energy, emissions, and other life cycle-related costs of production and recycling. According to a life cycle analysis by Franklin Associates, Ltd, [pdf] plastic bags create fewer airborne emissions and require less energy during the life cycle of both types of bags per 10,000 equivalent uses -- plastic creates 9.1 cubic pounds of solid waste vs. 45.8 cubic pounds for paper; plastic creates 17.9 pounds of atmospheric emissions vs. 64.2 pounds for paper; plastic creates 1.8 pounds of waterborne waste vs. 31.2 pounds for paper.
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. The numbers here assume that each paper bag holds 50 percent more than each plastic bag, meaning that it takes one and half plastic bags to equal a paper bag -- it's not a one-to-one comparison, even though plastic still comes out ahead.
It's important to note that all of the above numbers assume that none of the bags are recycled, which adds a lot of negative impacts for both the paper and plastic bags; the numbers decrease in size (and the relative impacts decrease) as more bags are recycled. Interestingly, the numbers for paper bag recycling get better faster -- the more that are recycled, the lower their overall environmental impact -- but, because plastic bags use much less to begin with, they still ends up creating less solid and waterborne waste and airborne emissions.
Paper and plastic bags' required energy inputs
From the same analysis, we learn that plastic also has lower energy requirements -- these numbers are expressed in millions of British thermal units (Btus) per 10,000 bags, again at 1.5 plastic bags for every one paper bag. Plastic bags require 9.7 million Btus, vs. 16.3 for paper bags at zero percent recycling; even at 100% recycling rates, plastic bags still require less -- 7.0 to paper's 9.1. What does that mean to me and you? Plastic bags just take less energy to create, which is significant because so much of our energy comes from dirty sources like coal and petroleum.
So, which is better: paper or plastic? Here's the conclusion