Reusable Shopping Bags: Which Is the Greenest of Them All?

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Dear Pablo: I want to switch to reusable shopping bags. (Yes I should have done it years ago.) However, all the stores in my area seem to sell bags made of polypropylene. Is the manufacturing process of these bags bad for the environment too? Is canvas or nylon any better? Which do I choose?

The greening of mainstream society has added additional complexity to the age-old "paper or plastic" dilemma (read more on the paper or plastic issue here.) We all understand that reusable shopping bags are more environmentally responsible than disposable paper bags or plastic bags. But which reusable shopping bag--a canvas bag, polyester bag, or polypropylene bag--is really the best eco-choice? Let's look at the options.

Shopping Bags: Canvas Bag

The first reusable shopping bag to gain popularity was the canvas bag. Canvas totes are available in conventional cotton, organic cotton, or even hemp. The environmental impact of conventional cotton cultivation is well known--a major percentage of the world's herbicides are used to defoliate cotton prior to harvesting. While organic cotton is better, both conventional and organic cotton use a significant amount of water, so the environmental impact of the fabric bag is directly proportional to its weight. One of my organic cotton shopping bags weighs 187 grams but another cotton bag that I have is made of a much thinner fabric and weighs only 75 grams. If you are looking for a canvas bag, look for a lighter one. It will still hold more weight than a plastic or paper bag.

Shopping Bags: Polyester Tote Bag

Polyester tote bags, such as the ChicoBag, are easily portable shopping bags made from a very thin but durable fabric. The bag is about the same size as a disposable plastic bag used for shipping and stows neatly in an integrated pouch that fits in the palm of your hand and clips to your purse or fits in your pocket. At 35 grams, the manufacturing of the polyester material for one bag creates 89 grams of greenhouse gas emissions, which compares to the manufacture of just seven disposable plastic shopping bags. ChicoBag now also makes a bag that is made from seven recycled soda bottles.

Shopping Bags: Polypropylene Bag

Another shopping bag that has been gaining popularity is made from polypropylene and is designed in the shape of a brown paper shopping bag. These bags, such as hose made by One Bag at a Time, can now be found at the checkout lines pretty much everywhere, from Safeway supermarkets to Ace hardware stores. One Bag at a Time's website provides some great information on the environmental benefits of using these bags. At 103 grams, the manufacturing of the polypropylene material for each bag creates 138 grams of greenhouse gas emissions, which compares to the manufacture of 11 disposable plastic shopping bags.

And the Winner for Greenest Shopping Bag Is...

The difference in environmental impact between the polyester bag and the polypropylene bag is negligible, especially when compared to the disposable paper and plastic bags. The impact of canvas bags is higher, but still negligible when compared with the disposable alternatives over time. Ultimately, what is most important, regardless of your choice, is that you use the reusable shopping bag.

Ask Pablo is a weekly column that aims to answer your pressing eco-quandries. Want to ask Pablo a question? Simply email Pablo(at)treehugger(dot)com. Wondering why Pablo's qualified to answer? As the Vice President of Greenhouse Gas Management at ClimateCHECK, he helps major corporations measure and manage their greenhouse gas emissions.