About a year ago, I decided to start using less plastic. I bought a thermos for my morning coffee, used beeswax wrappers instead of cellophane, and mostly ditched plastic shopping bags in favor of cotton ones.
I used to feel pretty good about myself until I saw a report from the Danish Ministry of Environment and Food earlier this year that found that plastic bags were better for the environment than organic cotton bags. In fact, of all the shopping bags the study looked at – from paper to recycled plastic – cotton bags performed the worst: they would have to be reused thousands of times to achieve the same environmental impact as lightweight plastic bags, the report found. A study published in 2011 by the UK Environment Agency came to similar conclusions. So is my decision to ditch plastic bags really bad for the environment?
The answer isn’t that simple. First, these studies, known as “life cycle assessments,” should be treated with caution. The study looked at the entire life cycle of different types of shopping bags, from the extraction of the raw materials needed to make the bags to how the bags are used and disposed of. The study then determined how “green” each bag is based on several impact categories, including climate change, toxicity, and water consumption.
Here’s the problem: It’s essentially impossible for one bag to score higher than all the others in every impact category, said David Taylor, a professor in the department of chemistry and biochemistry at the University of Oregon. “So when you’re talking about environmental impact, you have to decide, what environmental impact do I want to mitigate first?” Taylor said.
I decided to give up plastic bags because I wanted to do something about the problem of plastic pollution in our oceans. Scientists estimate that about 8 million tons of plastic waste ends up in the ocean every year. These types of plastic are not biodegradable and pose a threat to wildlife, including corals. Turtles can choke if they swallow plastic bags. Just last month, a dead whale in Spain was found with more than 60 pounds of plastic waste, including plastic bags, in its stomach. To address the waste problem, American cities like Austin, Los Angeles, and Seattle have banned single-use plastic bags. Last month, New York Governor Andrew Cuomo introduced a bill to ban plastic bags statewide for the same reason.
The Danish study didn’t look at marine debris as a factor. (Study author Anders Damgaard of the Technical University of Denmark said the researchers followed European Union guidelines for which categories to include, such as climate change and ozone depletion.) There’s no right or wrong answer, said Travis Wagner, a professor in the department of environmental science and policy at the University of Southern Maine. All of these durability studies have been done in different ways, and they’ve looked at bags that are available in a particular country but not in other countries. Wagner noted that the studies also require making a lot of assumptions about how people use the bags. Do you line your trash cans with plastic shopping bags? How much stuff do you put in your tote bags and paper bags when you go shopping?
However, in all of these life cycle assessment studies, plastic bags appear to be “greener” than cotton bags. That’s because cotton requires a lot of land, water and fertilizer to grow; it then needs to be harvested, processed and transported to market. “Cotton is a very water-intensive crop,” Taylor said. A 2007 study by the Australian government found that plastic bags also have a smaller carbon footprint than paper bags. Taylor noted that making paper from trees creates a lot of waste that ends up in landfills. In contrast, “petroleum is generally considered very valuable, so there’s very little waste,” he said. Additionally, Wagner said, it takes a lot more fuel to transport 1,000 paper bags across the country on a truck than it does to transport 1,000 thin plastic bags. “The carbon emissions are largely dependent on the weight of the bag,” he said. “That’s why it’s so hard to compare the two.”
Ultimately, it comes down to what you care about most. If marine debris is your biggest concern, paper bags are a better choice because they biodegrade and don’t accumulate over the years. In New York City, the Department of Sanitation spends more than $12 million a year to dispose of more than 10 billion single-use plastic bags, so the city has tried (unsuccessfully) to impose a 5-cent fee on plastic bags. In Africa, there are concerns that discarded plastic bags could also accumulate in water, nurturing disease-carrying mosquitoes.
So what should you do if you want to reduce your environmental impact? Many experts I spoke to said that using reusable plastic bags — whether made from recycled plastic, nylon, or woven polypropylene — is the best option. “They’ll last you hundreds of uses. The ones I have now, while a little worn, have lasted for years and are in great condition,” Taylor said. “You use the bag so much that you eventually break even.” The bags are durable and easy to clean, such as if gravy spills.
Whatever shopping bag you choose, try to reuse it, even if it’s a single-use plastic bag. You can use it to line your bin, pack a lunch, or just take it with you on your next shopping trip. “All of these bags are worth it if you use them regularly,” Wagner said. “That’s the goal: How many times can you reuse it?” When it comes to mitigating climate change, however, the impact of the shopping bags you use is relatively small, says Jonna Meikhoff Fry, a senior life-cycle management consultant who conducted a 2011 study in the U.K. What matters more is what you put in your bag (how much meat do you eat? Do you buy locally?) and how you get to the grocery store. (Do you drive or walk?)
As for me, my apartment is filled with bags—I’ve bought over 20 of them from my favorite bookstores and shops—so I have no problem using as many of them as possible. I won’t be buying any more, and the next time someone offers me a free bag, I’ll just say no.
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