The Green Space | Breaking Down Bags

Every time I shop at Trader Joe’s, I wrap up my limes and peppers and onions in little compostable produce bags that smell — weirdly, but comfortingly — like cotton candy. When I didn’t have a compost pile, I would just throw them in the regular trash (I know! I’m a sinner!), and I would always think about whether those bags even made a difference if you just threw them away. Then I would shrug and move on with my day because being an informed citizen is hard.

Thanks to a helpful SciShow video that popped up on my YouTube timeline a month ago, I now know the answer — and it’s pretty complicated. The video compares five types of bags — single-use plastic, paper, compostable, thick plastic and cotton. In order to calculate the total environmental impact of all five types, researchers had to consider a total of 15 effects, including ozone depletion, toxicity, water use, overall resource use and more.

When we haul a bunch of reusable bags along to the store, we’re usually thinking about all the plastic we’ll save from the landfill. It might surprise you, then, that the initial production of these bags is where they make the biggest environmental splash. It might surprise you even further that, at least in this arena, single-use plastic is the clear winner. Plastic bags are made of high-density polyethylene, which is made from petroleum. The production of this material, when compared to cotton or paper production, results in fewer carbon emissions and harmful byproducts.

Biodegradable plastic bags are often made of a mix of starches and citric acid — including sugarcane, no wonder those produce bags smell so good. Their production emits a similar amount of greenhouse gases as that of single-use plastic bags, but because of the fertilizers and pesticides used in growing the starches and the more intensive processes involved in turning them into plastic, biodegradable plastic results in more pollutants in the end. Add to this the fact that bioplastic production requires vast swathes of land that would then be unavailable for food production, and bioplastics aren’t looking so hot.

Paper bags don’t have much of a leg to stand on either. Depending on the fuel used at each paper mill, processing wood pulp into paper can emit a lot of greenhouse gases, and paper bag production can take up to four times as much energy as plastic bag production. To add insult to injury, paper bags have the same problem as compostable bags in that chemicals and fertilizers used in cultivating trees can have a negative impact, contributing to soil depletion, eutrophication and water pollution.

By this point, you’ve probably seen it coming — reusable bags, sadly, are the ultimate losers in the battle of production. Thick plastic bags require even more petroleum than their single-use friends, which leads to a larger environmental impact. Cotton bags may be even more detrimental because of the huge amounts of water and other resources needed to produce cotton, and the process of making the bag is similarly energy intensive. In terms of both climate change and overall impact, cotton bags are by far the worst.

Let’s get an idea of this total environmental impact with some cold hard numbers. According to a Danish study cited by the SciShow video, in order to have a similar environmental impact to a single-use plastic bag, paper bags must be reused 43 times, bioplastic 42, reusable plastic 54 and cotton — drumroll, please — 7,100 times. As SciShow tells us, if you shop three times per week, you will need to use your cotton bag for 45 years in order to cancel out its initial environmental impact. Note: if your cotton bag is organic, you’ll need to reuse it 20,000 times. Good luck!

But wait — we’re not finished yet. After production and use finally comes disposal, where plastic finally gets its day of reckoning. There are almost no good ways to dispose of plastic. About 8.8 million tons of plastic enter the ocean annually, and at least 700 species globally have been affected by plastic pollution. Because microorganisms don’t recognize plastic as food, plastics can technically never biodegrade — instead, they just break down under UV radiation from the sun into progressively smaller bits of plastic, which researchers suspect never fully decompose. Eventually these tiny granules might invade every level of the food chain.

Keep in mind, plastic bags can be recycled, but they almost never are because they tend to get caught in sorting machines or blow around recycling facilities and make a big mess. One estimate proposes that only one to three percent of plastic bags are ever recycled.

Though plastic is the worst, all of these bags, when put into a landfill, can end up emitting greenhouse gases. Really, the environmental impact of bag disposal depends on the actions of individuals — whether they recycle or compost their bags, or whether they just chuck them in the trash can. So yes, past Sarah, your lack of composting is a dirty crime.

This isn’t to say that plastic bags are the best option — their environmental impact after disposal is truly awful. The takeaway from all this is unfortunately not that simple — when you take into account every possible environmental impact, no bag comes out on top, despite our feelings of good citizenship when we whip out our reusable bags at Giant Eagle. Our overuse of plastic is a huge problem with no good solution.

But let’s not end on that sour note — we already have too many huge problems with no good solutions to think about. Instead, think of this — your actions make a difference. In this one tiny area of life, we can make a positive difference by using what we already have, and reusing it as many times as possible.

Don’t feel bad if you already own a cotton tote bag, but maybe don’t go out and buy another right after you finish this article. Consider recycling your paper bags. Reuse your plastic bags as trash bags, or even reuse them again as grocery bags. Single-use is not a binding promise. Actually put your compostable bags in the compost. But, most of all, always think critically about supposedly environmentally friendly products — there is almost always more to their impact than meets the eye.

Sarah writes primarily about trees, climate change and walking. You can reach her at sas503@pitt.edu.