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Paper, Plastic, or Reusable Bags?

One of the first things people do when they want to be environmentally friendly is grab a pack of reusable grocery bags. Surely the plastic bags aren’t good for the environment, but how “not good” are we talking? And how much better are the different types of reusable ones?

Let’s start by defining the most common types of grocery bags. The abbreviations get confusing, so I’ll note what they are commonly called by scientific literature, but we’re going to stick to the simpler names in this article.
Plastic:
The typical plastic grocery bag (high-density polyethylene, or HDPE) are the kinds that grocery stores will give you and are typically free of charge if no regulations are set in your area. Plastic bags have been the front for many news pieces and have been eaten (but not digested) by many birds and sea animals.

Degradable Plastic:
These bags look have the same feel as typical plastic bags, but sport big green logos stating they are “compostable” or “100% degradable”. They are made of the same high-density polyethylene (HDPE) as traditional plastic bags, but have a prodegradant additive to help them decompose faster.

Paper:
Simple paper bags are an alternative to the single-use plastics bags. Some are free, while other stores charge 5 or 10 cents each.

Reusable Plastic:
Reusable grocery bags (non-woven polypropylene) are for when you forget your reusable bags at home, but don’t want to take plastic ones. Where I live, Walmart has the dark blue bags for 50 cents, and Target has the red ones for a dollar. They have a rectangular, stiff bottom and are meant to be reused. If you live in a state where plastic bags are banned, these are likely the only option at checkout for some stores.

Cotton:
Cotton tote bags are an alternative to the above ones and come in many fun designs. Most eco-conscious people will buy a few of these to always have on hand, and like the reusable plastic ones, they are meant to last.

Now that we know the different types of grocery bags, let’s get into their environmental impact. The “global warming potential” for each type of bag was found using the cost, labor, and energy required for each bag to be made and transported to its destination, as well as their impact after being used.

* Note: the primary data for this article are sourced from the "Life cycle assessment of supermarket carrier bags" produced by the UK Environment Agency in 2006. The chart has been slightly adapted to fit this article, but the data is the same.

Every type of bag we discussed actually has a higher carbon footprint/global warming potential than traditional plastic bags but only if they are used once and discarded. To have a smaller impact than plastic ones, paper bags need to be used 4 times, reusable plastic bags need to be used 14 times, and cotton bags need to be used a staggering 173 times (growing and processing cotton takes a ton of work). It’s also important to note that the average American family takes home 1500 plastic bags per year, and the graph below shows the impact per one.
The carbon footprint is only one part of the environmental impact of shopping bags. If they are not disposed of properly, the chemicals that are used to make the bag can eventually seep back out into the ground or water that they end up in. Additionally, any bags made of plastic will wear away over time, producing microplastics that end up in the environment. Degradable plastic bags similarly pose this issue: while they claim to be better for the environment because they break down faster (a few months rather than many, many years), the problem is that they physically break down. We might not see them in a few years, but that doesn’t mean they haven’t done their share in polluting microplastics into the area.

(If you are curious about microplastics and their impact, check out this article.)

The most environmentally friendly option for any product is the one you already have. Before purchasing new reusable bags, check your home for the ones you’ve picked up over the years. Regardless of the material, the more uses you can give each bag, the more eco-friendly it becomes. If you hoard plastic bags from grocery trips, even giving them a second life as a trashcan liner will decrease their footprint on the environment. Paper bags are unlikely to be reused 4 times without ripping, and unless you really like cotton bags (and remember to bring them to the store every time), these options might not be the best choice. Reusable plastic (polypropylene or PP) bags that you purchase in checkout lines are a great choice because after only 14 uses, they leave a smaller carbon footprint than plastic bags. These bags are also typically made from recycled plastic; Walmart’s classic reusable bags are made from old water bottles. Reduce, reuse, and recycle!


References

Ahamed, A., Vallam, P., Iyer, N. S., Veksha, A., Bobacka, J., & Lisak, G. (2021). Life cycle assessment of plastic grocery bags and their alternatives in cities with confined waste management structure: A singapore case study. Journal of Cleaner Production, 278, 123956. https://doi.org/10.1016/j.jclepro.2020.123956

Edwards, C. and Fry, J., (2011). Life cycle assessment of supermarket carrier bags: a review of the bags available in 2006. Environment Agency. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/291023/scho0711buan-e-e.pdf

Jalil, M. A., Mian, M. N., & Rahman, M. K. (2013). Using plastic bags and its damaging impact on environment and agriculture: An alternative proposal. International Journal of Learning and Development, 3(4), 1. https://doi.org/10.5296/ijld.v3i4.4137

James, K. and Grant, T., (2005). LCA of degradable plastic bags. Centre for Design at RMIT University. https://www.researchgate.net/publication/228916289_LCA_of_degradable_plastic_bags

National Geographic Society. (2022). Sustainable shopping-which bag is best? National Geographic. https://education.nationalgeographic.org/resource/sustainable-shoppingwhich-bag-best

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