Plastic Bags or Reusables? Depends Where You Draw the Line


By Emily Busch

Reusable shopping bags have long been marketed as a sustainable alternative to plastic single use bags. Purveyors tout the reusable bag’s ability to reduce oil and water consumption and decrease the volume of waste sent to the landfill while also highlighting the bags strength and aesthetic appeal. These campaigns have largely been successful, as measured by how ubiquitous these bags have become. Many 3p readers have probably accumulated dozens of reusable bags. A recent scandal surrounding lead and bacteria in reusables had me eyeing the heap of bags sitting in my closet. After years of proudly toting my reusable bags and declining my arch nemesis (the single use plastic bag), I was left wondering what kind of effect reusables had on health and the environment. To find out, I performed my first Lifecycle Assessment along with my student team from Presidio Graduate School.

Lifecycle assessments are used to evaluate the environmental impacts of a product’s material components, manufacture, transportation, use, and disposal. In effect the LCA is a holistic assessment of the product’s impact from cradle to grave. We analyzed a leading, high-end line of reusable bags made from virgin polyester and used Sustainable Minds software to complete the assessment. After inputting the necessary data, the software generated a report highlighting the impacts of each material and lifecycle stage. We discovered that the highest impact of these bags came from the dyes used to color them. By adjusting the various inputs in the software, we were able to easily find substitute dyes with lower impacts.

Though virgin polyester did not cause the greatest impact, our team was curious to see if switching to recycled polyester or a natural textile would reduce the overall impact of the product. We chose 50% virgin/50% recycled polyester, 100% polyester, jute (a fiber similar to hemp), and viscose (a form of wood cellulose) for comparison. Counter to our initial assumptions, virgin polyester had the least impact.

An even more shocking find occurred when we attempted to perform an LCA on single use plastic bags as a reference point for determining the relative sustainability of the reusable bag we chose. We chose virgin polyester, the same material used for the reusable bag, applying the same weight, and same transportation distance for our single use plastic bag. The assessment generated a score for the single use plastic bag which was lower than the reusable bag. That was not a surprise, given that the single use bag is a lot lighter. The surprise came when we looked at the number of plastic bags one would have to use to equate the expected lifetime use of a reusable. We discovered that, much to our chagrin, using single use plastic bags has less of an impact than even one of the most sustainable reusable bags.

Now, I admit that I am a novice and first time user of lifecycle assessment software. We made many input assumptions because we were not privy to the actual company data necessary for a more exact and in depth analysis.

How can virgin material and single use bags possibly be less impactful than recycled reusable bags? The truth is, the results depend on where the boundaries to the assessment lie.

If the software did not consider the extraction of virgin materials and only focused on the impact from manufacturing, then virgin materials would seem less impactful because of the more energy and chemically intensive process required to reconstitute recycled items. Additionally, if the effect on society and wild life from the rampant improper disposal of single use plastic bags is not considered, then the impact of single use bags appears lower than it really is.

As with many of the disagreements over the impact of unsustainable behavior, one can make the argument for anything if externalities are not recognized as true costs.

Marketers have the ability to bring externalities to the forefront. Unlike debates over the impact oil consumption has on climate change, there is no argument over whether plastic bags are littering the streets or choking sea life. Marketers highlighting these downsides in their campaigns may work to appeal to a demographic that will not be swayed by “theory.” With this in mind, I will continue to tote my reusable bag with its little owl graphic declaring “Paper nor Plastic.”

2 responses

  1. L.C.A.’s can be “conservative”, in which case they can show that disposable can be the same or better. If one takes the full impacts into account, which gets very complicated and depends on assigning responsibilities, then the reuseable longer lived products start to shine.

    As you say “the results depend on where the boundaries to the assessment lie”. Conservative L.C.A.s’s can and have been used by industry to justify business as usual.

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