It’s Rarely Black & White

by Christa Huddleson 

We often see photos in the media of plastic harming wildlife, such as the classic sea turtle eating a plastic bag it has mistaken for a jellyfish. According to EcoWatch, 1 million seabirds and 100,000 marine mammals are killed annually from plastic in our oceans. What many of us don’t realize is that plastic litter in the ocean is only one of the many environmental impacts that materials have on our planet.

Scientists use studies called life cycle assessments in order to measure and compare the different environmental impacts of products and materials from their manufacturing to their death. These assessments include assumptions made about how many times a product is used and often look at a product’s carbon footprint, water usage, amount of waste in a landfill, and many more impacts.

David Tyler, a professor in the chemistry and biochemistry department at the University of Oregon, uses life cycle assessments in a class he teaches on sustainability.

“Most of the time what life cycle assessments tell us is that there is no best product or best thing to do for the environment because it depends critically on what environmental impact you most want to mitigate,” said Tyler.

Life cycle assessments show that the single use of a plastic bag, for example, has less of an impact on almost every front than the single use of a paper bag.


“Anything made out of plastic, compared to almost any other material, paper, cloth, cotton, whatever, plastic has a far smaller carbon footprint, meaning that the global warming impact is much smaller for something made out of plastic,” said Tyler. “Plastic bags are far better in terms of how much waste is produced. The third impact category that plastic is really good at is water use.”

A 2011 life cycle assessment published by the Environment Agency found that a cotton grocery bag needs to be reused 131 times in order to take the global warming impact of the bag below that of a plastic bag used a single time.

If the plastic bag is reused a second time as a trash can liner, which the study found is true 40.3% of the time, then the cotton bag needs to be reused 173 times in order to have a lower global warming impact than the plastic bag.

Yet, as many of us know, plastic does not come out on top in every category.

“The plastic that’s littering the countryside that gets into streams and lakes and oceans, if that’s your most important concern, then clearly plastic is not the way to go because plastics have been over engineered to not degrade,” said Tyler. “It’s not black and white, what environmental impact do you most want to alleviate?”

Chemists, Tyler suggests, could have the answer to this environmental dilemma.

“Chemists are problem solvers,” said Tyler. “There are all kinds of chemists out there working on the problem of degradable

plastics. It takes research money and a little time, but chemists are going to solve the problem.” Degradable plastics already exist. The problem, however, is that they need to degrade at the right time, not while you’re using them for instance.

Tyler’s research focuses on the environmental factors (such as weather, sunlight, and temperature) as well as the molecular factors that determine when a piece of plastic will start to degrade and it’s rate of degradation.

“We were looking at what are called photochemically degradable plastics, so they decompose or degrade in sunlight,” said Tyler. “When I say degradable, I don’t mean compostable. I mean like really degradable. Like if it’s litter and it’s blowing around a field it just degrades, you don’t have to stick it in an industrial composter at 120 degrees or something to get it to disappear.”

This type of degradable plastic is already being used by some in agriculture through a technique called plasticulture, during which farmers cover their fields with degradable plastic sheeting. It could also potentially be used in place of many everyday plastics such as your commodity plastics.

“I would like to see a case where instead of banning plastic bags, which are really useful and have all these really good environmental attributes with the exception of not being able to degrade, why not require manufacturers to use degradable plastics?” said Tyler. “Then you’d have all these good attributes and, in addition, they would degrade. And then because everybody's doing it, it would become much more of a commodity type of material. And because everyone has to use it by say law, then the price would go down.”

While degradable plastics find their way into our daily lives, there is a lot more we can learn from life cycle assessments. One of the clear takeaways life cycle assessments show us is the importance of reuse. Whether you’re using a plastic bag or a cotton bag, the easiest way to reduce your impact is by reusing it as much as you’re able.

Life cycle assessments illuminate the contradictions of ‘eco-friendly’ and plastic products and educate consumers about the true impacts of their choices.

“It’s really hard to say this is better for the environment than that,” said Tyler. “It’s subjective because you have to think about what impact category do I want to most alleviate. It’s rarely black and white.