Mugs Are Better for the Environment, Right?

Dan Lewis

Department of Materials Science and Engineering

Rensselaer Polytechnic Institute, Troy NY 12180

Delmar Presbyterian Church recently made a simple change with surprisingly big implications: we switched from disposable coffee cups to ceramic mugs. On the surface, it seems obvious that reusable mugs are better for the environment than disposable cups. But one of the interesting lessons from sustainability research is that the answer is rarely as simple as it first appears.

A classic case-study of environmental impact examines how a ceramic mug and a disposable cup compare in the task of delivering a hot drink. This particular study became a model for how best to understand sustainability tradeoffs in a systems-level mindset and it also served as a way to teach the basic concepts (and difficulties) of a Life Cycle Assessment (usually abbreviated as LCA). In my engineering classroom, I decided to use this model and a more recent analysis of the same model to teach my students about LCA. I wanted to share some of what I taught to my engineering students with you here in this blog post.

A life cycle analysis tries to account for the environmental impacts of a product from the beginning to end of life. Instead of asking only, "What gets thrown away?" it asks questions like:

• What materials were needed to make the mug and the paper cup?

• How did the materials get to the factory?

• How much energy was used in manufacturing?

• What waste streams were created during manufacture?

• After manufacture, how far and by what means was the product shipped?

• How is the product washed, reused, or disposed of?

• What happens at the end of its life?

• Does the product go into the landfill?

• Can all, some, or none of the product be reused?

In other words, an LCA attempts to look at the whole story. As a materials engineer interested in sustainable manufacturing, one reason to use an LCA is to show how materials flow back into new products and not back into landfills.

For a ceramic mug, that story includes mining clay and minerals, manufacturing the mug, transporting it, washing it over and over again, and eventually (and hopefully) discarding it years later. For a disposable cup, the story includes producing the foam or paper, transporting thousands of cups, and sending them to a landfill after a single use.

What makes this complicated is that the conclusions depend heavily on the boundaries you choose for the LCA. For example, the study found that washing reusable mugs uses electricity, water, and detergent, and those impacts vary dramatically depending on the dishwasher and even the local electrical grid. A dishwasher powered mostly by coal-generated electricity has a different environmental footprint than one powered by cleaner energy sources.

The researchers also pointed out that disposable cup studies sometimes leave things out: lids, sleeves, packaging, transportation distances, or landfill conditions. Those choices matter. If you change the boundaries of your analysis, you can change the result.

That does not mean life cycle analysis is useless. Quite the opposite. It reminds us to be humble about seemingly "simple" environmental answers. It teaches us that caring for our ecosystem involves systems, tradeoffs, habits, and long-term, systems thinking.

The study optimistically concludes that, in general, reusable ceramic mugs performed better across most environmental scenarios in the United States. This is especially true when mugs were reused many times and washed efficiently. But the deeper lesson may be even more valuable: caring for our planet means learning to see beyond the immediate and asking thoughtful questions about the full consequences of our choices.

In church life, that perspective matters. A coffee mug is not just a way to sip a hot beverage. It is connected to energy, labor, waste, transportation, habits, an ecosystem, and community. Even small decisions can become opportunities to practice stewardship with wisdom rather than slogans.

That is almost certainly one of the most faithful things we can do: not simply choosing what feels "green", but learning to think carefully, gratefully, and responsibly about the world entrusted to us.

Delmar Presbyterian Church is proud to be an Earth Care Congregation. We'd love for you to join us in some of our endeavors to live more sustainably. Look out for a book study on Waste Not in the summer, planting a garden for our friends at Family Promise in May, and removing invasive species with the Mohawk Hudson Land Conservancy in the fall.

Contact office@delmarpres.org or 518-439-9252 to find out more.

Source

"Reusable vs. disposable cups revisited: guidance in life cycle comparisons addressing scenario, model, and parameter uncertainties for the US consumer"

Laura Woods, Bhavik R. Bakshi

International Journal of Life Cycle Assessment (2014) volume 19 pages 931–940.