Recently I have been getting more and more questions regarding my very first AskPablo post. Michael and Phil both asked me about paper cups, which were not included in the initial analysis, and I also received an e-mail from Anna. So this week I will recap the results from my very first post and will incorporate an analysis of paper cups as well.
I chose styrofoam, ceramic, and stainless steel for my original comparison and looked at the material intensity and the greenhouse gas (GHG) intensity of each, taking into account the fact that one was disposable and the others were reusable. My conclusion was that the production of styrofoam cups has a much lower environmental impact than the other two in terms of resource extraction and GHG emissions. But, since the styrofoam cups are disposable you need a new one every time you have a cup of coffee. The environmental impact then adds up until, at 46 uses, the ceramic mug becomes the environmentally responsible choice. And after 369 uses, the stainless steel mug also become a better choice than styrofoam. Ultimately the ceramic mug is the best choice since it is infinitely reusable and has a lower impact than the stainless steel mug (Although you could factor in the convenience and portability of a stainless steel mug with a lid).
Now, to look at paper cups… Let’s assume that a paper cup is used only once, weighs 20 g, and is made from bleached virgin wood pulp domestically. The material intensity factor for this material is 11.73 g per g of paper so the material intensity of our paper cup is 234.6 g. Using this new number along with the previous results I created a chart that shows the fixed impact of the reusable cups and the variable impact of the reusable cups (the x-axis represents the number of uses and the y-axis represents the material intensity in grams). This shows that styrofoam has a lower material intensity than ceramic until 46 cups and that 24 paper cups are equivalent in material intensity to a stainless steel mug.
Keep in mind that these results are not an definitive result since there are many other factors involved. The primary difficulty of measuring sustainability is that it is nearly impossible to aggregate all of the various impacts into one number or score. Additional dimensions include the recyclability of the materials, their toxicity, the biodiversity of the raw material extraction site, and the working conditions along the supply chain.
What is clear is that reusable is better than disposable, assuming that you actually reuse! Many of us are guilty of owning too many reusable items when one would suffice. Maybe this mentality has been driven into us from living within a society built on disposables, where more is better, quantity over quality. If you are one of the many that get a new paper cup at your coffee shop every day make tomorrow different. Bring a travel mug with you and if you have a couple extra ones, bring one for a friend. Bring a ceramic mug to work and carry a Kleen Kanteen or Sigg bottle with you in your gym bag. The daily impact may seem small, but it adds up quickly, especially if you get your friends involved.