Making Sustainability Metrics Fun
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.
Click on image to enlarge
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.
Pablo Päster
Sustainability Engineer
www.AskPablo.org
I saw this article about the top 10 greenest cities: http://forum.skyscraperpage.com/showthread.php?p=3225220. I never thought I would see LA in front of Seattle and San Fran. I went to the site that published the list (www.earthlab.com) and took their carbon calculator. I got a 257 which is pretty good compared to what I think other people probably get. After I complete some pledges I think it will be much lower. Check it out it only took me like 3 minutes to get my score. The website is www.earthlab.com.
What about compostable cups? I seem to recall someone saying that they perhaps came out ahead of mugs, when you considered the resources in washing them.
Paul, I think this is a great topic for a future AskPablo! Thanks!
I second Paul's comment! I'd love to see your analysis!
Nicely done... A more complex idea is this: What if the paper comes from a combination of properly managed forests and post consumer waste? If the forests are replanted and efficiently managed, then even if the cups are not composted, then the material intensity migh approach neutrality. Wheras, the ceramic or steel mug may have involved mining and great heat to produce... just a few thoughts!
If you use your travel mug enough times chances are it will be more environmentally friendly than compostable. Compostables still need petroleum to be transported to the customer and then to the landfill/compost center unless you compost at home. The best bet for the environment I've found is using a reusable cup. If you don't have one go to a consignment store or garage sale. Buying one used will greatly reduce the environmental impacts!
Unless I missed it here, I do not see any consideration of the environmental cost of washing the ceramic or steel cup/mug. One could say that if it is being added to a daily dishwasher load that would be running anyway, the cost is nil. However, assigning a proportional share of the cost of running the load (electricity, hot water, detergent, etc.) might be more valid. If washed by hand, there is still the hot water and soap to consider. Do you consider these costs negligible?
Excellent point Neil! Most people overlook the "cost" of washing said reusable mug.
Here is a report that didn't
http://www.ilea.org/lcas/hocking1994.html
I'm unfamiliar with Material Intensity Factor. Can you explain and provide reference?
some years ago i saw photocopied flyer inside the window of a close coffee stand comparing the energy,transportation and disposal costs of paper coffee cups vrs Styrofoam. Styrofoam cups were the clear choice. i have been looking for a knowledgeable source for this information since. here it is, and the ilea.org page referenced by another commentator is very good. i have tried to tell people that in reality, the Styrofoam cup is the most efficient beverage delivery container. but no one EVER listens. people love to believe their illusions about what is truth, and they FEEL is the right thing to do. big sigh. but i detest the taste of espresso in styrofoam. wah.
I think you may be missing the point thaikarl -- most 'efficient delivery system'? The most efficient is - using the same one everyday!!! It's about garbage!!!! It does not matter to the landfill recieving the disposables if they were 'low energy' production garbage, or if they're 'efficint production' garbage disposables --- IT IS ALL GARBAGE!!!!! Trying to justify 'one time use' products is a little misguided and quite frankly sounds like scientific excuses to not have to carry a mug with you. Come on fella give that head a little shake! They will put your espresso in a fancy little REUSABLE mug for you! Try it and then you won't care if 'no one EVER listens' or what the 'FEEL IS THE RIGHT THING' it will all be a mute point won't it? Too many floating brains! There is a real world out there with real logic - real people and REAL ANSWERS! Keep it real.
Hi Pablo,
Just wanted to say "thanks" for putting the time and energy into this study. The research out there on this subject is few and far between. It's been mentioned already, but I'd love to see numbers for the compostable cup made by the International Paper Company (Tully's started using it about a year ago).
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