Welcome to the first installment of "AskPablo" where you get to ask me your burning sustainability questions like "paper or plastic?" and "driving with the window open or A/C?" I look forward to reading your e-mails and helping you understand the science behind sustainable decision-making. We engineers tend to use a language of our own so I will do my best to translate it to English.
This week's question comes to us from TriplePundit creator, Nick Aster: "What's better for my daily coffee in the context of as many different environmental and social impacts you can think of? - an aluminum mug, a ceramic mug, or a new paper cup every day?" To make things a bit more interesting I am going to take some artistic license and change the question to encompass a Stainless Steel Mug, a Ceramic Mug, and a Styrofoam Cup. Since we are such a caffeine fueled society I have chosen to compare each of these at a 16 oz. size.
Stainless Steel (SS) is a ferrous alloy (a combination of two or more elements that includes iron). It contains at least 10% Chromium, which gives it anti-corrosive properties (English: it won't rust). Each gram of SS is responsible for the use,displacement, or consumption of 14.4g of abiotic material (mineral substances including ore and fossil fuels), 205g of water, and is responsible for the release of 2.8g of greenhouse gasses (GHGs).
Ceramic is an " inorganic non-metallic materials whose formation is due to the action of heat" (hooray Wikipedia!). Basically it is a clay that requires kiln firing to remove moisture... Since it is made by heating up some dirt it's impact is relatively minimal. To create one gram of ceramic we inconvenience 2.11g of abiotic material (mostly the clay and some natural gas), 5.3g of water, and we create a mere 0.065g of GHGs.
Our final material for this analysis is polystyrene ("many styrenes", linked in a long chain), also known by the brand name Styrofoam. Polystyrene (PS) is a thermoplastic (meaning that it can be melted repeatedly, as opposed to a thermoset plastic like epoxy which can not be melted), making it recyclable. Unfortunately it is not recycled in many states, including California. The reason for this can be found in simple economics. Since expanded polystyrene (foam, as opposed to the PS that is found in many clear drinking cups, especially on many airlines) takes up a lot of space, relative to its low weight, it can not be economically transported over long distances to the nearest recycling plant that is capable of processing it. Pre-processing it locally before shipment requires expensive equipment which is not justified by the low value of the recycled material (since it's just so cheap to make it from scratch). So, to our dismay, most of it ends up in landfills (to be extracted by future generations, right?). To create 1 gram of PS requires the use of 2.51g of abiotic material (mostly the oil from which it is made), 164g of water, and is responsible for the release of 2.8g of GHGs.
Since the PS cup is considered disposable and the other two are intended for daily reuse we are comparing apples to oranges, right? Well, not if we compare them per "service unit." In this case our service unit is " the service of holding the caffeinated morning beverage of our choice while we drag ourselves to work." We have analyzed the materials, now we need to determine the material intensity per unit.
In my research I found the weights of each of the following 16 oz. beverage containers:
Polystyrene - 6g
Ceramic - 322g
Stainless Steel - 378g
Now, by multiplying the material intensity values that we found earlier by each container's weight, we can find their total material intensity. For each 16 oz. container we use the following amount of abiotic material:
Polystyrene - 14.8g
Ceramic - 679.4g
Stainless Steel - 5454.5g
Based on this result alone, you would have to use your mug at least 46 times (daily for a month and a half) and you would have to use your SS mug at least 369 times (daily for a year) to justify its higher material intensity. The results for water are a little more difficult to grasp since water is a renewable resource that continues through its natural cycles after we use it (PS - 966g, Ceramic - 1,706g, SS - 77,528g). For the highly-processed SS, we need 164 times as much water as the mug holds ( 77.5 liters)!
The results in the GHG category are also quite striking. Keep in mind that, based on UN figures on the cost of climate change and the annual global CO2 emissions, each ton of GHGs is responsible for $8 in damages. (PS - 16.5, Ceramic - 20.9, SS - 1068g) Again, the Stainless Steel has the greatest material intensity with over 1kg of GHGs, or roughly $0.01 in climate change-related damages.
This essentially concludes my analysis. In summary, a ceramic mug has the lowest material intensity of the three as long as you use it at least 46 times. Since most ceramic mugs enjoy long and happy lives in our kitchens this is quite feasible. But please remember that purchasing tacky or holiday-themed mugs that will recieve limited use actually have a higher environmental impact than styrofoam cups do! So, if you don't already have a reusable beverage container go out and get yourself something timeless and use it often.
I hope that I have helped you understand a little bit of the science behind sustainable decision-making. I welcome you comments and please keep the questions coming. See you next week!
Hey Pablo - check out the analysis here on TreeHugger. It's a little different from yours. What do you think?
The linked article seems kind of sketchy, mostly a teaser for yet another link. But the comments there do delve into some other aspects of the bigger system.
Seems like the consensus is for ceramic mugs, which makes intuitive sense to me.
Aren't there a few more things to consider in this analysis? Some things that came to mind for me were that PS is over 95% air (no other product is like this), environmental impact of pulling a bunch of clay out of the ground or metal from the earth, etc...let us know what other factors can be put into the equation. Thanks pablo
Yes, Expanded PS is mostly air but my analysis is based on weight, not volume, therefore the air is irrelevant. You will see in my analysis that the PS cup is much lighter than the alternatives, but since it is intended for single-use we reach a point when the reusable alternatives make more sense.
pablo, this is a fantastic article . with your permission I would like to repost this article on my blog, of course giving you credit for the article and a link back to your blog for readers to respond to you directly. My beanblog devotes itself to sustainablity and the coffee community. You can uderstand why this article would be a great addition.
You're missing out on the use of the cups: (hot) water and detergent for washing the reusable mugs. Since this happens practically on a per-use basis, it actually kind of builds up, especially since detergents are pretty energy-intensive. This is getting into behavioral stuff that's hard the quantify, and I don't think it changes your conclusions. On the other hand, it's not fair to disposable cups to cut out their advantage.
Allan, you make a great point about the variable impact of washing the reusable mugs. Like I said in the article, the use of water is a foggy subject. In areas with abundant water the impact may be negligible, in dry regions it may be critical. What is almost always the case is that we have to heat the water and we have to use soap. Water heaters typically use natural gas but the small amount of warm water that is used per cup probably produces a negligible amount of GHGs. The soap on the other hand carries its own material intensity and post-use issues. However, the material intensity analysis tool that I use (MIPS) does not have published material intensity (MI) factors for soap. While I have derived far more complicated MI factors I wasn't about to spend the rest of my Sunday night on soap. So, you got me... But luckily intellectual laziness is not a crime.
Soap? My coffee mug has never seen the stuff. A quick swish through the faucet and hang it back up! Now I'm feeling rather dirty.
Hey Pablo - well done! I'd still like to see an analysis of the daily paper - since that seems to be by far the most common form of coffe cup around. What's the impact of the (largely post consumer recycled) jackets that go on the paper cups? And what if they all came from some highly regarded sustainable tree farm source, or heck, hemp? The complexities go on and on... I wonder if we could ultimately derive an "ideal".
So, you got me...
I have to confess, I did a term project that was an LCA of two coffee delivery systems, so, I had a head start. ;)
And, like I said, I don't think it'll change any conclusions. By far, the most interesting thing is how energy intensive detergents seem to be (I'm speculating; I've only seen a report based on Proctor and Gamble ... laundry detergents, I think).
But I did want to bring up the point of looking at all phases of the two systems. With that in mind, a person could also compare solid waste production and recyclability of the various materials.
I wonder if we could ultimately derive an "ideal".
Again, this is almost a silly given the example, but I think part of sustainability has got to reject the idea of a generic ideal. Ideal has got to meet local conditions, as in Pablo's point about local water resources. I'm hard pressed to say how that'll impact mug choice (especially given what goes in it and how far that has to travel -- why aren't there any caffeine-bearing plants indigenous to the US?), but I feel it's an important point.
Don't you see? Simple IS beautiful? Make your coffee at home! YOU ARE the most efficient, cheapest and sustainable producer there is: ! $0.50 to make your coffee instead of...what again, $2, $3, $4...give it to charity instead; use your ceramic cup...a delight to drink in...or your mug if you need to travel...this is it...no more Starbucks chain...I was in the financial district of San Francisco the other day when I saw, at one glance, 3 outlets with my own eyes, without moving...how do you like that? Scary! Hey, and about washing, I am with Darien, a quick cold water wash with Your Hand - the new IN tool- and you are done!
Love the "Ask Pablo" concept...going to be pretty popular if you ask me, watch out Pablo! :-) M
Alright, alright... By popular demand I am now adding an analysis of a paper cup.
Let's assume that a 16 oz. paper cup from Starbucks (Why do they call the small one Grande?) weighs 15g. The MI per gram is as follows: 9.17g of abiotic material (fossil fuels, bleach, etc.), 2.56g of biotic material (the tree, of which 1.56g is wasted), 303g of water (check out the foaming rivers downstream of paper mills in Maine...), and 1.275g GHGs. Multiply the weight of the cup by the MI and you get: 137.6g of abiotic material, 38.4g of tree, 4,545g of water (that's 4.5 liters!), and 19.1g of GHGs.
So, you would have to use your ceramic mug just five times to have less abiotic input than the paper cup, despite the fact that the cup is 1/20th the weight. The GHGs are comparable and the water required is roughly 2.5 times as much for one paper cup.
Of course, if we look at the economics, Maryline is absolutely correct. If you make your coffee at home you will most likely recover the cost of your ceramic mug in one serving. And who really needs a venti, non-fat half-caff. mocha soy pumpkin frappacino with three espresso shots and two Splendas (hold the whipped cream)?
A 1994 University of Victoria study covered the disposable vs reusable cup question when it came to resources used in both creation as well as taking account displosal and cleaning...
See this source for a summary:
http://www.ilea.org/lcas/hocking1994.html
"This classic life-cycle energy analysis...compared three types of reusable drinking cups (ceramic, glass and reusable plastic) to two types of disposable cups (paper and polystyrene foam)."
Thank you for sharing this! There seem to be many ways to do this analysis, yet the results are never the same. This study uses the embodied energy while my study focuses on the embodied materials of four types (abiotic, biotic, water, and GHGs). Very interesting, thank you.
Pablo, would you be willing to assess the embodied energy differential between a Segway HT and a Megway TH? I saw a used Megway on Craigslist last week, and I wonder if a Transporting Human might be a more susty choice for my daily trip to Starbucks? Thanks!
Osborne, I would love to do an analysis of the Segway and the Megway but it would be far too complex and costly. I would require one unit of each to completely disassemble so that I can identify the composition and weight of each component. The most complex analysis that I have done on an electronic device is a DEL Ozone Spa Ozone Generator (compared to chlorine) and it contained over 100 unique parts. The only reason I was able to do that analysis was because I worked at DEL at the time. If you have contacts at both companies and they would be willing to donate one unit each and pay for my time I'll certainly do it. Until then I suggest riding a bike.
That actually brings up a neat myth that I have heard: "it takes more fossil fuels to produce the beef calories that you might burn to pedal a bike (assuming you eat beef) than it would take to power a car over the same distance." Is this just pro-vegan rhetoric, or is there something to it? If there is enough interest I just might take on the challenge of mythbusting this one.
Pablo - I suggest you google "Megway TH"
Ok, by bad... While everyone is out laughing at the latest online phenomenon I am usually hanging out at sites like www.eiolca.net and satisfying the engineer within. This is not to say that I haven't had the great displeasure of meeting meatspin (do NOT google it! I warned you.) or laughing at the silly antics of kitler (www.catsthatlooklikehitler.com) but for some reason Megway has completely escaped me, until now. So I guess I need to take back my previous statement about needing to take apart a Megway... It is now abundantly clear to me that a Segway is much more sustainable since it only requires electricity from coal-fired powerplants. Megway probably requires corn-fed beef, ding-dongs, and ho-hos, which we all now is much more damaging to the planet (and your body). But don't despair and resort to suicide to save the planet, just develop a gene that makes cows allergic to corn and the world will be saved... or will it? We'll save that for a later debate. In the meantime I will enjoy a nice grass-fed steak.
Hey, the beef powered bike vs. car scenario sounds like good fun. Please have at it. Sorry if the megway reference was misleading. It was a popular laugh for a short time back in 2002... something that Todd Fahrner turned me on to, before he left for the world of electric assist bicycles. I mention him because the comparison of a beef powered stokemonkeyed Xtracycle is probably more of a useful investigation than simply a bike. Regular bikes don't deliver the same service as a car. A stokemonkeyed Xtra comes a little closer anyhow.
Pablo,
I have been told that it is bad for my health to drink coffee from a ceramic mug that has crack lines on its inside. Have you heard of this before? Is there any validity to it?
John,
I have not heard of this but I would speculate that the cracks provide a place for bacteria to hide and multiply. I tried to find an answer for you online but am not finding anything. Perhaps one of our readers knows the answer...
Pablo
The health hazards of cracks in the coffee mug arise from the possibility of the cup breaking when you pour in hot water or coffee. watch out!
Wonderful string here. A couple thoughts:
Why does everyone talk about the energy/water cost of washing a ceramic mug but no one mentions the cost to collect, transport, and dump the disposables, including monitoring the landfill for toxic run-off (not due to the cups, but the more volume of waste = more landfills = more engineered liners and monitoring energy for years to come)! Of course, if the PS goes to an incinerator, it would reduce fuel demands for maintaining the temperature in the burning chamber since it burns well.
Cracks in mugs: I believe I heard somewhere that as natural materials, clays can contain heavy metals in low amounts which rely on the glazing to seal them against leaching by the hot liquids. Of course, the source and regulatory controls on the clays used in food contact items will vary based on the country of manufacture.
Polystyrene: funny how everyone loves the paper cups when it is clear the polystyrene wins in every analysis linked here in the disposable category. And it doesn't burn your hand. The ultimate proof that risk analysis cannot be a democratic value. We need a benevolent risctator!
This was great! I never new that the ps. ones where better for the environment than the paper ones.
Thanks Pablo.
This is truly a great dialogue.
One thing I haven't seen discussed re: environmental impacts of polystyrene cups are the impacts on the marine environment.
Not sure how one would quantify this, but petroleum-based trash (plastic products) in the ocean cause devastating damage to marine ecosystems...plastic/polystyrene trash never fully biodegrades, but rather breaks down into tiny particles that birds/fish/other creatures ingest, mistaking them for food.
petroleum-based particles act as sponges for ddt, pcb, other persistant pollutants in the ocean....which work their way up the food chain (small fish ingest particles, get eaten by larger fish, eventually we eat these fish) and eventually may have nasty effects on us humans....
not sure if this is possible/relevant to discussion, BUT tons of polystyrene cups make their way to the ocean via litter/human negligence, so seems to me this is another cost.
more about all of this at www.algalita.com
hope to see this discussion continue, awesome!
Well, that's 10 minutes I'll never get back....but well worth it! I'm gonna lose sleep over what to "Ask Pablo" now!
ciao from new orleans
Pablo,
What about heating my tea in the morning? Propane gas or microwave? My wife insists there are harmful effects to humans from using a microwave on anything so when heats our tea water it’s with propane. I respect her as a person and do not force her to believe what I believe. When I make tea just for me I use the microwave. Which is more energy efficient?
Thank you for your time.
Anonymous,
Please see my article on Microwave Efficiency at http://www.triplepundit.com/pages/askpablo-microwave-efficiency-002381.php
Microwave ovens excite water molecules, thereby heating them up. There is no molecular change to the water. The only issue that I see is the cup that you use. Ceramic and glass are fine but certain plastics may leach a minuscule amount of bad stuff into the water.
Pablo
What about the environmental cost associated with the rubbish collection and dumping?
One issue missing in the list of attributes of styrofoam is that the cancer-causing styrenes leach out of the styrofoam -- especially when the contents are hot. So drinking a hot beverage from a styrofoam cup does have detrimental health consequences.
What about paper cups? My coffee cup this morning is paper, not polystyrene. I wanted to find out what the waxy/plastic-y stuff inside it was made out of.
Great article, people have been asking me if I knew the difference environmentally in manufacture and use of different types of drinking containers. Thanks for doing this research. (If anyone is looking for really cool handmade coffee mugs, which will easily last more than 46 uses, check out my website, mugrevolution.com.) Thanks!
Peblo, This discussion is great but I need a more formal "White Paper" with references in order to convince my church to switch from paper to ceramic. Do you know of anything that would encompass much of the discussion on this site?
Hi Pablo,
I'm surious how a Glass mug would compare
to ceramic and stainless. I'm sure glass
would have a greater material intensity than ceramic but would it be less than Stainless steel?
Hi,
I'm curious how the environmental impact of the mining techniques used to obtain the base materials used in production of ceramic and stainless steel mugs are factored into your analysis?
Scott,
The emissions factor for stainless steel was 2.825 g/g, for ceramic was 0.063, and for glass it is .716. So the GHG impact of a glass mug is about 1/4 as much (by weight) as the stainless steel mug.
Thanks Pablo!
How does for the plastic/PVC/rubber trim, lids and cushion base on stainless mugs factor in to the analysis? Also Chromium content % for various grades of stainless?
Scott, The plastic components of the stainless steel meet the de minimus exclusion criteria. This means that, while they are not zero, they are negligible in the big picture. This is because stainless steel requires such a massive amount of energy to extract, and process. My results assumed 18%Cr/9%Ni Stainless Steel and includes all metals in the alloy.
Hi Pablo,
Our nature center is gifting its voluteers a mug with logo for the holidays. Did I miss it? Which is better: a glass mug or 100% corn plastic mug?
Hi Pablo,
Which is better: a glass mug or 100% corn plastic mug?
I'm completing a reusable mug analysis for a possible on-campus implementation program at my college. I am wondering the same about the 100% corn plastic mug and its markings versus all the others?
Dear Pablo,
Hello! I was wondering whether you could point me to the source. It's great information and all, but I'd like to know where you got this information. I'm actually doing research on a similar topic, and sources would be very helpful!
Thank you!
Best Regards,
Anna
Hi,
I started out looking for information about the toxicity of plastic liquid containers for all kinds of items i.e coffee, tea, my protein shake, soup etc. Can any one shed light on this issue???
hey its very good stuff, but could i please have the source? mainly for the calculation son environmental impacts created by the material and creating the products.thnaks
hey its very good stuff, but could i please have the source? mainly for the calculation son environmental impacts created by the material and creating the products.thanks
I am wondering about the corn plastic mugs as well
What about the trash? I am debating using ceramic cups for our church's weekly coffee hour instead of paper ones. While reusing ceramic cups may not save much (or perhaps may increase) on energy consumption, what about the trash produced by throwing away cups every week.
Hi Pablo,
Your article and the discussion here as well as at Treehugger are enlightening, particularly as I am part of a team trying to green our workplace. Our cafetaria is open to the public - so it will be a challenge to introduce ceramic cups. Even staff who come for a coffee do not remember to bring their mugs down. Banning paper cups won't work. Any other smart solutions?
Secondly, the cafeteria uses plastic forks, spoons, stirrers, sugar and salt sachets, plastic boxes for salad bar, foil trays for warm food, recyclable paper trays, transparent plastic glasses for drinking water. I am not sure what part of these items are recycable in New York or can be replaced with an economical and eco-friendly product.
Thirdly, and this is a behaviour observation. We have open recycle bins with large mouths. So even though one is garbage and the other for recycling, some people in a hurry and some who just dont notice/care just put food trash in either one without looking carefully. Again, any ideas? Keep in mind: the staff cafetaria cannot be too expensive as it helps with reducing staff stress, improves relations, etc... sorry for long post...
Hi Pablo,
Your article and the discussion here as well as at Treehugger are enlightening, particularly as I am part of a team trying to green our workplace. Our cafetaria is open to the public - so it will be a challenge to introduce ceramic cups. Even staff who come for a coffee do not remember to bring their mugs down. Banning paper cups won't work. Any other smart solutions?
Secondly, the cafeteria uses plastic forks, spoons, stirrers, sugar and salt sachets, plastic boxes for salad bar, foil trays for warm food, recyclable paper trays, transparent plastic glasses for drinking water. I am not sure what part of these items are recycable in New York or can be replaced with an economical and eco-friendly product.
Thirdly, and this is a behaviour observation. We have open recycle bins with large mouths. So even though one is garbage and the other for recycling, some people in a hurry and some who just dont notice/care just put food trash in either one without looking carefully. Again, any ideas? Keep in mind: the staff cafetaria cannot be too expensive as it helps with reducing staff stress, improves relations, etc... sorry for long post...
A burning question...
WHY is a coffee mug called a "MUG"? Some students wish to know.
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at May 6, 2008 5:37 AMI am not seeing the fact that styrofoam cups (and food trays, packing, etc for that matter) go into trash/landfills/ground after one use as a general rule and also what about the chemical components that I have heard are environmentally damaging found in styrofoam? Thanks, Quentin, PurePatrol
I am in a similar 'Green Team' like rema (see post above dated 2008-03-06 17:57). Any suggestions, Pablo? Thanks!
Hi Pablo,
Can you provide references for the GHG emissions per unit mass of ceramic, PS, and SS. The numbers seem odd, especially coincidental that PS and SS are exactly the same and 43 times more than ceramic?
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