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AskPablo: Electric Hand Dryer or Paper Towel?

| Monday February 19th, 2007 | 15 Comments

cnt00125.jpg So you’re standing in a public bathroom, having just washed your hands. You look to the paper towels, you look to the electric hand dryer on the wall, which one do you choose?


Electric hand dryers use a lot of energy; the one I looked at today uses 2,300 watts! But you typically only use it for about 30 seconds. 2,300 watts ( 2.3 kW) times 30 seconds (0.0083 hours) is 0.019 kWh, or about 1/4 of a cent worth.
A typical paper towel (depending on the type) may be around 2g and probably doesn’t contain any recycled content. Most people probably use two sheets. Let’s assume that one roll can take care of 42 people, and weighs 168g. To make it a fair comparison between the two I’ll scale it up a bit, so let’s look at 100 rolls worth, or 4200 people’s hands dried.
The electric hand dryer uses 0.019 kWh per person, so that would be 80.5 kWh for 4200 sets of hands. The California grid CO2 emissions factor is 0.51 mT/MWh, so 0.0805 MWh x 0.51 mT/MWh is equal to 0.04106, or 41.1 kg.
To compare, let’s look at the CO2 emissions from the paper towel production. According to the Wuppertal Institute’s MIPS data tables, paper pulp has a greenhouse gas intensity of 1.275 kg CO2 per kg of paper (or 0.05 for 100% recycled). One hundred 168g rolls weigh 16.8 kg, so they are responsible for 21.42 kg of GHG emissions (16.8 kg x 1.275 kg/kg).
According to these results it it better to use the paper towels than the electric hand dryer, from a GHG perspective. There might be other factors to consider though. Consider that a tree has to be cut down to make the paper towels and that that tree will no longer sequester CO2. I researched for a good half hour and wasn’t able to find a great deal of hard data on sequestration so the following is based on what little data I could find (if you have better data please share it with us by commenting below). It takes 2.56 kg of tree to make 1 kg of paper so we need 43 kg of tree to make our 100 rolls. Assuming that the trees used weigh around 900 kg we need about 0.05 trees. One tree sequesters 172 kg of CO2 per year and would probably live for at least 60 more years. So 493.16 kg of CO2 are not sequestered as a result of our 100 rolls.
I would take that last result with a grain of organic sea salt, unless you have some better assumptions to plug in. Personally I would advocate my favorite, and highly sustainable, hand drying method; your pant leg.
Pablo Päster, MBA
Sustainability Engineer
www.AskPablo.org
Pablo(dot)Paster(at)gmail(dot)com
View Pablo Paster's profile on LinkedIn


▼▼▼      15 Comments     ▼▼▼

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  • http://enviroletbuzz.com Scott Smith

    I’d definitely go with the paper towel because I can also use it to turn off the tap and open the door to avoid whatever is on them…

  • Pete

    I’ve always wondered about that!! Of course there are some factors missing: Transportation costs of the paper products, downstream waste water treatment from pulp processing, etc.
    But I don’t use my pant leg – I use my pockets.

  • Anonymous

    Uh, how about wiping your hands on your pants and skipping the whole mess? Evaporation = a renewable resource.

  • http://www.ecotality.com Janis Mara

    Hahaha! I love this thread! It’s like the “paper vs. plastic” debate. It’s way cool that you brought this up. My thought: Let’s do like we do for grocery shopping and bring our own. People used to carry cloth handkerhiefs all the time, yes? Maybe it’s time to bring back the tradition! (Wiping hands on pants? Puh-LEEZE!)

  • http://www.formax-shredder.com mike

    pablo, if i was going to be in your place i will chose the hand dryer machine. so good

  • less

    Hmm, I sort of agree with Anonymous. But if I had to pick, I’d say Paper Towels. I had to do an esay on Paper towel vs. Electric hand dryer.

  • Anonymous

    Just use your hair, it make you look better throughout the day too.

    • James

      What if you have cancer or are an old bald guy. Studies show that old bald guys dont wash their hands with soap. lols that isnt a real study.

  • Anonymous

    Pablo, I think you are missing some facts. Most paper comes from trees that are replanted (i.e., farming), so each tree harvested is replaced. Similarly, natural forests generally grow at about an equal rate to their decomposition. In both cases, this is carbon neutral, unless you are clear-cutting or slash and burn forests and replacing them with other uses (e.g., urban spawl, farms instead of rainforest).
    When you harvest wood for long term use (e.g., treat the wood and build a house), it will last for many years before decomposing, so you have, by delaying decomposition, sequestered the carbon.
    That’s not to say that paper towels are great. Like any disposable, not recycled, product, they are energy intensive and wastefull, transported from afar, etc. I’m sure those factors would bring paper towels cost higher than hand driers, even w/o the wood sequestration issue. Therefore, probably, hand driers are better.
    Think of it this way: every dollar you spend has greenhouse gas emissions related to it.

  • Pat

    From the Owner’s point of view, the electric hand dryer wins because of reduced costs for janitorial staff which would negate any power savings. Also, he saves the cost of plastic bag liners in the waste cans. You also have to figure the transportation costs of the paper towels (gas, oil, tires, roads, etc, etc) of the trees to the paper plant, from the paper plant to the paper towel factory, to the warehouse, to the distributor, and finally to the user — and then the transportation cost of the dirty towels to the land fill. Eventually, the electricity may come from wind turbines or solar panels. Dyson (the vacuum cleaner guru) is now selling an “air knife” hand dryer that “blows” the water off your hands with a high pressure air stream, so a heating element is not needed – and less power is consumed.

  • http://www.GreenOfficeSecrets.com Green Office

    I just wrote a book that includes a section on this exact topic, though it doesn’t go as deep into the techie details as you do.
    The way I look at it…whether you use the drier or the paper towels, I think the most important thing is to use less of it.
    Shake your hands to rid yourself of excess water first. Then, if you’re using the drier, only hit that button once. If you’re using the towel, take only one.
    And if you’re not entirely dry by the time you’re done, deal with it. The air will dry you in moments anyway.
    Great post, Pablo.
    (Oh, and if you’d like to be interviewed as part of my green office book (http://www.GreenOfficeSecrets.com), write me. You’ve got my email address.
    -Mark Gardner
    Green Office Secrets

  • Ed Sallia

    Pablo,
    Our private school is trying to decide (as a Green School) whether it makes sense to install the electric hand dryers and your information is very helpful. It is difficult to gather all the facts and crunch the numbers with so many variables. Some facts are obvious such as the cost of paper towels, can liners for disposal, disposal costs and custodial costs. Others challenge the mind such as the costs of manufacturing and transporting towels, CO2 sequestering, tree harvesting and replacement, etc.
    I think at some point you just have to make a decision based on what lessons we want to impart to our students about stewardship of the planet and good resource management.
    Thanks for the information. It is appreciated.
    Ed Sallia
    Catlin Gabel School

  • Kady

    Dear Pablo,
    I am writing a proposal to my high school asking to remove papertowel dispensers from the restrooms. Does this make sense?
    Sincerely,
    Kady H.
    P.S. does anyone else have any suggestions??

  • Anonymous

    Another site has a bunch of maths regarding this also and comes to the opposite conclusion. I wonder how and I agree with one of your posters that in our office at least the towels are recycled and from managed sources.
    But the real thing is, as I was informed today, is that most hand driers re-circulate the air from inside the room and do not have a feed from outside. Now considering that you are in a toilet you are having floating “matter” high pressured onto your hands with a nice warming effect to activate the bacteria.
    Do you still want to use the electric hand drier >

  • Tim

    Paper production actually helps the environment. Most all of the trees currently used for production of paper are in highly monitored and cycled fields. In these fields far more trees are planted than harvested, and therefore are using up far more c02 than if we simply stopped using paper. Watch Penn and Teller’s BS on the subject.