sustainability

This or That?

Paper Towels vs Air Dryers

June 10, 2014
by Jared KirschnerIsabeau LalondeSydney Bee

Context

Technological advancements are seen in the smallest of everyday activities, and public bathrooms are no exception. While newer spaces have gone paperless with space-age hand-dryers, often we’re given the choice between using them or going for age-old paper towels. While many bathroom patrons have a clear use preference between the two, we wondered how the comparison holds up from a sustainability perspective. We compared paper towels and air dryers to see which hand-drying method is greener.

How We Measured It

Our metric for comparison is the carbon dioxide equivalent (CO2 eq.)emissions resulting from drying one set of hands. The full lifecycle is considered: materials, manufacturing, transportation, use, and end-of-life.

Although people tend to see the waste produced by paper towels as the problem, the majority of the impact actually comes from production (materials and manufacturing). The materials phase consists of creating the paper pulp used to make paper products—paper towels in this case. This requires extracting fibers from sources such as wood and recycled paper, which actually takes a fair amount of energy to do. In the manufacturing phase, that paper pulp passes through rollers and dryers to remove water from the pulp and achieve the desired thickness. Drying, in particular, uses a lot of energy.

So far, we haven’t discussed the impact from forestry, the source of wood for paper pulp. That’s because life cycle assessments commonly exclude sources of CO2 emissions, like forests/wood, because they can emit no more CO2 than they have taken from the atmosphere and stored in their bodies while living. This doesn’t affect the results for 100% recycled paper towels, however, as the input to the manufacturing stage is waste paper, not wood.dryerchart-01

For air dryers, the majority of the impact comes during use—the energy required to heat and move air. Newer air dryers (like the space-age Dyson Airblade™ or Excel XLERATOR® models) have greatly reduced impact by operating more efficiently in use—lower temperatures require less energy for heating, and higher air speeds reduce the amount of time the dryer needs to run. While paper towels beat older, standard air dryers, newer air dryers are the clear winner.

What about manufacturing that clunky machine? It’s true that manufacturing an air dryer requires a lot of resources; manufacturing an air dryer has the same impact as the full life cycle of 15,000 to 37,000 paper towels. But considering a dryer may get 350,000 uses in its 5-10 year lifetime (context: about once every 5 minutes for 8 hours a day), the manufacturing impact associated with drying one set of hands gets smaller the more the dryer is used. As a newer air dryer is often used hundreds of thousands of times, its impact is considerably lower than that of paper towels. For owners and operators of busy bathrooms, air dryers also have added benefits—they require less maintenance (emptying paper towels from the trash) and have a lower lifetime cost.

But what about the hand-drying experience? For the average bathroom visitor, it’s about getting in and out as fast and as clean as possible. In terms of convenience, paper towels get gold stars for being significantly faster at drying hands and (generally) much more effective at removing bacteria.dryerchart-02

Luckily, new design solutions are improving the wet hands experience while also creating good green karma. No-door bathrooms, as in most airports, solve for those who use extra paper towels to avoid touching bathroom door handles. They also mean speedier, more hygienic trips to the loo for everyone. Keep in mind, though, that newer air dryers are pushing drying times below 10 seconds and getting better at removing bacteria.

impact-dryer-01

Impact

Still prefer paper? Newer paper-towel dispensing systems that (try to) modify behavior by encouraging the use of fewer paper towels are targeting the paper towel fans out there. Consider that the results discussed above assume the use of two paper towels per set of hands to dry. By using just one paper towel, the impact is cut in half! Sounds hard to do? Just try the “shake and fold” method…

Implications

Behavior change is hard, especially for age-old experiences like hand washing, but adding consumer-facing benefits like speed and hygiene can make greener designs work for everyone involved.

Sources

http://msl.mit.edu/publications/HandDryingLCA-Report.pdf

http://www.wmich.edu/sites/default/files/attachments/u159/2014/Hand%20Dryers%20Fall%202013.pdf

http://www.gaspaperdryer.org/Learn%20About/Paper_Manufacture.htm

filed in: sustainability

About the Author

  • Kirshner Jared
    Jared Kirschner
    Electrical Engineer

    Jared orchestrates electrons via software and circuitry to enable carefully considered user experiences defined in collaboration with design, strategy, and engineering colleagues.
    With a diverse set of competencies in software and electrical engineering, Jared applies the appropriate technology to the task at hand—whether developing firmware for a regulated medical device, prototyping an experience to inform the design process, building out the full stack for a web/mobile experience, or analyzing data and building quantitative models to understand and optimize engineering systems.
    Jared earned a B.Sc. in electrical and computer engineering with a concentration in sustainability from Olin College of Engineering.