1. Push button
2. Rub hands gently under warm air
3. Wipe hands on pants
Who hasn’t seen the instructions for heated-air hand dryers in public restrooms defaced with this practical advice? These types of hand dryers seem to be universally loathed, but that’s too bad: a recently published comparative life cycle assessment (LCA) of this and other hand-drying methods revealed that modern, high-speed blow dryers are actually our most sustainable hand-drying choice in a public restroom, at least with respect to global warming potential (GWP). (1)
Where does GWP enter into hand drying? For electric blow dryers, generating the electricity required for operation is the major source of greenhouse gas emissions. For a cotton roll towel system, the energy associated with laundering the towels is a major contributor. For paper towels, the manufacturing phase has the biggest carbon footprint.
What makes this LCA study so interesting is that the authors did a thorough job of investigating how their sustainability rankings for hand-drying methods might change depending on how they are used. For example, the authors asked how the LCA results would differ if electric dryer running time varied. Longer times use more electricity, which increases GWP, and shorter times use less electricity, which lowers GWP. After looking at a range of scenarios, the researchers concluded with a high degree of confidence that high-speed blow dryers have a lower GWP impact than paper towels and cotton roll towels. They further concluded that no environmental distinction (based on GWP) can be made between paper towels; cotton roll towels; and traditional low-speed, heated-air blow dryers.
Rest assured there is no need to use your pants! It’s okay to leave your hands in the high-speed blow dryer a little bit longer.
(1) Gregory, J.R., T.M. Montalbo and R.E. Kirchain. 2013. International Journal of Life Cycle Assessment doi:10.1007/s11367-013-0606-0.
David Tyler is the Charles J. and M. Monteith Jacobs Professor of Chemistry at the University of Oregon.