Hey Mr. Green,

Public restrooms often offer two choices: paper towels or blow-drying machines. Which is better for the environment? 

—Brenda in Washington, D.C.

With so many kinds of dryers on the market — RestroomDirect purveys 80-plus models from nine manufacturers — it’s even more complicated than the old paper-or-plastic query (answer: neither, but reusable plastic if you must).

MIT’s recent cradle-to-grave comparison of drying methods gives paper towels a slightly better grade than dryers, except for the super-­efficient Xlerator and Dyson Airblade, which have the lowest impact of all methods by far. (You put your hands in the Dyson, while the Xlerator blasts air out of a nozzle.)

Paper towels are less harmful than electric dryers overall, especially in terms of preventing CO2 emissions. Paper also uses less water than dryers, because so much H2O is needed to generate electricity for their heating elements.

Recycled paper beats virgin paper, of course — but another option, the old-fashioned cloth roll, handily beats most paper and dryers.

But it may be best to simply wash your hands of the whole matter — many people wipe their paws on pants and skirts after getting impatient with dryers anyhow. And here's an idea: Why not carry your own little towel in your pocket or purse instead of firing up dryers or yanking out paper?

And while every bit helps, do keep the debate in perspective: Drive your 25-mile-per-­gallon car to and from a restaurant just a mile away, and you’ll burn through at least 100 times more energy than you will in one session with a dryer or a paper towel in its john.