Increasingly, green advertising has become much more important among manufacturers and retail businesses. It seems many consumers would prefer given many options to select a product that is less stressful on the environment than another equally functional product. While the degree to which this is influencing each person today varies widely, it is clear that these companies are responding to a real pressure they feel in the marketplace. The current result has been an almost obligatory series of advertisements and public claims regarding a product's green-ness. However, as some of these claims may be contradictory, how can one know how to make the best choice? We'll examine one case in this article. After a quick trip into a public restroom to wash your hands, you are likely to find something near the exit with which to dry your hands. What is it? Commonly paper towels or an air dryer or sometimes both (or occaisionally cloth towels) are present for your benefit. On the face of an air dryer you can often find this statement: "Uses Less Energy Than Paper Towels." We are going to systematically address that claim.
First, paper towles require something to hold them, usually a steel or plastic box of some sort. The paper towels themselves are stored inside either folded together or on a large roll. We'll assume either two kilograms (kg) of steel or one kilogram of plastic is required. At 38 Mega-Joules (MJ)/kg for steel and 90 MJ/kg for plastic, the embodied energy content of the paper towel holder is approximately 80 MJ.
Then the paper towels themselves at 3.8 g per towel have an energy content in the case of virgin paper of 25 MJ/kg or recycled paper of 16 MJ/kg. Assuming 50% recycled content for our paper towels, we can anticipate an energy content of 0.0779 MJ per person using the towels.
The air dryer, on the other hand has a total manufactured mass of about 8.2 kg, which is divided between steel, copper (100 MJ/jg), brass, other alloys, and some plastic probably leaving us with an average energy content of approximately 60 MJ/kg. So, our dryer's energy content as installed is about 492 MJ.
The dryer when activated consumes power at the rate of 2300 Watts (W) for a period of 30 seconds. Therefore, for each person using the dryer, the dryer is consuming energy at the rate of 0.069 MJ per person. [ad name="Adsense Small Horz Banner"] So, now, for the paper towel option we have a intial usage of 80 MJ plus an ongoing energy cost of 0.078 MJ per person. Then, for the air dryer, we have an initial energy usage of 492 MJ, followed by an ongoing cost of 0.069 MJ per person. So, we have a situation where there exists a breakeven point in terms of the volume of usage, small traffic volumes will be more efficient using the paper towels, while large traffic volumes will be more efficient using the air dryer.
The breakeven point can be calculated by taking the difference of the two initial values, 412 MJ, and the difference of the two per person energy costs, 0.009 MJ/person, and dividing the former by the later. So, in the end, any location that expects to see more than 45,777 individual visits per dryer over the life of the dryer would be better off in terms of energy usage choosing the air dryer over the use of paper towels.