Interesting result here:

Dutch study (pdf in english) on the life cycle impacts of reusable vs disposable cups for coffee service found that hand-washed ceramic coffee cups are the most impactful way of consuming coffee, machine-washed porcelain coffee cups are the second-most impactful, and disposable single-use paper cups are the least impactful, with the notable exception of very high ozone depletion potential due to chemicals used in paper cup production. Polystyrene was middle-of-the-road.  But read on…

Looking closer, the assumptions of the study are a little eye-opening. In particular, the study assumes the reusable cups are washed after every use, and that hand-washing uses an always-on under-sink electrical water heater.  In this case, the environmental effects of the ceramic-mug system are “virtually entirely the result of using electricity” (46).  Electricity is also the culprit in dishwasher-cleaned porcelain mugs, although dishwashers are more energy efficient than standby electric water heaters.  Finally, the non-electricity-caused environmental impacts of the reusable systems come from eutrophication from detergents; non-phosphate detergents would mitigate this effect.

Most of these issues are considered in the sensitivity analysis (they didn’t talk about phosphate-free detergents).  All you coffee drinkers should be relieved to know that simply by washing your mug with cold water (which the study calls “hygienically questionable”), ceramic-mug drops to rock-bottom in terms of impact.  Even under their high-impact assumptions, washing with hot water is ok as long as you only wash after 4.5 or more uses.

The moral is that before you sneer at people drinking from disposable coffee cups (as I often do), you must first ask yourself, “are these the type of people who leave the hot water running when they do dishes and/or use a fresh cup every morning?”  If they are, maybe you should thank them for using disposables instead.

Now, back to work…