I suppose I think about the waste of disposable cups a lot, at least compared to the average person. My office at work has the upstairs water cooler in it, and some people come by to drink water and use the clear plastic cups once, then toss the cup. Personally, I hate that. It’s just completely wasteful.
I use one of a couple of insulated plastic mugs or a plastic pint glass to drink water out of, plus I have a tea mug that I use for hot drinks. I really have become British, in the sense that when it’s chilly or cold a hot drink really does the trick for me!
Anyway, this scientist did an interesting study comparing the various ecological effects of using disposable or reusable cups for drinking, taking into effect not only the manufacture of the cup but the washing of the reusable cups, which I had never considered. Making the soap and supplying the heat (electric or gas), etc., take energy, just as making the cups in the first place.