A study into the energy life-cycle of reusable vs. disposable cups is interesting. The findings are that disposable cups aren’t as bad as we expect mainly down to the high cost of washing a reusable cup.
One thing I’d like to know, and which I assume would help the reusable cup arguement, is the energy involved in transporting disposable cups. Both transporation to the place of use and then transporation to the rubbish dump. Or would the cost of transporting the heavier (and less space efficient) reusable cups make up for the unit cost of disposable cup transportation?
There are other environmental issues to think about too, beyond just energy use. Disposable cups get into the wild environment and can be litter and be dangerous to animals.