What can we do at the circulation desk that will help to save the environment?

We have a café here at the library- and it's a rather unique situation. We essentially run the café, but receive not monetary gain from it, as it all goes to a larger corporation. This corporation supplies us with the food and supplies needed to run it, but we staff it.

The corporation provides us with Styrofoam cups- we wonder how easy it would be to convince them to allow us a bring-your-own-cup for a discount service. Or, we could charge them for a small not matter what size of cup they bring, if they bring their own. Is this ethical? Thoughts?

Some of our ideas are reflected in our proposal.