Office coffee grounds... what can I discretely do with them?

I have recently got a coffee machine in my classroom. I make a pot of filter coffee each morning, which lasts me the day. I'm getting one filters worth of sterilised, damp coffee grounds each day. They have been going in the normal bin here at work, but I'm thinking if i could set up a system for turning them into mushrooms in my teaching space.

Criteria

It needs to be discrete. A bin with a tight fitting lid. It needs to look like a bin, not a science project.
It needs to cope with the bin being opened daily and more coffee being added. This breaks the usual requirement for the media to stay sterile. I'm thinking I need something aggressive (oysters?).

Probably I would take a full bin home about once per month, by car - rather than let it fruit in my classroom. After all, I'm unlikely to want to cook with them while I'm teaching.

Any thoughts from the more experienced mushroom folks on here?