I'm sure you are aware that here in the US we have these recycling programs for cans and bottles and when we first purchase these drinks at the grocery store, we are charged a small fee up front, and upon our turning these collected cans and bottles in to a recycling center, we gain back the money we were charged at the store in the first place. Is this money subject to khums?

When you receive the money from the recycling center if that money is excess when your khums date arrives then you will need to pay khums on that amount.