If you bring in empty cartridges and have a rewards card - they will scan it and enter how many you have turned in. You will then get a staples check in the mail periodically equalling $3.00 per cartridge you returned. It is a great way to recycle and earn some money. You do have to use the money at Staples (but who couldn't do that!)
You are allowed to return 10 cartidges a month, but the salesclerk told me that you need to keep track of how many you brought in. If you bring in more than 10 in 1 month, you won't get the $3 for the extra.
They take all ink cartridges now, and they recently changed the policy so you can turn in all 10 at one time. You can check online to keep track of how much you have too, you sign in using your teacher rewards card.