A Reverse vending machine is a device that accepts used (empty) beverage containers and returns money to the user (the reverse of the typical vending cycle). The machines are popular in places that have mandatory recycling laws or container deposit legislation. In some places, bottlers paid funds into a centralized pool to be dispersed to people who recycled the containers. Any excess funds were to be used for general environmental cleanup. In other places, such as Norway, the state mandated that a vendor pay for recycled bottles, but left the system in the hands of private industry.

http://en.wikipedia.org/wiki/Reverse_vending_machine