Methods are provide for dispensing a product to a user, the product releasably incorporated within a carrier. In one embodiment, the method comprises the step of providing a first user comprising at least one storage vessel for receiving and storing fresh and at least one vessel for receiving and storing spent. The method further includes the steps of: collecting spent from a storage vessel of the first user; detecting a chemical or physical property of the collected spent; and comparing the detected chemical or physical property of the collected spent with a predetermined criteria. In a second embodiment, the method comprises the step of providing the first user, and further includes the steps of: determining an estimated amount of product to be transferred to the first user; optionally, collecting and validating information concerning the purchaser; transferring fresh to the storage vessel of the first user; collecting measurement data concerning fresh transferred from the first user; removing spent from a storage vessel of the first user; collecting measurement data concerning spent collected from the first user; optionally, calculating the net amount of product transferred; and determining whether the transfer of fresh and removal of spent has been performed on a substantially equal exchange basis. In a third embodiment, the method comprises providing a first user and a seller, the seller transferring fresh to the first user, collecting measurement data, and assigning a monetary price to be charged to the user.