Abstract: A vessel is assigned a unique vessel identifier (620). Before or after the vessel is filled, the vessel identifier is encoded into a machine-readable code that is printed or etched onto the vessel (630; 640). The code may have the property that it can be quickly read by a scanner from a variety of different angles and vessel orientations. When the vessel is sold to a user, the user may scan the machine-readable code (or a different code placed on a label associated with the vessel) using a smartphone (710), and the unique vessel identifier is linked to a user account associated with the user (740). Later, when the user places the empty vessel in the recycling stream, a scanner or camera placed in the recycling facility scans or captures the machine-readable code on the vessel and extracts the vessel identifier from the code (810; 820).