A chain of custody model in which the generation, assignment, and transfer of sustainability credentials is not linked to the physical flow of materials in a supply chain.

• Under credit trading systems, producers may generate sustainability credentials by producing materials in accordance with specified sustainability criteria, while buyers may purchase such credentials for a specified volume of the same product from any origin.
• Credit trading differs from other chain of custody models in that it does not include physical traceability of materials and thus the end product with which the sustainability credentials are associated does not necessarily contain any physical volume that was produced in accordance with the corresponding sustainability criteria.