Renewable energy (RE) registries are centralized systems that track and manage Renewable Energy Certificates (RECs) that provide a proof that the claimed RE activity has occurred. In this work, we study the Western Renewable Energy Generation Information System (WREGIS), a widely used web-based tracking system in the western United States and Canada, and motivate the need for decentralization. We then propose a blockchain-based system for green credit management for WREGIS that uses a combination of private and public blockchains to remove the intermediaries, to allow small producers to directly receive green credit tokens for their energy production and be able to participate in the renewable energy market. The system allows verification of users’ claims and issuance of tokens using smart contracts on a private and public blockchains, respectively. We show the correctness and security of the token generation process, and that the system provides a high level of privacy for energy producers. We give descriptions of smart contracts in the two chains and details of our proof-of-concept implementation of the system, and evaluate transaction costs and efficiency of the system. Our work serves as an approach to the tokenization of other green credit systems.