Energy Web, a non-profit organization, has launched a free sustainability registry for bitcoin miners called Green Proofs of Bitcoin (GP4BTC). The registry will score miners on two metrics that take into account the mix of energy they use: their purchases of renewable energy credits (RECs) and their participation in demand response programs.

The project aims to act as a "certification layer" that can be referenced by different organizations based on what the miner wants to share. The registry is currently free, but Energy Web may introduce a fee for miners looking to get certified or for users looking to access the data in the future.