Washington, D.C.—The hype around blockchains—the programming protocol originally created for the Bitcoin—is bidirectional, ranging from apocalyptic predictions of bitcoin energy use that will “destroy our clean energy future” to rosy scenarios that “blockchain technology can usher in a halcyon age of prosperity for all.” Given this lack of clarity, how do we ensure that the environment profits in the end? Fortunately, a new “inventory of blockchains” will help policymakers head toward the right direction.