  Blockchain, pivotal in shaping the metaverse and Web3, often draws criticism
for high energy consumption and carbon emission. The rise of
sustainability-focused blockchains, especially when intersecting with
innovative wireless technologies, revises this predicament. To understand
blockchain's role in sustainability, we propose a three-layers structure
encapsulating four green utilities: Recording and Tracking, Wide Verification,
Value Trading, and Concept Disseminating. Nori, a decentralized voluntary
carbon offset project, serves as our case, illuminating these utilities. Our
research unveils unique insights into the on-chain carbon market participants,
affect factors of the market, value propositions of NFT-based carbon credits,
and the role of social media to spread the concept of carbon offset. We argue
that blockchain's contribution to sustainability is significant, with carbon
offsetting potentially evolving as a new standard within the blockchain sector.
