On-Chain Minting
How verified MassIDs become immutable on-chain assets — from metadata creation through IPFS storage and minting on blockchain.
From verified data to on-chain assets
After a MassID passes methodology verification, it is minted — transformed from an off-chain verified record into an immutable on-chain asset. Minting creates a permanent, publicly verifiable link between the physical recycling work and its digital representation on-chain.
On-chain minting is the bridge between the dMRV verification process and the credit lifecycle that ultimately produces tradeable environmental credits.
The minting process
1. Verification complete
The MassID has passed all methodology checks. Its material type, weight, and chain of custody are validated, and all compliance conditions defined by the applicable methodology are satisfied. The MassID is marked as ready for minting.
2. Metadata creation
Structured metadata is compiled for the MassID. This metadata captures the complete provenance record:
| Field | Description |
|---|---|
| Material type | The waste material classification (e.g., clear glass, plastic, organic food waste) |
| Weight | The verified weight in kilograms |
| Chain of custody | Every participant who handled the material, identified by wallet address and role |
| Timestamps | When each event in the chain of custody occurred |
| Methodology | Which methodology rules were applied and the version used for verification |
| Verification references | Links to the verification records that confirmed material validity |
This metadata becomes the permanent, immutable description of the MassID once it is stored on-chain.
3. Decentralized storage
The compiled metadata is uploaded to IPFS (InterPlanetary File System), producing a content-addressed URI. This URI is unique to the metadata content — any change to the data would produce a different URI, making the stored record tamper-evident.
The IPFS URI is then referenced by the on-chain token, linking the lightweight blockchain record to the full metadata stored in decentralized storage.
4. On-chain minting
The MassID NFT is minted on-chain. The token is a soulbound ERC-721 NFT — non-transferable and permanently held by the Vault contract. The minting transaction records the IPFS metadata URI on-chain, creating an immutable association between the token and its provenance data.
Because MassIDs are soulbound, they cannot be traded or transferred between wallets. This ensures the provenance chain remains intact and prevents speculative activity on verification records.
5. Record linking
The platform updates its internal records to connect the off-chain verified MassID with its on-chain token ID. This linkage ensures that the platform, the blockchain, and the Carrot Explorer all reference the same underlying data — creating a consistent, auditable record across systems.
What happens next
Minted MassIDs are the foundation upon which the rest of the credit lifecycle is built. Once a MassID exists on-chain:
-
Certificates are generated — When MassIDs pass methodology verification at a facility accredited by independent third-party auditors, certificates (RecycledID or GasID) are minted, referencing the underlying minted MassIDs as proof of the physical work performed.
-
Credits are created — Each certificate generates fungible credit tokens (TRC or TCC), representing 1 metric ton of verified environmental impact. These credits are the tradeable assets that buyers purchase to meet their environmental commitments.
-
Full traceability is established — From a retired credit, any party can trace back through the certificate, to the minted MassID, to the IPFS metadata, and ultimately to the specific waste batches and supply chain participants that performed the work. This traceability is publicly verifiable through the Carrot Explorer or any blockchain block explorer (e.g. PolygonScan).
Related pages
- Credit Lifecycle — The MassID, Certificate, and Credit lifecycle and relationships
- Smart Contracts — The on-chain infrastructure that manages minting and custody
- MassIDs — The foundational data unit representing verified waste batches