Using a blockchain for issuing these Credits has multiple advantages:
Immutability: once the NFTs are set up with their data on the blockchain, the core data is locked in place permanently. There's no altering of records possible on the baked-in features in the token and also the track record of all transactions is permanent
Transparency: due to the nature of the transaction & wallet handling of a blockchain, every transaction can be traced by anyone publicly. That also means e.g. that everybody can see if a buyer that wants to compensate a footprint with buying Impact Credits still holds the NFTs bought (so, is still compensated) or has sold these Credits again (and therefor is not compensated anymore).
Tradability: our Credits are listed on a widely used public blockchain (Solana), which also means that no one is bound to any proprietary marketplace for selling the Credits again. Our Impact-NFTs can be sold on any secondary marketplace that supports the Solana chain (like OpenSea, MagicEden etc.).