[Zababa]

> just certify CO2 offsets for example for each coin purchased

We have something like this in France. Energy providers (for example EDF, Electricité De France) must buy a certain number of CEE (Certificats d'Economie d'Energie, I think the concept is white certificates) every year, or face heavy fines (big enough that buying certificates is a big part of their activities).

As an example: let's say I want to change my window to have more isolation, which will reduce my energy consumption. This can produce a CEE, that I can "sell" to EDF, which will help financing the change.