Beginner help with selling emissions rights (e-car)

Hello dear finance community, after previously only traveling electrically in my company car, I registered an electric car privately for the first time last month. Apparently I had a real gap in my knowledge, because I learned for the first time about the possibility of selling one's own emission rights as a private individual through an information letter from the car insurance company. As we all know, nothing comes as a gift, so I was a little skeptical at first and had beginner questions: About what