Carbon neutrality means carbon dioxide neutrality. Carbon is just an element and literally everything you see and don’t see has some of it in it.

Also, around 2% of our sun’s energy production involves the Bethe-Weizsäcker cycle which is a cyclical fusion reaction using carbon, nitrogen and oxygen. (The main source of energy production is through a proton-proton chain since our sun is too small to rely on the CNO-cycle entirely)