/johnny
Check the content of volcanic gasses, Black and White Smokers (=undersea vents), etc., and you will find a wide variety of compounds with Carbon in them, all coming from deep in the Earth.
In Arkansas there is a Federally maintained top of a Kimberlite Pipe where anyone can go and find pure Carbon from the base of the Mantle in the form of DIAMONDS !
All Living things have the 4 elements CHON in them. The process of photosynthesis converts CO2 into C that is in a form that can be utilized by the plant.
My point in all of this is that the junk scientists insist that “Any idea is true until proven false.”
This concept is probably taken from the US Legal System that states: “Anyone is innocent until proven guilty.”
Science, however demands that every idea be tested repeatedly, and after much successful testing they will say that the idea might be at least partially correct.
What about diamonds?