no to much sulfer
I think you're thinking of activated charcoal?
Activated charcoal is just charcoal that has a very large surface area. (It is very "fluffy" on the molecular scale.)Perhaps someone more experienced in horticulture can correct me, but I am not aware of any reason why you would use activated charcoal in an ordinary garden rather than wood char or ash.
Coal, charcoal, graphite, diamond, graphene, nanotubules, etc. are what is known as inorganic or "black" carbon. When not exposed to air, these can be broken down (slowly) by certain bacteria, but are generally speaking not available to plants.This is why scientists working on reducing greenhouse gases were so interested by the discovery that buried inorganic carbon can remain largely locked away in the soil for centuries. In normal complete combustion, carbon dioxide is produced that immediately ends up in the ocean and atmosphere, and thus in plants that can burn or rot. On the other hand, when wood is undergoes incomplete combustion, the resulting charcoal remains sequestered in the soil and takes a long time to get back into the carbon cycle. Now, wood charcoal is a fine soil additive that can be used to break up soil and reduce acidity. But the residue of burning coal, called fly ash, is not something you want to put around plants, as it can contain any number of toxic metals. It is much better to recycle it as bricks or cement.
No, it's not good stuff, see iPodGuy's comment, "soot" might also be something you're thinking at?L