I will agree that limestone, starch, borax, and sodium nitrate are things that are found naturally in our earth, but I really don't want to cook with any combination of them. Hydrogen, nitrogen, magnesium and phosphorus are also natural things, but I'm not going to fire off my cooker with a load of them.
A lot of folks use briquettes and a lot of those use KBB. Make no mistake, Kingsford sells a hell of a lot of product. I do use a small amount of RO briqs in my chimney to light my lump. I use briqs to light the lump, lump for a good bed of coals and wood to cook with. Just my preference, but I am not going to cook with briqs and especially not with KBB.
That's my opinion and I'm sticking to it.