Charcoal is a traditional element of most mixes. I read one book that stated there's no scientific evidence that it really does much of anything. I don't know, personally. Some people claim that it has anti-bacterial benefits and others say it filters toxins. Neither of those claims makes much sense to me. My personal opinion is that it lightens up the mix because it doesn't hold any water and it doesn't deteriorate. Actually the fact that it doesn't break down is probably the most important quality. I will probably continue to use it in my mixes even though I'm not sure why.