Activated carbon, to point out an issue here, will filter out mercury and other toxic or unwanted material. The question we must ask is: Where is all that by-product carbon thrown away? Alright, you can reactivate it; but where do you put all the filtered unwanted materials? Back to the environment? Perhaps not. Recycled for industrial use? That would be wise. It is a problem that may never be answered directly by these companies, in the same way that they keep their real targets or real income as well-guarded secrets.