Originally posted by Complaintdesk:

Now that I have built The Obliterator, in two major bases, I never use my charcoal kilns. I keep a chest in my treasury full of Dwarf Eyes & Resin. If these chests are full, I place overflow items of these reagents into The Obilterator, which turns all items into coal.

There IS a use for dwarf eyes at one point, later in the game.