This recent article from Thisoldhouse.com shows the myriad of uses for unused charcoal...
"Don't let that half-empty bag from last summer sit around. Charcoal—the natural lump variety made from hardwood—can do more than cook burgers and smoke ribs.
Don't let that half-empty bag from last summer sit around taking up space. Charcoal—the natural lump variety made from hardwood—can do more than cook burgers and smoke ribs. Find another use for the black pieces and finally toss out that almost-empty bag in the garage."