I have an "old smokey" bbq pit that is past its prime and is about to be trashed. Then, just now, I realized that the lid would make a great planter for some of my lettuce. It is about 18" in diameter and maybe 10" deep. Problem is, I burned charcoal for years in this bbq pit so would that make it a bad candidate for growing veggies?
I assume you ate the food that the charcoal cooked so the lettuce should be safe. If you think there is too much ash, put a small high pressure nozzle on you hose (available at HD and Lowes for a bout $2) and wash the residue out. I wouldn't bother and I already have the nozzle. Give it a try with a few seeds or plants this year.