What difference would it make if it was "food grade?" You are not planning on filling the thing with cherry jelly! Any unused drum would be fine! "Food Grade" would mean it is OK to fill it with food, then eat what was in it. Obviously, you don't want a drum that had plutonium in it, but I would think that you could burn out most contaminants with a weed burner?
"I was born to cook for people"