Can Natsu eat fire from objects he burns?
As per the Fairy Tail Wiki


  In addition, the user can consume external sources of fire to restore their body to a healthy state and regain their reserves of strength, something that also makes them immune to most types of fire, due to their capability of nullifying fire-based attacks by sucking them in and eating them; the consumed fire also seems to possess a different “taste” according to its “quality”. However, the user can’t eat their own flames, or things set on fire by them, to reinvigorate themselves.