I'm not sure what good an essay will do. I say this because most emotionally disturbed children (and yes, anyone who sets fires like this is emotionally disturbed) has issues expressing themselves. If they could write an introspective, thought provoking, 1000 word essay on a subject, then chances are the wouldn't need to set fires and do other such destructive things in an attempt to find a voice, to express themselves which is typically what they are doing when such manifestations become destructive.
Yeah, I know that it sounds like psycho-babble, and maybe the kids needs that stiff boot up the arse, but...
...I agree with several others. The best way to have this kid see the reality of what his actions have done and could have done is to force him to volunteer at a burn unit.
I was a first responder to a car accident with fire and watched a former classmate of mine die from burn injuries. He was looking right into my eyes telling me to tell his mother he was "sorry" (the accident wasn't his fault).
The problem with being a kid is that you often don't think things through. Yes, it's easy for us who think we are good parents and have good kids to say that this kid just needs a good "fear of God" beating...but whatever is wrong and went wrong in his life probably has happened years ago, and for several years, and it's going to take a lot to right this kid now...
TJR