Well, when we die, it goes into the ground as nutrients that then transfers to something else etc.
But, I believe some sort of energy remains after we die beyond this...Nightline sure convinced me a couple years ago. This could be what at least some aspects of hauntings are.
Well, the scientists/physicists that spoke of this talked about the electrical energy that powers the heart and brain, not the static nutrients. There is no question that when we die this "energy" that powers our body changes form in some way. I don't pretend to understand this, but it is very interesting.