A chemist named Jonathan Harrolson in 1863 figured out how to create more potassium nitrate or nitre by extracting it from urine. The men were all away fighting. But women could collect their urine out of bedpans and pour it into a huge truck pulled by a horse around town and they would make potassium nitrate out of it.
Morgan’s crime is that he couldn’t let go of the past; he couldn’t shoot his dead wife, and so his dead wife eventually killed his son. So now he has nothing to live for, but he doesn’t have the strength of will left to take his own life. Which leaves him trapped. He can’t join up with Rick’s grip, no matter how much Rick wants him to, because that would mean connecting with people again, becoming vulnerable, risking himself and having to suffer when his new friends die. And he can’t commit suicide, because that would require a different kind of courage. So he’s stuck building his traps, covering the walls with his writing, sending messages to strangers he’ll never see.