I think we can all agree that, in the early 1800s, there were a lot of problems with the world. One man saw those problems and came up a solution... a solution involving poop.
Pierre Leroux liked society, but not authority. Born in the late 1700s, he somehow found a way to be both a utopian and an economist. Perhaps he managed it by being a philosophical economist, rather than a practical economist. Leroux looked for ways to let a country maintain its citizenry without exerting authority over them, and for people to retain their property without using it to deprive others.
One of the things that would drive the world to desperation and authoritarianism, Leroux believed, was scarcity. He was a Malthusian, who believed the rising population would inevitably lead to deprivation. Looking for ways to stave off the food crisis he saw coming, he hit on a novel theory. Though he wasn't a farmer, he knew that animal manure could improve the crops. Though he wasn't a public health expert, he knew that human feces had to be collected and disposed of. Currently, feces was piped as far away from population cities as possible and then let go indiscriminately.
This seemed, to Leroux, like a waste. To stop the disposal of so much wealth, he came up with Circulus theory. Human feces would be collected and reused as fertilizer, leading to better crops and less starvation. Most people did not care for the idea. Leroux sulkily proclaimed that if people were more educated, then "Each would religiously gather his dung to give to the State, that is to say the tax collector, in place of tax or personal levy. Agricultural production would double immediately and poverty would disappear from the face of the earth."
Few were swayed, but Leroux did have some admirers. Among them was Victor Hugo. In Les Miserables, Hugo at one point describes the sewer as "gold flowing from full hands," and makes a passionate defense of Circulus theory, though he never calls out the theory by name.
If that were in the musical, I'd finally watch it.
Top Image: kargaltsev.