Human waste has been of interest to a number of philosophers and I call them — and I do not mean this in a derogatory way — toilet philosophers.
Among them are Georges Bataille, who André Breton called “excremental philosopher” and Peter Sloterdijk, famous for his remarks on the role of the arse in his book Critique of Cynical Reason.
Then there was Slavoj Žižek in a review of a book of Timothy Garton Arsh who connected toilets to Buñuel to Lévi-Strauss to Hegel to Erica Jong.