This is one of the few positive things humans can do for the environment. Shit is something unclean and never mentioned in decent company. Having shit in our vocabulary as a swear word has set our civilization back drastically in ecological terms. The soils of China could not have supported such a vast population for such a long time if they had invented the flush toilet way back when they invented paper. The fertility of their would have been flushed out to sea.
Human beings are terrestrial animals and our excreta breaks down best in a terrestrial environment.
Despite this, our technological way of life persists in equating civilization with a flush toilet. We waste billions of litres of water washing away our excreta, fouling all that perfectly clean water with vast numbers of bacteria and with organic matter that burns up the oxygen supply in the water. Every town or city has millions of dollars invested in dams, pumps, pipes and filtration plants and a significant proportion of this financial outlay and ecological damage is merely to dispose of our excreta politely. Once we have polluted all that water we have to spend billions of dollars on sewage works to clean up the waste once more before we put it back into the natural aquatic environment. Even worse, we pump this polluted water out into the ocean, breaking the cycle of nutrients that starts with the soil and should return to the soil.