1. Edo, where human waste was bought and sold
"Night soil" is a fertilizer made by fermenting human waste. It had been used since the late Kamakura period and became common during the Sengoku (Warring States) period, but trading it widely for cash or vegetables only became common around the Kyōhō era, roughly 1716 to 1736[1].
As Edo's population approached a million, demand for night soil grew, and clear market prices emerged. According to one record, selling a year's worth of waste from a single tenement housing 20 to 30 people could bring in around 1 to 2 ryō — a real sum of money at the time[1].
This huge demand created an opening for specialized collectors and brokers to enter the business.
2. "Kinban" fetched a higher price than ordinary "machigoe"
Edo's night soil was ranked clearly by how effective it was thought to be as fertilizer. Waste from a daimyo's residence was called "kinban" and considered the top grade — by one account, it sold for four to five times the price of "machigoe," the ordinary waste collected from commoners' homes[2].
The reasoning behind this price gap was that samurai, who ate a richer diet, were believed to produce waste that made more effective fertilizer. The right to collect a household's waste was negotiated by contract with landlords, and later became something people speculated on, buying and selling the collection rights themselves[2].
As demand kept rising, so did the price of those collection rights.
3. Why Edo and London handled human waste so differently
London, in the same era, also had a trade in selling human waste to nearby farmland. But it never became as organized as Edo's system — untreated waste often seeped into the ground and contaminated well water instead, and this is thought to have contributed to major cholera outbreaks later on[3].
Part of the reason for the difference comes down to diet. In Japan, Buddhist values had long discouraged eating meat, so large-scale livestock farming never developed the way it did elsewhere — which meant a chronic shortage of livestock manure. Human waste stepped in to fill that gap, and demand for it grew stronger in Japan than it did in London[3].
4. In 1789, villages demanded the shogunate lower night-soil prices
In the 11th month of 1789, villages near Edo submitted a petition to the shogunate's (the samurai government's) finance office demanding lower night-soil prices. The movement spread to 1,016 villages by the following year, 1790. The stated reason: collection fees had risen roughly threefold compared with the Enkyō-Kanen era (the 1740s-1750s)[4].
Night soil was an essential fertilizer for farming villages, and it seems sellers took advantage of that dependence to push prices higher and higher. The petition went all the way to the shogunate, and the dispute was finally resolved in June 1792.
5. In the Meiji era, waste changed from something sold to something thrown away
By the late Meiji era (the late 19th and early 20th centuries), the amount of human waste produced in the growing cities had outpaced how much surrounding farmland could actually use as fertilizer. A public sanitation law passed in 1900 — mainly aimed at preventing disease — put municipalities in charge of waste disposal, though trading night soil as a commodity continued for a while even after that[5].
A 1930 revision gave municipalities the authority to charge fees for waste collection[5]. For a period after World War II, chemical fertilizer became hard to get, and demand for night soil briefly rose again — but as chemical fertilizer production recovered in the 1950s, and concerns grew about parasitic infections spread through night soil, its use declined for good. A new law passed in 1954 replaced the 1900 law and made waste disposal the responsibility of municipalities nationwide.
6. When collected waste was shipped out to sea
Before Japan's sewer network was extensive enough to handle it, human waste collected from cities was often loaded onto ships and dumped in the ocean. Tokyo City began operating this kind of sea dumping directly in 1935, and Tokyo continued the practice all the way until 1999. The dumping zone, originally close to Tokyo Bay, gradually shifted farther offshore over the decades[6].
Collection itself was done using "vacuum trucks," first put into practical use by the city of Kawasaki in 1951 and considered a hygienic improvement — they spread nationwide from there. Even so, much of what they collected still ended up dumped at sea. In the summer of 1953, E. coli contamination in Tokyo Bay got bad enough that swimming there was banned for a time[6].
7. Ocean dumping was fully banned in 2007
Following an international treaty on marine pollution (the 1996 Protocol to the London Convention), a Japanese law took effect in 2002 restricting the ocean dumping of night soil and septic tank sludge. Operators who were already dumping were given a five-year grace period, and once that period ended, ocean dumping of this kind of waste was fully banned across Japan starting February 1, 2007[6].
Today, Japan's sewer network has expanded considerably, and household wastewater is treated at dedicated facilities before being returned to rivers and the ocean. This modern wastewater treatment system is covered in more depth in a separate article on this site, "Where Does the Sewer Go? What Happens to Used Water" (currently available only in Japanese)[7].
If you want to look for yourself
Look into how your own town or city handles food waste today — some places turn it into fertilizer or biogas through composting or similar programs, and comparing that modern resource-recycling approach with Edo's night-soil economy can be an interesting way to see both the similarities and the differences. It's also worth looking up what a sum like "1 or 2 ryō" would be worth in today's money, to get a feel for just how much value people placed on this trade.