By Fola Akinnibi When a 72-inch sewer pipe near Washington, DC, burst last January, more than 240 million gallons of untreated wastewater flowed into the Potomac River. It was one of the largest sewage spills in US history.

The district’s water authority redirected the flow and is now remediating the area, which is both a popular place for fishing and boating and the main source of DC’s drinking water. The incident, which drew the attention of the White House and cost about $20 million to fix, was a stark reminder of the vulnerabilities facing the massive, often aging, network of pipes under cities that carries sewage out of sight and out of mind.

One of the things I argue in the book is that for most of human history, human waste probably wasn’t conceived of as waste at all. Among the Aztecs, they had over a thousand individuals that were tasked with collecting various types of organic waste and manures, and that was being actively managed as a resource for fertilization. In East Asia, there’s a long history of the use of this material, what’s known as night soil. It was commodified.

If we jump to 19th century Europe, we also see that there’s a history of collecting this material and using it by figures known as night men who would collect that organic waste from pits and privies under the cover of night and then bring it out into the countryside.

It was really in the mid-19th century when we started to have these massive outbreaks of cholera in places like London where people started to rethink the system. That’s what eventually prompted the development of modern sewer networks in which there was an impetus to transport that material away from urban centers, away from wells and direct it outside of the city.

If you have a flush toilet that is connected to a sewer, then in most cities that sewer will direct it to a wastewater treatment plant. Eventually it reaches primary treatment where all of that material, the solids will slowly settle and then grease will kind of float to the top and will be skimmed off. Then it’s directed to what’s called secondary treatment where it’s really just exposed to large communities of microbes that consume all of those solids. That is where our sewage is largely transformed through these biological processes.

At the end we get this product that’s sometimes known as sewage sludge and more recently has been rebranded biosolids. One of the things that I became really fascinated by was where all that material ends up going. I found in a lot of cities it’s being redirected back to the land, into agricultural fields, into urban gardens, into landscaping and even into elite golf courses.

There are still a lot of cities that incinerate this material. Where I live in Ohio, the city of Columbus has adopted an approach in which pretty much 100% of this material is returned to land. But in Cincinnati and Cleveland, the other two largest metro areas in Ohio, still a significant percentage of biosolids is being incinerated.

One of the problems with incineration is that it contributes to air pollution. It can create problems with public health, especially folks who have asthma or other respiratory diseases or illnesses. The problem is with this kind of flush-and-forget system, we wanted to get it out of our homes, out of our businesses, but there is no way in an absolute sense. It has to be dealt with one way or another.

This is the part that was in some ways the most exciting for me. There are a lot of communities that are looking for opportunities to develop systems that they themselves can manage autonomously and not rely on these broader industrial infrastructure systems. They want to capture resources from their bodies, where there’s vital organic matter and nutrients that can be redirected into the land. They want to do it safely so that people are not being exposed to pathogens or undue harm.

Inside the Secret Lives of Sewers In a lot of places in the world, these alternative dry sanitation systems are being adopted, especially considering that three and a half billion people in the world don’t have access to what’s considered basic sanitation. That’s not just a problem outside the United States. It’s also been a problem here. In California both in Santa Cruz County and Mendocino County, the housing crisis and the climate crisis have created conditions where just a lot of Californians don’t have access to flush toilets that are connected to sewers or have failing septic systems and really need an alternative. These simple dry toilets or composting toilets have become a way to really address that crisis.

I think as an anthropologist, I’ve strongly felt that it wasn’t enough to just talk to people and observe what they were doing. I really had to learn about these processes firsthand. So I had a 16-month experiment in my own home. My wife told me very explicitly, because the compost toilet is in the basement, “If it starts to smell or something goes awry, I will cancel this.”I agreed to those terms, but it never really became an issue.

After a year of using it, I composted all that material and returned it back to my gardens where I planted zinnias and sunflowers. There was something both deeply satisfying about seeing material that oftentimes inspires disgust or shame managed in a way that was productive. Being able to complete that cycle was revealing and meaningful for me.

I really want to invite people’s curiosity about the system. A technology that allows you to just flush and forget means you don’t really have to think deeply about the consequences of this activity for others, for society, for your relationship to the environment. It obscures the fact that these private acts do have broader public consequences. Right now, almost half of the US is in a drought and yet we continue to flush with fresh potable water. That feels crazy to me.

I wouldn’t advocate for a complete overhaul of the system. That doesn’t really make sense. We’ve invested all this time and effort and labor and technology and infrastructure into building the system, but there are still really persistent gaps. In those gaps where a lot of people are not getting their needs met or where there’s disruption for climate disasters or extreme weather events, I think we really need these alternative ecological systems.