Humanure: Safety and Handling
What is humanure? According to Joe Jenkins, author of the Humanure Handbook, it’s a term he chose to use instead of “human waste”. And indeed, humanure has become a widespread and accepted term that describes recycled human feces. Jenkins argues that anything that can be reused, shouldn’t be called waste. Since almost a third of the human population on Earth can’t have access to basic sanitation, making toilets convenient and accessible by breaking the taboo of human feces as something to get rid of, can change the narrative and actually help people and the planet… So how do we make use of the “waste” that is humanure?
Why the taboo?
Aside from the obvious reasons, such as odor, the main concern is that feces can pose a health hazard. Indeed, fresh human fecal or fecal that has been stored under suboptimal conditions, may contain human pathogens, presenting risks to individuals that handle it and to those who may come into contact with food, soil, or water in areas where non-decomposed “night soil” is applied.
If the fecal is not properly treated, the practice may promote fecal-borne diseases. The eggs of Schistosoma japonicum, the parasite that causes intestinal schistosomiasis in Asia, and S. mansoni, which causes intestinal schistosomiasis in the Americas, Africa, and the Middle East, are excreted in the stool. Schistosome eggs can survive for several days (S. mansoni) or weeks (S. japonicum) in the excreted stool. Helminth eggs are particularly hardy and may require longer storage and/or higher temperatures and pH for destruction relative to other pathogens found in human stool.
Another reason for collective disgust towards our own fecal matter is our own history of pandemics due to poor hygiene. Human feces and urine were contained in a bucket, and once the bucket was full, the occupants of the cell and house would throw the feces and urine onto the street. The uncleanliness of the cities in Europe during the 14th century was a large problem that caused the further spread of the plague.
For a long time, we have put effort into collective solutions for handling our shit poorly, each system bringing more problems to solve. The lack of personal responsibility towards our own “waste” fell on the shoulders of lower-class people whose job was to get rid of our shit (emptying our latrines and chamber pots and carting “night soil” out of town to nearby agricultural areas).
In recent centuries, this system was replaced with a more aesthetically pleasing flush toilet system.
History of a good practice
But we did not always have such a distant relationship with our own excrement. In the 18th century Japan, there are records of a dispute between two local villages near Osaka over a sewage system. But unlike in Europe, they didn’t argue over whose job removal of waste was, rather whose right it was to collect it. This was due to humanure’s immense importance to Japan’s agriculture. When the Japanese population started to grow, they needed more food, and to grow it – they needed more fertilizer for the soil since Japan wasn’t blessed with forests and fertile ground. Ultimately, it was the citizens’ job to provide the fertilizer. In fact, humanure was so valuable, that the landlords retained the right to renters’ solid waste.
Breaking the taboo
One of the reasons we mentioned Joe Jenkins is he’s a pioneer of changing our own narrative towards waste. He argues two main points, the first one being that in composting toilet systems, nothing gets wasted. The second is in regards to how we view composting toilets: they don’t collect waste, they don’t dispose of waste – in fact, there is no waste at all.
Finally, although the term composting toilet is widespread, most of the toilets we think of as “composting” toilets are actually just “dry” toilets.
As with any other manure, when recycled right, it can be used for fertilization, thus bringing back nutrients into the soil, instead of contributing to the water pollution and degrading the quality of the soil itself.
The right timing to take it out
The timing really depends on the type of your composting toilet design (whether it’s the bucket, big chamber system, or other) and the composting process of your choice. Another factor is the presence of microorganisms and whether they do their work at lower or higher temperatures. All of these affect the timing and the way we take out our compost.
In the bucket system, due to the fact, there’s not enough time and space to wait for the composting process to begin in the bucket. The best choice would be to close the bucket once it’s full and make sure there are holes for the air to go in. Once you do this, leave the bucket for a few months for the composting process to begin, before you empty it onto the humanure compost pile. Another option would be using home-compostable bags. They’re handy because you can seal them when full, and leave them on the compost pile – their degradation process is basically the same duration as the one feces go through.
Big chamber system
Big chamber systems are the most grateful ones for dealing with solid waste. If the chamber is big enough, roughly around 1m3 or bigger, the composting process already begins in the chamber, so you basically handle the compost, not fresh feces. However, this compost may still contain some pathogens, which is why further composting is required.
Roughly saying, the feces need to compost somewhere between 4-6 months before it’s safe enough to lay it on the compost pile outdoors. After this period, another 6 – 12 months is required for it to become safe enough to be used as a fertilizer. Once it has been taken out of the chamber, we treat humanure as any other regular compost, meaning: we don’t bury it, we cover it to protect it from rain, and regularly turn it and take it into another box for adequate aeration.
If you have another composting process that works for you, you can apply it here as well!
So, is there a safe way to handle our shit? (pardon our French).
The main goal is to make the human excreta safe for handling. We do this by making sure that we reduce the risk of pathogens getting into the soil and in our food chain.
First things first, pathogen reduction can occur by either dehydration or exposing it to high temperatures.
What is necessary to be done is the control of:
- presence (to be the exact – absence of) pathogens in the pile
- stirring the compost heap (aeration)
- solar exposure
- the temperature of composting material (temperature is an essential component of any quality compost pile. As organic matter decomposes energy is released, which results in an increase in heat. This heat provides an environment wherein bacteria (good bacteria) can work to break down waste.)
- high diversity of microorganisms (you can find a useful guide on preparing a compost starter here)
- time (the feces usually take somewhere between 6 -12 months to biodegrade)
It’s important to note that all of the above are steps of the process – meaning, by the time the process is complete, the end product is basically soil, and therefore safe to handle. Some would say recycling human waste can be extremely dangerous to your health, the health of your community, and the health of the soil.
We are sure that recycling humanure is easy and simple, and this is why:
It is well known that humanure contains the potential to harbor disease-causing microorganisms (pathogens). This potential is directly related to the state of health in the population which is producing the excrement. For example, if a family is composting its own humanure, and it is a healthy family, the danger in the production and use of the compost will be VERY LOW.
When disposing, extra precautions must be taken to ensure maximum pathogen death. Compost temperatures must rise significantly above the temperature of the human body (37°C or 98.6°F) in order to begin eliminating disease-causing organisms. This is because human pathogens thrive at temperatures similar to that of their hosts.
Due to the activity of nitrifying bacteria and nitrobacter, the temperature usually rises above the point of 37.5°C in the soil. All of this is an essential part of the composting process – anything that decomposes over time, raises the levels of nitrogen, therefore raising the temperature of the composting pile. Because of this property, there are even heating systems that rely on composting piles for providing heat!
In addition, most pathogens only have limited viability outside the human body, and given enough time, will die even in low-temperature compost (low-temperature being 36-40 degrees Celsius)!
Have we forgotten to mention something important? Let us know in the comments!