Humanure Taboo: Human Feces As Fertilizer?

On Thursday, October 12th, Calaveras officials in West Point, California discovered a sizeable illegal cannabis grow consisting of 445 plants and 60 pounds of processed marijuana. While searching the premises, the officers soon realized that surrounding the plants was human feces. As it turns out, the two individuals responsible were using their own poo to fertilize their crop. If the thought of puffing on bud that was grown using human waste makes you cringe, then you aren’t alone. But here’s a shocking revelation for you: they are just one of millions of farmers doing the same exact thing.

What is “humanure”?

Humanure (human manure) is human fecal material and urine recycled for agricultural purposes via thermophilic composting. Humanure contains valuable soil nutrients that enhance plant growth. For these reasons, humanure should be recycled whenever possible. Human excrement can be a major source of environmental pollution around the world. It also can be a source of disease organisms. When discarded into the environment as a waste material (“human waste”), it creates pollution and threatens public health. When recycled by composting, the pollution and health threats can be eliminated.

Studies reveal that 200 million farmers are using human feces as fertilizer.

According to a study published by the International Water Management Institute (IWMI), “nearly 200 million farmers in China, India, Vietnam, sub-Saharan Africa, and Latin America harvest grains and vegetables from fields that use untreated human waste.” While this practice doesn’t come without risks, IWMI environmental scientist Pay Drechsel believes the benefits outweigh the potential health hazards, especially for poor urban farmers.

In developing countries, farmers frequently face water shortages. And with fertilizer prices on the rise, affordable food isn’t always obtainable. So to them, it only makes sense to turn to raw sewage. After all, it does contain the same vital nutrients as pricey chemical fertilizer, including phosphorous, nitrogen, and potassium. Plus it’s free of charge.

Humanure – Yes or No?

Although human wastewater and feces could be the key to helping urban farmers escape poverty, the health hazards are still there.
According to The Humanure Handbook by Joseph Jenkins, there’s a fine line between raw humanure and treated humanure.
“Humanure” is a neologism designating human excrement (feces and urine) that is recycled via composting for agricultural or other purposes. The term was popularized by a 1994 book by Joseph Jenkins [1] that advocates the use of this organic soil amendment.

Humanure is different from night soil, which is raw human waste spread on crops. While aiding the return of nutrients in fecal matter to the soil, it can carry and spread a vast number of human pathogens. Humanure kills these pathogens both by the extreme heat of the composting and the extended amount of time (1 to 2 years) that it is allowed to decompose. Raw humanure, in particular, puts you at risk for a variety of disease pathogens, including hepatitis, cholera, and intestinal parasites, just to name a few. By tossing it onto a field, you are essentially promoting the spread of such diseases.

Humanure is not traditional sewage that has been processed by waste-treatment facilities, which may include waste from industrial and other sources; rather, it is the combination of feces and urine with paper and additional carbon material (such as sawdust). A humanure system, such as a composting toilet does not require water or electricity, and when properly managed does not smell.

By disposing of feces and urine through composting, the nutrients contained in them are returned to the soil. This aids in preventing soil degradation. Human fecal matter and urine have high percentages of nitrogen, phosphorus, potassium, carbon, and calcium. It is equal to many fertilizers and manures purchased in garden stores. Humanure aids in the conservation of fresh water by avoiding the usage of potable water required by the typical flush toilet. It further prevents the pollution of ground water by controlling the fecal matter decomposition before entering the system. When properly managed, there should be no ground contamination from leachate.

As a substitute for a flush water process, it reduces the energy consumption and hence greenhouse gas emissions associated with the transportation and processing of water and waste water.

Humanure may be deemed safe for humans to use on crops if handled in accordance with local health regulations, and composted properly. This means that thermophilic decomposition of the humanure must heat it sufficiently to destroy harmful pathogens, or enough time must have elapsed since fresh material was added that biological activity has killed any pathogens. To be safe for crops, a curing stage is often needed to allow a second mesophilic phase to reduce potential phytotoxins.