In general, dung is the droppings of birds and herbivores, and even bat droppings, which are very rich in ammonia, can be used as fertilizer. When it comes to our stools, We can break our prejudices and look at this idea a little warmly.

What about human feces? What is the trajectory of the switch to agricultural fertilizer?

Let’s first examine whether the idea of ​​recycling human waste really makes sense.

When it is predicted that the world population will reach approximately 8.5 billion people by 2030, the idea arises that this rapid population growth will also bring rapid urbanization. Moreover, this situation is common in urban and semi-rural areas. Various problems in human waste disposal It also entails.

On the other hand, rapid population growth also requires sufficient food supplies to support the population. Food production must also increase It means.

So what’s in human feces?

Urine and feces are considered waste products, but surprisingly It contains nutrients that nourish the soil. Namely human urine; It contains 90% water, 14-18% nitrogen, 13% carbon, 3.7% phosphorus and potassium.

Urea, a waste product that the kidneys filter from the blood, is is responsible for 50% of the organic components in the urine and 85% of the nitrogen is fixed in urea. The remaining 5% nitrogen is total ammonia.

Urea is hydrolyzed by bacteria immediately after urine production converted into bicarbonate and carbonate. 90% of the nitrogen remains as ammonia.

In addition, stool contains 75% water and 25% solids.

These include 50% carbon, 5-7% nitrogen, 3-4% phosphorus and 1-2% potassium. In addition, urine and feces It also contains micronutrients such as magnesium and selenium. In fact, all of these nutrients are very effective at recycling for growing crops.

For example, one study found 520 kilograms of human feces; It is predicted to be able to produce 7.5 kilograms of phosphorus, nitrogen, potassium and micronutrients that enable the production of 250 kilograms of grain. this too It means food that is enough for 1 person in 1 year.

On the other hand, human feces; heavy metals, various drugs, pathogens and synthetic hormones also contains. In this case, we need to treat human waste before using it in fields or gardens.

The idea of ​​turning human feces into fertilizer is actually not new.

These fertilizers have been used for agricultural purposes since the 9th century, and since the 16th century, countries such as China and Japan have also benefited from this idea of ​​transformation. Moreover, in Japan in the 18th century, human waste It was very valuable because it was used as fertilizer on farms.

For this reason, human feces were transported from densely populated cities to agricultural areas, and even farmers who could not afford to buy the feces to use as fertilizer would happily steal these feces.

In the 19th century, European farmers used human manure for a while, but then switched to synthetic fertilizers. However, some smallholder farmers in Southeast Asia, Africa, China and Latin America still use human feces as fertilizer.

However, despite the benefits of using human feces as fertilizer, people and some farmers are sometimes not keen on this idea due to socio-cultural taboos.

These taboos generally include the bad smell of feces, visual disgust and the risk of contracting various diseases. For example, a survey among 400 farmers in Ghana shows; 87% of people concluded that handling or other contact with human feces poses a health risk, but They also agreed that it was productive for the crops.

Additionally, researchers in Germany grew three types of cabbage, two from human urine and one from human feces, and compared their yields with organic fertilizer.

While the efficiency obtained from urine-based fertilizers is higher than that of commercial fertilizers; crop fertilized with feces, was 20-30% lower than commercial fertilizer. On the other hand, manure-based fertilizer improved the carbon content of the soil.

More important; Researchers have attempted to assess the safety of these fertilizers by testing human feces for chemicals such as rubber additives, painkillers, hormones and insect repellents. However, these studies failed to reach a conclusion in 93%.

As a result, farmers are realizing the benefits of using human waste in reducing operating costs and increasing the nutritional value of the soil.

However, as we mentioned, there are sometimes hesitations about using human feces due to social taboos and concerns about consumer acceptance. To overcome these hesitations, human waste treatment technologies are needed. The risks of this process to human health can be further investigated.

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