In several parts of the world today, human feces are regarded as succulent piles of nutrient-filled treasures to many. Often the secret to success for many farmers, these tiny treasures have been used as fertilizers as far back as 2000 years ago. So just what in particular makes human feces such a great fertilizer? Human fecal matter contains phosphorus, a key element in plant growth. Aside from this, however, why might farmers want to use human feces as fertilizer, despite the many pathogens it contains and its distinct odor?
Produce. Source.
Without the use of processed mineral fertilizers, which contain high amounts of phosphorous, the food we have today would not be available. As phosphorous is a chemical element on the periodic table, it cannot be substituted synthetically; rather, it must be sourced from phosphate rock reserves. The demand for phosphorous increases correspondingly with the rise of annual global growth rates. Due to a number of additional factors such as over-fertilization, and an increase in popularity of meat-based diets in China and India, reserves could reach depletion within the next 50-100 years. However, unlike fossil fuels, phosphorous can be recovered from the food production and consumption chain and be reused. This is where human fecal matter comes in; recycling phosphorus lowers the global demand for mineral phosphate fertilizers. In developing countries, human excreta also provides farmers who have limited access to globalized fertilizer markets with an opportunity to yield crops.
The phosphorous cycle. Source.
Currently, nearly 200 million farmers in places such as Canada, the US, South Africa, India, China, and Vietnam, use human feces as fertilizer to harvest grains and vegetables. I know what you’re all probably wondering: is using human feces as fertilizer safe? Well, according to the World Health Organization (WHO), the presence of pathogens does in fact present a potential threat to human health. However, for an actual risk of disease, an infectious dose of the excreted pathogen must reach a human host. For that reason, the use of human feces is, according to the WHO, considered safe if it has been treated first.
Rural cropland. Source.
The treatment of human feces usually involves three phases: sedimentation, biological treatment, and stabilization of odours. Collectively, these three phases ensure the breakdown of pathogens through the use of high temperatures and basic agents. Thus, it is actually the presence of heavy metals and other toxic wastes in the industrial wastewater which mix with residential wastewater in sanitation systems, that poses as a human health risk, as these contaminates cannot be broken down in the treatment process.
Though the thought of using human excreta as fertilizer may be difficult for some of us to stomach, the products attached to this practice are nonetheless very economically and environmentally favorable; but at what cost? If these potential dangers were offset by raising more awareness and urging policymakers for the successful removal of heavy metals in wastewater, human excreta could indeed be the fertilizers of the future.
References: NBC Philadelphia, PRI.org, World Health Organization, National Public Radio, Slate.
– Cindy Hu
