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Faced with water shortages exacerbated by climate change, scientists around the world are constantly looking for ways to slow water shortages by proposing more responsible and more sustainable practices. Agriculture is one of the sectors where application changes are most demanded, both to limit water consumption and to fertilize farmland in a way that is less harmful to the environment. Scientists then recently proposed using urine as a fertilizer: an alternative that pollutes the environment less and also saves a lot of water. However, despite the urgent need for alternatives to conventional fertilizers (which was further accentuated by the rapid increase in prices due to the conflict in Ukraine), is the world ready to overcome assumptions and use urine to produce food?
Accelerated climate change, directly linked to irresponsible practices for several generations, has led (inevitably) to water shortages, which are felt a little more each year. Across the planet, thousands of freshwater sources have dried up very quickly due to anthropogenic factors, giving rise to millions of hectares of “new” deserts.
These anthropogenic factors include agricultural practices where a single crop can consume millions of liters of water. For example, it takes 1600 to 5000 liters of water to produce one kilogram of rice, and 900 to 590 liters of water for soy and wheat, respectively. To meet these water needs (to meet the downstream trend of overconsumption), people go so far as to alter the flow of rivers and streams to draw water from them, sometimes drying them out completely.
But agriculture isn’t the only thing causing the depletion of freshwater resources. Toilets are among the world’s largest consumers of water, as millions of liters of water are discharged every day. For example, in France, 20 liters of drinking water per day and per person are used only for siphoning, which represents about 20% of each person’s drinking water consumption.
The consequences of this excessive water consumption are already being seen all over the world. The drop in the level of Lake Mead (fed by the Colorado River) in the United States is one of the most striking examples. This lake, in particular, is the largest artificial water reserve in the country and has experienced a historic 40% reduction in capacity in recent years due to drought and human consumption.
This water scarcity has led to the emergence of water-saving solutions, such as recycling wastewater. Recycled wastewater can be reused for agriculture rather than discharged, while urine can apparently be used as fertilizer. However, the adoption of such an alternative is still difficult a priori due to fear of foul odor, fear of consuming food derived from them, or quite simply the fear of contamination. However, urine is not usually the main carrier of the disease (unlike stool) and requires little treatment to be used. Otherwise pasteurization is also possible.
Urine: healthy, natural fertilizer at your fingertips
To grow well, plants need nitrogen, phosphate and potassium. These three essential elements are then artificially added to chemical fertilizers to fertilize farmland. Therefore, most farmers use NPK (nitrogen-phosphate-potash) fertilizers to maximize their agricultural yield. However, the production and overuse of these fertilizers contribute to a large proportion of the world’s greenhouse gas emissions and pollute groundwater and waterways.
Research from the Rich Earth Institute in the United States has shown that human urine can naturally provide NPK, as it contains about 80% of the nitrogen and more than half of the phosphates in wastewater. Most of the nutrients we absorb through our diet are excreted mainly in our urine, which is discharged into the waterways. one of the main sources of food pollution explains Julia Cavicchi, a researcher at the Rich Earth Institute. Intelligently channeling these nutrients into agriculture could replace chemical NPK fertilizers. In addition, the water contained in the urine can also be used to water the plants.
However, in order to implement this alternative, it would be necessary to completely rethink urban pipe systems in order to collect urine or urea efficiently. Therefore, those most likely to adopt the solution are developments not connected to sewerage. On the other hand, researchers at the Rich Earth Institute are currently developing technical solutions to facilitate the transport and spread of urine-based fertilizer to be as inexpensive as possible for Farmers.