This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For thousands of years, human urine has had real value. After our bodies absorb nutrients from our food, they excrete the rest—mainly via urine.
An adult produces about 500 liters (132 gallons) a year. This liquid gold is very rich in nitrogen, phosphorus and potassium, three nutrients vital for plant growth. Ancient civilizations from Greece to China to Rome used it as fertilizer for crops, alongside feces.
Synthetic fertilizers have largely replaced natural fertilizers such as urine. Half the world's population now relies on food grown using synthetic fertilizers. Urine is still used as fertilizer by smallholder farmers who cannot afford synthetic fertilizers or want a sustainable alternative.
This year, the Iran war has made synthetic fertilizers more expensive. If the era of cheap fertilizers is ending, urine-based fertilizers could make a comeback. Call it "peecycling." Before modern toilets, humans were much more intimately acquainted with the waste they produced.
Peasants and smallholders would store their collective waste in cesspits. In cities, people used privies or chamber pots. As cities grew, so did the volume of waste.
While people slept, night soil workers would go door-to-door collecting human waste. Often, it would be transported for use on farms. In the 19th century, modern central sewage greatly improved sanitation and cut rates of infectious diseases.
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