The reuse of human urine allows for the production of sustainable fertilizers for urban agriculture, offering significant environmental benefits. A recent study evaluates the environmental impact of nitrogen recovery from the yellow waters of buildings. In addition to promoting sustainable agriculture, it also reduces CO2 emissions and water consumption.
The global demand for fertilizers in agriculture continues to grow, making it necessary to reduce dependence on non-renewable sources. The demand for nitrogen as a fertilizer increases annually by 1%, amounting to an increase of over a million tons each year. The production of these fertilizers relies heavily on non-renewable energy sources such as natural gas, oil, and coal, leading to significant energy consumption and CO2 emissions.
A new study presents human urine nutrient recovery as a solution to transforming urban agriculture. The use of urine allows for the exploitation of local resources while minimizing external inputs, contributing to agricultural sustainability. It reduces reliance on limited resources and supports an environmentally responsible cycle.
Human urine, also known as “yellow water,” is a rich source of nutrients, particularly nitrogen, essential for agricultural production. Beyond its benefits as a fertilizer, it also reduces greenhouse gas emissions and water pollution, particularly in rivers and aquifers.
To evaluate its feasibility, researchers tested the process in a bioclimatic building equipped with a pilot plant for nitrogen recovery and a rooftop greenhouse for tomato cultivation. The process begins in an underground plant, where urine from waterless male urinals is collected and stored before being directed to a specialized reactor. In this reactor, the urine is mixed with a base to regulate its acidity, while microorganisms convert the urea into nitrate, a form of nitrogen more easily absorbed by plants.
The nitrate produced in the reactor is then used to irrigate hydroponic tomato crops in the rooftop greenhouse. According to the study, one cubic meter of treated yellow water yields 7.5 kg of nitrogen, which can support the cultivation of 2.4 tons of tomatoes outdoors.
While this research remains at the laboratory scale, the findings indicate that the environmental and economic impact would be significantly reduced if urine recovery were implemented on a larger scale. This could be achieved by connecting all urinals in a building to a nitrogen recovery reactor. Further experimental work is being conducted to analyze potential concerns, such as the presence of pharmaceutical compounds in urine and their possible effects on crop tissues.
The use of human urine as a fertilizer provides a promising alternative to conventional synthetic fertilizers. It enhances sustainability by utilizing a readily available resource while reducing pollution and reliance on non-renewable energy sources. As research progresses, this innovative approach could become a practical solution for sustainable urban agriculture, addressing both environmental and economic challenges in food production.
