This article was developed by ICTA-UAB (edited by RFF)
The Institute of Environmental Science and Technology at the Autonomous University of Barcelona (ICTA-UAB), a key contributor within the FOODCITYBOOST consortium, released research exploring the transformative potential of human urine as a sustainable fertilizer source for urban agriculture. The study evaluates the environmental impact of recovering nitrogen from yellow wastewater in buildings and concludes that urine reuse can enable the production of sustainable fertilizers with significant environmental benefits. By promoting local nutrient recovery, this approach not only advances sustainable agriculture but also helps reduce CO₂ emissions, energy and water consumption, and reliance on non-renewable resources, offering a novel solution rooted in circular economy principles and real-world experimentation.
An alternative, yet promising source of fertilisation
The global demand for fertilizers for agriculture is growing every day, making it imperative to reduce dependence on non-renewable sources. According to the Food and Agriculture Organization of the United Nations (FAO), global demand for nitrogen for use as fertilizer is growing annually by 1%, equivalent to 1.074 million tons each . The production of these fertilizers relies heavily on non-renewable energy sources such as natural gas, oil, and coal, which represents significant energy consumption and CO2 emissions. (photo credits: UAB).
This new study, led by the Sostenipra group at ICTA-UAB in collaboration with the GENOCOV group from the Department of Chemical, Biological, and Environmental Engineering, demonstrates the recovery of nutrients from human urine as a solution for transforming urban agriculture. The article, published in the scientific journal Resources, Conservation and Recycling, explains that the use of urine makes it possible to take advantage of local resources and minimize the use of external inputs, which contributes to the sustainability of the agricultural process. Furthermore, it reduces the dependence on limited resources, while promoting a more environmentally responsible cycle.
In this context, human urine, or “yellow water,” is a rich source of nutrients, particularly nitrogen, which are essential for agricultural production. In addition to its benefits as a fertilizer, it reduces greenhouse gas emissions, as well as polluting emissions into water, such as rivers and aquifers. To evaluate its feasibility, researchers have tested the process at ICTA-UAB bioclimatic facilities, where they have a pilot plant for nitrogen recovery and an integrated rooftop greenhouse (iRTG) to test the impact of recovered nitrogen on tomato crops. The process begins underground, where urine from dry urinals is stored and directed toward a specialized reactor. In this reactor, the urine is mixed with a base to regulate its acidity, while microorganisms transform the urea contained in the urine into nitrate, a form of nitrogen that plants can absorb with greater ease.
The nitrate produced in the reactor is subsequently used to irrigate hydroponic tomato crops in the greenhouse located on the building’s roof. According to the study, one cubic meter of treated yellow water produces 7.5 kilos of nitrogen, which would allow 2.4 tons of tomatoes to be grown outdoors, significantly reducing the costs and environmental impact of agricultural production. Although this is still a laboratory-scale study, the results show that the environmental and economic impacts would be reduced if urine recovery were carried out on a larger scale, connecting all the urinals in the building to the nitrogen recovery reactor. Experimental work is currently ongoing, such as analyzing the content of pharmacological compounds consumed by people and their possible appearance in crop tissues.
A valuable path for sustainable urban agriculture
While this research was conducted independently of the FOODCITYBOOST project, it resonates strongly with our mission to foster innovative, sustainable approaches to urban agriculture. The study illustrates how nutrient recovery from human waste can enhance resource efficiency and reduce environmental impact, principles at the heart of FOODCITYBOOST. As we work across Europe to co-develop resilient food systems through our Living Labs, insights like these provide valuable direction for integrating circular practices and boosting sustainability in urban environments.
Reference article:
Maiza, M. V., Muñoz Liesa, J., Petit Boix, A., Arcas Pilz, V., & Gabarrell, X. (2024). Urine luck: Environmental assessment of yellow water management in buildings for urban agriculture. Resources, Conservation and Recycling. https://doi.org/10.1016/j.resconrec.2024.107985
