Researchers from the University of Birmingham and L’Institut Agro Montpellier, France, have found that human urine is just as viable as synthetic fertilisers when it comes to sustaining soil bacterial communities, making it a potential eco-friendly option for agricultural use. Published in Applied Soil Ecology the study shows that even in high doses, urine stored for one year caused minimal disruption to the soil microbiome, with negligible effects on soil pH and salinity. This research could open the door to using human urine as a sustainable alternative to synthetic fertilisers, which are commonly used but carry environmental drawbacks. The study highlighted that urine, after being stored, offers bioavailable nutrients, such as nitrogen, that can support plant growth. Fresh urine is 95% water, with the remaining 5% composed of nutrients like urea, creatinine, and salts. This composition makes it a valuable fertilizer for agricultural crops, especially since it provides essential micronutrients. During this study, a spinach crop was fertilized with two different types of medical urine.
These are compared with artificial fertilizers and water treatments under closed conditions. An important finding is that despite the high salinity of urine, it has little effect on the soil bacterial community. Only 3% of the bacterial groups were affected. However, the researchers observed that urine fertilisation increased the relative abundance of nitrifying and denitrifying bacteria, compared to synthetic fertilisers, which could lead to higher emissions of nitrogen oxides – potent greenhouse gases. Urine was shown to lose much of its microbiome after 12 months of storage, inactivating most human pathogens and breaking down extracellular DNA due to increased pH levels (around 9). This made the stored urine safer for use in agriculture without posing a threat to soil health. Co-author Manon Rumeau emphasised the potential for recycling human urine to enhance agricultural sustainability while reducing wastewater pollution and dependence on synthetic fertilisers. The study paves the way for further research into the long-term effects of urine fertilisation, particularly concerning nitrogen oxide emissions and soil salinity. Researchers are calling for further exploration of how human urine can be stored and used in new agricultural practices, with environmental and crop health benefits.