Research has emerged showing that nitrogen in human urine can be converted into expensive fertilizer while also increasing electricity production efficiency. This technology solves both hygiene and power shortage issues simultaneously.
A research team from Stanford University's School of Engineering announced on the 19th in the international journal 'Nature Water' that they have developed a solar-powered electrochemical treatment device that can turn urine into a resource for producing both fertilizer and electricity.
The urine treatment device converts nitrogen compounds in urine into ammonia fertilizer using electricity generated from solar cells. As urine passes through the partition structure inside the device, electricity attracts ions, accumulating ammonia, which is ultimately converted into ammonium sulfate, a fertilizer commonly used in agriculture.
The researchers also utilized waste heat generated from the back of the solar cell panels during the urine treatment reaction. The solar cells heat up more as they receive more sunlight; when this waste heat is collected and transferred through copper pipes, the ammonia separation process speeds up. Simultaneously, the panels that send waste heat cool down, increasing electricity production efficiency. Thus, both the urine and heat that were about to be discarded are used as resources.
Nitrogen, a key component of fertilizers, has traditionally been produced in large chemical plants. However, this process is associated with a high emission of greenhouse gases, and production facilities are concentrated in developed countries. This makes fertilizer prices inevitably high in developing countries. Urine can help bridge this fertilizer gap. According to the researchers, the nitrogen contained in urine produced by humankind can cover about 14% of the global fertilizer demand.
As a result of applying the device developed by the research team, electricity production increased by 60%, and ammonia recovery rates improved by over 20%. William Tarpeh, a professor of chemical engineering at Stanford, noted, 'This project turns waste problems into opportunities to obtain resources,' adding, 'We can capture nutrients that have been previously wasted or caused environmental harm and convert them into fertilizer.'
The researchers also indicated that electricity needed for fertilizer production can be supplied through solar power without relying on existing power grids. Economic analysis revealed that in Uganda, where fertilizer prices are high and electricity grids are lacking, the recovered nitrogen could have a value of up to $4.13 (5,737 won) per kilogram. This represents over double the revenue compared to the United States.
Removing nitrogen from urine leaves water that can be safely reused for irrigation or discharged. Given that over 80% of wastewater globally is discarded untreated, this technology has significant implications for solving hygiene issues.
Orisa Coombs, a doctoral student and the first author of the paper, stated, 'The urine from one person per day can fertilize a small garden, and it is possible to produce fertilizer on-site using only sunlight without large chemical plants or power grids, even utilizing the surplus electricity,' describing it as 'an innovative technology that can solve water, food, and energy problems simultaneously.'
References
Nature Water (2025), DOI: https://doi.org/10.1038/s44221-025-00477-w