QAZAQ GREEN.  A new solar-powered technology could transform human waste into a valuable resource for sustainable farming and energy, according to Stanford University citing a study published August 19 in Nature Water.

The system, developed by a Stanford University-led team, recovers nitrogen-rich fertilizer from urine while generating electricity and improving sanitation. The prototype uses solar panels to power an electrochemical process that separates ammonia from urine and captures it as ammonium sulfate, a widely used fertilizer. At the same time, waste heat from the solar panels is used to speed up the chemical reaction and increase efficiency.

“Each person produces enough nitrogen in their urine to fertilize a garden,” said lead author Orisa Coombs, a PhD student in mechanical engineering. “With enough sunshine, this system can produce fertilizer where it’s needed most, while also generating electricity that could be stored or sold.”

Nitrogen is a key ingredient in commercial fertilizers, traditionally manufactured in carbon-intensive factories located mostly in wealthier countries. Human urine alone contains nitrogen equivalent to about 14% of global fertilizer demand.

Tests showed that integrating solar panel heat boosted power generation by nearly 60% and improved fertilizer recovery by more than 20% compared to earlier designs. A model of system economics suggested that in countries like Uganda, where fertilizer costs are high and energy access is limited, the technology could generate over $4 per kilogram of recovered nitrogen — more than double the potential in the United States.

Beyond agriculture, the system also improves sanitation. By removing nitrogen from urine, it makes wastewater safer to discharge or reuse for irrigation. This could be especially impactful in low- and middle-income countries, where over 80% of wastewater remains untreated.

“This project is about turning a waste problem into a resource opportunity,” said William Tarpeh, senior author and assistant professor of chemical engineering. “It’s clean, scalable, and powered by the sun.”

The researchers are now building a larger prototype capable of processing more waste at faster rates. They believe the innovation could support farmers and communities worldwide, while also offering lessons for industries like wastewater treatment.