At Stanford, researchers have done what sounds unthinkable: they’ve turned human urine into a clean source of both fertilizer and energy. Their solar-powered system, small enough to operate without a grid, separates ammonia from urine and converts it into ammonium sulfate—one of the world’s most common fertilizers. What makes the breakthrough even more impressive is its efficiency. By capturing and reusing the waste heat from solar panels, the process doesn’t just accelerate—it also boosts power output by nearly 60% while improving ammonia recovery by over 20%. The very act of keeping solar panels cooler makes them perform better, creating a virtuous cycle of energy and production.
Every person produces enough nitrogen in their urine to fertilize a garden, and human waste contains enough nitrogen overall to cover nearly 14% of global fertilizer demand. Today, most nitrogen fertilizers are produced in giant, resource-intensive plants located in wealthier countries. That drives up costs and leaves many communities—especially in Africa and Asia—locked out of affordable access. With this system, fertilizer could be created directly where it’s needed, without shipping or expensive infrastructure. In regions like Uganda, researchers estimate the system could generate more than $4 per kilogram of nitrogen, doubling the economic benefit compared to similar efforts in the U.S.
But agriculture isn’t the only winner. The system also improves sanitation by removing nitrogen from wastewater, making it safer to discharge or reuse for irrigation. With over 80% of global wastewater going untreated—much of it in developing countries—the potential to reduce contamination and protect drinking water supplies is enormous. It’s a rare engineering innovation that strikes at three of the world’s toughest challenges at once: food, water, and energy.
The Stanford team is already working on scaling up with larger prototypes that can process more urine and operate faster in direct sunlight. If expanded further, the same principles could be applied at industrial wastewater plants, mining operations, or even urban centers, where nutrient-rich waste streams often go untapped. By closing the loop between waste and value, this work points toward a future where we no longer flush resources away but instead transform them into local energy and agriculture solutions.
Related Stories:
- Engineers turn wastewater into fertilizer and fuel
- Human urine tested as sustainable fertilizer source
