Fertilizers are costly in much of the world, electricity is unreliable, and clean water is scarce. At the same time, most wastewater goes untreated, leading to severe health and environmental issues.
The new model provides a workable solution, converting a steady stream of waste into something valuable: power and fertilizer, all while treating wastewater to make it safer.
This system uses solar panels to recover nitrogen from urine – without needing a power grid, chemical plants, or fancy equipment.
From urine to crop nutrients At the heart of the system is a clever trick: pulling ammonia – a form of nitrogen – out of urine and turning it into ammonium sulfate, a type of fertilizer. It does this with a series of chambers and specialized membranes. Solar energy drives ions through the system, separating and capturing ammonia in the process.
Solar panels do more than generate electricity. They also generate heat – typically wasted – that this system captures and uses.
Copper tubing draws heat from the back of the panels and uses it to warm the system. That heat accelerates the process of separation, allowing the gas to become fertilizer more quickly.
There’s an added benefit: when solar panels are cool, they actually generate more electricity. By capturing the heat and putting it to work, the system not only functions at a higher speed – it also produces more energy.
The power of nitrogen in urine “This project is about turning a waste problem into a resource opportunity,” said William Tarpeh, assistant professor of chemical engineering at the Stanford School of Engineering.
“With this system, we’re capturing nutrients that would otherwise be flushed away or cause environmental damage and turning them into something valuable – fertilizer for crops.”
Why does that matter? Because nitrogen is essential for growing food. It’s the main ingredient in most fertilizers. But producing nitrogen fertilizers the traditional way uses a lot of fossil fuels. It’s also centralized in wealthier countries, making it expensive and harder to access in lower-income areas.