The air around us holds a solution for a more sustainable future in agriculture. Researchers at Stanford University, in collaboration with King Fahd University of Petroleum and Minerals in Saudi Arabia, have unveiled an innovative prototype capable of producing ammonia—a vital ingredient in fertilizers—by harnessing wind energy to draw air through a specialized mesh.
This transformative approach has the potential to replace the century-old process that uses high pressures and temperatures to combine nitrogen and hydrogen, a method that consumes 2% of global energy and accounts for 1% of annual carbon dioxide emissions due to its dependence on natural gas.
The study involved the first on-site – rather than in a lab – demonstration of the technology. The researchers envision someday integrating the device into irrigation systems, allowing farmers to produce fertilizers directly from the atmosphere.
“This breakthrough allows us to harness the nitrogen in our air and produce ammonia sustainably,” said study senior author Richard Zare, the Marguerite Blake Wilbur Professor in Natural Science and professor of chemistry at the Stanford School of Humanities and Sciences. “It’s a significant step toward a decentralized and eco-friendly approach to agriculture.”
To prepare for designing their device, the researchers examined how various environmental factors—such as humidity, wind speed, salt concentration, and acidity—affect ammonia production. They also investigated the influence of water droplet size, solution concentration, and the interaction of water with insoluble materials on the process.
Finally, they experimented with the optimal combination of iron oxide and an acid polymer containing fluorine and sulfur to determine the best conditions for ammonia production and to understand the interactions between these catalytic materials and water droplets. The Stanford team’s method produces ammonia in a clean and cost-effective manner, utilizing ambient air to extract nitrogen and hydrogen from water vapor.
By directing air through a mesh layered with catalysts to promote the necessary reaction, the researchers generated an ammonia yield with a concentration suitable for use as hydroponic fertilizer in greenhouse environments.
Unlike traditional production methods, this innovative technique operates at room temperature and standard atmospheric pressure without requiring an external voltage source. Farmers could use this portable device on-site, negating the need to purchase and transport fertilizer from manufacturers.
“This approach significantly reduces the carbon footprint of ammonia production,” said study lead author Xiaowei Song, a chemistry research scientist at Stanford.
In laboratory experiments, the team showcased additional potential by recycling water through a sophisticated spraying system, achieving ammonia concentrations that can effectively fertilize greenhouse plants in just two hours. By utilizing an innovative filter crafted from microporous stone material, this method holds the promise of generating ample ammonia to support extensive agricultural applications.
The device is two to three years away from being market-ready, according to study co-author Chanbasha Basheer of King Fahd University of Petroleum and Minerals. Meanwhile, researchers are focused on developing larger mesh systems to maximize ammonia production.
As a clean energy carrier, it offers a more efficient means of storing and transporting renewable energy compared to hydrogen gas, thanks to its higher energy density. This innovative approach positions ammonia as a crucial element in the decarbonization of essential industries such as shipping and power generation.
“Green ammonia represents a new frontier in sustainability,” Zare said. “This method, if it can be scaled up economically, could drastically reduce our reliance on fossil fuels across multiple sectors.”
Journal reference:
- Xiaowei Song, Chanbasha Basheer, Jinheng Xu, Richard N. Zare. Onsite ammonia synthesis from water vapor and nitrogen in the air. Science Advances, 2024; DOI: 10.1126/sciadv.ads4443