£20 ultrasound device could decentralise fertilizer production, Glasgow scientists say

Researchers at the University of Glasgow believe a low-cost device that uses ultrasound to generate nitrate fertilizer from air and water could help decentralise fertilizer production and reduce agriculture’s environmental footprint.

University chemists and engineers have developed a £20 prototype that produces nitrate—an essential nutrient for plant growth—without relying on traditional fossil-fuel-intensive processes. The approach uses sound waves to trigger chemical reactions in deionised water containing dissolved nitrogen and oxygen.

A new study in Cell Reports Physical Science details the process, which begins by bubbling air through water to introduce nitrogen and oxygen. Focused ultrasound waves then create microscopic bubbles that oscillate and collapse under pressure, generating extreme temperatures of up to 5000°C. These conditions allow nitrogen molecules to break apart and combine with oxygen, forming nitrate.

In lab tests, the device produced a 40 micromolar concentration of nitrate in 20 millilitres of water over an eight-minute period. While the concentration remains modest, the researchers believe the process can be scaled up to produce fertilizer in quantities suitable for on-farm use.

Professor Mark Symes of the University of Glasgow’s School of Chemistry, a co-author of the study, said the method offers an alternative to the Haber-Bosch process, which dominates global ammonia production and accounts for about 2% of annual carbon dioxide emissions.

“Currently, the world relies on factories which can cost hundreds of millions of pounds each to produce vast quantities of fertilizer,” Symes said. “We wanted to explore whether we could make something that produces one farmer’s needs for as little capital outlay as possible.”

The device, roughly the size of a coffee can, was assembled by lead author Dr Engr. Lukman Yusuf using off-the-shelf components. Advances in ultrasound technology and renewed interest in sonochemistry enabled the team to revisit methods first identified in the 1930s but never widely adopted.

The researchers acknowledge that their prototype consumes more energy than the Haber-Bosch process. Further work is underway to improve energy efficiency and determine the effectiveness of the nitrate produced in supporting crop growth.

Dr Paul Prentice, co-author from the university’s James Watt School of Engineering, said: “We’re now working towards building improved prototypes capable of producing nitrate continuously at higher concentrations, making the process more useful for real-world applications.”

The study, titled Towards decentralized nitrogen fixation using pulsed ultrasound, was funded by the UK’s Engineering and Physical Sciences Research Council (EPSRC) and the Royal Society.