Chemical researchers develop “green” ammonia

Ammonia has sustained humanity since the early 20th century, but its production leaves a huge carbon footprint. Now researchers have found a way to make it 100 per cent renewable.

The researchers used a bubble column to break down nitrogen, creating reactive water which was then processed in a second electrochemistry reactor. Credit: Professor Patrick ‘PJ’ Cullen.

Ammonia is one of the world’s most important chemicals that supports global food supply, used primarily in the production of fertilizer, enabling better agricultural productivity.

However, the production of ammonia is incredibly energy-intensive, accounting for roughly two percent of global energy consumption. It is also highly eco-destructive, comprising 1.4 percent of total global CO2 emissions.

A collaborative effort between researchers at the University of Sydney and the University of New South Wales has found a way to make ammonia production “green”, using only air, water and renewable energy sources such as solar.

Published in the journal Energy and Environmental Science, the key innovation is combining atmospheric plasma, the fourth state of matter, with electrochemistry; a field of chemistry that uses electricity to influence a chemical change.

“In recent years, the potential of using ammonia directly as a fuel source or as a means of transporting hydrogen has been increasingly explored, with researchers aiming to make the production process sustainable,” said Professor of Chemical and Biomolecular Engineering, Patrick “PJ” Cullen, who led the team of researchers at the University of Sydney.

“Atmospheric plasma is increasingly finding application in green chemistry. By inducing the plasma discharges inside water bubbles, we have developed a means of overcoming the challenges of energy inefficiency and process scaling, moving the technology closer to industrial adoption,” said Professor Cullen.

David Alam, a PhD student at the University of Sydney and co-author of the paper said: “by advancing plasma technology synergistically with electrolysis, we have created sustainable ammonia, which provides an exciting new path for future chemical production.”

Ammonia as an energy storage solution

Leading the UNSW team, Scientia Professor Rose Amal, co-director of the ARC Training Centre for Global Hydrogen Economy, said that in addition to the advantages of being able to scale down the technology, the team’s “green method of ammonia production could solve the problem of storage and transport of hydrogen energy.”

“Hydrogen is very light, so you need a lot of space to store it, otherwise you have to compress or liquify it,” she said.

“But liquid ammonia actually stores more hydrogen than liquid hydrogen itself. And so there has been increasing interest in the use of ammonia as a potential energy vector for a carbon-free economy.”

The plasma technology supporting this research has already been successfully spun-out by PlasmaLeap Technologies, which is based at the Sydney Knowledge Hub, the University of Sydney’s technology startup incubator.

DISCLOSURE:

The research was financially supported by the Australian Research Council under the Discovery Early Career Research Award and the Laureate Fellowship Scheme. Financial support was also received from the Office of the Deputy Vice Chancellor (Research) of the University of Sydney.

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