Researchers from the University of New South Wales (UNSW) and the University of Sydney (USYD) have put their big heads together and managed to produce ‘green’ ammonia from air, water, and solar energy in a fashion that does not also require high temperatures, high pressure and enormous amounts of infrastructure. The researchers believe the new production method, which has so far only been demonstrated in a lab, could play a role in the global transition to a hydrogen economy.
Ammonia, a hydrogen product, is currently used mainly in the fertiliser industry but could play a pivotal role in the evolving hydrogen economy, particularly as a shipping fuel in its liquefied form. This, says Rystad Energy’s Head of Global Energy Systems, Marius Foss, is for the simple reason that ammonia can be safely liquefied at only 33 degrees Celsius – making it much easier and more efficient to store and transport than H2.
However, the traditional way to make ammonia, the Haber-Bosch process, is only cost-effective at enormous scale, expense and emissions. As UNSW’s School of Chemical Engineering and co-author of the research published in Energy and Environmental Science, Dr Emma Lovell, says: “The current way we make ammonia via the Haber-Bosch method produces more CO2 than any other chemical-making reaction. In fact, making ammonia consumes about 2 percent of the world’s energy and makes 1 percent of its CO2 – which is a huge amount if you think of all the industrial processes that occur around the globe.”
Lovell added that the carbon footprint of the Haber-Bosch process is amplified because such a large-scale project requires a centralised location which necessarily entails a great deal of global transportation. Moreover, as was shown with the catastrophic ammonium nitrate explosion at a warehouse in Beirut last year, storing large amounts of ammonia in one place is very dangerous.
Wanting to avert further events like that tragically seen in Lebanon, Lovell and her team have found a way to produce ammonia cheaply, locally, and greenly. Indeed, Lovell believes that once the technology is available commercially that farmers would be able to produce their own green ammonia to make fertiliser on site.
“So if we can make it locally to use locally, and make it as we need it,” said Lovell, “then there’s a huge benefit to society as well as the health of the planet.”
The fourth state matters
The key to this breakthrough is found in the fourth state of matter – plasma. According to ARC DECRA Fellow and co-author Dr Ali Jalili, converting atmospheric nitrogen (N2) directly to ammonia using electricity “has posed a significant challenge to researchers for the last decade, due to the inherent stability of N2 that makes it difficult to dissolve and dissociate.”
However, by using plasma (a form of lightning in a tube) Jalili and his colleagues were able to convert air into an intermediary called NOx (either NO2 or NO3) which is more reactive than N2 in the air.
“Once we generated that intermediary in water,” said Jalili, “designing a selective catalyst and scaling the system became significantly easier. The breakthrough of our technology was in the design of the high-performance plasma reactors coupled with electrochemistry.”
Solar-powered storage solution
Thus, not only has this team of researchers made a breakthrough in the ammonia industry, which could, among other things, nullify the possibility of a disaster like that witnessed in Beirut happening again, but they may have also solved the problem of storing and transporting hydrogen.
UNSW’s and ARC Training Centre for Global Hydrogen Economy‘s Scientia Professor Rose Amal, said that though hydrogen is exceptionally light, it therefore requires an exceptional amount of space for storage, “otherwise you have to compress or liquify it.”
“But liquid ammonia actually stores more hydrogen than liquid hydrogen itself,” continued Amal, “and so there has been increasing interest in the use of ammonia as a potential energy vector for a carbon-free economy.”This is all to say that allied with this technological breakthrough, ammonia could be made from solar energy and be essentially ready for export.
“We can use electrons from solar farms to make ammonia and then export our sunshine as ammonia rather than hydrogen,” concluded Amal. “And when it gets to countries like Japan and Germany, they can either split the ammonia and convert it back into hydrogen and nitrogen, or they can use it as a fuel.”
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