Researchers at two leading Sydney universities have found a way of making "green" ammonia and say their discovery could provide a major boost to farmers and speed up a global push to renewable hydrogen fuel.
Chemical engineers at the University of NSW and University of Sydney say their method of making ammonia (NH3) from air, water and renewable electricity does not require the high temperatures, high pressure and big infrastructure now needed to commercially produce the gas.
They say their new production system - demonstrated in laboratory trials - could potentially provide a solution to the problem of storing and transporting hydrogen energy.
The research team said ammonia synthesis was one of the major achievements of the 20th century as a source of nitrogen fertiliser which allowed farmers to quadruple the output of food crops to feed the world's growing population.
But since the start of the 1900s when it was first manufactured on a large scale, production of ammonia had been energy-intensive requiring high temperatures and pressures produced by fossil fuels.
Dr Emma Lovell, a co-author of the report and from UNSW's School of Chemical Engineering, said the traditional production of ammonia - known as the Haber-Bosch process - was only cost-effective when produced on a massive scale due to the huge amounts of energy and expensive materials required.
"The current way we make ammonia via the Haber-Bosch method produces more CO2 than any other chemical-making reaction," she said.
"In fact, making ammonia consumes about 2 per cent of the world's energy and makes 1pc of its CO2 - which is a huge amount if you think of all the industrial processes that occur around the globe."
Dr Lovell said besides the big carbon footprint caused by the Haber-Bosch process, producing millions of tonnes of ammonia in centralised locations meant large amounts of energy were needed to transport it around the world.
She and her colleagues have been looking at how to produce ammonia cheaply and on a smaller scale using renewable energy.
"The way that we did it does not rely on fossil fuel resources, nor emit CO2," Dr Lovell said.
"And once it becomes available commercially, the technology could be used to produce ammonia directly on site and on demand," she said.
"Farmers could even do this on location using our technology to make fertiliser which means we negate the need for storage and transport."
Fellow co-author Dr Ali Jalili said trying to convert atmospheric nitrogen (N2) directly to ammonia using electricity had 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.
Dr Jalili and his colleagues devised proof-of-concept lab experiments that used plasma (a form of lightning made in a tube) to convert air into an intermediary known among chemists as NOx - either NO2 (nitrite) or NO3 (nitrate).
The nitrogen in these compounds was much more reactive than N2 in the air, he said.
"Working with our University of Sydney colleagues we designed a range of scalable plasma reactors that could generate the NOx intermediary at a significant rate and high energy efficiency," he said.
"Once we generated that intermediary in water, 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."
Professor Patrick Cullen, who led the University of Sydney team, said atmospheric plasma was 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 efficiency and process scaling, moving the technology closer to industrial adoption."
Scientia Professor Rose Amal, who is co-director of ARC Training Centre for Global Hydrogen Economy, said 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," Professor Amal 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."
Professor Amal said ammonia could potentially be made in large quantities using the new green method ready for export.
"We can use electrons from solar farms to make ammonia and then export our sunshine as ammonia rather than hydrogen.
"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."
The team now wants to commercialise their breakthrough and is seeking to form a spin-out company to take its technology from laboratory-scale into the field.
Another big supporter for what is now dubbed the "ammonia economy" is Professor Doug MacFarlane from Melbourne's Monash University.
He has forecast that by 2050 ammonia could replace fossil fuels "in almost any application".
Professor Macfarlane was the lead author of a paper, A Road Map to the Ammonia Economy.
The story Researchers claim breakthrough in making 'green' ammonia first appeared on Farm Online.