Australian chemical engineers have found a way to make ‘green’ ammonia from air, water and renewable electricity – while avoiding the need for high temperatures, high pressure and major infrastructure.
They believe the new production method has the potential to play a role in the global transition towards a hydrogen economy, where ammonia is increasingly seen as a solution to the problem of storing and transporting hydrogen energy.
Their work is outline in a paper published in Energy and Environmental Science.
Dr Emma Lovell, a co-author on the paper from UNSW’s School of Chemical Engineering, said the traditional way to make 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 says.
“In fact, making ammonia consumes about 2 per cent of the world’s energy and makes 1 per cent of its CO2 – which is a huge amount if you think of all the industrial processes that occur around the globe.”
She and her colleagues looked at how to produce it cheaply, on a smaller scale and using renewable energy.
“The way that we did it does not rely on fossil fuel resources, nor emit CO2,” Dr Lovell says.
“And once it becomes available commercially, the technology could be used to produce ammonia directly on site and on demand – farmers could even do this on location using our technology to make fertiliser – which means we negate the need for storage and transport. And we saw tragically in Beirut recently how potentially dangerous storing ammonium nitrate can be.
“So if we can make it locally to use locally, and make it as we need it, then there’s a huge benefit to society as well as the health of the planet.”
ARC DECRA Fellow and co-author Dr Ali (Rouhollah) Jalili said trying to convert atmospheric nitrogen directly to ammonia using electricity had posed a significant challenge to researchers for the last decade, due to nitrogen’s inherent stability.
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 is much more reactive than N2 in the air.
“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.”
The team will next turn its attention to commercialising this breakthrough, and is seeking to form a spin-out company to take its technology from laboratory-scale into the field.