Breakthrough brings green ammonia production closer to reality

Chemistry professor Doug MacFarlane has long known that ammonia (NH₃) can potentially be made directly from the nitrogen (N₂) that makes up 78% of the air we breathe, plus hydrogen (H) from the water we drink.

If the electricity used to make this ammonia comes from renewable sources, then the ammonia would be green, or carbon-free.

This means the most important fertiliser on Earth – responsible for the increased agricultural yields that allows the planet to sustain its present population – could be created sustainably.

Most ammonia is produced in large plants, employing a process devised by Germans Fritz Haber and Carl Bosch more than a century ago. Haber-Bosch ammonia plants are responsible for roughly 1.8% of global greenhouse emissions.

Professor MacFarlane and collaborators Alexandr Simonov and Bryan Suryanto have now devised a method of producing green ammonia that has the potential to make Haber-Bosch plants obsolete. Their process is similar to the electrolysis approach to producing hydrogen.

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Fuel for thought: Charting a course towards the ammonia economy

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Green ammonia can also be used to replace fossil fuels “in almost any application”, Professor MacFarlane says. (This was first demonstrated in Belgium during WWII, when Belgian buses were adapted to run on liquid ammonia.)

The International Marine Organisation has already mandated that marine-generated carbon emissions must be halved by 2050 – ammonia is the leading candidate to replace the more common diesel oil.

Cars, buses and even jets can also be run on ammonia, Professor MacFarlane says. In engines, ammonia runs similar to LPG, he explains.

Dr Suryanto made his green ammonia breakthrough in 2020, during Melbourne’s long COVID lockdown.

He had special permission to work on Monash’s Clayton campus in a collaboration with local company Verdant, which wanted to make bleach from saltwater by electrolysis. The bleach could be used to disinfect surfaces, and the alkaline solution also produced could be used to wash hands – it’s kinder to the skin than soap, and popular in hospitals, Professor MacFarlane says. Both products were needed during the COVID emergency.

While working with Verdant, Dr Suryanto also conducted experiments to see if phosphonium salts – a category of the ionic liquids that Professor MacFarlane has spent his career researching – could be used to make green ammonia by electrolysis.

Previous attempts to make green ammonia were only able to produce small amounts – not enough to be commercially viable.

With phosphonium, a surprising outcome

To Dr Suryanto’s amazement, the phosphonium salt allowed him to “produce ammonia at room temperature, at high, practical rates and efficiency”.

Neither Professor MacFarlane nor fellow chemist Dr Alexandr Simonov were on campus to share the excitement. Dr Suryanto had to communicate news of his breakthrough via computer link.

“To be honest, the eureka moment was not really ‘Eureka!’, it was more like, ‘Are you sure? I think you need to do that again,’” Professor MacFarlane says.

“It takes a long time to really believe it. I don’t know that we’ve yet really had a proper celebration. The launch of our spin-out company will possibly be the time that we genuinely celebrate all of this.”

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Read more: Renewables can still play an important role in Australia's energy roadmap

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Dr Suryanto’s discovery has since been verified, and the results published in Science.

And a company, Jupiter Ionics, has been formed to develop commercial applications. It will be headed by Dr Charles Day, former CEO of the Office of Innovation and Science Australia.

“The technology opens a broad range of possibilities for future scale-up to very large production facilities for export, attached to dedicated solar and wind farms,” Professor MacFarlane says.

Japan and Korea have expressed interest in importing green ammonia as a replacement fossil fuel.

But the company’s initial focus will be fertiliser production.

An advantage green ammonia has over Haber-Bosch ammonia “is that we can make our green ammonia plants really small”, Professor MacFarlane says. “You don’t need a huge chemical engineering setup. They can be as small as a thick iPad, and that could make a small amount of ammonia continuously to run a commercial greenhouse or hydroponics setup, for example.

“It means that the distributed production of fertilisers becomes possible, because the ammonia manufacturing unit is so small and simply constructed.”

Seed funding for Jupiter Ionics has come from philanthropists Lesley and Roger Gillespie, the founders of the bread-making franchise Baker’s Delight. Lesley worked part-time in a bakery with Roger – a fourth-generation baker – while she was a chemistry student at Monash.

The Monash team’s ammonia research has been funded by the Australian Renewable Energy Agency (ARENA).

Not all great being green

Green ammonia isn’t as well-known as green hydrogen, but it’s a more practical replacement for fossil fuel because it’s less combustible and the infrastructure for transporting ammonia already exists, thanks to the global network of Haber-Bosch plants, and the ships that service them.

But extensive green ammonia use has a potential disadvantage, too.

The intensive use of synthetic fertilisers over the past 100 years has vastly increased the planet’s exposure to nitrogen compounds. “It’s approximately double what it would have been, say, 200 years ago,” Professor MacFarlane says.

NOx is a generic term for the nitrogen oxides that cause atmospheric pollution. Fertiliser run-off, in the form of nitrates, are pollutants in rivers and seas.

“They go through a number of processes in the ocean, and eventually get emitted back to the atmosphere as N₂ [nitrogen] gas,” Professor MacFarlane says. “But some of those cycles and some of the intermediate materials involving nitrogen in the ocean have very long half-lives – more than 100 years.”

This means their long-term effects remain unknown. More research into the nitrogen cycle is essential, Professor MacFarlane says.