Ammonia could be the ‘fuel of the future’ for shipping
On the high seas of the Norwegian continental shelf, cargo ships are a familiar sight. If scientists have their way, however, a new type of ship could soon appear over the horizon, powered not by a dirty pollutant but ammonia.
Last month, Wärtsilä, a Finnish manufacturing firm, announced that it was working on the world’s first full-scale test of ammonia as a green fuel in ships. And for good reason. The International Maritime Organisation is pushing the sector to cut its emissions in half by 2050.
“It is a huge undertaking to change the shipping industry,” says Egil Hystad of Wärtsilä. “Shipping is emitting carbon dioxide corresponding to more than 500m personal cars every year. That’s one billion tonnes of carbon dioxide.”
At one level, ammonia is just a gas made of nitrogen and hydrogen, better known for its use as a fertiliser as well as its pungent smell and corrosive nature.
But like Wärtsilä, many see ammonia’s potential serve as a sustainable fuel by carrying hydrogen, helping to decarbonise operations and face up to the challenges of climate change.
Earlier this year, companies including British engineering firm Lloyd’s Register and Samsung’s shipbuilding division signed on for a project to build an ammonia-fuelled tanker. So has its time arrived for ammonia?
For the shipping industry, there is little choice but to try to use it. Hydrogen alone, tabled as an alternative, falls flat as a fuel given its rapid boil-off rate, which means a significant portion of it would be lost on a long trip across the seas.
Any hopes of electrifying ships are likely to fail too, given the batteries required would be “too large”, according to Dr Tristan Davenne, engineer on a green ammonia project in Harwell. “They’re certainly not scalable up to that level at the moment,” he says.
One challenge for sectors such as shipping looking to ammonia as a potential green fuel is to find a way of producing it that doesn’t generate harmful emissions.
Typically, ammonia is made in a process known as steam reforming. Hydrogen is generated from a reaction involving methane, water and air, and then combined with nitrogen in a process known as the Haber method. However, carbon dioxide is produced as a byproduct.
Dr John Constable, director of the Renewable Energy Foundation, sees one fix for this that banks on carbon capture and storage, a relatively unproven technology that reels carbon dioxide from the air and stores it deep underground. “If you can capture the carbon from steam methane reforming, it may be clean at the point of consumption,” he says.
Another method picking up traction from Wärtsilä involves the use of electricity generated by wind farms to split water into its constituent components of hydrogen and oxygen through a process known as electrolysis.
That hydrogen can then be combined with nitrogen pulled from the atmosphere to create ammonia in a way that has cut carbon emissions altogether. For years, the method has proved too costly given the high price of renewable energy, but it is getting cheaper. Hystad claims 400gW of wind turbines are due to be installed in the North Sea between now and 2050, more than 20 times the current output.
With clean options of generating ammonia emerging, the next challenge involves turning it into a form that can be used as fuel. Wärtsilä is exploring the possibility of pumping ammonia 70m below sea level where high pressure can turn it into a liquid, while another option involves cooling the gas to -40 degrees C to liquefy it.
Once in a liquid form, ammonia can be used in a retrofitted internal combustion engine, such as the ones Wärtsilä are looking at in existing ships, or can generate electricity in a reaction driven by a device known as a fuel cell.
The ability to create green ammonia is opening up potential applications far beyond the high seas too. A study led by Davenne’s team in Harwell has been investigating the potential for ammonia to replace kerosene as the go-to fuel in the aviation industry.
At a cruising altitude, ammonia could sit in the wings of a plane as a liquid, given the sub-zero temperatures 30,000ft in the air, and the engine would need few changes to accommodate for ammonia according to their research.
But there are some real hurdles to overcome to get ammonia working as a fuel.
In planes, ammonia could struggle as its energy density is a lot lower than kerosene, meaning much more fuel will be needed onboard. On the ground, wings would have to be “refrigerated as ammonia is a gas in that atmosphere”, Davenne says
There are challenges for the shipping industry too. The corrosiveness of ammonia presents “a real problem for the integrity of the engine” in a vessel, according to Constable, and could pose safety threats to operators.
Ammonia burns slowly too and can be difficult to ignite in a combustion engine, so a real feat of engineering will be required in projects currently using ammonia in older engines. Industry experts see fuel cell boats coming, but they remain years away.
Both processes of generating ammonia require large amounts of fresh water too, a grave concern at a time when water shortage is a risk.
“You’re taking fresh water and turning it into a fuel. Bear in mind it won’t be returned to the water table because when it’s burned it obviously goes off as water vapour,” Constable says. “This is much worse than a leak in your water system.”
Constable sees the focus on ammonia as a consequence of policies “bearing down on industries to decarbonise where there is no option but to use ammonia”.
Though ammonia is unlikely to emerge as a useful fuel for other modes of transport, seafarers may have no choice but to accept ammonia’s time has come. “It is the only way of decarbonising it 100pc for that transport,” he says.
Tämän aamun lehdessä Jukka Oksaharjun mukaan 40% suurista yhtiöistä ”ei ole kertonut lainkaan arvioita tulevaisuuden näkymistään”, joten Wärre ei sikäli ole ainoa.
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