Everybody knows the acrid, distinctly unpleasant smell of ammonia. But I bet that not many of us understand that it could save our tiny planet from the environmental devastation we’re struggling to prevent.

It’s one of the most produced industrial chemicals in the world, somewhere between 70% and 85% of it used to make agricultural fertilizer (nobody seems to agree on that figure). Sometimes it’s directly injected in pure form into the ground to increase yields of crops like maize and wheat. Then there’s refrigeration. And lots of it, heavily diluted with water, is found in ordinary household cleansers. It’s also a critical ingredient in making methamphetamine, but we won’t go there. Ammonia has dozens of other legitimate industrial applications, and it may well fit one of our own needs in trucking quite well.

Partly because it’s free of carbon, but perhaps most importantly because it’s an efficient carrier of hydrogen.

Some time in the near future, you won’t be able to buy a new diesel-fueled truck. Maybe as soon as 2035. And I’d wager serious money that some jurisdictions – lookin’ at you, California – will ban all such trucks from entering their territory as soon as 2025. Some cities will do the same, and quite a few in Europe and elsewhere already have, like Paris, Mexico City, Madrid, and Athens.

But you may not be limited to battery electric or conventional hydrogen fuel cell vehicles as the only alternatives. Ammonia could do the job, in a couple of ways. Possibly as a liquid fuel injected into internal-combustion engines, or perhaps as a carrier of hydrogen (its chemical makeup is three hydrogen atoms and one nitrogen). Its official moniker is NH_3.

Amogy’s successful tests

Among others, a small start-up company based in Brooklyn, NY, with significant operations in Norway, is showing us how. In mid-January Amogy Inc. announced the successful testing of the first-ever ammonia-powered, zero-emission semi truck. After integrating its technology into a 5kW drone in July 2021 and a 100kW John Deere farm tractor last May, the company scaled its ammonia-to-power technology to 300 kW. Following an eight-minute-long fueling, a Freightliner Cascadia tractor with 900 kWh of total stored net electric energy onboard, was tested for several hours on the campus of Stony Brook University on Long Island, N.Y. Full-scale testing on a proper test track is set to follow quickly.

“Unlocking ammonia’s potential, Amogy’s proprietary technology enables the on-board cracking of ammonia into hydrogen, which is then sent directly into a fuel cell to power the vehicle,” the company explains. “Liquid ammonia has an energy density that is approximately three times greater than compressed hydrogen and it requires significantly less energy, making it cost-effective to store and transport.

“Ammonia presents a clear path to a zero-carbon fuel value chain across all heavy-duty transportation sectors thanks to existing transportation and storage infrastructure. A global commodity, 200 million tons of ammonia are already produced and transported each year, making it an ideal and accessible alternative fuel.”

An optimal fuel

“Beyond its incredible energy-density and liquid phase at an ambient temperature, ammonia is an optimal fuel to achieve rapid decarbonization of heavy transportation because it is available globally with… infrastructure already in place,” said Seonghoon Woo, chief executive officer at Amogy. “In the near future, we look forward to further scaling and tackling other hard-to-abate sectors, such as global shipping.”

A company based in Mississauga, Ontario, Hydrofuel Canada, has another way to use ammonia — by directly injecting it into an internal combustion engine along with a small amount of diesel or biodiesel to help with combustion. It demands some smallish modifications to the engine to make it a multi-fuel motor, but it’s said to be an easy retrofit. There’s a test running in two heavy-duty tractors in fleet service now.

According to company chairman Greg Vezina, ammonia “is the most environmentally benign fuel when compared with gasoline, gaseous or liquid hydrogen, liquefied petroleum gas, diesel, compressed natural gas, electric (where electricity is created from fossil fuels) and hybrid electric vehicles”.

None of this is altogether new. In fact, such uses of ammonia go back to the 1800s. For instance, an ammonia-fueled streetcar in New Orleans was launched in 1871. And during World War II it was relatively common to see liquid ammonia replacing hard-to-find diesel or gasoline in all manner of vehicles. There are presently many projects all across the world aimed at to using ammonia as a carbon-free fuel, especially in power generation, off-grid applications, as well as internal combustion engines.

In the larger picture it’s clear that the most important role for ammonia will be its use not as a zero-carbon fuel but as an effective energy carrier for hydrogen to power fuel cells. Chemists and others say it will create the road to the hydrogen economy.

The energy density

Ammonia smells awful and is dangerously caustic but compared to hydrogen its energy density by volume is nearly double. It’s also easier to ship, store, and distribute using existing infrastructure. And that resolves one of the greatest barriers to the adoption of hydrogen, namely the cost of storage and transportation.

The key here is that while hydrogen needs to be cryogenically frozen to -253 Celcius, ammonia only needs to be cooled to -33 to remain in a liquid state. Liquified ammonia contains nearly 50% more hydrogen by volume than liquid hydrogen itself and can be ‘cracked’ using inexpensive catalysts to provide hydrogen.

It’s all somewhat ironic and circular – we’re going to make hydrogen, extract ammonia from it, then store and transport that ammonia to wherever it’s needed, and finally drag the hydrogen back out to use in a fuel cell.

“You can store it, ship it, burn it, and convert it back into hydrogen and nitrogen,” says Tim Hughes, an energy storage researcher with manufacturing giant Siemens in Oxford, U.K. “In many ways, it’s ideal.”

Green ammonia

But of course we want ‘green’ ammonia to make green hydrogen, which isn’t possible in the usual production method – which is to strip hydrogen from natural gas using steam and then combine that hydrogen with nitrogen from the air at high pressure and extremely high temperatures. That’s the Haber-Bosch process, invented in the early 1900s by a couple of smart Germans and in use ever since. Problem is, it’s dirty, spewing two tons of carbon dioxide into the atmosphere for every ton of ammonia made.

So we must take natural gas out of the equation and instead make hydrogen by electrolysis using electricity sourced from renewables – and then make ammonia out of it. Projects from Canada to Australia are being built as we speak to accomplish this, the biggest in Saudi Arabia, which will make a million tons of ammonia a year after it comes on stream in 2025. A more modest green ammonia plant in Louisiana is expected to produce 20,000 tons annually this year.

While pure hydrogen has been seen by many as the fuel of the future, it looks like ammonia is the better route to the same place.

“It ticks all the boxes,” says Jimmy Faria, a chemical engineer at the University of Twente in the Netherlands.

Now, does any of this mean anything to you folks running trucks today? Maybe, if you want to try a multi-fuel engine retrofit. But really, the significance of ammonia here is that the day you can buy a truck powered by a hydrogen fuel cell is closer, at a lower cost. And unless battery technology develops such that you get the range you may need, which seems doubtful at this point, you will eventually need that truck.