Should the Hydrogen Economy Actually Be an Ammonia Economy?

Fritz Haber won the Nobel Prize in 1918 for inventing what became known as the Haber-Bosch process (Bosch made it more efficient), which takes nitrogen out of the air and reacts it with hydrogen to make ammonia. Seventy-five to 90% of this ammonia is turned into fertilizer, used in half of all food production. It was also used for other, less salubrious things, which is why Haber is known as "The Monster Who Fed The World."

The process uses a lot of hydrogen (its formula is NH₃ so there are three hydrogen atoms for every nitrogen atom that is fixed) and a lot of energy. According to C&EN, as much as 1% of the world's production (a Royal Society report says 1.8%) and "it belched up to about 451 million tonnes of CO2 in 2010, according to the Institute for Industrial Productivity. That total accounts for roughly 1% of global annual CO2 emissions, more than any other industrial chemical-making reaction." And that doesn't even account for the CO2 released making the hydrogen by steam reformation.

But what if all that hydrogen was "green," made with electricity that was, as they used to promise with nuclear energy, too cheap to meter? Then it could be used to make "green" ammonia, which could be a very useful way to store and ship hydrogen. That is what they are talking about doing in Australia. According to Adam Morton of the Guardian, there are plans for an Asian Renewable Energy Hub with "1,600 large wind turbines and a 78 sq km array of solar panels working to power 14 gigawatts of hydrogen electrolysers" and turning a lot of it into ammonia.

Hydrogen is a battery, a medium for storing electricity, and a lousy and inefficient battery at that. I have called it a folly, not a fuel. Converting it to ammonia is even lousier and less efficient. But if you have square miles of Australian sunshine and new cheaper Chinese electrolyzers, who cares?

We have also complained about how hard it is to store and transport liquid hydrogen, but storing ammonia is comparatively easy, at far lower pressures and at room temperature, with an energy density twice that of liquid hydrogen. Adam Bandt of the Greens tells the Guardian:

“With green hydrogen, Australia can export our sunlight."

Green ammonia is also stored sunlight, a way to export electricity long distances from places with more sun than they can use, like the Sahara or Australia, and ship it efficiently and cheaply to places that need clean energy.

All About Ammonia

Ammonia is interesting stuff all on its own. It can actually be used as a fuel directly; cars, rockets, and fuel cells can be powered by it. Ammonia engines powered the streetcars in New Orleans in the 1880s, and in the Second World War, it powered buses in Belgium. And of course, it can be turned back into hydrogen.

It's certainly not the perfect fuel, given that it is toxic (one reason it is no longer used as a refrigerant in household fridges), can be turned into explosives, and it's the reason meth labs blow up so often.

But green ammonia might be the answer to many problems. From C&EN:

“Ammonia as it’s produced today for fertilizers is effectively a fossil-fuel product,” says Douglas MacFarlane, an electrochemist from Monash University. “Most of our food comes from fertilizers. Therefore, our food is effectively a fossil-fuel product. And that’s not sustainable.”

Even if green ammonia just took over the fertilizer market, it would be huge. But imagine if it could also be a battery, a cheap way of moving sunlight.

Perhaps we should stop dreaming of a hydrogen economy, and start talking about an ammonia economy.