Ammonia as an engine fuel?


I was interested to read that a South Korean shipyard has received approval in principle for a large container ship powered by ammonia.  It’s the most recent use of ammonia as a fuel, but far from the only one.  A Chinese shipyard has also received initial approval for such a design.  However, no operational, production-line ammonia engine has yet been built;  the concept has only been tested on a smaller scale.

I’d never thought of ammonia as an engine fuel, so I did some research.  Ammonia was first used as a fuel in the 1870’s and 1880’s.  It seems ammonia doesn’t combust evenly or predictably on its own, but if another fuel (e.g. hydrogen, natural gas, etc.) is added to it, the combination burns very well.  If hydrogen is used, there are no carbon emissions whatsoever – a completely “green” fuel.  This is already attracting attention for use in jet engines for aircraft.

Another advantage is that ammonia is already produced in vast quantities for fertilizer and other applications.  It’s a very well-known industrial process, that could easily be expanded to meet increased demand.  There’s currently plenty of liquid natural gas to blend with it, and hydrogen production is ramping up for fuel cell use, which would be a preferable blend from a zero-carbon-emissions point of view.  Finally, ammonia can also be used in fuel cells, making it a useful product from more than one aspect of power generation.

Ammonia has the disadvantage that it’s toxic;  but so is gasoline or diesel, in a different way.  Hydrogen has its own hazards (as the Hindenburg disaster proved).  However, if the hazards of other fuels can be overcome, I daresay ammonia can be safely managed as well.

I must admit, I’m intrigued.  My late father (who worked in the oil industry) said for decades that hydrogen would be “the fuel of the future”, because there are literally unlimited supplies available in seawater.  Simply “cracking” it into its component elements of hydrogen and oxygen would produce fuel.  However, I don’t think he ever thought of hydrogen as a catalyst to burn another fuel like ammonia.

Will we ever see our own automobiles powered by ammonia?  Not in the immediate future, I’m sure – all the research I’ve seen so far has been with large engines, for ship or jet aircraft.  However, existing vehicles have been tested using ammonia fuel, with success.  If distribution networks can be set up, so that it’s as freely available as gasoline or diesel, I don’t see why ammonia can’t be more widely used.  After all, if you can adapt an existing engine to use ammonia, why not go all the way and build ammonia automobile engines?

Of course, it might make the drug problem worse.  Ammonia is used in the production of methamphetamines, as farmers already know to their cost – their agricultural ammonia, for use as fertilizer, is often targeted by drug-makers.  If it were available at every service station, I’m sure it would be misused even more.  I guess we’ll have to see whether there are ways around that.



  1. The thing about Ammonia is that it has to be manufactured in a chemical process beyond conventional fractional distillation of hydrocarbon fuels. So, it will always be more expensive. And yes, it is more toxic than gasoline and kerosene. This mean special handling procedures during refueling.

  2. Hydrogen is even worse than Ammonia. It is a very small molecule that leaks out of conventional natural gas pipes and tanks. It can also spontaneously combust in normal atmosphere (this is called re-combination). Lastly, there are no hydrogen well. Hydrogen has to be manufactured as well. Currently, it is manufactured from natural gas. The only way it can be made from sea water is if you have lots and lots of electrical power coming from say one thousand one Gigawatt nuclear plants across the U.S.

    BTW, did you know there were plans to go to a completely electric economy in the early 70's that would have involved building those 1,000 one gigawatt plants through out the country, along with the breeder reactors to recycle the nuclear waste?

    If you're anti-nuclear, you're not serious about global warming.

  3. Per wikipedia:
    The raw energy density of liquid ammonia is 11.5 MJ/L,[73] which is about a third that of diesel.
    This means you need roughly 3 times as much fuel compared to diesel/jet fuel.
    A ship or locomotive or stationary engine (think generators) might do well with that, but the weight of fuel is a big factor for cars, trucks, and airplanes.

    1. For hydrogen in planes, volume is also a consideration. Even in liquid form, it's just not very dense and will require larger tanks.

  4. Hydrogen was (probably) not the cause of the Hindenburg disaster; I'm surprised you didn't know that.
    Hydrogen is so light it doesn't burn visibly 9on its own) and couldn't have produced the big fireballs seen in Hindenburg videos. It is more likely that the aluminum based 'dope' used on the skin was what burned visibly and catastrophically. It was essentially rocket fuel and VERY dangerous. How did the fire start? A good question…

  5. I would think that Ammonia would burn into water and nitroxides. Or exactly what they are sabotaging diesel motors to get rid of.

  6. Further downsides are it's toxic – Deadly in confined spaces – and it stinks. It used to be used in refrigeration where it killed you if the system leaked.

  7. +1 Old NFO

    Also burn NH4 with O2 and you make oxides of nitrogen.
    None of that is not without it's own issues for the environment.


  8. Anhydrous Ammonia IS used in commercial and industrial refrigeration systems. The control systems used have lots of safety features including leak detection with automatic notification of both fire and hazmat teams. Anhydrous Ammonia is something you do not mess around with lightly.

  9. Back in 1976, a tank truck carrying ammonia went off an overpass in Houston Texas and exploded. I was a quarter mile away and it sounded like a bomb going off. Storing ammonia requires a pressurized and/or refrigerated container which makes it unsuitable for fuel for vehicles.

    1. There was a derailment in Pensacola in 1977 where two tanker cars of anhydrous ammonia were punctured. Two dead, 46 injured, and had it happened in town rather than at the edge of Escambia Bay, it could've been a lot worse.

  10. When young I worked in a pharmaceutical plant. Half a city block, five stories tall. Somebody broke a bottle of "panther piss", 12 oz of 28% ammonia.

    Nobody had to say a thing. The whole building self evacuated.

    One 12 oz bottle. Can't wait for the 12 gallon tznk.

  11. It's way more likely that they'll use some form of artificially produced hydrocarbon than pure hydrogen. I've seen research papers written on what they termed "rectified hydrocarbon fuel" that essentially consisted of artificial hydrocarbon fuel that was interchangeable with gasoline in the distribution system. This sort of fuel does away with all the problems of hydrogen, and uses the existing infrastructure to store and transport the fuel. As well, it solves the majority of the pollution problems because the fuel is basically as pure as it can get.

  12. I'm not worried about the meth-heads getting ammonia. Let'em have all they want. Make them take their poisonous drugs until they Darwin methamphetamine into extinction.

    1. Now theres a happy thought!
      Back in the 70s-80s when I was a kid, I remember the US had a heroin problem. Without Narcan, that problem largely "died out" on own…

  13. Jaime:

    A fair percentage of damaged RV's are due to fires that originate from the refrigerator. Very obvious damage, that leaves a large hole in the side and the roof. Insurance total. In some cases, it shows no obvious internal damage due to good insulation of the surrounding cabinet.

  14. First of all, the first comment here kurt9, he's exactly right x 10.

    Now, about ammonia. That's all mighty interesting, if it weren't for the fact that the key ingredient for industrial ammonia production is natural gas.

    Like so many Green Schemes, all this does is push the Carbon impact somewhere else, hopefully out of sight. It's psuedo-scientific virtue signalling. You have to follow the whole energy chain from concept to consumption to understand whether a Green Scheme idea has any merit to it. They are all scams until proven otherwise, in the current climate scare.

  15. Whole lotta "NOPE" there…higher cost to produce compared to even low energy renewable ethanol, far more acutely toxic than any hydrocarbon fuel, converts immediately to a gas in all environments on release (impossible to control and fills your "vessel" guaranteeing everyone dies), turns into acutely toxic gasses when burned incorrectly, and is still explosive in containment like hydrocarbon vapors. To many potential failure points due to human nature. Plus you get the added bonus of some sort of compressed hydrocarbon or hydrogen gas to go along with it (see all above, except swap the rankings for acute toxicity and flammability/explosive atmosphere). It's a genuine two-fer in the "enhanced risk" department. As a former certified HazMat tech and trainer, the idea fills me with dread.

Leave a comment

Your email address will not be published. Required fields are marked *