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Hydrogen Engine Center Demonstrates Ammonia/Hydrogen Engine

Hydrogen Engine Center, Inc. (HEC) demonstrated its proprietary ammonia/hydrogen-fueled Oxx Power engine (earlier post) just prior to the annual shareholders’ meeting in Algona, Iowa on 30 May.

The test engine—one of the company’s 4.9-liter, 6-cylinder units—was designed to use HEC’s proprietary Oxx Boxx engine controller and a dual-fuel injection system. Although the engine is capable of running exclusively on hydrogen, the test was conducted using 95% ammonia and 5% hydrogen used as a combustion catalyst.

The increased density of hydrogen associated with the ammonia fuel provides the engine with significantly more power than hydrogen alone. The small amount of hydrogen needed can be generated onboard the engine, thus eliminating the need for a second fuel. Because ammonia contains no carbon, emissions byproducts include only slightly increased amounts of water vapor and trace amounts of NOx.

We have been awaiting the day when we could add ammonia to the world’s list of potential fuels and today is the day. The performance of the engine is very impressive. This demonstration clearly shows that anhydrous ammonia can be used as a fuel.

—Ted Hollinger, HEC President

HEC has filed 5 patents on its ammonia engines. The company will continue endurance testing, then will install an ammonia/hydrogen-fueled engine in the Oxx Power hydrogen-fueled genset that is currently powering the company’ dyno room.

Ammonia (NH3) is the second-most prevalent chemical in the world, and is widely used as the primary input for the majority of worldwide nitrogen fertilizer production.

Worldwide ammonia production is largely based on modifications of the Haber-Bosch process in which NH3 is synthesized from a 3:1 volume mixture of hydrogen and nitrogen at elevated temperature and pressure in the presence of an iron catalyst.

Nitrogen used is obtained from the air, while the hydrogen is obtained from the steam reforming of natural gas or other light hydrocarbons, or by the partial oxidation of heavy fuel oil or coal. According to a June 2004 review of greenhouse gas emissions in fertilizer production prepared for the IEA Bioenergy Task Force, about 85% of world ammonia capacity is based on natural gas.

The synthesis of ammonia is a very energy demanding process, with the current fertilizer manufacturers typically consuming around 25-35 GJ/tonne ammonia through the steam reforming process.  Thus, due to consumption of natural gas or other hydrocarbons both for the hydrocarbon feedstock and to meet energy requirements of the process, CO2 emissions are the major component of GHG budgets for ammonia manufacture.

The IEA report cites a number of studies that identify the greenhouse gas emissions associated with ammonia production as ranging from 1,150 grams to 2,163 grams of CO2-equivalent emissions per kilogram of ammonia produced. 

For the US, the Department of Energy has estimated average specific energy in ammonia manufacture of 14.8MJ/lb, or 32.6 GJ/tonne, and CO2-equivalent emissions of about 2,440 pounds/ton of ammonia (or 1,220 grams/kg).




They get A+ for alternative thought. I wouldn't have believed a 5% H2 mixture was rich enough with 95% ammonia.

This eases the problem of storing/carrying a lot of H2. Ammonia is sure to add an offsetting problem to compensate, I am unfamilar with how it is handled.

Off topic (but only a little). Using H2 to improve combustion. Discussed here about two months ago.

Ford is funding research on directly injecting a minute amount of H2 into a conventional ICE engine. Research in Australia shows that this can greatly improve the combustion.


Anhydrous ammonia is very easy and safe to handle and store.


I can't beleive they're serious. Besides the fact that they're talking about getting the hydrogen to create the ammonia from hydrocarbons, there is no safe way to use it in an automobile. Some here have derided battery powered autos because they might cause a hazard in a crash yet we've all gotten used to the idea that the gasoline in our tanks can cause massive fires and explosions. Still, there's no way that we're going to accept that a crash could release ammonia and potentially kill everyone in a 100 meter radius. Perhaps they're advocating it only for stationary use?

Mark A

For however good this idea is, I feel it is doomed to failure. Correct me if I am wrong, but wasnt ammonia, in the form of "anhydrous ammonia", what went into the Oklahoma City bomb? And of course hydrogen is what was in the Hindenburg. A readily available supply of both, for transportation needs, would probably never be allowed to enter the open market. Perhaps I am wrong.

Michael Pereckas

The rocket engine in the X-15 burned ammonia and liquid oxygen. Rocket fuels are often odd, expensive, and toxic, since low cost is usually not the top priority in rocketry. I have not been able to figure out why one would want to run a normal engine on ammonia. I suppose it's denser than CNG, but surely vastly more expensive, plus the toxicity. Is this really more sensible than propane? I just don't understand the purpose, other than to show everyone that they could really do it.


Anhydrous ammonia will stay anhydrous in air only as long as the next water molecule comes by (some microseconds); also, all living beings contain lots of water - and they won't win the fight over it against gasous ammonia. Once in contact with water, ammonia is quite alkaline. And living organic matter doesn't stand a base as good as an acid.

Overall, the only benefit of ammonia over methane is that it's much easier to compress, and more dense.

Ammonia (LNH3): Ts -33,4 °C, 0,682 kg/l
Methane (LNG): Ts -161,5 °C, 0,423 kg/l

However, i doubt that the toxicity, and inefficiency producing ammonia in the first place (even less efficient than hydrogen directly, as you'll need the hydrogen first - already inefficient - and then convert it to ammonia) will result in a consumer product...


Ammonia is a very toxic substance. It will eat into the skin, or cause lung damage on exposure.


I guess it's because of being posted on Green Car Congress that people have assumed, but if you go to their website this is not an auto targeted technology. It's for distributed generation as an alternative to fuel cells.

Bill Young

Any chemists on the site got a clue as to how they are combusting NH3 without getting NOx? Maybe with a lean burn you could get N2 instead of NOx. I don't know the thermodynamics on this.

Rafael, are you listening?

The Oklahoma city bombing was with NH3NO3 (Ammonium nitrate) mixed with diesel fuel. It was not straight ammonia. Ammonium nitrate is a solid, not a gas. It is used extensively as a fertilizer but not as straightforward to get as it used to be.


I'm not a chemist but have bought and sold 10's of thousands of tons of NH3 (and ammonium nitrate, urea, etc). Natural gas is the feedstock, CO2 is the waste stream (unless used to make urea.) Large storage is cryogenic (large compressors keep it cool.) I wouldn't exactly call it safe or easy to store.


Ammonia is easier to store then hydrogen, and less explosive then gasoline, its just really really toxic, but lucky a leak is easily detectable, unless of course the vapor concentration is high enough then it just blows out your sense of smell and then you just need to wait for the sweet release of death as you convulse. Great stuff


I don't know who wrote this story, but I'd give them ten out of ten for balance - the fact that ammonia was easier to store (pressure or temperature) was implied, the results from emissions tests were quoted, but then quite nuetrally and without sensationalism, they went into the energy balance of ammonia production, the CO2 output and the fossil feedstocks used. Well done!

We can all see that for that source of ammonia it's not a great idea. As for toxicity and risks of explosion... I'd be much more scared of CNG or compressed hydrogen myself. 50 litres of gasoline in a vehicle scares me enough on a hot day!

Thinking out of the box to temper the drive towards a Hydrogen economy by some high powered people is a noble cause. I say to the ICE industry - keep up the experimentation, and keep up the neutral reporting like this article, that's how progress is made. Bravo!

Tim Acland, UK


Any chemists on the site got a clue as to how they are combusting NH3 without getting NOx? Maybe with a lean burn you could get N2 instead of NOx. I don't know the thermodynamics on this. -- Bill Young

Complete combustion gives you nitrate, so your exhaust will either be particulate nitrate or nitric acid (maybe in a non-automotive setting you can recover for fertilizer). Less complete, and less efficient, combustion makes NOx. Even less complete and less efficient combustion would give you N2, but you'd need to control conditions pretty carefully. You sure won't make up the energy you lost in making ammonia from N2, though.


The first commercial application of the ammonia engine will be for power generation for irrigation equipment in California. The testing should start in July. As diesel generators are phased out in the state and anhydrous ammonia is already being delivered to the agricultural areas, the clean burning ammonia engines would be a logical replacement.


Why only a little NOx?

Normally in an internal combustion engine (ICE) both unburned fuel and NOx remain after combustion. The unburned fuel in this case is NH3 - which is worse than NOx. Because hydrocarbons aren't present there is no carbon particulate or CO.

While complete oxidation would lead to formation of H2O and N2O5 (equivalent to the 'nitrates' or nitric acid referred to by cidi), complete oxidation is not only undesirable but is not required. (There is a whole class of catalysts for application in diesel aftertreatment aimed at oxidizing NH3 without producing NOx.)

NOx produced in an ICE is a function of flame temperature. I'm not familiar enough with combustion chemistry to know for sure, but I believe that this indicates equilibrium reather than kinetic control of the resulting NOx level, so at the same temp, pressure, and total concentration of nitrogen NOx production by the flame may may be similar in hydrocarbon and ammonia (and H2) fueled engines.

Regardless of the NOx produced, the ammonia fueled engine has an advantage: a NOx reduction system is inherently present. The reaction

NOx + NH3 --> N2 + H2O

takes place spontaneously above ~600C. What this means is unburned ammonia fuel and NOx will neutralizeeach other. To produce a low NOx engine, combustion is simply tuned so that the unburned fuel (NH3) and produced NOx approximately balance. In practice, a little more NOx is desirable because NH3 emissions are less desirable than NOx emissions.


Am I the only person that knows combustion of NH3 results in H20 and just plain Nitrogen.....

Some of the nitrogen present in a spark ignition engine will invariably form Nox, but thats a function of a spark ignition engine, not ammonia fuel.



I can see a niche market for this!
Al-Qaeda would buy a few.



Nitric acid is produced commercially by catalytic oxidation of NH3. In that case NOx is the end product, not N2. The relative proportions of N2 and NOx are dependent on T, P, and composition.

No spark required. Compression ignition gets NOx too.


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Homs- Syria


ive used nh3 for years safely as a fertilizer .It also now can be produced straight from water with wind power evan cheaper than with natural gas.

Henri du Plessis

It is sad to see the wide-spread negativity when viewing comments here. And comments frequently show commentators have not read the original article properly. some pointers:
1. It has already been proven the Hindenburg burnt due to the dope used to waterproof the outer skin, not due to hydrogen. And the Hindenburg did not explode, it burnt. the hydrogen burnt off rather quickly, due, I believe, to the lightness of the gas. By itself, it would have caused very little harm.
2. BMW has proven that compressed hydrogen storage on a car can be completely safe by putting their hydrogen cars through crash tests according to strict EU requirements.
3. Show me an inert, edible, safe to handle fuel and I will show you wood. The only problem is, it is not practical.
4. Could commentators please refrain from making silly comments about using ammonium for bombs - in the form required for the technology described, it is not possible and such comments are rather childish.
Even though still in its infancy, I believe the technology described in this article is exciting and holds possibility if developed further.

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