Considering Ammonia

Figure 1. An integrated ammonia, fertilizer and explosives plant uses the Haber-Bosch process. Photo by author.

Kevin Kilty

Among the substances on which modern society depends are many with a large “carbon footprint”.  This makes them targets of the carbon is bad club. A couple of days ago a copy of the American Institute of Physics (AIP) newsletter Scilight came into my inbox, and one of the featured articles involved research into using a cold plasma over water to fix a number of nitrogen species in the water. This got me thinking about the production of ammonia, which is one of those maligned but indispensable substances. During the summer before I started college in 1971, and for the next three summers, I worked as a maintenance roustabout in a fertilizer and explosives plant. My search of the WUWT archive didn’t turn up an article about ammonia per se, and so this essay was born.

To say that ammonia makes fertilizers and explosives doesn’t do justice to its importance. Probably one-half the human race depends on anhydrous ammonia or fertilizers derived from it for their food. In the form of high density ammonium nitrate prill it provides a safe and economical explosive.[1]  Since our elites are obsessed with remaking the modern world, a good question to ask is “what alternatives do they have to produce this essential substance without using fossil fuel?”

 Estimates are that industry produces about 150 million metric tons of ammonia per year, and that this activity releases around 1.2% of the human emissions of CO2 each year. A new role suggested for ammonia is as a carrier of hydrogen for a transportation fuel. The ammonia molecule (NH3) contains three hydrogen atoms which can be released via reforming onboard a vehicle to provide hydrogen for a fuel cell to then power electrical motors. If technology should go this direction, then the manufacture of ammonia will increase some 30 times over its present amount, taking the need for efficient and economical manufacture from merely desirable to imperative.

How we make ammonia

There are two separate issues in the quest for a carbon free manufacture of ammonia. The first is to find effective ways of producing hydrogen. The second is to find effective ways of combining this hydrogen with nitrogen to produce ammonia. In the course of this brief essay I will use the terms “manufacture of ammonia” or “nitrogen fixing” interchangeably. 

A source of hydrogen

Many people probably think of making hydrogen by passing an electrical current through water in the process of electrolysis — a demonstration they probably saw in high school chemistry. However, industrial sources of hydrogen more often come from fossil fuels, or in fact any source of carbon, by using the water gas-shift reaction or the alternative dry reforming of natural gas using reactions between methane and CO2.

The water-gas reaction uses steam (generated with fossil fuels typically) which reacts at high temperature with carbon to produce hydrogen, contributed by water vapor, and carbon monoxide. When followed by the shift reaction, the carbon monoxide reacts with additional steam to produce carbon dioxide and yet more hydrogen. With coal as its feedstock the water-gas shift reaction produces two molecules, or a bit more, of hydrogen and one molecule of carbon dioxide per atom of carbon. Using natural gas (methane) as a feedstock will produce two extra hydrogen molecules. Since natural gas as a feedstock has better economics in most cases, it has come to dominate the feedstock for ammonia production worldwide. I will mention no more about the reforming process from here on to concentrate on ammonia synthesis. However, since chemical reactions rarely run to completion, it should be apparent that the output gas stream from reforming natural gas, or from the water-gas shift reactions, will contain water vapor, methane, carbon dioxide and carbon monoxide in addition to hydrogen. This has important considerations for ammonia synthesis.

The Haber-Bosch process

The introduction of the Haber-Bosch process in 1913 was a world changing event. Figure 2 shows a simplified diagram of the process. Components needed to make ammonia, nitrogen from air typically, and hydrogen are put into a reactor at high pressure (20-40 MPa) and high temperature (400-650C) in the presence of iron catalysts to carry out this ideal model of the reaction

N2 + 3H2 -> NH3 – Energy

That energy leaves on the right side of this equation tells us the reaction is exothermic — it releases heat. Note also that the left side of the equation consists of four kMoles of gasses (one of nitrogen and three of hydrogen) while the right side involves only two. Between these two observations we can employ Le Chatelier’s principle to predict that high pressures will push equilibrium toward the products, ammonia, which is good, but that high temperature will push equilibrium toward reactants. The reason for high temperature is to nudge the reaction to occur at a useful rate. It is imperceptibly slow at room temperature.

The real mixture of gasses input to a reactor consists also of argon from the air, and CO2 and carbon monoxide, CO, from chemical equilibrium in the reforming or water-gas reactions. Carbon monoxide is the most troublesome component because it will poison the iron catalyst.[2] To remove it the gas is put through a methanation step to turn carbon monoxide into methane. This represents an energy loss, but is unavoidable. Carbon dioxide is easily captured and can be sold as a coproduct to make fertilizer grade or cattle feed grade urea,[3] or it can be sold for carbonated beverage production.

In a single pass through a reactor only about 20% of the reactants combine to produce ammonia and so after refrigeration of the output stream to remove ammonia, the residual gasses are compressed again and go back in the reactor for another pass. Thus, the origin of the name Haber-Bosch loop.

Minimum energy input

No matter how we produce ammonia there is a minimum energy input required by the first and second laws of thermodynamics. We can estimate this minimum input by studying the process of burning ammonia in oxygen

4NH3 + 3O2 -> 2N2 + 6H2O – Gibbs Free Energy

From a chemistry tables book (CRC, Lange’s or Perry’s tables) we find that for each kilogram of nitrogen we obtain a maximum of 19.2 Mj of free energy. Thus, reversing this process, for each kilogram of nitrogen fixed as ammonia we must supply a minimum of 19.2 Mj of energy. This is true no matter what process we employ – there is no magical route requiring no energy. The current best practice of Haber-Bosch ammonia production requires 27Mj per kilogram. The difference of 7.8Mj between best practice and minimum comes from losses (irreversibilities in the parlance of the engineer) in the compression work involved, the heat losses from high temperatures in reactors, and even from the work needed to separate the product ammonia from other gasses in the output stream. There are many irreversibilities involved, but nonetheless the process energy efficiency is 70%!

Seventy percent sounds pretty good, but for global warming advocates the sin of the Haber-Bosch is that it produces any CO2 at all. Even 1.2% of global emissions is intolerable.

Alternative production routes for ammonia

One route to greening ammonia production is using a fully electrical process.[4] First, we would produce hydrogen through electrolysis of water, then provide high pressure using electrically driven compressors rather than the more typical steam turbines or methane fueled industrial engines. All of the components of this version of the Haber-Bosch process are at a technical readiness level (TRL) of 9 (see [5] for an explanation TRL) and in that sense are ready for deployment. However, this version of the process is not market ready as the energy inputs are three times the fossil fuel version of Haber-Bosch. Electrolysis of water, for instance, is itself only about 60% efficient. No one makes hydrogen this way except those with extremely cheap hydroelectric sources. 

Most natural fixation of nitrogen occurs through symbiotic bacteria on the roots of certain plants, legumes mainly, and other bacteria. This suggests that fermentation might be another route to nitrogen fixing, or even ammonia production. By comparison world-wide production of beer is about 190 million metric tons; so there are analogous bio-industrial processes at this scale.

Additionally it is possible to use metallorganic compounds in a chemical mimicking of biological pathways. Both of these ideas have very low TRL, and resemble the fine chemicals industries which are noted for their very large waste to product ratios.[6] This is an impediment to making ammonia by these routes.

Finally, the AIP reading suggestion [7] which initiated this essay, promotes making reactive nitrogen species using a cold plasma in air above a water surface followed by dissolving the produced species in the water. This method presents some advantages when ammonia is used as a fertilizer as the nitrogen fixing can be done on site and put through irrigation water. However, the energy input per kilogram of nitrogen quoted in the article, 3.5Gj/kg, is one-hundred times that of the Haber-Bosch process. Taking a small 25kW turbine as typical of what a person might install near an irrigated field, and assume 20% capacity factor during the irrigation season (see this for typical summer c.f.), this energy figure represents only about four kilograms of nitrogen in a month. In other words, unless the energy input is improved tremendously, it is neither a technically ready nor market ready process. 

Ammonia as a transportation fuel

The maximum work output indicated in Equation 2, 19.2 Mj per kg, is what we could obtain, sans irreversibilities, in using ammonia as a transportation fuel. This represents only about one-half the energy density of comparable fossil fuels like diesel or gasoline (40+ Mj/kg). Moreover, using ammonia as a transportation fuel requires either direct use in ammonia fuel cell or its conversion back to nitrogen and hydrogen for use in a hydrogen fuel cell. Reforming of ammonia can be done by cracking at 400C, or done by electrolysis, with the addition of a minimum 5.6 Mj/kg of electrical energy. In addition the electrolysis conversion requires quite a bit of overvoltage (another irreversibility) on electrodes in order to make the process run at a useful rate. Either way, in a vehicle this energy has to come from the ammonia fuel itself. Both electrolysis and thermal reforming leave a trace of ammonia in the hydrogen stream, which is a poison to the membranes, and electrodes of fuel cells. Finally there are serious issues of needed cryogenics or high pressure involved in storing ammonia onboard a vehicle.

The alternative to using a hydrogen fuel cell is to use ammonia in a direct fuel cell.  According to [8] the technology pieces for this are at a TRL of 6 (ready for a demonstration project) but they provide this assessment without much justification and a careful reading of their analysis could convince a person that the true TRL is much lower.

Small is beautiful?

One of the great handicaps of renewable energy is its intermittent availability and overproduction at inconvenient times. One potential solution to these problems is to dedicate renewable energy sources to nitrogen fixing for fertilizer or fuel production. [4,7,9] Can a small scale version of some nitrogen fixing technology be constructed on a very local basis, even down to individual wind turbines?

Here we run into two deep problems with “Small is Beautiful” ideas. First, how does one gather small units of product to distribute it without having collection costs dominate the whole endeavor? Advocates of ammonia as a transportation fuel speak of reusing much of the current distribution system for fossil fuels to distribute ammonia. However, none of a collection system for ammonia exists at all.

Second, I spoke early in this essay about irreversibilities as the source of the 30% of losses in the current Haber-Bosch process. All sorts of new irreversibilities will appear in small scale systems resulting from starting, stopping, ramping up, ramping down, enhanced parasitic losses, and so forth. Imagine the efficiency and expense of a home furnace just getting the plenum warm enough to start its fan, when it’s called to shut down — and does this repeatedly.

At one time in China the communist authorities thought backyard blast furnaces were a wonderful small is beautiful idea. What they got was a lot of poor quality iron. Considering the low state of readiness of many alternative means of producing ammonia, or their poor economics at present, I predict ammonia made by the remarkably efficient pairing of methane reforming with a Haber-Bosch loop will dominate industry for many decades to come. 


1-Academics, it seems, only think of explosives as war materiel. One paper credited ammonia in explosives as having determined current geopolitical borders! This is silly and misses the point. Without safe and inexpensive explosives mining and construction would return to the 1850s.

2-Carbon monoxide poisons people and catalysts, and for similar reasons.

3-Urea plants are often co-located with ammonia plants for this reason.

4- Smith, et al Energy Environ. Sci., 2020, 13, 331

5- TRL ranges from 1-“a mere idea” to 9-“ready for deployment.” For an interesting discussion of the meaning of readiness level see:

6-N. Cherkasov et al.,Chemical Engineering and Processing 90 (2015) 24–33.

7-Subramanian et al, Plasma-activated water from DBD as a source of nitrogen for agriculture: Specific energy and stability studies, J. Appl. Phys. 129, 093303 (2021);


9-Marika Wieliczko, and Ned Stetson, Hydrogen technologies for energy storage: A perspective Published online by Cambridge University Press:  09 December 2020

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April 29, 2021 2:42 am

“one of the featured articles involved research into using a cold plasma over water to fix a number of nitrogen species in the water”

Before the Haber process, a way of fixing nitrogen was the Birkeland-Eyde process. This used an electric arc to combine nitrogen and oxygen. It lost out by requiring more energy than Haber, although nowhere near one hundred times as much. It mainly used renewable (hydroelectric) power. Of course it doesn’t yield ammonia, but went straight to oxides and so to nitric acid. 

Last edited 12 days ago by Nick Stokes
Kevin kilty
Reply to  Nick Stokes
April 29, 2021 5:58 am

Ineed, Nick, as you probably know each lightning strike fixes some 3 kg of nitrogen in the form of oxides — so does driving your car. Or used to.

Reply to  Nick Stokes
April 29, 2021 10:12 am

Nick is not from California or he would realize that hydroelectric power is not renewable. So his process solution, while an interesting artifact from the 19th century, is a non starter.

Reply to  Nick Stokes
April 29, 2021 1:23 pm

All of the production was done in Norway and produced a calcium nitrate product after contacting the acid with lime.. It is highly inefficient and was only successful compared to mining nitrate. The electricity was basically free. This is not a solution, and you don’t get the side benefit of producing plant food called carbon dioxide.

Steve Case
April 29, 2021 2:58 am

“To remove it the gas is put through a methanation step to turn carbon monoxide into methane.

…for global warming advocates the sin of the Haber-Bosch is that it produces any CO2 at all. Even 1.2% of global emissions is intolerable.

Methane is also in the crosshairs: 

Senate Democrats Slam Trump Administration’s
Environmental Record, Urge Legislation To Cut Methane

You Tube

Kevin kilty
Reply to  Steve Case
April 29, 2021 5:59 am

We are presently battling a world of ignorance.

Reply to  Kevin kilty
April 29, 2021 9:54 am

Determined, entitled ignorance convinced of its own rightness.

Reply to  Chaswarnertoo
April 29, 2021 10:19 am

The correct word to use is righteousness.

Reply to  Doonman
April 30, 2021 12:15 am


April 29, 2021 3:12 am

Ammonia is also used in refirigeration systems.

Joseph Zorzin
Reply to  Krishna Gans
April 29, 2021 3:38 am

I guess we’ll have to give up our refrigerators to save the planet. Any volunteers?

Reply to  Krishna Gans
April 29, 2021 5:56 am

Yep, only big industrial sites with evacuation plans and a wind sock on site

Reply to  Krishna Gans
April 29, 2021 5:59 am

Big industrial refrigeration systems – with evacuation drills every so often….

Reply to  Krishna Gans
April 29, 2021 6:44 am

Given my only knowledge of these systems – in recreational travel trailers – it seems like there will be less of this. In RV’s, modern compression systems use a fraction of the energy. And between better batteries and cheaper, more efficient solar, electricity will be available for the longest of boondocks.

Yes, it’s wandering off subject. But this is WUWT, so, C’mon Man….

Last edited 12 days ago by bigoilbob
Reply to  bigoilbob
April 29, 2021 7:43 am

Ammonia refrigeration mostly used in skating rinks, ice hockey arenas,
Carl von Linde was the inventor of the ammonia cooling system,

comment image

first used in most breweries at this time.

Industries use it often for special cooling process, air drying and so on.

Reply to  bigoilbob
April 29, 2021 1:41 pm

Great you are using ammonia.. You won’t notice the difference when it leaks.

Last edited 11 days ago by fred250
Reply to  fred250
April 29, 2021 2:14 pm

“Great you are using ammonia.. You won’t notice the difference when it leaks.”

When my fridge quits cooling, I will. It will be my signal to tear out that fridge and install a modern compression version.

I notice you said “methane” and then edited it to “ammonia”. That, and your many hours feverishly cloud yelling on this site tell me you don’t get out much. RV’s use propane, not methane, for heat and fridge power…

Last edited 11 days ago by bigoilbob
Reply to  fred250
April 29, 2021 9:29 pm

Reminds me of when I was a work experience student in a survey office. I drew the duty of making the plan copies in the ammonia copier. Wowsers, the fumes took your head off!

April 29, 2021 3:19 am

While I have always said you dont want a cylinder of hydrogen in a car fire I worked with ammonia for about 20 years and you certainly dont want ammonia in a car crash its terrible stuff. Blind you flay the skin off your body and strip the lining of your lungs

Doug Huffman
Reply to  sid
April 29, 2021 4:27 am

I periodically directed a cleaning process that used two 5,000 gallon tanks of ammonium hydroxide. Great stuff and I love the smell of traces of it, but we had to carry Emergency Escape Breathing Devices in the facility because of it. We mixed the solution by sparking N2 through it and walking in and smelling the ammonia was pleasant. The nannies say any detectable odor is too much.

Doug Huffman
Reply to  Doug Huffman
April 29, 2021 4:27 am

stupid spielchecker. SPARGING

Reply to  Doug Huffman
April 29, 2021 4:42 am

During training we were told 3 breaths and you are ‘down’, incapacitated/had it

Reply to  Doug Huffman
April 29, 2021 9:29 am

???? Ammonia smells like industrial window cleaner, no Windex flavourings, super harsh stuff, eats away your mucus membranes!

Doug Huffman
Reply to  PCman999
April 29, 2021 4:31 pm

So you are not familiar with HORMESIS. It’s not the poison, it is the dose. I like the smell of ammonia, and ozone too.

Kevin kilty
Reply to  sid
April 29, 2021 6:05 am

We had very few incidents in the plant where I worked, but there was a lot of potential for them. We made nitric acid from ammonia in or to produce ammonium nitrate and I has nitric acid from an improperly blocked line dumped on me. Luckily the emergy shower was two steps away.

John Dueker
Reply to  Kevin kilty
April 29, 2021 6:20 am

The anhydrous truck that drove off the overpass in Houston and killed so many is a reason for rerouting hazardous cargo.

Kevin kilty
Reply to  John Dueker
April 29, 2021 7:21 am

I had not heard about that accident.

John Dueker
Reply to  Kevin kilty
April 29, 2021 9:36 am

It happened May 11, 1976 at 11 am.

“tank truck carrying 7,500 gallons of anhydrous ammonia lost control, crashed through a guardrail and careened off a ramp to the freeway below.

The tractor-trailer struck a column on the way down, and landed on the Southwest Freeway, rupturing the tank and releasing a deadly cloud of ammonia over the busy 610 at 59 interchange.”

Six dead 178 injured from the cloud of ammonia especially in low areas.

Reply to  John Dueker
April 29, 2021 10:13 am

When I did my hazmat training, the instructors considered anhydrous ammonia to be about the worst incident you could encounter.

Doug Huffman
Reply to  TonyG
April 29, 2021 4:35 pm

Rank ignorant safety-ism.

They are probably still wearing face-panties soiled by puking a year of ignorance into them. “Ooohh, I’m safer and more sensitive than you.”

Reply to  Doug Huffman
April 30, 2021 7:50 am

Doug, I have no idea what you’re talking about. Are you suggesting that an anhydrous ammonia incident isn’t dangerous? I also dont’ understand what masks have to do with anything.

Reply to  TonyG
April 30, 2021 7:58 am

anyone in the Uk remember the tanker of Oleum crash way back. A lady in a following car walked forward to try and help the driver. A year or so later the report on the accident said the only found a fragment of pelvis bone

Reply to  Kevin kilty
April 29, 2021 1:27 pm

Acid is a lot less nasty than industrial hydrogen peroxide. That stuff eats immediately. With acid you have time to reach a safety shower.

Reply to  JamesD
May 1, 2021 7:15 am

In the late ’50s my father worked at Vickers in Barrow-in-Furness, Lancs, on the hydrogen peroxide powered submarines. He used to tell some interesting stories and often mentioned that the Explorer was often called the Exploder. The experiments didn’t last long and we found ourselves regularly travelling to Didcot whilst he learnt about nuclear physics. Funny how these articles bring back childhood memories.

Reply to  Kevin kilty
April 30, 2021 7:54 am

I said to the guy loading my lorry so what pie goes where? As I listened I realised he made a mistake, stop stop I yelled as he then went to uncouple I tried to stop him as I knew it was pressurised. As I turned away he hosed me down with ammonia. Ran to emergency drench shower, jumped on plate, nothing happened, jumped again, the shower head fell off onto my head. When I later asked depo boss why that particular guy was responsible for ammonia he said “no one else is stupid enough to want to deal with ammonia”.
International fertiliser company

Clyde Spencer
Reply to  sid
April 29, 2021 9:31 am

I once accidentally received a shot of ammonium hydroxide from the pump on a blue line machine. It felt like someone had shot me in the eye with a paper clip launched from a rubber band sling shot. Fortunately, water was nearby, and I didn’t suffer any permanent damage, although I had to wear sunglasses, even at night, for a couple of weeks. It is nasty stuff!

Reply to  Clyde Spencer
April 29, 2021 2:24 pm

 It felt like someone had shot me in the eye with a paper clip launched from a rubber band sling shot.”

When did that happen? It must have hurt a lot.

Reply to  sid
April 29, 2021 7:24 pm

In 1975 the Vehicle Research Institute at Western Washington University in Bellingham WA managed a economy rally from north to south, the SEED Rally. One car entered from the Musashi Institute of Technology ran on liquid hydrogen. It was a converted Datsun B210. Each car required an observer from another team to ride along to make sure rules were followed. Many students were afraid to ride along in that car. The entire back seat held a Japanese engineer managing the system constantly. I was part of the team for Viking 2, the WWU entry. Very fun times.

mike macray
Reply to  sid
May 3, 2021 1:25 pm

Any other reasons to switch to CFCs? Colourless, odorless non flammable and generally inert and then they found the Ozone hole to ban them!

April 29, 2021 3:20 am

“At one time in China the communist authorities thought backyard blast furnaces…”
No the backyard blasts for China, just upfront rocket blast into space of the first module of their very own ‘space station’ which contains living quarters for crew members was launched from the Wenchang Space Launch Centre on a Long March-5B rocket. In the near future no other country beside China will have its own orbiting space lab.

Joseph Zorzin
Reply to  Vuk
April 29, 2021 3:40 am

“no other country beside China will have its own orbiting space lab”
where they’ll only do pure science research- nothing military of course

Michael S. Kelly
Reply to  Vuk
April 29, 2021 9:15 am

I recall a Popular Mechanics article circa 1970 that featured an ammonia fuel cell electric motorcycle. The article gushed over this marvelous machine, citing its noiseless operation, and exhaust consisting of only nitrogen and water. What I can’t remember is whether the thing actually worked or not (there was a photograph of it, not just an artist’s rendering). Does anyone else know of such a thing?

[Sorry, this was meant to be a post elsewhere in the comments, but I can’t figure out how to delete it and put it in the right place.]

Last edited 11 days ago by Michael S. Kelly
Reply to  Michael S. Kelly
April 29, 2021 11:53 am

I couldn’t find delete either, deleted the intended entry and just typed +1 in the reply to xyz, posted it and restarted in the correct place.

Michael S. Kelly
Reply to  Vuk
April 29, 2021 7:29 pm

Good thinking! I’ll have to adopt that!

Anders Valland
April 29, 2021 3:56 am

You can use ammonia as fuel in an internal combustion engine or a gas turbine. There are different routes to these as well. Some talk of enhancing flammability by mixing in hydrogen (i.e. reforming or cracking of ammonia into nitrogen and hydrogen), most would go the route of dual fuel gas engines and have an as yet undefined amount of secondary fuel to enhance combustion. Ammonia really does not burn well, but it can be forced that way.

Since anhydrous ammonia has a liquid state density of 680 kg/m3 the energy density should be stated per unit volume rather than per unit mass. In this case it has a energy density of 12,7 MJ/liter compared to 32,9 MJ/liter for diesel – i.e. shy of 39% of diesel.

The volume perspective is even more pronounced for storage, since most systems need either pressure tanks of 10 bar or insulated pressure tanks to hold the -33°C liquid ammonia with a safety factor. Refrigerated ammonia might be held in prismatic tanks which would require less space, but safety issues may negate this. Emission to surroundings is not desireable.

The reformer, or cracker, you mention is still not developed for any motive application. Its usefulness is even less understood since it is a thermal process which is designed for stable operation and thus would need a daytank/storage tank system in addition. The ramp-up and -down are critical phases that would need treatment and storage of products. It also reduces system efficiency.

PEM and HT-PEM fuel cells are not contenders for ammonia as fuel since they require extremely pure hydrogen for operation and any ammonia, CO2 and especially CO will poison the FC. SOFCs are not practicable for motive applications, in addition to being extremely expensive. All others are well below TRL 6 although I am aware that the different congregations advertise otherwise.

In shipping there are some trials and possible demos on pure hydrogen FC systems on small vessels operating on short routes. Other FC technologies are only suggested for small applications.

Reply to  Anders Valland
April 29, 2021 4:31 am

Tubes and mountings have to be in steel, no copper, no brass, as ammonia is very aggressive.

Clyde Spencer
Reply to  Krishna Gans
April 29, 2021 9:36 am

Yes, like water, it is virtually a universal solvent. I have speculated that planetoids rich in ammonia might have evolved life that depended on ammonia or ammonium hydroxide rather than hydrogen hydroxide.

Geoff Sherrington
Reply to  Anders Valland
April 29, 2021 5:13 am

Thank you for the practical observations from experience rather than the what-if sector. Appreciated. Geoff S

Crispin Pemberton-Pigott
Reply to  Anders Valland
April 29, 2021 9:11 am


Given the options available there is merit in using the same inputs to make LPG (CH3OH). It is liquid at only 5 bars and is essentially a method of storing hydrogen. It contains 49 MJ/kg and is easily converted to combustible gas. Just heat it slightly, which can be obtained from the local environment.

A good reason to make ammonia is for fertilizer.

The metric to use for transport is mass, not volume, because the mass of the system has to be dragged around. Candidates for transport fuel are propane, butane, butanol and anything that liquifies a small pressure and evaporates at a temperature below -30.

Reply to  Anders Valland
April 29, 2021 9:37 am

Ammonia for fuel is the stupidest thing ever to come out of the econazis, replace safe and relatively harmless fuels with toxic chemicals like ammonia. Even more stupid than saving the environment by cutting down forests to cover with solar panels and wind turbines (and many miles of transmission lines and towers), and to turn into wood chips to ship thousands of miles to burn in the Drax power plant (that is sitting on top of a coal mine…).

Reply to  PCman999
April 29, 2021 10:37 am

Hey, lets pump water uphill at night so we can release it to generate power in the daytime. Don’t worry, all that nighttime nuclear energy is free.

April 29, 2021 4:00 am

Back in 1967 ICI had ammonia plants at Billingham, NE England, which used 1200 tons of coal per day via the water gas process. In 1968 three new ammonia plants were designed by Kellogg ( not the breakfast cereal company! ) to run on North Sea gas, but initially were run on naphtha. These created so many problems that the three plants were nicknamed Snap, Crackle and Pop after the noise supposedly made by the Kellogg breakfast cereal ( Rice Krispies ).
Once the plants were turned over to North Sea gas they ran without problems.
The other ICI ammonia plant at Severnside sold much of the CO2 produced for fizzy drinks, dry ice and tankerloads were sent up to a nuclear power station in North Wales for use as a coolant.
The Severnside plant produced about 1200 tons of ammonium nitrate per day for use as fertiliser, ( much to the horror of some chemists who thought of it only as an explosive ).
But it does need treating with respect as demonstrated by very big bangs in Beirut recently, and Halifax, Canada, in the1940s.
Ammonia was also produced as a by-product of town gas production, and was sold as a relatively weak solution for farmers to use for fertilising grassland, applied by a contractor.
For a period ammonia was injected directly into grassland, but this method caused a lot of damage to the grass sward, and I don’t know of it being used now.
As regards to its being used as a fuel I would have grave reservations, especially in the event of an accident.

Reply to  StephenP
April 29, 2021 4:47 am

I used to do that and pump it into straw for cattle. 30 -32 %, used to ‘bump’ out of solution on hot days. Grassland was mainly injected in the frost to limit speed of gassing off. Stopped due to economics

Kevin kilty
Reply to  StephenP
April 29, 2021 6:10 am

Texas city had a devastating blast in 1946 from a ship being loaded with ammonium nitrate. Snap, crackle and pop is a good story.

Michael S. Kelly
Reply to  Kevin kilty
April 29, 2021 7:36 pm

You beat me to it. The ship that blew up in Galveston Bay had the same load of ammonium nitrate on board as did the warehouse in Beirut. A wiseacre boss of mine, years ago, commented on the Texas City disaster, “quipping” that the ship blew up and leveled Texas City, doing $700 worth of damage.

One might wonder why ammonium nitrate is produced in such large quantities, both as a fertilizer and an explosive. Simple: the ammonium nitrate is much cheaper than the ammonium dayrate.

Last edited 11 days ago by Michael S. Kelly
Peta of Newark
April 29, 2021 4:09 am

Two ammonia generators for you,
They’ll get get the ol’ grey matter working too. Maybe more 😉

  1. Look in a mirror. You’ll see one there. Struvite
  2. Visit a sunny desert. Take some plain window glass, some Tioxide & some, notta-lot of, water. Tada> Ammonia (solution)

Points arising:

  • Well, that’s me marked down as a complete tree hugging raving loony 😀
  • The figure I remember for ‘ammonia dependence’ was/is 80% of World Population
  • Someone very recently here at wwwt noted that CO2 levels in the sky had only really started ramping up since shortly after end of WW2. I am gobsmacked. Does anyone actually pay attention to my ravings or has someone out there had an Original Thought? curiouser and curiouser. (U R aren’t U?)

Will now go for a coffee, with a little touch of Epsom Salt mixed into the sugar I make it with. (sweet strong black coffee = one of my few remaining vices apart from tree hugging)

Q:Why Epsom Salt?
A: Heart attacks hurt and I don’t ‘do’ pain.
Nor do I want to spend the last decade of my life forgotten my own name and wearing a nappy.
Magnesium wards off both those eventualities.

Because of nitrogen fertiliser ***, there is almost zero zilch nada Magnesium in the only food ### there is left to eat on This Planet.
or copper. or zinc. or selenium, or manganese. or cobalt, or sodium. or iodine

*** Simple aqueous ammonia and/or diluted nitric or nitrous acids work well as plant growth enhancers – also as a very real cause of Global Greening as it ‘appens.
You don’t need to make ammonia, or CO2, to make plant and bacterial fertiliser.

### i.e. The Nutrient Free Tasteless Mush haha Food that tells us constantly, via the Magical Thinking it induces, that ‘Things Have Never Been Better
Better because of the mountains of it we create using: Ammonia.
Nice feedback loop innit- if you’re partial to Positive Feedback that is.
I ain’t.

There are no Free Lunches and Ammonia is a poison in many more ways than one.

We are in a really hideous jam right now, Ehrlich’s prediction is actually playing out right here, now and in real-time.
And where is everyone?
All gone to signal their virtue at the Emperor’s Fashion Parade, count the dancing faeries and watch clouds (visible and invisible) in the sky.

words fail

Last edited 12 days ago by Peta of Newark
Geoff Sherrington
Reply to  Peta of Newark
April 29, 2021 5:28 am

I used to manage a pilot plant making TiO2by stripping the iron out if ilmenite with pressurised chlorine gas at 1050 degrees C. But I cannot work out its path to ammonia.
BTW, those dreamers currently advocating unusual industrial processes based on hydrogen or ammonia might benefit from hands on experience. That pilot plant used 10 tons a day of that very hot chlorine. We were on the uphill edge of a town of a few thousand people who had an uncertain future from an accidental release. I was 28 years old and primarily responsible. Now at 80 I still have nightmares from that scenario. So much for “She will be right mate, people will get used to it after a while.”
Some people do not. Geoff S

Reply to  Peta of Newark
April 29, 2021 9:50 am

Um Peta, BOTH low and high levels of magnesium have been implicated in dementia (but not shown to cause it).

If you eat a diet deficient in magnesium a 1/4 teaspoon of Epsom Salts daily would give you the recommended daily allowance. However, contrary to your false claim, a lot of foods have magnesium – nuts, spinach and other greens, beans, whole grain wheat and oats, avocados, dark chocolate, salmon, and other foods so, depending on what you eat, you may already be getting enough magnesium. If you are, supplementing with Epsom Salts might actually be increasing your chance of dementia. Judging from your typical garbage rants about nutrient-free dirt causing fewer trees which causes climate change, you might already have it.

Reply to  Peta of Newark
April 29, 2021 1:19 pm

peta you so smart
me so dumb
But I’ll just forget what you say after I fall asleep napping on my air mattress IN MY VAN DOWN BY THE RIVER!

Reply to  Peta of Newark
April 29, 2021 2:29 pm

Hows about potash….do you like a sprinkle of potash on your food?….except ice cream of course.

Roger Knights
April 29, 2021 4:33 am

About 30 years ago a Time Magazine cover story touted the use of ammonia in diesel-electric locomotives. A company near Buffalo was behind it. But the venture failed due to business-related conflicts.

Reply to  Roger Knights
April 29, 2021 5:26 am

A major use of urea now is for DEF (diesel exhaust fluid) that is used to reduce NOx from diesel vehicles, especially trucks. As stated above, urea is made from ammonia and carbon dioxide.

Fred Souder
April 29, 2021 4:50 am

I thought ammonia was more toxic than chlorine gas. Not sure I want this in a vehicle.

Reply to  Fred Souder
April 29, 2021 5:43 am

Or save you the trouble – this is the salient bit:-

“The smelling salts release ammonia (NH
3) gas, which triggers an inhalation reflex. It causes the muscles that control breathing to work faster by irritating the mucous membranes of the nose and lungs.
Fainting can be caused by excessive parasympathetic and vagal activity that slows the heart and decreases perfusion of the brain.The sympathetic irritant effect is exploited to counteract these vagal parasympathetic effects and thereby reverse the faint.”

Smelling bottles which release chlorine are probably not the best idea in the world.

Kevin kilty
Reply to  Fred Souder
April 29, 2021 6:45 am

Ammonia is pretty rough on tissues especially the lungs but nitrogen dioxide which could be released in places in the nitric acid plant was worse. We also produced some formaldehyde in the urea plant — not corrosive but pretty tough on tissue also,

Tom Abbott
Reply to  Fred Souder
April 29, 2021 7:13 am

I breathed in some chlorine gas once. I wouldn’t want to do it again. One breath was too much.

H. D. Hoese
Reply to  Fred Souder
April 29, 2021 7:27 am

Some animals excrete lots of ammonia. There was a case in the literature where I was in graduate school when a dense colony of rats produced enough to kill fish in an adjacent room. Think water solubility and fish kill. It will produce quite a permit stream.

Steve Z
Reply to  Fred Souder
April 29, 2021 8:41 am

Ammonia is actually less toxic (for inhalation) than chlorine gas–the IDLH threshold for ammonia is 150 ppm, while it is only 3 ppm for chlorine, meaning that chlorine is 50 times more toxic than ammonia (on a mole or volume basis).

Still, using ammonia as a vehicle fuel has other disadvantages, since it needs to be either compressed or refrigerated to be liquid in a fuel tank (its energy density per unit volume as a gas would be extremely low). Ammonia is only slightly less volatile (boiling point = -33.4 C) than propane (boiling point = -42.0 C), and would anyone seriously want to drive a vehicle with a tank full of propane under the trunk? If it was released into the air, ammonia would be less explosive, but more toxic than propane.

Clyde Spencer
Reply to  Steve Z
April 29, 2021 9:44 am

A former friend (now deceased) converted his Chevy Nova to run on propane. The tank was kept in the trunk.

Patrick MJD
April 29, 2021 5:01 am

More energy in than energy out.

Kevin kilty
Reply to  Patrick MJD
April 29, 2021 6:46 am

Well, yes.

Geoff Sherrington
April 29, 2021 5:07 am

In 1970 I was a chemist setting up a lab in the brand new urea plant in Brisbane Queensland. WG Grace &Dow Chemical trading as Austral-Pacific to service the sugar industry mainly. Haber process.
In those days and since, we used the spelling ‘gases’. Minor in pick to a good article. Reaction energetics dominate the economics as you show. Maybe some advance will happen.
Question: Does the molecular structure of ammonia make it another greenhouse gas? It is surprisingly hard to find an answer by Internet search, so I still do not know. That might affect its acceptance. Geoff S

Reply to  Geoff Sherrington
April 29, 2021 5:22 am

NH3 has IR absorption bands that are relatively weak where they don’t overlap with water bands. The most important factor would be its low concentration and short atmospheric lifetime. It’s very soluble with water so is scrubbed by rain and bodies of water, soil, and it reacts directly with carbon dioxide and other acid gases, as well as aerosols.

Geoff Sherrington
Reply to  Scissor
April 29, 2021 9:28 pm

Scissor, thank you, but what is meant by weak?
Does ammonia have a low optical density in the broad sense when IR is shone through it?
Or, is the energy gap between ground and excited states low for allowed transitions?
Or, are there not many spectral lines in the main absorption bands compared with other GHGs?
Once a spectroscopist, I seek the science behind the expressions such as “gas A is 63 times stronger than B as a greenhouse gas”.
Can you elucidate?

Also, when any gas is considered for industrial large scale use, one needs to look, to be trendy, not only at its greenhouse damage potential, but also that of its downstream products. There are established paths from ammonia to nitrates ad nitrites, usually in soluition rather than gases, but also to nitrogen oxides, some of which like NO2 are already designated as deadly greenouse gases. One wonders if this might affect more industrial adoption of ammonia as some are forecasting? Geoff S

Reply to  Geoff Sherrington
April 29, 2021 5:39 am

“Does the molecular structure of ammonia make it another greenhouse gas?”

Maybe a little bit. The absorption peak at ~1000/cm is the one of interest. It is probably a bit too far upscale to have any meaningful GHG effect. Also this region is somewhat blanketed by water vapor.
Here is the spectrum:
Here is carbon dioxide for comparison:
Here you see that the peak of interest is down further at ~660/cm.

In any event, this issue is so political that any compound with *any* IR spectrum at all, and people will screech *Global Warming* and *DOOM!* at you. You can then rest assured that the person doing the screeching can not read an IR spectrum.

Kevin kilty
Reply to  Geoff Sherrington
April 29, 2021 6:34 am

Good point Geoff, I should have looked up the IR spectrum and made mention of it, but as you see there are many folks who post here who will fill in details missed quickly. There are so many things to discuss about ammonia that an article could go on too long. Main bugaboo for environmentalists is the use of fossil fuels and release of CO2.

Aleksandr Zhitomirskiy
Reply to  Geoff Sherrington
April 29, 2021 9:37 am

Of course, ammonia absorbs in the infrared region of the spectrum and is therefore, by definition, a greenhouse gas: We can recall hundreds of other synthetic and natural compounds that the IPCC, for its own reasons, decided not to include in the list of greenhouse gases.

Ben Vorlich
April 29, 2021 5:08 am

For natural fixing of nitrogen you havn’t mentioned lightning, from the web – a flash of lightning produced 4 × 10^26 molecules of NOx, with an uncertainty of from one-fourth to twice that amount. Also doesn’t the internal combustion engine fix nitrogen? Again from the web Among the air pollutants gasoline and diesel engines emit are oxides of nitrogen—NO and NO2, generically abbreviated as NOx. Nitrogen oxides.

The NOx from vehicles is regarded as a pollutant the NOx from lightening as a fertiliser

Reply to  Ben Vorlich
April 29, 2021 5:35 am

Good comment! It seems to be an open secret that we depend on natural fertilizers and especially CO2, the building block of life.

As mentioned above, NOx is removed from diesel exhausts through the use of urea based diesel exhaust fluid (via selective catalytic reduction process).

Kevin kilty
Reply to  Ben Vorlich
April 29, 2021 6:26 am

I did fail to mention lightning, responded to Nick Stokes above about it. I suppose that just as ammonia is very soluble in water that the oxides of nitrogen are also, and I imagine there was a pretty good fertilizing effect downwind of urban areas before pollution controls on automobile engines.

Ron Long
April 29, 2021 5:10 am

My little macho dog, part pitbull and adopted off the street, knows how to make ammonia at “room temperature”. He is available for analysis if you wish.

Clyde Spencer
Reply to  Ron Long
April 29, 2021 9:47 am

Probably methane as well!

Joel O’Bryan
April 29, 2021 5:31 am

hydrazine. slightly more toxic than ammonia, but ran the standby generators on the Space Shuttle and emergency generator on some fighter jets.

Reply to  Joel O’Bryan
April 29, 2021 6:00 am

The Messerschmitt Komet 163B jet fighter used hydrazine and hydrogen peroxide as fuel.
The mixture provided incredible thrust but IIRC it was imperative to use up every drop of fuel before landing as even a spoonful of fuel left could result in a fireball.

Kevin kilty
Reply to  Joel O’Bryan
April 29, 2021 6:23 am

Very strong reducer, that hydrazine. Some small impulse engines for attitude control run on just hydrazine. And in the form of UDMH (unsymmetric dimethyl hydrazine) is extraordinarily poisonous. I think the Titan missile ran on UDMH and red fuming nitric acid, or nitrogen tetroxide.

John Dueker
April 29, 2021 6:27 am

By far the best use of ammonia is to grow food but it’s used in ammoxidation reactions to make many useful and essential chemicals like acrylonitrile which makes ABS plastics, acrylics, medical supplies and clothes. Curtailing the ammonia supply would be catastrophic. But reality never slowed down the green march to the cliff.

April 29, 2021 6:30 am

Ref note [1] re: explosives — can’t wait until you tell them about Alfred Nobel.

April 29, 2021 6:31 am

Kevin, a top notch descriptive essay…good work

Kevin kilty
Reply to  DMacKenzie
April 29, 2021 7:13 am


Bruce Cobb
April 29, 2021 7:11 am

A new role suggested for ammonia is as a carrier of hydrogen for a transportation fuel.

The only reason it is being suggested is because of the “carbon pollution” nonsense. So, I wouldn’t hang my hat on that absurdity.

Kevin kilty
Reply to  Bruce Cobb
April 29, 2021 7:16 am

I agree entirely. Since I worked around ammonia, and its derivatives like fuming nitric acid, urea, and ammonium nitrate for so long I became quite inured to its unpleasantness, but i wouldn’t be anxious to drive a vehicle with a couple hundred kilograms of it compressed onboard.

Rick C
Reply to  Bruce Cobb
April 29, 2021 10:01 am

From Kevin’s essay: “If technology should go this direction, then the manufacture of ammonia will increase some 30 times over its present amount…” If ammonia production currently produces 1.2% of CO2 emissions, that’s 36% if ramped up for H2 economy. I see a bit of a problem with the ammonia as hydrogen carrier idea.

April 29, 2021 7:24 am

This discussion reminds me of some preliminary design work we did to build a plant for UF6 to UF4 conversion. (Our normal process is UF6 to UO2, with UF4 being merely a step along the way.) Working with our chemical process engineers, the discussions included so many *similar* considerations.

On a separate note, the tobacco fermentation rooms in Nicaragua are almost unbearable due to the heavy presence of ammonia. Actually, what we were told is the process of fermentation is essentially the off-gassing of ammonia from the tobacco. Interestingly, they also told us their volcanic soil is so rich, they sometimes have to plant a crop of corn to strip the soil before planting the tobacco (this is cigar tobacco, btw).


Kevin kilty
Reply to  ripshin
April 29, 2021 9:09 am


Carlo, Monte
April 29, 2021 7:37 am

According to a recent article in the woke IEEE Spectrum, Japan has decided to go PV—>ammonia for general energy production & storage, and had pictures of a big system built near Fukushima.

April 29, 2021 7:50 am

Your discussion doesn’t consider catalysts which lower the energy requirements we already know the MoFe molecule does it with little energy input. There is currently a race on to build a QM stack to calculate the QM pathway a reasonable write-up to read

Once you understand that you understand the importance of a functional QM stack and you can read up on the race to develop it .. a reasonable writeup

Kevin kilty
Reply to  LdB
April 29, 2021 9:37 am

I am a tad baffled by your comment. What you seem to say is that with special catalysts we can find a pathway to synthesis that requires less than the Gibbs free energy. If this were so then we could go around a process on a particular Born-Haber diagram and create energy from nowhere — violating “Hess’s law” the first law of thermodynamics.

Catalysts improve reaction kinetics by lowering intermediate energy barriers, but they do not change over-all reaction energy requirements.

Reply to  Kevin kilty
April 29, 2021 1:40 pm

A better catalyst will lower temperature and increase yield, but Gibbs Free energy sets the limit for energy input.

April 29, 2021 8:08 am


Really enjoyed this read!

This equation:
N2 + 3H2 -> NH3 – Energy

seems unbalanced to me (despite my very tenuous grip of basic chemistry resulting from a brush with it in college 20 years ago.)

should it read:
N2 + 3H2 -> 2NH3 – Energy

Kevin kilty
Reply to  Joey
April 29, 2021 9:10 am

Oopsie! You are correct.

Clyde Spencer
Reply to  Joey
April 29, 2021 9:52 am

And here I thought that the extra molecule of ammonia had been transmuted into energy! 🙂

Crispin Pemberton-Pigott
April 29, 2021 8:56 am

“… the sin of the Haber-Bosch is that it produces any CO2 at all. Even 1.2% of global emissions is intolerable.”

Well, this is a bit silly. The point of creating most of the ammonia is to fertilize crops. If they are so interested in “total system” emissions, they have to include the drawdown of CO2 created by using the product.

When the product is “used” (same as burning a fuel and looking at emissions) it causes an increase of CO2 absorption by growing biomass.

It may cause 1.2% of CO2 emissions but how much of the absorption? Complete the equation. Is it a net drawdown? Five-fold? How much exactly?

Kevin kilty
Reply to  Crispin Pemberton-Pigott
April 29, 2021 9:14 am

This is a good point, but as you realize I am sure, the full life-cycle of many things doesn’t get considered. As there is a fossil fuel input, then people think this is bad and we must find an alternative route. I can’t answer your question at present, but the accounting of this might demonstrate that the enhanced plant growth provided by nitrogen fertilizers ends up sequestering more CO2 than the burning of fossil fuels releases. This would depend on crop management among other complications.

April 29, 2021 9:11 am

“there is no magical route requiring no energy.”

Red and Green dreams are based on magical thinking and tyranny.

(1) Assume there is such a process.
(2) Force all other processes to shut down.
(3) The zero energy process will magically appear.
(4) When it does not appear, blame Capitalism.
(5) Kill everyone involved in the search.
(6) Claim success.
(7) The media will verify this success.
(8) Send away everyone who knows different.
(9) Go back to the old process in secret.

Andy H
April 29, 2021 10:06 am

In lockdown I calculated how much energy it would take to make all the ammonia needed to make the fertilizer we use in UK. If everything went organic, food production would halve so we need this fertilizer. To use electrolysis it would take all the current renewable energy output. We are not getting away from using natural gas any time soon.

April 29, 2021 10:29 am

Years ago I recall an article in Scientific American I believe, when it actually wrote about science.

The article pointed out that combining N2 and H2O produces nitric acid plus energy. All that would be required to produce jet engines that ran on air and water would be a means to efficiently overcome the activation energy. And as I recall both the Soviets and the Americans were talking about producing water-air fueled engines.

The article also pointed out that should the human race ever discover an efficient catalyst for this reaction, over time our oceans would be converted to nitric acid. Hopefully space aliens don’t use this approach to invade.

So the obvious question is, why bother with NH3 as a fuel, when air and water are as plentiful as they are. As a bonus, the nitric acid waste product is extremely valuable in many chemical processes. Energy crisis solved.

Last edited 11 days ago by ferdberple
Kevin kilty
Reply to  Ferdberple
April 29, 2021 11:01 am

I am about to quit this thread and go ride my Mt. bike on such a beautiful day, but yours is such an interesting comment I need to respond.

N2+3H2 -> 2NH3 is exothermic and will run spontaneously, but at about zero rate. A catalyst could speed the process, but the issue in the open air is lack of free H2 around. What goes on with this process you suggest?

My equation number [2] way back up top, 2N2 + 6H2O -> 4NH3 + 3O2 (?) Well, Lange’s handbook has NH3 at a Delta G of (-3.94) and water vapor at (-54.6), all in kcal/mole; so it looks a long climb up the energy hill to me…I have no idea what the U.S. and Soviets were thinking, but keep in mind the U.S. Navy financed the infamous Gamgee ammonia motor. Ammonia is magical stuff.

Reply to  Kevin kilty
April 29, 2021 11:22 am

The name Bob Gardner? comes to mind as the possible author. I recall the activation energy was huge, but the full reaction released a tiny amount of heat, making all sorts of machines practical in theory (but not in practice).

And then looking around I found the following which suggests it is microbes, not humans that are creating global warming. Maybe as a result of us adding fertilizer to soils combined with the massive increase in agriculture? More fun with ammonia? War of the Worlds, only we are the Martians. The microbes are trying to bake us to serve us.

“Nitrous oxide (N2O) is an important greenhouse gas that contributes to climate change. Because it has a long atmospheric lifetime (over 100 years) and is about 300 times better at trapping heat than is carbon dioxide, even small emissions of N2 O affect the climate.

Nitrous oxide is produced by microbes in almost all soils.”

Last edited 11 days ago by ferdberple
michael hart
April 29, 2021 2:43 pm

“Can a small scale version of some nitrogen fixing and be constructed on a very local basis, even down to individual wind turbines?
Here we run into two deep problems with “Small is Beautiful” ideas. First, how does one gather small units of product to distribute it without having collection costs dominate the whole endeavor? Advocates of ammonia as a transportation fuel speak of reusing much of the current distribution system for fossil fuels to distribute ammonia. However, none of a collection system for ammonia exists at all.”

The question is a reasonable one. But I suspect that the best solution would still be using an electricity grid to transfer energy to locations where it is used to form some sort of energy storage on a large scale. I still don’t see any reasonable alternatives to simple storage of electrolytic hydrogen. Sure, it has known inefficiencies, but so do most other options. It is simple and costs and inefficiencies are easily quantified. There are no hidden gremlins in distributing energy this way.

All it needs is cheap, DEPENDABLE, electricity, which means the full embrace of nuclear power. Wind and solar can suck my shit.

Michael S. Kelly
April 29, 2021 3:42 pm

A better solution for transport fuels would be with the addition of one nitrogen and one hydrogen to the molecule, resulting in N2H4 – the dreaded hydrazine. Daihatsu was developing a vehicle fuel cell system using hydrazine back in the 2000s, and it appeared to have great promise:

The comment section in the article may shed some light on why it has never come to be. It reflects the hysteria surrounding the word, which was actually generated and promoted by the “green” rocket propellant lobby so they could hawk their (TRL – 1) wares. For example: “HYDRAZINE!!!!!
Holy cow, lets take one of the most toxic substances we can find and make a fuel cell out of it…” and “The manufacturing process is difficult and inefficient, and the material is a wonderful combination of poisonous, carcinogenic, explosive, flammable, and unstable.”

Daihatsu’s system used hydrazine hydrate as a fill transfer medium. The acute toxicity classification of the hydrate is 3 for ingestion and skin contact (practically non-toxic). For inhalation, it is category 1. However, its vapor pressure is only 1 kPa at normal temperatures (it boils at 120 C), which is pretty benign compared to ethanol (12.4 kPa), methanol (16.9 kPa), and gasoline (~55 kPa). The carcinogenic potential is disputed, because those who think it is a carcinogen do so because they think it should be, while actual studies of people who are exposed to lots of it (my wife was in a subject group of one such study) show no carcinogenic effect. The firefighting instructions state that it is non-flammable, so there goes that one. And it’s quite stable, which is one reason why it is widely used in a number of industries.

Daihatsu’s storage technology was the real winner, though. The vehicle tank would be filled with polymer beads having an exposed carbonyl on the surface, and the hydrazine would bond with that as solid hydrazone – a substance even more benign that the hydrate.

If anyone has more information on this, I’d be interested in reading it.

Loren C. Wilson
April 29, 2021 5:58 pm

Nice to see some real thermodynamics in a paper.

Greg Locock
April 29, 2021 11:57 pm

One other way to use ammonia in a vehicle is to burn it directly, typically in an internal combustion engine such as a gas turbine. The energy density is not amazingly high, but is probably more practical than a battery electric aircraft.

April 30, 2021 7:37 am

I used to work for ICI. I love this stuff.

May 2, 2021 11:37 am

The only recourse against idiocy entrenched in the ruling elite is ridicule. It was always this way with state-adopted religion.

Joe D
May 2, 2021 4:44 pm

Free ammonia… harvest baby diapers that have been stored in diaper pails!

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