Ammonia- the "Ship of Fuels"? (more like the fuel of fools!)
Paul Martin
Chemical process development expert. Antidote to marketing #hopium . Tireless advocate for a fossil fuel-free future.
TL&DR:? ammonia is a toxic and corrosive gas, and using it as a fuel aboard ships fails the 1st principle of safety in design.? It is an insane idea, and those pushing this toxic idea should give their heads a serious shaking.
I am a chemical engineer with many decades of experience handling chemicals.? I’ve safely handled chemicals both in the laboratory and industrially, which sometimes made ammonia look like mother’s milk. ?I have a healthy respect for chemicals, but I am not a chemophobe. ?Even in light of that experience, the notion of using ammonia, an extremely toxic and corrosive gas, as a fuel- especially aboard ships- absolutely terrifies me.? And that fear is, in my opinion as a chemical engineer, ?a very reasonable response to very real danger.
Ammonia is an extremely important commodity chemical.? It is not only the base of the entire nitrogen chemicals industry, but also the key technology which enables roughly half the humans and their food animals currently on earth, to be fed in the style and at the cost to which they’ve become accustomed.? We humans are only a small fraction of the carbon cycle on earth, though our continuous addition of fossil carbon to the atmosphere is already altering the climate.? But as far as the nitrogen cycle is concerned, we humans are already responsible for 50% of it by way of making ammonia and molecules like nitrates and urea that we make from ammonia.? About fifty percent of the nitrogen atoms in the proteins in our bodies, were human-produced ammonia at some time in the recent past.
Ammonia is also an extremely poisonous and corrosive gas.? Ammonia dissolves readily in water, breaking it apart in the process to form hydroxide ion (OH-) and ammonium ion (NH4+).? While we’ve all had experience with dilute ammonia used as a household cleaner, most of us haven’t played around with concentrated ammonium hydroxide.? I certainly have. ?It is nearly as strong a base as sodium hydroxide (caustic soda or “lye”) that you might be familiar with.? And strong bases are very damaging to human tissues because they cause them to hydrolyze, i.e. to react with water and fall apart (hydro-lysis- breaking apart something with water).
Of course it doesn’t matter where the water is- the reaction is the same.? So if that water happens to be deep in your lung tissues, your eyes, nose, throat, ears…you get the picture, and that picture is horrifying. ?It causes pulmonary edema- your lungs fill up with fluid (your own body fluids) and you start to drown. ?It will turn your fatty tissues (including the lipid bilayers of your cells) into soap, hydrolyze and dehydrate your proteins, and cause your various body tissues exposed to it, to die.? There is no antidote that will reverse this for you after exposure.? Though victims exposed to small amounts of anhydrous ammonia definitely can survive, even short acute exposures can lead to permanent loss of lung function.
Ammonia is also a very potent environmental toxicant.? 50% of certain aquatic organisms are killed by as little as 0.5 milligrams per litre (ppm) of ammonia.? Ammonia also reacts with other toxic species ?in the atmosphere such as SOx and NOx (products of fuel combustion, the latter also formed by the combustion of ammonia or hydrogen in air) to produce ultra-small aerosols or particulate solids containing ammonium ion that are harmful to the lungs.? While ammonia itself is fairly rapidly scrubbed out of the atmosphere by rain and snow, ammonium ion aerosols can travel much longer distances, leading to transborder pollution.? Ammonia itself is a regulated air pollutant.
Ammonia is also flammable.? It burns with difficulty and has a narrow range of concentrations in air where it is flammable.? While it does represent a fire/explosion risk, its toxic risks are much greater- rather like other flammable but toxic gases like H2S and carbon monoxide.
Ammonia, with a molecular weight of 17 g/mol, is less dense than air (with a molecular weight average of 29 g/mol)- but that’s only true if the ammonia and air are at the same temperature.? Whether ammonia is stored as a compressed gas or refrigerated liquid, releases during a leakage or pipe rupture event are always ?cold, and hence tend to accumulate low to the ground until they spread out and mix with air sufficiently to warm up.? In this way it is very different than the hydrogen it is made from, which is both less dense than air and tends to heat up as it expands, accumulating near ceilings before it diffuses outward and mixes with the air.
Emergency response in the case of an anhydrous ammonia leak therefore has to contend not just with toxic effects, but corrosivity and flammability risks too.? Mere respirators are not sufficient to protect emergency response crews.? Pressurized chemical suits (Level A protection) are required, which must be supplied air from either SCBA tanks or a hose connected to a breathing air blower drawing air from a safe location.? Having worked in such a suit, I can tell you that it is not conducive to either speed of response, productivity, agility, or calm!
Making Ammonia
We make ammonia almost exclusively from hydrogen that we make by reforming of natural gas or coal.? GHG emissions associated with ammonia production are, to a first approximation, about equal to the current emissions from the entire shipping industry.? And a powerful and persistent greenhouse gas, nitrous oxide (N2O), is produced by soil organisms when we add ammonia-derived fertilizers to soils.? Nitrogen fertilizers, when over-applied, can also run off into watercourses, causing eutrophication (the blooming of algae and other species which can turn parts of lakes and even ocean areas like the Gulf of Mexico, anoxic and essentially lifeless).
While we could make ammonia from hydrogen made from water using renewable or low emission electricity, the cost is prohibitive.? Even black ammonia costs more per joule than fossil bunker oil fuels or fossil LNG, and green ammonia costs a multiple of what black ammonia costs.? And no, that’s not likely to change any time soon, either.
Wow, this is a troublesome molecule!? But it’s also an essential one.? A real dichotomy.
The (Simpleminded) Appeal of Ammonia as a Fuel
Ammonia does have several points of (very arguable) appeal, which explain why someone would even think for a moment about its use as a ship’s fuel.
The idea is that the ammonia would be made from electrolytic green hydrogen, made from renewable electricity and water.? And that burning it, whether directly or via first “cracking” it over a catalyst using heat (from somewhere) back into hydrogen and nitrogen, would have low GHG emissions.? There’s no carbon in ammonia itself, you see.? So that’s the big appeal.? Let’s ignore the extreme inefficiency of all those transformations- electricity to hydrogen, hydrogen to ammonia, ammonia transport and storage, and then ammonia in an engine back to mechanical energy- and their associated costs.
Furthermore, there are people imagining that they will have heaps of stranded renewable electricity that can be made in places where nobody who needs electricity lives even within reach of a practical HVDC cable.? And those people know they can’t ship electricity, and have contended with the fact that shipping hydrogen itself is also more or less an economic and practical impossibility.?
They therefore want to make ammonia, because the only other reagent needed (nitrogen) is 79% of the atmosphere so no problem to obtain.? However, they know nobody (not farmers, food customers or governments) will pay them the premium for green ammonia to use as a fertilizer, and that the fertilizer market is tied up by some large incumbent manufacturers who understandably don’t want new competition for their fossil-derived ammonia supply. ??So new markets for that (imaginary future) green ammonia are desperately needed.? And shipping, which has no simple electrification alternative, seems a perfect place to use it.
Potential future market competitors for decarbonized ammonia as a shipping fuel include green methanol.? Methanol is toxic, but it’s a liquid at room temperature and hence far, far safer and more practical as a fuel.? However, not only will green methanol also be more expensive than the fossil fuels used today in ships, it will also likely cost quite a bit more per joule than green ammonia at scale.? The problem is that to make green methanol, you need a biogenic carbon source and green hydrogen.? Sites where wind + solar are also found with large amounts of waste biomass or, in the more expensive and energetically wasteful case, biogenic CO2, are fairly limited, and direct air capture (DAC) as a way to collect the necessary CO2 is just FUBAR.
?The problem with green methanol therefore seems to be one of scale, leading to higher costs at scale.? Ammonia, in contrast, seems “scalable”.
Uses and Handling of Anhydrous Ammonia
Anhydrous ammonia once found heavy use as a refrigerant, even in home refrigerators, until safer molecules were invented- but it is still widely used as a refrigerant in certain applications, including ice rinks.? Anhydrous ammonia is also applied directly to soils by farmers in certain places, solely because it is cheaper than using ammonia derived compounds like urea or nitrates.?
Ammonia itself can be shipped as a pressurized liquid (17 bar at 45 C), a semi-refrigerated liquid (4-8 bar at ~ -10 C) or ?as a fully refrigerated liquid (atmospheric pressure at -50 C).? Ships designed for other low pressure refrigerated or pressurized liquid gases like LPG (propane) are often used.? About 8% of world ammonia is transported as anhydrous ammonia currently by ship.
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There is, however, a world of difference between carrying a cargo of a poisonous, corrosive gas aboard a cargo ship, or using it as a refrigerant, and using ammonia in any open system use such as feeding it to engines. ?The hazard class of a fuels use, i.e an open versus a closed system use of a toxic gas, is orders of magnitude higher in my engineering assessment.
Bunkering and Fueling Ships With Ammonia
Storage of ship’s fuel is referred to as “bunkering”, a hangover term from the days when coal was stored aboard ships in literal “bunkers”.?? To use a fuel for shipping, it must be transported from where it’s made, to ports, and then stored there in fairly large quantity.? When liquid fuels are used, barges containing fuel are often towed alongside ships by tugboats.? ?With heavy oil fuels, these operations are routine, in stark contrast to loading a compressed or refrigerated gas tanker with its cargo.? The latter is carried out in very limited locations specifically designed for that purpose, by highly trained staff. ??It’s clear that a new set of hazards would arise not just from more numerous and larger stores of toxic gas, but also more routine handling of it by less trained staff than are currently called on for fuel handling.? All of these operations involve the risk of leakage, both routine and accidental.? And with a proliferation of containers of toxic gas in ports, terrorism also cannot be discounted as a very real risk.
Storage and Use Aboard Ship
Once the ship is loaded with its toxic fuel, that fuel would need to be stored, potentially moved around from tank to tank, and of course conveyed to the ship’s engines.? Ammonia is difficult to ignite, so a “pilot fuel” such as diesel fuel is often used along with the ammonia, meaning that the ship would actually have two fuels to manage, one of which will still have some GHG emissions potential.
Ammonia proponents will tell you that they will take every measure possible to engineer out the risks of using their toxic, corrosive gas as a fuel- aside from the obvious one, i.e. not doing it! They will also say that the certifying agencies responsible for insurance-related regulation of every system aboard a ship- companies like DNV, Bureau Veritas, Lloyds Register and the like, will never let unsafe ships go to sea.? They will make every line carrying the fuel to the engine, a piece of jacketed pipe as one for-instance.? That way, a pinhole in the inner liner will not cause a leak into the engine room.? But of course containment at every joint in that pipe along the way- every valve, every flange, every instrument etc.- will not have full double containment.? And no, you cannot eliminate all such connections from any piping system, ever.? The best you can do is imagine some kind of emissions control or leakage monitoring system, interlocked to shut off the fuel supply, likely backed up with some high-rate ventilation system to keep breathing air safe and possibly a scrubber system to de-inventory leaking components to safely.? And it is important to remember that an engine is an open system- if the fuel is not ignited, it leaves via the exhaust.? When the fuel is toxic, the exhaust becomes toxic too.? To be clear, I don’t design ships or ship-board systems.? But I do design piping, and have worked on process units that were intended at some point to be operated aboard ship.? Even in my comparative ignorance relative to a ship’s engineer, I can see problems that are rather difficult to manage to a high level of certainty.
Of course the 1st principle of safety in design, is to eliminate hazards by substitution if safer alternatives exist, rather than trying to make a fundamentally unsafe choice “adequately safe” by means of engineered controls.? And that is, honestly, the only thing we should be thinking of here, if we care about the lives of sailors.? Remember, aboard ship, accidents tend to happen during storms- and there is literally nowhere to run in the case of an accident aboard ship.
Emissions from Ammonia Combustion
The primary notion here is that ammonia contains no CO2, so it will not generate CO2 as a GHG upon combustion.? That of course ignores GHG emissions from upstream manufacture (99% of world ammonia production is made from fossil natural gas-derived hydrogen, without carbon capture), and also ignores the rest of the combustion chemistry involved.? While the major products of burning ammonia are nitrogen and water, those are definitely not the only products.
Because ammonia is difficult to ignite, some “ammonia slip” would be expected. And since ammonia is both toxic and corrosive and a regulated air pollutant, a pollution abatement system would be required to ensure complete combustion.? This could take several forms.
Burning anything in air causes oxygen and nitrogen in the air to react with one another to form NOx, which consists of two toxic smog-forming species and N2O, nontoxic but a persistent GHG.? NOx formation is however made much worse if the fuel contains nitrogen itself, and even worse still if that fuel is almost entirely nitrogen by mass (14 of every 17 grams of ammonia is nitrogen).?
NOx is often controlled by means of a selective catalytic reduction (SCR) catalyst, where a reductant is fed to react with the NOx to produce nitrogen.? Of course if ammonia is the fuel, ammonia would be used as the reductant, and some of it would likely be “slipping” by the engine anyway.? However, the important thing to know about SCR systems is that while we could feed a nontoxic, non-GHG reductant in excess to allow the catalyst to drive NOx concentrations to near zero, no such reductant exists.? Ammonia must therefore be very carefully added to the flue gas being fed to the SCR, to precisely match the reduction demand.? The normal result will be that either some NOx will not be removed, or both NOx and ammonia will be released.? Both are regulated pollutants which cause environmental harm.
Engines also combust their lubricants over time, generating particulate emissions. And if a pilot fuel is used, its emissions must be counted too.
The notion therefore that ammonia is a “clean fuel”, is basically a greenwash.? And a recent MIT report, agrees with me on that:
The study found that switching world shipping to ammonia fuel could cause as much as 600,000 additional premature deaths per year, largely from particulate matter generated by ammonia and NOx emissions.? Remember that shipping is already a massive source of fine particulate emissions from combustion, so this result is rather shocking.? The study recommends not only further work, but tighter air pollution regulations to address ammonia’s particular hazards.
Final Thoughts
Basically, this is all about money, and nothing more.? The very best thing you might say about ammonia is that it could be, at some future time, a cheaper alternative to methanol as a green shipping fuel, especially at scale.? It remains to be seen, however, if the extra costs of safe bunkering, safe fueling, and all the safety requirements aboard ship that might be acceptable to the likes of DNV etc., will add to the raw cost of the fuel.? It is not even clear to me that ammonia will end up cheaper than methanol once these provisions are in place.? Methanol handling is, relative to ammonia, more or less childsplay- although it does require more provisions and different systems than required for heavy bunker oils.
What is also certain to me is that if we foolishly choose to use a poison gas as a shipping fuel, despite the concept’s failure of the very first principle of safety in design, the result will be deaths and environmental damage that would otherwise have been entirely preventable.
History has rarely looked well on people who made the decision to knowingly put people’s lives at risks in order to save money, whether those people be employees or the general public.? Such crass cost-benefit analysis type thinking should have gone out of favour in the 1970s with the likes of the exploding Ford Pinto!?
(the Ford Pinto- note the ironic “reverse flames” paintjob.? To save installing a ~$10 part, Ford knowingly allowed a car where rear end collisions led frequently to gas tank ruptures and fires.? Lawsuits ate every bit of savings and nearly killed the company)
The imagined savings are usually blown out in the end by legal liability costs, even if you don’t value human lives intrinsically.? And let’s face it, we don’t all have the same values.? Some people aren’t troubled by the thought of others killed or injured in what they can write off as “accidents”.
As a professional engineer, it is my duty to hold the public safety as paramount.? And so it’s also my duty to inform the public when I see something that clearly will lead to needless loss of life.? It’s my hope that others with the same knowledge and experience with chemical handling will step up and speak out publicly about this.? Ammonia as a shipping fuel is yet another in a long list of bad ideas that are being put forward as decarbonization solutions whereas at best they are merely distractions and subsidy-harvesting schemes.? The difference here however is that not only is public money likely to be wasted on yet another dead end, this time it could also come with a body count.? I just can’t sit here silent about that.
Disclaimer:? this article was written by a human, and humans are known to make mistakes from time to time.? If you find a mistake, please bring it to my attention with good references and I will edit the article with gratitude.
If however your chief objection is that I’ve taken a dump on your pet idea, or one that you intend to use to make money for yourself or your company, please reach out to my employer Spitfire Research Inc., who will be happy to tell you to piss off and write your own article.
PhD candidate in Life Cycle Assessment
2 个月Aaron Paris
Anne B. Knudtzon (and for the record, I am not saying you are fool!)
Director Hydrogen Northwest Europe and Nordics hos Equinor
3 个月Ammonia is already widely used in maritime operation as an refrigerant in keeping goods cold during the voyage. Both an ammonia based fuel system or a refrigerant system contains the same risk and needs to be addressed in same manner from a safety-in-design perspective. A refrigerant system is not inherently more safe than a fuel system as you claim - in fact incident review of ammonia shows significant number of incidents from refrigerant system due to leaks in valves, fitting and process equipment. Proper design, maintenance and training of operators is the key to mitigate the risk. Luckily ammonia is by far the biggest chemical commodity where we have most experience and can extract learning so ammonia can play its vital role as an important element in meeting climate neutrality as fertiliser, refrigerant, fluid for industrial heat pump and as fuel/hydrogen carrier.
Consultor especializado em gest?o de opera??es e negocia??es de gases
3 个月Paul Martin Congratulations on a very interesting article! I have worked for many years in the gas industry and managed some hydrogen plants. I understand that each chemical has its own risks and can be handled safely, but I agree with you that using NH3 as a fuel will add another layer of risks in the operation. Your article presents that in a very comprehensive way. Thank you!