How Green Ammonia Will Power Ships and Farms

Ammonia is one of the most important chemicals on Earth and one of the least celebrated. Roughly half the food the world eats is grown using nitrogen fertiliser made from it, which means about half of humanity depends on a molecule most people never think about. It is also, at present, a serious climate problem. Making the world's 180 million tonnes of ammonia a year releases somewhere around 450 million tonnes of carbon dioxide, because the hydrogen it requires is stripped out of natural gas or coal. Green ammonia proposes to fix that by making the same molecule using renewable electricity instead of fossil fuels, and then, more ambitiously, to use it as a fuel in its own right. Because it contains no carbon atoms at all, burning it produces no carbon dioxide, which makes it one of the leading candidates to decarbonise deep-sea shipping. The chemistry works. The engines are arriving. Whether the economics can be made to work is the question the next decade will answer. Here is how the whole chain fits together.

 

1. Renewable Electricity Is Generated

 

Everything begins with clean power. Wind, solar, or hydroelectricity provides the energy input, and this is what puts the green in green ammonia, because the colour designations used in this industry refer entirely to how the hydrogen was made rather than to any property of the final product. Ammonia made from natural gas is grey, ammonia from coal is brown, ammonia from fossil sources with carbon capture is blue, and ammonia made with renewable electricity is green. The molecule itself is identical in every case.

The quantity of electricity involved is the first thing to grasp about this technology. Producing a single tonne of green ammonia takes roughly ten to twelve megawatt hours of renewable electricity with current commercial electrolysers, a figure expected to fall toward eight or nine as the technology matures. Scaled to global ammonia demand, that implies an enormous new build-out of renewable generation, which is why the most credible green ammonia projects cluster in places with exceptional wind or solar resources and cheap land, from Chile and Morocco to India, Australia, and the Gulf.

 

2. Green Hydrogen Is Produced

 

The renewable electricity is used to run electrolysers, which split water into hydrogen and oxygen. The hydrogen is the feedstock that matters; the oxygen is a saleable by-product. This single substitution, replacing hydrogen made by steam methane reforming with hydrogen made from water, is what eliminates almost all of ammonia's carbon footprint, taking lifecycle emissions from roughly 1.8 to 2.0 tonnes of carbon dioxide per tonne of ammonia down to something in the region of 0.03 to 0.1.

Electrolysis is also the expensive part, typically accounting for something like 40 to 60 percent of a green ammonia plant's capital cost, which makes electrolyser cost the single biggest lever on whether green ammonia ever becomes competitive. There is an engineering complication too. Wind and solar are intermittent, while the ammonia synthesis loop downstream prefers to run steadily, so plants need hydrogen buffer storage and flexible synthesis designs to bridge the lulls. Skimping on that buffer has caused real projects to trip repeatedly during calm spells, with the thermal cycling that follows damaging equipment. Matching a variable power source to a process that wants to run flat out is the defining technical challenge of the whole design.

 

3. Nitrogen Is Captured from Air

 

The other ingredient is far easier to obtain, since the atmosphere is 78 percent nitrogen. An air separation unit, typically using cryogenic distillation, chills and separates air to deliver a stream of pure nitrogen.

This step is mature, unglamorous, and cheap relative to the rest of the plant, and it carries a rather elegant implication. Green ammonia is made from water, air, and sunlight or wind, with no mined or drilled input at all. That is genuinely remarkable for an industrial commodity produced at this scale, and it is part of why ammonia attracts so much attention as an energy carrier: the raw materials are available almost anywhere, so production can be sited wherever renewable electricity is cheapest rather than wherever a resource happens to lie.

 

4. Green Ammonia Is Synthesized

 

Hydrogen and nitrogen are then combined through the Haber-Bosch process, the century-old reaction that fixes atmospheric nitrogen into ammonia at temperatures of around 400 to 450 degrees Celsius and pressures of 150 to 250 bar. Crucially, this step is unchanged from conventional production. The Haber-Bosch process is one of the most consequential inventions in human history, credited with enabling the population growth of the twentieth century, and green ammonia does not replace it.

That continuity is a significant practical advantage. Green ammonia is not a novel substance requiring new handling rules, new safety codes, or new customer acceptance. It is chemically identical to the ammonia the world already produces and consumes by the hundred million tonnes, which means the entire downstream system, the pipelines, the tanks, the ships, the terminals, and the regulations, already exists. Only the front end of the plant changes. The main adaptation required is that Haber-Bosch loops must become more flexible, capable of ramping with the availability of renewable hydrogen rather than running at constant load.

 

5. It Becomes a Clean Marine Fuel

 

Ammonia's appeal as a ship fuel comes down to one fact: the molecule contains no carbon, so burning it emits no carbon dioxide. For deep-sea shipping, where batteries are hopeless over long distances and where the industry faces binding decarbonisation targets, that is a powerful proposition. The technology has moved rapidly from concept to reality. Ammonia-capable two-stroke marine engines from WinGD and MAN Energy Solutions became commercially available through 2025 and 2026, Wärtsilä's four-stroke ammonia engine has been deployed in a retrofit, and the first ammonia-fuelled commercial vessels have entered service, with Exmar naming its first two ammonia dual-fuel gas carriers in April 2026 and further orders from Fortescue, Trafigura, and Mitsui O.S.K. Lines following through the late 2020s.

Three genuine challenges come with it, and they are worth stating plainly. First, energy density. Ammonia carries roughly 12.7 megajoules per litre against about 35.7 for marine gas oil, so a ship needs something like two and a half to three and a half times more fuel volume for the same range, which eats into cargo space. Second, nitrogen emissions, since combusting a nitrogen-rich fuel can produce nitrogen oxides and nitrous oxide, a greenhouse gas around 270 times more potent than carbon dioxide, along with unburned ammonia slip. The industry is acutely aware that it must not solve a carbon problem by creating a nitrogen one, and the test results are encouraging: MAN and WinGD both report nitrous oxide below roughly three to five parts per million in engine testing, equivalent to under two percent of the carbon-dioxide-equivalent emissions of a fuel oil engine, with selective catalytic reduction available to clean up the rest, yielding overall greenhouse gas reductions above 90 percent. Third, and most seriously, toxicity. Ammonia is acutely poisonous to humans in small concentrations, which is why classification societies have issued extensive new guidance, why Exmar chose to fuel only its main engine with ammonia on its first vessels, and why the entire sector is proceeding cautiously in the knowledge that a single serious release could set the fuel back years.

 

6. It Produces Low-Carbon Fertilizer

 

The larger and more immediate opportunity is not at sea but on land. Over 80 percent of global ammonia goes into nitrogen fertilisers, and because green ammonia is chemically identical to the conventional product, it can be dropped straight into existing fertiliser manufacturing with no change to the downstream process at all.

This makes fertiliser the natural first market. There is no need to build new engines, retrain crews, or write new safety codes, only to substitute the input, so decarbonising fertiliser is a matter of economics rather than technology. Given that ammonia production accounts for somewhere between one and two percent of global energy-related carbon dioxide emissions, and that food security depends on it absolutely, this is one of the most consequential industrial decarbonisation targets in existence. It is also why India's reverse auctions for green ammonia supply to fertiliser producers have become such a closely watched price benchmark for the entire industry.

 

7. Storage and Transport Are Scaled

 

Ammonia's decisive practical advantage over hydrogen is that it is far easier to handle. Hydrogen must be compressed to extreme pressures or chilled to around minus 253 degrees Celsius to be transported in useful quantities. Ammonia liquefies at a comparatively mild minus 33 degrees Celsius or under modest pressure, and it carries more hydrogen per unit of volume than liquid hydrogen itself does.

Beyond the physics, there is the infrastructure. The world already moves roughly 20 million tonnes of ammonia across borders every year, with established terminals, storage tanks, pipelines, and a fleet of purpose-built gas carriers, plus a workforce with decades of experience handling it. This is the strongest argument for ammonia as an energy carrier: it is the only way to move large quantities of renewable hydrogen around the world using infrastructure that already exists. Some proposals envisage shipping green ammonia from sun-rich regions to industrial consumers and cracking it back into hydrogen on arrival, though that cracking step carries significant energy losses of its own.

 

8. Emissions Are Reduced Across Sectors

 

Put together, green ammonia offers a route to cut emissions from fertiliser production, from deep-sea shipping, and potentially from power generation and heavy industry, three sectors that are otherwise stubbornly difficult to decarbonise. The theoretical case is compelling and the technology is largely proven.

The obstacle is cost, and it is a serious one. Green ammonia currently sells at a substantial premium to conventional ammonia, with reported prices commonly in the range of roughly 600 to 900 dollars a tonne, and in some markets higher, against grey ammonia benchmarks around 500 dollars. India's competitive auctions have driven bids down toward the high 500s, which is closer than many expected, but a persistent gap remains, and it is widest precisely where renewable electricity is most expensive. Analysts generally expect parity in favourable locations around the end of this decade as electrolyser costs fall below 500 dollars per kilowatt, but such projections have slipped before, and the green hydrogen sector has seen a wave of cancelled and delayed projects as developers confronted the difficulty of securing offtake at prices buyers will pay. The realistic assessment, then, is that green ammonia's chemistry and infrastructure advantages are genuine and its engines are arriving on schedule, but its future depends on two things outside the laboratory: the continued fall in the cost of renewable electricity and electrolysers, and policy, particularly carbon pricing and the fuel standards emerging in shipping, that puts a real price on the emissions the conventional product creates. Ammonia is not guaranteed to win. It is, however, one of the few candidates with a credible path to decarbonising both the world's food supply and its long-haul ships with the same molecule.

 

Did You Know?

 

Around 80 percent of global ammonia production goes into fertilisers, which is why the Haber-Bosch process is often described as the invention that feeds half the world, and why decarbonising it matters so much: conventional ammonia production emits roughly 1.8 to 2.0 tonnes of carbon dioxide for every tonne of ammonia made, adding up to some 450 million tonnes a year. Meanwhile demand for green ammonia as a zero or near-zero carbon marine fuel and hydrogen carrier is growing rapidly, with the first ammonia-fuelled commercial ships now on the water and orders stretching into the 2030s. It is a striking prospect: the same molecule, made from nothing but water, air, and renewable electricity, potentially feeding the world and moving its cargo at the same time.

 

Note: This article reflects the state of green ammonia technology and markets as of mid-2026, drawing on sources including the IEA, IRENA, the Ammonia Energy Association, classification societies including Lloyd's Register and DNV, and engine manufacturers. Price figures vary considerably by region and contract, and cost projections for green ammonia remain uncertain.