Green ammonia is ammonia (NH₃) produced using renewable energy instead of fossil fuels. Conventional ammonia manufacturing is one of the most carbon-intensive industrial processes on Earth, generating about 2.4 tons of CO₂ for every ton of ammonia produced. Green ammonia aims to cut those emissions by up to 90% by replacing natural gas with clean electricity, water, and air as the primary inputs.
The chemical end product is identical. What changes is the energy source and, in many cases, the method used to obtain hydrogen, the key ingredient. That distinction matters because global ammonia production currently accounts for roughly 450 million tons of CO₂ per year, a footprint equivalent to the total energy system emissions of South Africa.
How Conventional Ammonia Is Made
Nearly all ammonia today is produced through the Haber-Bosch process, a century-old method that combines nitrogen from the air with hydrogen at extremely high temperatures and pressures. The hydrogen comes from steam methane reforming, which strips hydrogen atoms from natural gas and releases CO₂ as a byproduct. This is called “gray ammonia.” When the CO₂ is captured and stored underground rather than vented, the product is called “blue ammonia,” though capture rates are imperfect and the process still relies on fossil fuel extraction.
How Green Ammonia Is Different
Green ammonia replaces the fossil-fuel-derived hydrogen with hydrogen made from water electrolysis, a process that splits water molecules into hydrogen and oxygen using electricity. When that electricity comes from wind, solar, or hydropower, the entire chain from raw materials to finished product generates little to no carbon emissions.
The nitrogen still comes from the air, which is about 78% nitrogen by volume. Once you have clean hydrogen and separated nitrogen, they can be combined through the traditional Haber-Bosch reactor or through newer electrochemical methods that operate at lower temperatures and pressures. The electrochemical route is still largely in development, but it holds promise because it could simplify the process and reduce the massive energy demands of the conventional reactor. The core challenge in all ammonia synthesis is breaking nitrogen’s triple bond, one of the strongest molecular bonds in nature, which requires significant energy input regardless of the method.
Why Ammonia and Not Just Hydrogen
Green hydrogen gets a lot of attention as a clean fuel, but hydrogen is notoriously difficult to store and transport. Liquefying pure hydrogen requires cooling it below negative 253°C, and the energy cost of that cooling alone eats up roughly 45% of the energy contained in the gas. Ammonia solves this problem. It liquefies at just negative 33°C at normal atmospheric pressure, or at room temperature under modest pressure. That makes it far easier to ship in bulk using infrastructure that already exists.
Liquefied ammonia also packs more energy into the same volume: 3.83 MWh per cubic meter compared to 2.64 MWh per cubic meter for liquid hydrogen. In practical terms, a tanker full of ammonia carries about 45% more energy than the same tanker filled with liquid hydrogen, under far less demanding storage conditions. This is why ammonia is increasingly discussed not just as a fertilizer ingredient but as a carrier molecule for moving clean energy around the world.
The Efficiency Tradeoff
Using ammonia as an energy carrier comes with a significant efficiency penalty. When you factor in the full cycle of producing green ammonia, storing it, shipping it, and then converting it back to electricity, the round-trip efficiency is roughly 28%, meaning about 72% of the original renewable energy is lost along the way. That’s comparable to the round-trip efficiency of green hydrogen pathways, so ammonia doesn’t lose ground relative to its main competitor. But both numbers highlight that ammonia and hydrogen are best suited for applications where direct electrification isn’t possible, not as replacements for batteries or grid-connected renewables.
Fertilizer and Agricultural Impact
Ammonia’s single largest use is in fertilizer production, which accounts for about 2% of global greenhouse gas emissions. Roughly 70% of all ammonia produced worldwide goes into nitrogen-based fertilizers that support food production for billions of people. Switching to green ammonia could reduce those emissions by up to 90% without changing the final fertilizer product at all. This makes green ammonia one of the most straightforward decarbonization pathways for agriculture, a sector that has few easy options for cutting emissions.
Shipping Fuel
The maritime industry is actively exploring green ammonia as a zero-carbon fuel for ocean-going vessels. A notable example is the feasibility study led by Grieg Maritime Group, which evaluated whether a ten-year-old open hatch bulk carrier could be retrofitted to run on green ammonia for transatlantic routes. The project brought together more than 20 companies including engine manufacturers, ship designers, and fuel suppliers like Yara and Wärtsilä. While ammonia-powered ships aren’t yet common, these pilot programs are testing whether the fuel can work in real commercial operations.
Ammonia has an advantage over other alternative marine fuels because it contains no carbon, so burning it produces no CO₂ at the point of combustion. The main challenge is managing nitrogen oxide emissions during combustion and ensuring safe handling onboard, since ammonia is toxic in concentrated form.
Safety Considerations
Ammonia is not a benign substance. It’s a colorless gas with a sharp, suffocating odor that causes irritation to the eyes, nose, and throat at low concentrations. Workplace safety standards set by NIOSH recommend a maximum exposure of 25 parts per million over an eight-hour workday, with short-term limits of 35 ppm. At 300 ppm, ammonia is classified as immediately dangerous to life and health. Direct contact with liquid ammonia can cause severe skin burns and frostbite.
The industrial world has decades of experience handling ammonia safely in fertilizer plants, refrigeration systems, and chemical processing. That existing expertise and infrastructure is one reason ammonia is considered a more practical near-term option than hydrogen for large-scale clean energy transport. But scaling up its use as a fuel will require new safety protocols, especially in settings like ports and ships where workers may have less familiarity with the chemical.
Major Projects and Costs
The largest green ammonia facility currently under construction is the NEOM Green Hydrogen Project in Saudi Arabia. Powered entirely by renewable energy, the plant is designed to produce approximately 1.2 million tons of green ammonia per year. The project reached 80% completion in early 2025 and is expected to begin commercial operations by 2026 or 2027. It represents the world’s largest utility-scale, commercially based green hydrogen facility.
Cost remains the biggest barrier to widespread adoption. Green ammonia is currently more expensive than gray ammonia, primarily because electrolyzers and renewable electricity still cost more than natural gas in most regions. The gap is narrowing as renewable energy prices fall and as policy incentives take effect. In the United States, the Inflation Reduction Act established a production tax credit (known as 45V) for clean hydrogen, which directly benefits green ammonia producers since hydrogen from electrolysis is their primary input. To qualify for the largest credit tier, producers must source between 90% and 97.5% of their electricity from zero-carbon sources.
The IEA projects that under aggressive decarbonization scenarios, direct CO₂ emissions from ammonia production could fall by 70% to 95% by 2050 relative to current levels, depending on how quickly green production methods scale up and how effectively policy drives adoption.