Ammonia as Fuel: The Next Frontier in Clean Energy

Ammonia as fuel is increasingly being discussed as a key element in the future of global energy. As the world seeks to reduce CO₂ emissions and move away from fossil fuels, industries, transport, and power generation all require reliable, high-capacity energy sources. In this context, ammonia is emerging as a potential alternative to oil, coal, and even hydrogen.

Ammonia (NH₃) has long been used as a fertilizer and is one of the most important industrial chemicals, with hundreds of millions of tons produced annually for agriculture. Today, it is also seen as a hydrogen carrier, a carbon-free fuel, and a cornerstone of tomorrow's energy systems. Its main advantage: when burned, ammonia contains no carbon, so it does not directly emit CO₂.

Unlike hydrogen, which is notoriously difficult to store and transport, ammonia benefits from a mature global infrastructure for storage, port logistics, and international shipping. This makes it especially attractive for countries planning to import "green" energy in the form of chemical fuels.

However, behind the promising outlook lie significant challenges:

• How environmentally friendly is ammonia production?
• Is it safe to store?
• Can it truly be used in engines and turbines?
• Can ammonia really replace hydrogen?

This article explores how blue and green ammonia are produced, how ammonia compares to hydrogen, the existing storage technologies, and what risks might hinder its widespread adoption.

Why Ammonia Is Back in the Spotlight as a Fuel

Interest in ammonia as an energy source isn't new. Experiments with ammonia-powered engines date back to the 20th century, especially during oil shortages. Back then, technology was underdeveloped, and cheap oil made alternatives unprofitable.

Today, the situation has changed for three key reasons:

1. Global decarbonization. Nations aim for carbon neutrality, and industries seek to cut CO₂ emissions. Ammonia, being carbon-free, does not produce CO₂ when burned, making it a strong candidate for carbon-free fuel.
2. Hydrogen's challenges. Hydrogen, though promising, requires either extremely high pressures or cryogenic temperatures for storage. That's why ammonia is increasingly discussed as a hydrogen carrier: it's easier to transport and store as a liquid under moderate conditions.
3. Existing infrastructure. The world already has ammonia plants, storage facilities, tankers, and port terminals. This lowers the entry barrier for a new energy model-much of the infrastructure already exists and only needs adaptation.

Additionally, ammonia offers high volumetric energy density compared to compressed hydrogen, which is particularly important for shipping, heavy industry, and gas turbines.

Nevertheless, ammonia is far from perfect. It is toxic, has specific storage risks, and burning it can produce nitrogen oxides (NOₓ), which require additional treatment.

The central question: How environmentally and economically viable is ammonia production?

How Ammonia Is Produced: Grey, Blue, and Green

To judge whether ammonia is truly the fuel of the future, its production sources must be understood. Ammonia is not a primary energy source but an energy carrier, and its environmental impact depends directly on how it's produced.

Grey Ammonia

Currently, most ammonia is produced using the Haber-Bosch process, where nitrogen from air is combined with hydrogen under high temperature and pressure. The issue lies in hydrogen sourcing: it's typically derived from natural gas via steam methane reforming, resulting in significant CO₂ emissions. This product is called grey ammonia, and its production accounts for 1-2% of global CO₂ emissions. Using grey ammonia as fuel brings little climate benefit.

What Is Blue Ammonia?

Blue ammonia is made similarly to grey ammonia but incorporates carbon capture and storage (CCS) to reduce emissions. While not completely eliminating CO₂, it significantly lowers the carbon footprint. The search for "what is blue ammonia" is growing, as this technology is seen as a transitional stage, allowing the use of existing gas resources while reducing emissions.

However, blue ammonia has limitations:

• CO₂ capture efficiency is not 100%.
• Dedicated infrastructure for CO₂ transport and storage is needed.
• It still depends on fossil fuels.

Green Ammonia: Carbon-Free Production

The most promising option is green ammonia. Here, hydrogen is sourced from water using electrolysis powered by renewable energy-wind, solar, or hydro. If the electricity is fully renewable, ammonia production is nearly CO₂-free, making it a genuinely carbon-neutral fuel.

However, this raises new challenges:

• Electrolysis is highly energy-intensive.
• Green ammonia is currently much more expensive than conventional types.
• Large investments in renewable generation are required.

Still, many countries are already investing in green ammonia exports, viewing it as a way to "package" renewable energy for global trade.

It's important to note: ammonia is often seen less as a competitor and more as a replacement for hydrogen in logistics.

Ammonia vs. Hydrogen: What Are the Advantages?

One of the most common questions is "ammonia vs. hydrogen." Chemically, ammonia is a compound of nitrogen and hydrogen, but energetically it can serve as a more practical way to store and transport hydrogen.

The Problem with Pure Hydrogen

Hydrogen is a lightweight, energy-rich gas, but its physical properties pose major hurdles:

• Requires storage at up to 700 bar pressure
• Or cryogenic cooling to −253°C
• Hydrogen molecules easily leak through materials
• Infrastructure is almost nonexistent

This makes hydrogen logistics expensive and technically challenging. Alternative storage methods, such as chemical carriers, are increasingly attractive.

Why Ammonia Is More Convenient

Ammonia contains 17.6% hydrogen by mass and:

• Liquefies at −33°C under atmospheric pressure
• Can be stored at moderate pressures at room temperature
• Has a well-established global infrastructure for storage and transport

Ammonia can be transported by sea tankers, just as fertilizers are shipped today, drastically lowering the barrier for global "green energy" trade.

There are two main energy use pathways:

1. Direct combustion of ammonia in engines and turbines
2. Cracking ammonia back into hydrogen and nitrogen, then using the hydrogen

In the second scenario, ammonia acts as a convenient hydrogen carrier.

Energy Density

Liquid ammonia's volumetric energy density far exceeds that of compressed hydrogen. This is vital for:

• Maritime shipping
• Heavy industries
• Gas turbines
• Remote energy systems

Hence, ammonia is actively explored in shipping as an alternative to fuel oil and LNG.

However, advantages come with drawbacks: ammonia is toxic, has a pungent odor, and requires strict safety measures. Burning it can produce nitrogen oxides (NOₓ), requiring additional scrubbing.

In summary, ammonia is not a "better hydrogen," but a compromise between logistical convenience and chemical risks.

Storage and Transportation of Ammonia: Infrastructure and Safety

One major reason for considering ammonia as a fuel is the already existing global infrastructure. Unlike hydrogen, ammonia doesn't require an entirely new buildout.

How Ammonia Is Stored

Ammonia can be stored in two main ways:

• As a refrigerated liquid at around −33°C under atmospheric pressure
• As a compressed gas at moderate pressure and room temperature

This is much simpler than storing hydrogen at −253°C or 700 bar. Large chemical terminals already have ammonia storage tanks, and in terms of storage complexity, ammonia is closer to propane or LNG than to hydrogen.

Transportation

For decades, ammonia has been transported by:

• Maritime tankers
• Rail tank cars
• Road tankers
• Pipelines

This is a significant advantage during the global energy transition, allowing countries exporting green ammonia to utilize existing logistics networks, adapting them to new energy standards.

Ammonia Storage Safety

However, ammonia is toxic. At high concentrations, it can damage the respiratory system and cause burns. That's why storage safety is paramount in energy applications.

Main risks include:

• Leaks at terminals and on ships
• Formation of toxic clouds during accidents
• Strict industrial safety requirements

On the plus side, ammonia's strong odor enables rapid leak detection, and the chemical industry has decades of experience handling it safely.

New Challenges

If ammonia becomes a widespread fuel for energy and transport, its usage volume will multiply. This means:

• Stricter storage standards
• Upgrading port infrastructure
• Developing new leak monitoring systems
• Mandatory personnel training

Thus, ammonia's infrastructure advantage is real but requires large-scale adaptation for energy use.

Current Applications of Ammonia as Fuel

While a full-scale transition to ammonia hasn't happened yet, pilot projects are underway in key sectors. Ammonia as fuel is not just a theoretical idea but a technology undergoing real-world validation.

Shipping

Maritime transport is one of the most promising sectors for ammonia fuel. Ships are difficult to electrify, and emission reduction regulations are tightening.

Ammonia offers several advantages:

• High volumetric energy density
• Ability to store in large tanks
• No CO₂ emissions when burned

Major shipbuilders are already testing engines that can run on ammonia or ammonia-fuel blends. The first commercial ammonia-powered vessels are expected in the coming years.

Gas Turbines and Power Plants

Ammonia is also considered as fuel for gas turbines. Some energy companies have tested partial or full ammonia combustion in turbine systems. Key challenges include:

• Stabilizing combustion
• Reducing NOₓ formation
• Adapting combustion chambers

If these technologies reach commercial levels, ammonia could be used to generate electricity with zero direct CO₂ emissions.

Industry

Heavy industry is another potential sector. Steel and chemical plants require high-temperature heat, and ammonia could replace coal or natural gas in these processes.

Hydrogen Extraction

Some projects do not burn ammonia directly but crack it back into hydrogen and nitrogen, using the hydrogen in fuel cells or industrial processes. This is especially relevant for countries importing green ammonia and extracting hydrogen locally.

Despite growing trials, large-scale adoption is still hindered by costs and environmental concerns.

Environmental Impact and CO₂ Emissions

The main argument for ammonia is the absence of carbon in its molecule. Theoretically, burning ammonia does not produce CO₂, making it attractive as a carbon-free fuel for energy and transport.

However, the reality is more complex.

Emissions During Production

If grey ammonia (from natural gas) is used, the carbon footprint remains high, simply shifting emissions from combustion to production. Blue ammonia lowers emissions via carbon capture but does not solve the problem entirely. Only green ammonia, made with renewables, delivers a genuinely low-carbon cycle.

Therefore, ammonia's environmental benefits directly depend on the energy source used in production.

Nitrogen Oxides (NOₓ)

Burning ammonia can produce nitrogen oxides (NO and NO₂), which contribute to smog and acid rain. To reduce NOₓ emissions, engineers use:

• Special combustion modes
• Catalysts
• Selective catalytic reduction systems

These solutions are technologically feasible but raise equipment costs.

Potential Leaks

Ammonia is toxic. As its use as fuel grows, so does the volume stored and transported, increasing the risk of accidents. Although ammonia rapidly decomposes in the atmosphere and is not a greenhouse gas, leaks can pose serious threats to people and ecosystems near incident sites.

Full Lifecycle Analysis

For a true "well-to-power" assessment, factors include:

• Hydrogen sourcing
• Energy required for synthesis
• Transport losses
• Combustion or cracking efficiency

Only a comprehensive analysis can determine whether ammonia truly reduces emissions in a given energy model.

In summary, ammonia can be part of a carbon-free energy mix-but only with green production and strict NOₓ emission controls.

Risks and Safety Issues of Ammonia in Energy

Despite technological advantages, safety risks are the main argument against mass adoption of ammonia as fuel.

Toxicity

Ammonia is toxic. At high concentrations, it:

• Irritates respiratory tracts
• Causes chemical burns
• Can have serious consequences if inhaled

Leaks form dense gas clouds that can spread over large distances, posing special challenges in ports or densely populated areas. However, industry has decades of experience with ammonia, supported by international storage standards, emergency systems, and operational know-how.

NOₓ Formation During Combustion

Even if ammonia emits no CO₂, it can generate nitrogen oxides. Without treatment systems, NOₓ emissions can become a significant environmental concern. Addressing this requires:

• New combustion chamber designs
• Catalytic converters
• Continuous emission monitoring

The technology exists but currently costs more than traditional fuel solutions.

Economic Risks

Green ammonia remains expensive. Mass production requires:

• Cheap renewable electricity
• Large-scale electrolysis plants
• Modernization of Haber-Bosch factories

Without subsidies or carbon pricing, it is still less competitive than fossil fuels.

Scaling Infrastructure

Widespread use of ammonia in shipping and energy would dramatically increase its volume in circulation, leading to:

• Increased port traffic
• Stricter safety requirements
• Need for insurance and regulation

Any major accident could seriously undermine trust in the technology.

Ultimately, ammonia is not a perfect solution. It is a compromise between storage convenience, carbon-free chemistry, and toxicity risks. Its future depends on whether technology can make its production green and its use safe.

Conclusion

Ammonia as fuel is now being seriously considered, not as a fringe idea but as a real component of the energy future. It offers several strategic advantages: a carbon-free molecule, an established global storage and transport network, and the ability to serve as a convenient hydrogen carrier.

But ammonia is no "magic bullet." Its environmental impact is directly tied to how it is produced. Grey ammonia merely shifts CO₂ emissions from combustion to synthesis. Blue ammonia reduces the carbon footprint but does not eliminate it. Only green ammonia, made with renewable energy, can become part of a truly carbon-free energy system.

From a technical perspective, ammonia is moving out of the lab: marine engines, gas turbines, and industrial systems are being tested. However, significant challenges remain-toxicity, NOₓ control, the cost of green production, and infrastructure scaling.

Most likely, ammonia will not entirely replace hydrogen or electricity but will find its niche in heavy industry, maritime transport, and international trade of "packaged" green energy.

Will ammonia be the fuel of the future? The answer depends not only on chemistry but also on economics, regulation, and the pace of renewable energy development. One thing is clear: in the energy transition, ammonia now plays a far greater role than it did just a decade ago.

Read more about hydrogen energy: breakthroughs and future prospects