Cities against climate change
Oct 24, 2024
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Green ammonia, a compound of nitrogen and hydrogen, emerges as a highly promising energy carrier for the decarbonisation of certain sectors, such as fertiliser production and maritime transport. As a hydrogen carrier, it facilitates efficient and safe storage and transport from remote production regions.
During the production and use of renewable energy, there are periods when production is high but demand is low. At these times, it is crucial to store and utilise surplus energy to prevent it from going to waste.
Energy carriers are compounds that allow energy to be stored and transported for later use. Renewable hydrogen is among the most promising of these carriers, owing to its carbon-free composition and its versatility in producing other renewable derivative molecules, most notably green ammonia.
In the process known as ammonia synthesis (i.e., combining hydrogen and nitrogen to produce ammonia), we find a key factor for hydrogen storage. When green ammonia is decomposed, it becomes an efficient hydrogen carrier, with nearly 18% hydrogen content by mass.
When green ammonia is decomposed, it becomes an efficient hydrogen carrier
Furthermore, due to its high energy density, green ammonia offers a significant advantage: it can be stored and transported in smaller and lighter tanks compared to hydrogen.
Currently, most of the global demand for ammonia (which is fossil-based) is used in fertiliser production. Green ammonia is used primarily to decarbonise these industries that rely on it as a raw material. It can also be used to generate carbon-free electricity through fuel cells or gas turbines, and in internal combustion processes for maritime transport and aviation.
While pipeline transport of hydrogen is considered the most efficient solution, ammonia is highly valuable as a carrier for transporting hydrogen from distant locations where pipelines are not feasible. Ammonia, is a gas that is manufactured, stored, and transported on an industrial scale, and hence has a relatively low cost.
Green ammonia has a boiling point of -33 degrees Celsius and, in both its gaseous and liquid forms, requires minimal storage conditions. This makes it simple and versatile to store and transport, whether in small cylinders in hard-to-reach locations or in large tanks at industrial sites for powering machinery.
The storage requirements for ammonia are minimal, making it easy and versatile to store and transport
Once it reaches its destination, green ammonia can be converted back into green hydrogen for industrial use, or used directly as a feedstock or as fuel in maritime transport, among other applications.
With simple technology and low investment, this fuel can be produced anywhere in the world.
Consequently, green ammonia, derived from green hydrogen—which is itself produced using electrical energy from the sun, wind, or sea—is critical for the development of these renewable energies.
Green ammonia plays a vital role in advancing renewable energies
It can also be used as a fuel, either through combustion in engines or via a chemical reaction with oxygen in a fuel cell to produce electricity.
Its utilisation is key to achieving the European Union’s decarbonisation targets set for 2050.
Green ammonia, produced from renewable energy sources, does not emit carbon dioxide (CO₂) during its production. This makes it highly effective in reducing greenhouse gas emissions in sectors that currently rely on conventional ammonia made from carbon-intensive natural gas.
Moreover, green ammonia helps reduce dependence on fossil fuels, as it can be produced from local resources.
According to the RePowerEU plan, which supports Europe’s transition to clean energy and aims to create a more resilient energy system, 20 million tonnes of renewable hydrogen will be needed by 2030 to decarbonise European industry. It is anticipated that 10 million tonnes will be produced domestically, while a further 10 million tonnes will be imported. Of these imports, 4 million tonnes are expected to be in the form of ammonia or other derivatives.
Of the renewable hydrogen required by 2030, 10 million tonnes are expected to be produced domestically, with an additional 10 million tonnes to be imported. Of those imports, 4 million tonnes would be in the form of ammonia or other derivatives