„The production of green ammonia
has the capability to impact the
transition towards zero-carbon.“
Production of green ammonia
Ammonia has the potential to revolutionize renewable energy storage and distribution due to its high energy density of approximately 3 kWh/litre and the existence of a global transportation and storage infrastructure. It could become a competitive option for zero-carbon energy transportation by road, rail, ship or pipeline.
Despite being primarily used as a fertilizer for over a century, ammonia production accounts for 1.8% of global carbon dioxide emissions as it is currently manufactured through the steam reforming of methane to produce hydrogen, followed by the Haber Bosch process. Decarbonization efforts are mainly focused on hydrogen production through carbon capture and storage or sustainable electricity-based water electrolysis. However, using ammonia for energy storage and transportation presents challenges, such as negative environmental impact due to human alteration of the nitrogen cycle, which can lead to biodiversity loss, air quality issues, and greenhouse gas emissions. It is crucial to decouple new uses of ammonia from its environmental impact and prevent emissions of nitrogen oxides and ammonia release.
Overcoming these challenges, demonstrating technical feasibility, establishing appropriate regulations, and implementing safety procedures will be essential in developing a low-carbon energy future. Ammonia has the potential to contribute substantially to reducing greenhouse gas emissions and enabling the shift away from global dependence
on fossil fuels.
The discovery of ammonia synthesis from hydrogen and nitrogen by Haber and Bosch in Germany at the beginning of the 20th century has had a significant global impact. Currently, ammonia is primarily used as the basic feedstock for inorganic fertilizers that support food production for around half of the world‘s population.[1] Additionally, ammonia is an efficient refrigerant that has been widely used since the 1930s in industrial cold stores, food processing industry applications, and large-scale air conditioning. It also plays a vital role in the production of AdBlue for vehicle NOX control, as well as in the pharmaceutical, textile, and explosives industries.
Today, global ammonia production is about 176 million tonnes per year, with steam methane reforming being the primary method of production to generate hydrogen for ammonia synthesis via the Haber Bosch process. However, ammonia production is an energy-intensive process, accounting for about 1.8% of global energy output each year, with steam methane reforming responsible for over 80% of the energy required. As a result, ammonia production generates approximately 500 million tonnes of carbon dioxide emissions, equivalent to about 1.8% of global carbon dioxide emissions.[2,3,4]
Ammonia synthesis is among the largest carbon dioxide-emitting chemical industry processes, along with cement, steel, and ethylene production, and requires a decarbonization plan to meet the net-zero carbon emissions target by 20505.
„The present production of ammonia
results in the emission of 500 million
tonnes of carbon dioxide.“
1. Smil V. 2000 Enriching the Earth. ISBN 9780262194495.
2. Institute for Industrial Productivity. Industrial Efficiency Technology Database – Ammonia.
4. IEA, ICCA, DECHEMA. 2013 Technology Roadmap – Energy and GHG Reductions in the Chemical Industry via Catalytic Processes.
5. McKinsey & Company. 2018 Decarbonization of Industrial Sectors: the next Frontier.
Ammonia, besides its established uses, has the potential to serve as a versatile, sustainable, and zero-carbon energy carrier and fuel. Like fossil fuels, ammonia is both an energy store and a fuel, releasing energy by the creation and destruction of chemical bonds. For ammonia (NH3), the energy gain occurs when nitrogen-hydrogen bonds are broken, producing nitrogen and water when combined with oxygen. This means that if renewable energy powers the production of green ammonia, it can be manufactured sustainably using only air (which is mostly nitrogen) and water.
Ammonia‘s energy storage properties are similar to methane‘s, with both having chemical bonds that can be broken to release energy. However, the difference lies in the central atom, with methane‘s carbon atom producing carbon dioxide upon burning, while ammonia‘s nitrogen atom results in nitrogen gas. Ammonia is a colorless, strong-smelling gas at room temperature and atmospheric pressure. To store it in bulk, it must be liquefied through compression or chilling. In this state, ammonia has an energy density of about 3 kWh/litre, which is less than fossil fuels but comparable. In contrast, hydrogen must be compressed to 350-700 times atmospheric pressure or cryogenically cooled to -253°C to be stored at scale, making hydrogen storage more challenging, energy-intensive, and expensive than ammonia storage.