Ammonia

Ammonia is a compound of nitrogen and hydrogen with the molecular formula NH₃. In its pure, anhydrous form, it is a colourless gas with a pungent odour at room temperature and atmospheric pressure. Its boiling point at this pressure is about −33.3 °C; at higher pressure it can also be liquefied without such strong cooling. Anhydrous ammonia must be distinguished from aqueous ammonia solutions.

In the energy system, ammonia is considered a chemical energy carrier and a transport form for hydrogen. Electricity-based production belongs to Power-to-X. Ammonia can be used directly or split again at the destination. Which route makes sense therefore depends largely on the required end product.

Production and existing industrial uses

Industrial synthesis combines nitrogen with hydrogen. Conventional production routes mainly use natural gas and, in addition, in particular coal. They cause substantial CO₂ emissions. In electrolysis-based production, by contrast, hydrogen is obtained from water by electrolysis. Nitrogen supply and ammonia synthesis follow. These process steps also require energy; the origin of the hydrogen alone therefore does not describe the entire production.

"Green" usually denotes production with renewable hydrogen and renewable energy. "Blue" stands for fossil-based production with CO₂ capture and permanent storage. The colours do not replace a quantified emissions balance.

Ammonia is already a major industrial basic chemical, especially for nitrogen fertilisers. Further applications include, for example, plastics and synthetic fibres. Renewable production can thus initially replace existing fossil production without having to create a new energy consumption market. However, lower-emission fertiliser production does not automatically eliminate the environmental impacts of the subsequent use of fertilisers.

Transport, storage and hydrogen recovery

When refrigerated, liquid ammonia can be stored at approximately −33 °C and atmospheric pressure; at 25 °C, approximately 10 bar absolute pressure is required. About 17.6 percent of its mass is chemically bound hydrogen: one tonne theoretically contains about 176 kilograms of hydrogen. This is not a practically guaranteed yield.

For pure hydrogen at the destination, an ammonia cracker is required. It decomposes NH₃ into nitrogen and hydrogen with the input of energy. Separation and purification are added. The calorific value of ammonia is about 18.6 megajoules per kilogram, or 5.17 kilowatt-hours per kilogram. This chemical energy content must not be equated with the amount of electricity obtained later.

Reconversion to electricity causes further losses. An efficiency figure for hydrogen recovery therefore does not describe the efficiency of the complete electricity–ammonia–electricity chain. Production, storage, transport, reconversion and auxiliary energy must be considered within the same system boundary.

Classification in the electricity system

Fluctuating wind and solar power generation makes supplying a chemical production plant more difficult. High utilisation tends to lower specific capital costs. Hydrogen buffers, adapted synthesis processes and complementary generation profiles can support integration. Flexible electrolysis therefore does not mean that the entire ammonia production can respond to surplus electricity arbitrarily quickly or free of cost.

For an assessment, the task should be named first: Should an industrial site receive ammonia, should hydrogen be imported, or should an electricity reserve be created? Only then does a comparison with alternatives make sense. Direct electrification should be examined as a comparison option, not as a fundamentally interchangeable application: a chemical feedstock requirement is a different task from supplying an electric motor.

A storage assessment also needs a concrete yardstick. Different questions matter for a rarely used reserve than for a storage unit charged daily: How much energy must be available? How quickly must it be available? What power is required? What costs arise even during standstill? A blanket statement such as "ammonia is a good electricity store" leaves these decisive differences open.

Climate, environment and safety

Ammonia contains no carbon; no CO₂ arises from the NH₃ molecule itself during use. Climate neutrality does not follow from this. Emissions from production and the supply chain remain relevant. Combustion can produce nitrogen oxides and nitrous oxide, a highly climate-active gas. Ammonia released unburned must also be limited.

Ammonia is harmful to health and, with corresponding exposure, life-threatening. It can severely damage the eyes and respiratory tract; liquid ammonia can additionally cause cold injuries. Certain materials, including copper and galvanised surfaces, are incompatible. The intense odour therefore does not replace a technical protection concept. Pressure vessels, pipelines and handling points must be designed appropriately for the substance; suitable monitoring, protective measures and emergency planning are required. Under certain conditions, flammable mixtures with air are also possible.

When is ammonia considered renewable?

For recognition as a renewable fuel of non-biological origin, RFNBO for short, special electricity sourcing rules apply in the EU. Delegated Regulation (EU) 2023/1184 distinguishes between different proof routes. For regular grid electricity sourcing, the additionality criterion, temporal correlation and geographical correlation are particularly important. An ordinary green electricity contract alone does not prove that these are met.

According to the regulatory status checked as of 11 November 2026, temporal correlation is in principle provided for on a monthly basis until the end of 2029 and on an hourly basis from 2030; exceptions and earlier national application options must be taken into account. For production plants commissioned before 1 January 2028, certain additionality requirements apply only from 2038; later capacity expansions are not included across the board. These rules are not a general definition of every ammonia marketed as "green". The purpose of recognition, production date, plant category and proof route must fit together.

Assessing benefits and limits correctly

With regard to security of supply, the question should not only be which export countries are possible. The assessment also includes port availability, storage autonomy, replacement deliveries and the failure of individual plants. A new import option is not yet proof of a resilient supply. Likewise, additional energy demand should be considered together with the existing demand for fertiliser and chemical feedstocks.

The decisive assessment question is therefore not whether ammonia is fundamentally "good" or "bad". What must be examined is whether its transport and storage function for a precisely specified task justifies the additional plant effort, energy demand and protection effort. The distinction remains particularly important: Is ammonia itself needed, or does it merely serve as an intermediate step on the way to hydrogen, heat or electricity?

Existing demand and new use

Ammonia is already an important industrial basic material. Its use for fertilisers exists regardless of whether ships will run on it or power plants will generate electricity from it in the future. Two tasks must therefore be distinguished: First, lower-emission production can meet the existing material demand in a more climate-compatible way. Second, new applications as an energy carrier may require additional ammonia. For assessing a project, what matters is the purpose its production serves. A plant that replaces ammonia previously produced from fossil sources fulfils a different task from a supply chain that additionally provides hydrogen for a power plant. Both applications require production plants and infrastructure; their benefits and alternatives must each be considered separately.

A cost comparison should also extend to the service actually required. Anyone who needs hydrogen must consider transport, storage, cracking and, where applicable, purification in addition to the ammonia price. Anyone who needs electricity must additionally include reconversion to electricity. Low costs at the production site therefore do not yet mean low costs at the point of consumption. Conversely, existing port and storage infrastructure can offer advantages. A comprehensible calculation therefore states the system boundary, the assumed utilisation and all conversion steps. This makes it possible to see whether two offers really compare the same usable amount of energy at the same handover point.

Sources

Innovation Outlook: Renewable Ammonia — International Renewable Energy Agency (IRENA) und Ammonia Energy Association (AEA); 2022-05. S. 12, 16–18, 33–34 und 69–70: Nutzung, Anlagenintegration, Herstellungsbezeichnungen und Umweltwirkungen
Ammonia Technology Roadmap — International Energy Agency (IEA); 2021-10-11. Berichtsübersicht und Executive Summary, insbesondere bestehende Verwendungen und emissionsarme Produktionswege
NIOSH Pocket Guide to Chemical Hazards: Ammonia — Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health (CDC/NIOSH); unbekannt. Formula; Physical Description; Boiling Point; Incompatibilities & Reactivities; Symptoms
Clean Ammonia Roadmap report — Institute for Sustainable Process Technology (ISPT); 2024-01-03. Abschnitte zu Transport und Wasserstoffrückgewinnung; Anhang 2, S. 62: Main properties and conversion factors
Delegierte Verordnung (EU) 2023/1184 — Europäische Kommission, veröffentlicht auf EUR-Lex; 2023-02-10. Artikel 1 und 4–7 sowie 11; EUR-Lex weist die konsolidierte Fassung vom 10. Juni 2024 als aktuell aus

Related glossary entries

Edited by eCMS on 11.11.2026 13:58