Ammonia II - Green ammonia

Posted in: bioenergy

This article explores the differences between conventional and green ammonia and discusses the applications and benefits of ammonia as fertiliser and shipping fuel.

For all living organisms, nitrogen (N) is one of the building blocks of the amino acids which make up proteins and enable metabolic function. More specifically, in plants, N is involved in the production of chlorophyll – the green pigment that makes photosynthesis possible and enables the conversion of solar energy into the chemical energy that is essential to the survival of plants.

Plants can acquire N through the uptake of ammonium (NH4+) or nitrate (NO3-) in soils and water, with species preferring one form to the other depending on their N uptake mechanisms and adaptations. These two main compounds are made available in soils thanks to the process of nitrogen fixation. Nitrogen fixation, defined as the combination of atmospheric nitrogen (N2) with other elements to form more reactive compounds that plants can uptake from their root systems, may occur in two different ways: when lightning strikes, providing sufficient energy for a reaction between nitrogen and oxygen to produce nitrogen oxide and nitrogen dioxide; and when diazotrophic soil bacteria fix nitrogen into ammonia, nitrites, and nitrates, while often forming a symbiotic relationship with the plant. The latter provides most of the “fixed nitrogen” in soils. The fixed N then provides the basis of the entire N cycle which benefits all living organisms on the planet.

As a result of the increasing need for food production, contemporary agricultural practices favour the use of products which increase soil nutrient content, so that crops can access sufficient nutrients and grow fast, big and nutritious. N-fertilisers are designed to increase the content of immobilised N in the soil in the form of ammonium or nitrate (and sometimes nitrites). Fertilisers, including nitrogen fertilisers, have become ubiquitous. According to the IPCC, their use has risen by 800% since the 1960s. Further increase is expected in the next years, and decades, with the global N-fertiliser market projected to amount to around $125 billion by the end of 2022.

In this article we look at the production pathways for the manufacture of ammonia destined for N-fertilisers. We compare conventional fossil-derived ammonia and sustainably produced “green ammonia”, and their respective markets. We also look at the use of “green ammonia” as a potential biofuel for maritime shipping.

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This article was written by Thea Allary and Krishan Mistry, Senior Research Analyst and Research Analyst at NNFCC.

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