What is Green Ammonia?

Hydrogen and Ammonia – Reinventing energy, transport and geopolitics

A sustainable planet needs global greenhouse gas emissions to start reducing immediately and reach zero by 2050.1  If, as seems likely, the reductions are neither fast enough nor soon enough, we will have to remove massive amounts of excess CO2 from the atmosphere.  This could be by a combination of nature-based solutions and capture by machine, but the sheer scale of the challenge leaves little room for carbon-based biofuels and synthetic fuels.  Every tonne of such fuel adds three tonnes of CO2 to the challenge.  A sustainable future needs carbon-free fuels.

Hydrogen Turbine
Hydrogen Turbine developed by GE

Electrification based on renewables is key to a true net-zero carbon economy, with batteries as the supporting act. However batteries cannot do everything; they won’t let us fly long distances, they won’t power ships or trains, they will struggle with heavy earth moving equipment, and they will never power an entire economy such as India or the UK for days when the sun doesn’t shine and the wind doesn’t blow. For these tasks we need new fuels that do not contain carbon, are easy and safe to store and use, and are cheap to produce.

Ammonia is hydrogen’s sister fuel; a nitrogen atom with three hydrogen atoms attached. It liquefies easily, is cheap to transport and can be used as a fuel almost as easily as hydrogen.  It is even straightforward to break down ammonia into hydrogen and nitrogen at the point of use.  Ammonia is in effect a neat way to store and transport hydrogen.2

Ammonia powered bus in Brussles
Ammonia powered bus in Brussels in 1943 when there was no diesel

To make green ammonia you have to make hydrogen first, by electrolysing water.  Conversion to ammonia needs only one more step, the long-established Haber Bosch process.  Using ammonia is also very similar to using hydrogen; both can be burned in engines or used in fuel cells to make electricity.  Some engines and fuel cells will even be able to use both fuels.  Thus ammonia and hydrogen aren’t different solutions to a zero carbon economy, but complementary components with different roles.   Ammonia will thrive where hydrogen struggles to compete; planes and ships can be powered by ammonia fuel cells and electric motors, power grids can rely on globally traded ammonia to back up renewable energy.3

The first ammonia powered ship using a fuel cell and electric motors to replace engines will be converted from this in 2023
The first ammonia powered ship using a fuel cell and electric motors to replace engines will be converted from this in 2023

Adding the Haber Bosch process makes ammonia a little more expensive than hydrogen, but because it is easy to store and transport, it can be made where the major cost, electricity, is cheapest.  The extra cost will be compensated by the lower cost of transport and of storage. Nonetheless significant advances are being made in reducing the costs of ammonia synthesis.4    

Key to a viable hydrogen/ammonia economy is the dramatically falling cost of renewable energy, especially solar.  Solar is already hitting record lows, and new technologies such as perovskite tandem cells will reduce it substantially even further.5,6  Because fuel cells are more efficient than engines burning fossil fuels, the cost of the actual usable energy delivered is likely to outcompete fossil fuels within a few years.  

A hydrogen/ammonia economy will be game changing.  Hydrogen and ammonia will take over many of the key roles of gas and oil respectively, but they will do more; they can turn iron ore into steel, replacing coal and charcoal, and make green fertilisers – key to agriculture and feeding the world.

There is enough energy in a kg of ammonia to make it a viable aircraft fuel.  Fuel cells can convert it to electricity to power electric propellers, a very efficient form of propulsion.  This could make air travel the most sustainable, fastest, and safest form of transport.
There is enough energy in a kg of ammonia to make it a viable aircraft fuel.  Fuel cells can convert it to electricity to power electric propellers, a very efficient form of propulsion.  This could make air travel the most sustainable, fastest, and safest form of transport.

A well-developed hydrogen/ammonia economy is crucial to decarbonising our economies totally yet affordably.

Hydrogen and ammonia could provide energy cheaper than fossil fuels in only a few years.

Broad Linkages

The diagram below shows many of the key linkages in the Hydrogen/ammonia economy.  Whereas development in each of the blocks shown will contribute to the progress of decarbonisation, the dark red blocks highlight key areas where R&D will enable ammonia and hydrogen to outcompete the fossil alternatives.  The diagram shows how a limited number of developments in these key areas can transform swathes of the economy.

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A Plan of Action

More detailed analysis of these high priority R&D areas has shown that many of the advances needed are already in laboratories, or, as in the case of aviation for example, are a matter of engineering research and development rather than new science.  A first objective must be to focus attention, and thus funding, on these key R&D targets.

In addition to research, to get costs competitive with fossil fuels, industry will have to build plants to help it learn and move down the cost curve, financiers will have to become comfortable with the risks, and users will have to be able to rely on supply.  Bringing these different elements together in parallel, fast enough to save the climate, is a major challenge.  A second objective will therefore be to help accelerate this development and deployment.

The transition to a hydrogen/ammonia economy will be made easier because we already have global industries making ammonia and hydrogen.7 Although both of these currently rely on coal and gas for their operations, they bring 100 years of experience in handling and transporting the products safely.  Nonetheless using hydrogen and ammonia as fuels at large scale may raise public concerns over safety.   A third objective will therefore be to build a clear safety case, and to stimulate development of the procedures and regulations needed to deliver that safety and maintain public confidence and acceptance.

Key References

  1. Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.). IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. (2018).
  2. The Royal Society. Ammonia: zero-carbon fertiliser, fuel and energy store. (2020).
  3. MAN Energy Solutions: an ammonia engine for the maritime sector. Ammonia Energy Associationhttps://www.ammoniaenergy.org/articles/man-energy-solutions-an-ammonia-engine-for-the-maritime-sector/.
  4. MacFarlane, D. R. et al. A Roadmap to the Ammonia Economy. Joule S2542435120301732 (2020) doi:10.1016/j.joule.2020.04.004.
  5. New tandem perovskite-silicon solar cell breaks efficiency record. New Atlashttps://newatlas.com/energy/tandem-perovskite-silicon-solar-cell-efficiency-record/ (2020).
  6. Cholteeva, Yoana. Record Breaking Solar perovskites. Power Technology https://www.power-technology.com/features/record-breaking-solar-perovskites/ (2020).
  7. Industry report sees multi-billion ton market for green ammonia. Ammonia Energy Associationhttps://www.ammoniaenergy.org/articles/industry-report-sees-multi-billion-ton-market-for-green-ammonia/.

Read more about Ammonia Production

Illustration of the process steps of making green ammonia