Executive summary
Future zero-carbon energy scenarios are predicated on wind and solar energy taking prominent roles. Matching demand-driven energy provision with low-carbon energy security, from these intermittent sources, requires long-term sustainable energy storage.
This briefing considers the opportunities and challenges associated with the manufacture and future use of zero-carbon ammonia, which is referred to in this report as green ammonia.
The production of green ammonia has the capability to impact the transition towards zero-carbon through the decarbonisation of its current major use in fertiliser production. Perhaps as significantly, it has the following potential uses:
- As a medium to store and transport chemical energy, with the energy being released either by directly reacting with air or by the full or partial decomposition of ammonia to release hydrogen.
- As a transport fuel, by direct combustion in an engine or through chemical reaction with oxygen in the air in a fuel cell to produce electricity to power a motor.
- To store thermal energy through the absorption of water and through phase changes between material states (for example liquid to gas).
With its relatively high energy density of around 3 kWh/litre and existing global transportation and storage infrastructure, ammonia could form the basis of a new, integrated worldwide renewable energy storage and distribution solution. These features suggest ammonia could readily be a competitive option for transporting zero-carbon energy by road, rail, ship or pipeline.
Ammonia has been used as a fertiliser for over a century and has been of fundamental importance in providing sufficient food to feed our planet. Current ammonia manufacture is predominantly achieved through steam reforming of methane to produce hydrogen which is fed into ammonia synthesis via the Haber Bosch process. Ammonia production currently accounts for around 1.8% of global carbon dioxide emissions.
Decarbonisation options mainly target the production of hydrogen either by integrating carbon capture and storage or through the production of hydrogen via water electrolysis using sustainable electricity.
Ammonia use does present challenges. Human alteration of the global nitrogen cycle, mainly through the application of ammonia-based fertilisers, is a contributor to global declines in biodiversity, widespread air quality problems and greenhouse gas emissions across the world. New uses of ammonia, in the storage, transportation and utilisation of renewable energy, must therefore be decoupled from environmental impact, with particular emphasis on avoiding and effectively eliminating emissions of nitrogen oxides and ammonia release.
Finding affordable and effective solutions to all these challenges, demonstrating technical feasibility, developing the appropriate regulations and implementing safety procedures will be vital to open up more flexible routes on a global scale towards a low-carbon energy future.
Over the coming decades, ammonia has the potential to make a significant impact through enabling the transition away from our global dependence on fossil fuels and contributing, in substantial part, to the reduction of greenhouse gas emissions.