Ammonia key to reducing shipping’s carbon emissions

Green ammonia could be the zero-carbon replacement for fossil fuels for international shipping, according to a Royal Society report published today. This could have a significant impact on reaching net-zero as the shipping industry currently accounts for 2.2% of global anthropogenic carbon dioxide emissions. The United Nations International Maritime Organisation has outlined an ambition for full decarbonisation by 2050.

Ammonia: zero-carbon fertiliser, fuel and energy store makes the case that green ammonia can contribute significantly towards attaining future net-zero greenhouse gas emissions across a range of energy sectors.

Professor Bill David, the lead author of the report, said “Green ammonia is not only set to have a major impact on reducing the greenhouse gas emissions associated with agriculture and industry but is also increasingly viewed as a strong zero-carbon option for both transportation and large-scale, long-term energy storage”.

The report concludes that the greening of ammonia, which is the global feedstock for inorganic fertilisers, will contribute substantially to the decarbonisation of the agriculture sector by removing the carbon dioxide emissions associated with existing ammonia production. In 2020, global ammonia manufacture will produce around half a billion tonnes of carbon dioxide which, in terms of industrial processes, is third largest after cement and steel manufacture.

Ammonia has been used as a fertiliser feedstock for over a century to improve crop yields. It is credited with providing sufficient food for half the world’s population and there is a mature regulated global infrastructure for its production, transportation, storage and use.

In terms of the potential for ammonia to replace fossil fuels, the report highlights the existing international ammonia infrastructure where the global trading of around 25 million tonnes of ammonia per year is based around deep-sea shipping routes and established large-scale port facilities across the world. This familiarity with ammonia has led the international maritime industry to rank it as one of its leading choices for the decarbonisation of shipping. Importantly, it has been shown that this can be achieved today with low disruption by retrofitting existing marine engines. Ammonia is one of the very few net-zero carbon options that can address the challenges of scale associated with long-distance, deep-sea international shipping.

Green ammonia is, de facto, a zero-carbon fuel where the resources required for its synthesis are renewable energy, air and water. Its proposed use for decarbonising deep-sea shipping invites further consideration for large-scale stationary applications, buses, lorries, trains and aviation. There are a number of routes from ammonia to power such as fuel cells, turbines and internal combustion engines—technologies where the UK has significant expertise.

Ammonia: zero-carbon fertiliser, fuel and energy store recognises the regulatory and public acceptance issues associated with the extended use of ammonia to transportation; it also discusses the environmental damage resulting from the current uses of ammonia and the necessity for the proactive reduction of ammonia and NOx emissions. These challenges can be addressed and the UK is a leader in many of the technologies to make this a reality.

Professor David added “Despite its mature global infrastructure, high energy density and ubiquitous raw resources, ammonia has been largely overlooked in terms of its potential to address transportation and large-scale, long-term interseasonal energy storage. Ammonia is essentially the quintessential non-carbon hydrocarbon. It is a natural successor to natural gas and is highly complementary to the short-term energy storage provided by batteries. Over the coming decades, with appropriate development and deployment, green ammonia can make a significant impact in enabling us to transition away from our dependence on fossil fuels.” 

Read more about the Royal Society's low carbon energy programme.