Decarbonising long-haul shipping

The University of Nottingham is leading a £5.5m project to investigate the potential of green ammonia to fuel and decarbonise the long-haul shipping industry, and to boost the UK’s powertrain sector.

With 80 per cent of goods being transported by sea, shipping produces more carbon emissions than most countries, and pollutes oceans. In fact, nine per cent of transport CO₂ comes from shipping and of that, around 80 per cent of shipping’s greenhouse gases specifically come from merchant vessels, including tankers, cargo ships and passenger liners.

The UK Government’s Department for Transport has established a new £200m body, UK Shore, to decarbonise the marine sector. Secretary of State for the Department for Energy Security and Net Zero, Grant Shapps has said; “Climate change is a global challenge and it’s essential that, with our maritime sector’s rich history of green travel, dating back thousands of years, we tackle shipping emissions”.

A green alternative for future fleets and retrofit

Professor Alasdair Cairns, principal investigator on the project and director of Nottingham University's Powertrain Research Centre, said: “There’s currently significant interest in green ammonia as a fuel for decarbonised commercial shipping. Green ammonia is a gas easily converted into a liquid in a process that is 100 per cent renewable and carbon-free, such as using hydrogen from water electrolysis and nitrogen separated from the air.

“One of the challenges with international shipping is the sheer size and range of the vessels producing the majority of the greenhouse gas emissions and issues with energy density for competing solutions such as electric and fuel cell.

“The problem is, when you look at competing energy vectors like batteries or fuel cells, they just don’t have the energy density. Ammonia could have diesel-like efficiency and energy density, and is cheap and easy to store as a liquid fuel. Electric or fuel cell propulsion would work for smaller boats, but it’s not really an option in mega tonne ships that are sailing across oceans in a single voyage. Our work will provide a road map of vessel size, types and propulsion types.”

In addition to identifying alternatives to fossil fuel power in future fleets, retrofitting existing vessels is a major obstacle to tackle for the project. Big ships have engines that are in service for up to 30 years; many of which will still be out on the seas for decades to come.

Working with industry

The five-year MariNH3 programme, which includes partners such as Cummins, Rolls-Royce, MAHLE Powertrain and the Department of Transport Maritime and Coastguard Agency, hopes to solve this problem by exploring retrofit engine technology solutions that can address issues around engine efficiency, with minimised end energy use and reduced pollution.

A key concern is the current approach being adopted by some marine engine manufacturers, which involves ammonia dual fuelling, which means replacing some of the marine diesel with ammonia as a ‘clean fuel supply’ as a retrofit solution. Typically, up to 40 per cent natural gas (diesel) is still used in these engines, which doesn’t help with local pollution and limits decarbonisation efforts.

As a group, the MariNH3 consortium firmly believe a mix of technologies will be required for the most effective decarbonisation of marine as there is no “silver bullet” fuel or technology to get to Net Zero. However, green ammonia is set to play a key role in marine’s decarbonisation efforts.

In liquid form, ammonia not only has significant cost advantages in terms of fuel storage, it can also be used in existing marine engines, however it burns roughly five times slower under like-for-like conditions than fossil fuels and it produces NOx emissions – both major issues that need to be addressed by the MariNH3 team.