How the tech to decarbonize shipping already exists, part 2: Ammonia


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As shipping races to find eco-friendly alternatives to fossil fuels, green ammonia is gaining international attention and discourse in the media for its potential as a ‘fuel of the future’ due to its zero-carbon credentials. The International Energy Agency (IEA), for example, has advocated for greater attention on ammonia as one of the main low-carbon options in the growing basket of future fuels.

Ammonia as a marine fuel has substantial potential to support shipping’s decarbonization. At the same time, it also presents significant, yet manageable technical and safety hurdles. On many of these counts, the technology already exists to address the risks – such as those associated with potential leaks and emissions, for example. Technology is not the barrier to full-scale adoption of ammonia; cost and investment are what is restricting its commercialisation, as green ammonia is not yet produced at the required quantities. Ammonia's viability as a marine fuel will be supported by reducing the cost of renewable energy and increasing the production of green hydrogen to produce green ammonia.

Many major investors are betting big on ammonia. In December 2021, Amazon announced it was investing in Amogy[1], a US-based start-up that is developing ammonia-driven power systems for ships. The technology converts liquid ammonia into hydrogen gas, which then runs through a fuel cell. Two months before the Amazon story broke, Swiss commodity trading company Trafigura[2] revealed plans to finance large-scale, low-carbon ammonia production plants for powering vessels. Meanwhile, shipping giant A.P. Moller-Maersk[3] is looking to help build Europe’s largest green ammonia production facility.

As outlined in recent reports from Bureau Veritas and industry consortium Together in Safety,[4] solutions exist that safeguard end-users while supporting the industry’s zero-emissions goal. The challenge for maritime decarbonization can be addressed by existing technologies, new fuels, infrastructure and ship designs, enabling carbon-neutral or zero-carbon solutions, on the condition that regulations are in place to support them.

There’s no easy answer to finding the most effective energy source to steer maritime towards a zero-carbon future. But we can look at the viable onboard ship design options and the technologies already available for reducing emissions via the commercialisation of ammonia, and what this means from a systems integration perspective.

Green ammonia

If ammonia is to be truly zero-carbon, it must be ‘green ammonia’ – produced via electrolysis powered by clean, renewable energy to produce hydrogen, which is then reacted together with nitrogen at high temperatures and pressures. This approach, known as the Haber-Bosch process, is efficient and fully scaled. Ammonia is not easily combustible, so the first generations of technological solutions to use it as a fuel will likely rely on pilot fuels for ignition, however, these pilot fuels can also be zero-carbon.

Ammonia presents enormous potential, but also a unique set of challenges that need addressing. One such pain point is its toxicity, part of the reason that Together for Safety flagged it as particularly risky. Exposure to ammonia beyond certain levels and durations can have serious health consequences. It is essential to protect crews and passengers from any exposure during all operations, including maintenance and bunkering.

For example, Bureau Veritas and TotalEnergies compared the concentrations of ammonia in the air with those of LNG. They found that LNG becomes dangerous at around 50,000 parts per million (ppm), while ammonia starts to have health effects above just 30 ppm when permanently exposed or around 300 ppm when exposed for one hour. However, as previously stated, the required technologies to avoid even the smallest leaks already exist and can be implemented on board today, such as stringent leak management and vapour gas processing.

The main attraction of ammonia is that it contains no carbon, enabling the production of energy onboard a ship without emitting CO2. However, burning ammonia presents another risk; the release of substantial quantities of nitrogen oxides (NOx) emissions. NOx is a group of poisonous pollutants resulting from the combustion of ammonia. Therefore, if ammonia is to be used as a marine fuel in a combustion engine, exhaust gas treatments such as scrubbers will be required to mitigate harmful emissions. This poses no challenge, however, as the technology already exists, and can be easily installed.

What does this mean for marine systems?

As with any new fuel, it will be important for systems integrators and energy systems experts to be involved from the outset in the design of ammonia-fuelled vessels and carriers. Successfully innovating this new segment requires a new level of systems expertise that is often overlooked in the design process. Automation and fuel-handling systems must be integrated and must be prioritised accordingly.

Using ammonia as a power source comes with a unique set of design and engineering challenges, requiring strict temperature and pressure-control mechanisms to manage fuel specific characteristics, such as boil-off gas development. Another challenge is the corrosivity of ammonia, demanding choosing specific materials in the fuel supply system components. Therefore, it is essential that vessels are equipped with safe, reliable, effective Fuel Gas Supply Systems and enhanced controls.

To keep options open, retrofits of dual-fuel systems to ammonia can partially de-risk the choices of today and future-proof the investment decisions made amid uncertainty over alternative fuels. For newbuilding buyers, installing an ammonia fuel system or paying extra for an LNG fuel system with features like stronger fuel tanks (to manage ammonia with a comparably higher density) will lower the cost of converting a ship to ammonia or another future fuel in the coming years. Building an ammonia or multifuel suitable system today will be cheaper than replacing equipment to retrofit later.

Ultimately, truly green ammonia will require a major upscaling of renewable production to become a widespread option for zero-carbon shipping. But the technology is here already to ensure that ships can use it safely and efficiently as it becomes more widely available.