Green credentials of ammonia ship engines depend on fuel supply chain

Late last month, Japan Engine Corporation (J-Eng) revealed a full-scale ammonia ship engine, the 7UEC50LSJA-HPSCR. Incorporating a robust SCR system to deal with ammonia’s high nitrogen-oxide (Nox) emissions, the engine will enter service next year.

Small vessels, such as Fortescue’s Green Pioneer, are already on the water running on ammonia, and a handful of such engines are due to deliver before next year. But J-Eng’s seven-cylinder engine is certainly one of the largest so far, and will be installed on a medium gas-carrier  being constructed at the JMU Ariake shipyard.

It is not surprising that Japan is jostling to the front of the pack, given that its government is a stalwart supporter of ammonia, in principle. Japan hopes to use ammonia for ‘co-firing’ at its coal plants, theoretically offsetting a proportion of direct emissions. Ammonia has the opportunity to be a low-emission fuel, emitting only water vapour at the point of combustion, making it possible for individual ships to claim zero-emissions.

“J-Eng is extremely pleased and proud to be able to deliver to customers ahead of the rest of the world this safe and reliable engine, the result of a meticulously planned, long-term development programme that accumulated extensive operational data over an extended period,” said the company.

The validity of the zero-emission claims, though, will only be as good as the supply chain of the fuel. If the ammonia is generated and transported using only clean renewable energy, emissions will indeed be zero; if it is made using fossil fuels, the additional industrial processes involved in its production will be enough to increase well-to-wake emissions well above 100%.

Currently, Japan plans to buy its ammonia from Australia, where it is being made using gas. In October, two vessels, Navigator Global and Green Pioneer, conducted the first ship-to-ship transfer of ammonia off Port Dampier, Australia.

As Tokyo’s Renewable Energy Institute (REI) describes it, in reference to power generation: “The only stage where CO2 is not emitted directly from burning ammonia is the use of ammonia… all other processes generate CO2 due to methane leaks and energy consumption.”

This would be the case even if carbon capture is used, the REI confirmed: “Even if CO2 emissions from the production of fossil fuel-derived hydrogen and ammonia are 100% captured and stored, GHG emissions from methane leakage and energy use during the upstream processes are unavoidable.”

If shipping lines intend to beguile customers with zero-emission ammonia claims, they will be in for a tough sell. In the container segment, a niche of shippers intelligent enough to comprehend the combustion and by-products of ammonia, but not enough to wonder where and how it is produced, could be hard to find.