Wärtsilä’s ammonia-fueled four-stroke engine

First commercially available four-stroke engine-based solution for ammonia fuel announced

Technology group Wärtsilä announced what it said is the marine sector’s first commercially available four-stroke engine-based solution for ammonia fuel. The ammonia solution is part of the Wärtsilä 25 engine platform, which was launched in September 2022.

The Wärtsilä 25 Ammonia solution can reduce greenhouse gas emissions by more than 70% compared to diesel. (Photo: Wärtsilä)

“It’s a big milestone for us in Wärtsilä, but also for the whole industry,” said Juha Kytola, Director of R&D and Engineering at Wärtsilä, of the engine’s launch. “Ammonia [is known to be] an attractive fuel. It’s a hydrogen carrier so it contains a lot of hydrogen, and it does not contain carbon at all. So, this is a carbon-free fuel.”

Sustainable ammonia is one of the leading candidates in shipping’s search for alternative clean fuels. The Wärtsilä 25 Ammonia solution can immediately reduce greenhouse gas emissions by more than 70% compared to a similar-sized diesel solution, the company noted, meeting current EU targets until 2050 and even exceeding the IMO target for 2040.

Because ammonia is still a relatively new fuel to most shippers, especially on four-stroke engines, the full solution includes an AmmoniaPac, a fuel gas supply system for bunkering, storing and managing ammonia fuel onboard of a vessel; the Wärtsilä Ammonia Release Mitigation System (WARMS); and the Wärtsilä NOx Reducer (NOR) for optimal exhaust aftertreatment.

“All of these are integrated into the automation system, so it’s a full package for ships that need that equipment for treating, handling and using the energy of ammonia,” Kytola said.

Based on existing platform

The ammonia-fueled engine uses the same base engine as the Wärtsilä 25, with only a limited number of differing components. This means existing engines will be convertible to ammonia use with minor modifications.

The ammonia-fueled engine uses the same base engine as the Wärtsilä 25, with only a limited number of differing components. (Photo: Wärtsilä)

“The ammonia solution is based on Wärtsilä’s well-proven LNG system, from which we have gained invaluable experience. The Wärtsilä 25 engine has been designed for easy adoption of sustainable fuels, and now, in addition to its previous capability of operating on diesel, LNG or on gas or liquid carbon-neutral biofuels, we are proud to add ammonia to its specifications,” said Roger Holm, president of Wärtsilä’s Marine Power business. “This makes Wärtsilä 25 a thoroughly future-proof engine platform that combines operational efficiency with environmental sustainability.”

Stefan Nysjö, vice president of Power Supply, Wärtsilä Marine Power, said the current engine family is only the beginning: “The Wärtsilä 25 is the first Wärtsilä engine to run on ammonia as a fuel, and this is an important milestone, but we do not stop here. While we are planning for additional ammonia engines in our portfolio over time, we are also committed to continue development and testing of technologies and solutions that can continue to support the industry with reducing greenhouse gas emissions even further in the future.”

Carbon-free partnership

Viridis Bulk Carriers, a partnership between Amon Maritime, Mosvolds Rederi and Navigare Logistics and noted to be the “world’s first zero-emission shipping company,” is scheduled to be the first shipowner to benefit from the new ammonia solution. Earlier this month, Wärtsilä and Viridis Bulk Carriers signed a Letter of Intent for the Wärtsilä 25 ammonia engine solution, targeting to sign a commercial contract in early 2024.

Viridis Bulk Carriers is planning to deliver a carbon-free transportation service for the European short sea bulk market based on a series of ammonia-powered newbuild vessels.

“The maritime industry must significantly reduce its emissions if we are to succeed in reaching the goals set in the Paris agreement. The adoption of new technologies and ammonia as a carbon-free fuel is central to this,” said André Risholm, board member at Viridis Bulk Carriers. “We are delighted to partner with Wärtsilä on another important milestone for our ammonia-powered short sea bulk vessels.”

Håkan Agnevall, president and CEO of Wärtsilä added: “Wärtsilä is a leader in shaping the decarbonization of marine and energy industries. This industry-leading solution is yet another flagship moment in Wärtsilä’s extensive program to ensure future marine fuels are both viable and safe. Working in partnership with Viridis Bulk Carriers, we take the next step in our decarbonization journey, enabling the transition to greener fuels and accelerating towards net-zero emissions shipping.”


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