Posted on May 28, 2025
Technology group Wärtsilä’s 4-stroke engine-based solution for ammonia fuel now delivers higher than ever levels of efficiency and performance. Following its introduction to the commercial marine sector in November 2023, the ammonia solution has undergone extensive testing to optimise its performance parameters. The latest results, assessed against the FuelEU Maritime reference and measured on both a Well-to-Wake and Tank-to-Wake basis, show that a 95 percent ammonia energy share now achieves up to a 90 percent reduction in greenhouse gas emissions compared to equivalent diesel engines. This represents a further 18 percent improvement on the solution’s emissions performance.
The Wärtsilä 25 ammonia engine, which is available as part of the Wärtsilä 25 engine platform, was developed based on the company’s vast safety and operational experience gained from low pressure dual-fuel (DF) engines running on LNG. The recent tests have shown ammonia to be a suitable fuel for the low-pressure Otto cycle concept which is the design that Wärtsilä has utilised for its ammonia engine solution. The decision to opt for a low-pressure Otto cycle concept was based on several factors, including safety, efficiency and overall potential for greenhouse gas reduction, among several other parameters. Comprehensive tests conducted on different engine sizes have shown that the efficiency of the low-pressure Otto cycle concept is consistent with, and equal to, that of dual-fuel LNG engines. Ammonia is also highly knock resistant, with robust combustion capabilities across a wide range of engine settings.
“With decarbonisation front and centre of our company strategy, we have continued to enhance the capabilities of our ammonia engine solution – adding even more safety features and further improving its performance. This is in line with our commitment to “continuous improvement”, whereby we continue to develop, test and enhance new and current technologies and solutions which will support the industry with making meaningful reductions in greenhouse gas emissions. For our ammonia engine we opted for the low-pressure Otto cycle concept as we are confident this will deliver the best levels of safety, efficiency and reliability for our customers,” comments Stefan Nysjö, Vice President of Power Supply, Wärtsilä Marine.
The enhancements made to the Wärtsilä 25 ammonia engine’s performance benefit the entire ammonia solution, which comprises of an AmmoniaPac fuel gas supply system, the Wärtsilä Ammonia Release Mitigation System (WARMS), and the Wärtsilä NOx Reducer (NOR) for optimal exhaust after-treatment. Safety, efficiency and reliability are central to the solution design, maximised by a highly sophisticated automation system and maintenance agreement to ensure safe and efficient onboard operations. Alongside future engine orders, the enhanced performance will also be integrated into engines already contracted as first deliveries are due to take place from 2026 onwards.
Ammonia has emerged as a promising alternative fuel as the shipping industry looks for more sustainable fuel options. With global regulations having set a clear destination for shipping – net zero emissions by mid-century – ammonia will play a significant role in enabling the shipping industry to reduce its emissions. A report from Wärtsilä highlights the role that sustainable fuels will play in achieving this target which is set by the International Maritime Organization (IMO). According to the report, existing decarbonisation solutions, such as fuel efficiency measures, can cut shipping emissions by up to 27 percent; however, sustainable fuels, such as ammonia, will be a critical step in eliminating the remaining 73 percent.
Image caption: Wärtsilä’s 4-stroke engine-based solution for ammonia fuel now delivers higher than ever levels of efficiency and performance © Wärtsilä Corporation
Wärtsilä Marine in brief
Wärtsilä Marine is a global pioneer in power, propulsion and lifecycle solutions for the marine market. We develop industry-leading technologies, advancing maritime’s transition to new fuels. We support building an end-to-end digital ecosystem where all vessels and ports are connected. Ultimately, Wärtsilä Marine is driving the shipping industry forward on its journey towards a decarbonised and sustainable future through our broad portfolio of engines, propulsion systems, hybrid technology, exhaust treatment, shaft line solutions and digital technologies, as well as integrated powertrain systems. Our offering, which is underpinned by our performance-based agreements, upgrades, lifecycle solutions, decarbonisation services, as well as an unrivalled global network of maritime expertise, delivers the efficiency, reliability, safety, and environmental performance needed to support a safe and sustainable future for our customers, our communities and our planet.
www.wartsila.com/marine
Wärtsilä in brief
Wärtsilä is a global leader in innovative technologies and lifecycle solutions for the marine and energy markets. We emphasise innovation in sustainable technology and services to help our customers continuously improve their environmental and economic performance. Our dedicated and passionate team of 18,300 professionals in more than 230 locations in 77 countries is shaping the decarbonisation of our industries across the globe. In 2024, Wärtsilä’s net sales totalled EUR 6.4 billion. Wärtsilä is listed on Nasdaq Helsinki.
www.wartsila.com
