New version of the Wärtsilä 31DF engine reduces methane emissions by an additional 41% on average, when compared to previous market best

Wärtsilä Corporation, Trade press release 1 November 2023 at 11:00 UTC+2
  • Wärtsilä 31DF engine has helped Wasaline further reduce methane emissions by 10 percent onboard the Aurora Botnia ferry  © Wasaline
  • Wärtsilä’s new ultra-low emissions version of the Wärtsilä 31DF engine © Wärtsilä

Technology group Wärtsilä has introduced a new ultra-low emissions version of its already efficient Wärtsilä 31DF engine. Whilst operating on LNG, this new version can further reduce methane emissions on a 50 percent load point by up to 56 percent and nitrogen oxide (NOx) by up to 86 percent. On a weighted average, this new technology can reduce methane emissions by 41 percent more than the standard Wärtsilä 31DF engine, which has already the lowest emission levels on the market.

The new version, which is applied on one of the four engines on board Wasaline’s Aurora Botnia ferry, has already helped the Finnish-Swedish ferry operator further reduce the Aurora Botnia’s methane emissions by 10 percent. As part of the EU co-funded Green Ray and SeaTech projects*, Wärtsilä piloted the ultra-low emissions concept onboard the Aurora Botnia with exceptional results verified through an independent study conducted in December 2022 by VTT, the Technical Research Centre of Finland. Encouraged by the positive results, Wärtsilä has now launched the new ultra-low emissions version of the Wärtsilä 31DF engine to the commercial market.

This latest collaboration forms part of a long-term partnership between Wärtsilä and Wasaline to reduce emissions onboard the Aurora Botnia, the world’s most environmentally friendly RoPax ferry today.

“We are very committed to decarbonisation, and we have worked closely with Wärtsilä to make sustainable shipping a reality. It is a goal-oriented partnership that benefits both companies, as well as the industry as a whole. We have been pleased to allow the ‘Aurora Botnia’ to be utilised as a floating laboratory, and we are excited to see the success of this latest Wärtsilä technology breakthrough,” commented Peter Ståhlberg, Managing Director of Wasaline.

Launched in 2015, the Wärtsilä 31DF engine platform is widely recognised for its exceptional fuel economy, high performance, and minimal GHG impact. The engine, as a standard version, already meets today’s regulatory requirements. The new version will enable operators to go even further in reducing methane emissions, helping to futureproof their vessels in the longer term against potentially tightening global requirements. What’s more, improving dual fuel technology to enable methane emissions reduction will have a major impact on the long-term viability of LNG as a marine fuel.

“Our work around reducing methane slip and GHG emissions is part of Wärtsilä’s effort to continuously improve efficiency and reduce emissions of our products, and this new innovation is one more very important step along the road to decarbonisation,” commented Stefan Nysjö, Vice President of Power Supply, Wärtsilä Marine Power.

Nysjö continued: “The building of an LNG fuel infrastructure has been an important factor in shipping’s transition towards cleaner operations, and Wärtsilä continues to create solutions that support this journey. Our focus has always been to improve and optimise existing solutions, and to develop exciting new ones. With this latest introduction, we are clearly delivering on this commitment.”

Although methane slip from engines is a relatively small amount, from a percentage standpoint, it is significantly more potent than CO2 – up to 28 times greater. Across the shipping industry, cutting methane emissions is one of the most effective ways to decrease overall GHG emissions from engines over the next 10 years, complementing other efforts to reduce CO2 emissions.

Media contact for more information on this release:

Isabella Alder
Positioning and Strategic Communications Manager 
Wärtsilä Marine Power
Tel: +44 (0) 7792 681 757


Image caption: Wärtsilä’s new ultra-low emissions version of the Wärtsilä 31DF engine (captured - © Wärtsilä Corporation) has helped Wasaline further reduce methane emissions by 10 percent onboard the Aurora Botnia ferry (captured - © Wasaline). Encouraged by the positive results, Wärtsilä has now launched this new version to the commercial market.

All Wärtsilä releases are available at and at where also the images can be downloaded.

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 17,500 professionals in more than 240 locations in 79 countries shape the decarbonisation transformation of our industries across the globe. In 2022, Wärtsilä’s net sales totalled EUR 5.8 billion. Wärtsilä is listed on Nasdaq Helsinki.

Wärtsilä Marine Power in brief: 
Wärtsilä Marine Power is a global leader in power, propulsion and lifecycle solutions for the marine market. From our end-to-end digital ecosystem planning to our future fuels development, Marine Power is driving the shipping industry forward on its journey towards a decarbonised and sustainable future. Our broad portfolio of engines, digital technologies, propulsion systems, hybrid technology, and integrated powertrain systems delivers the efficiency, reliability, safety, and environmental performance needed to support our customers. Our offering includes real-time insights into operations, performance, and energy use, performance-based agreements, lifecycle solutions, and an unrivalled global network of maritime expertise.

Wasaline in brief:
Wasaline is the northernmost shipping line in the world, which transports passengers and freight daily between Vaasa in Finland and Umeå in Sweden. In addition to being the most environmentally friendly sea route between Finland and Sweden, the route is also important for security of supply. The company's hybrid ferry, Aurora Botnia, is equipped with dual-fuel engines and batteries. Aurora Botnia is the most environmentally friendly passenger ferry in the world and Wasaline invests in sustainability in all its processes. The Key Flag has been awarded both to Aurora Botnia and Wasaline’s services as a recognition of Finnish work. For more information, please visit

*Acknowledgement of external funding:

This project is co-funded by the European Union.