Technology group Wärtsilä has introduced its innovative NextDF feature for the Wärtsilä 25DF dual-fuel engine. While operating on liquefied natural gas (LNG), the NextDF feature reduces methane emissions to less than 2% of fuel use across all load points, achieving as low as 1.1% in a wide load range. The nitrogen oxide (NO_x) emissions are lower than on the standard Wärtsilä 25DF engine which already has low emission levels below IMO Tier III.

The main component of LNG is methane and when burned as a fuel, a very small amount may not combust properly, leading to methane escaping into the atmosphere.

Across the shipping industry, the use of LNG and cutting methane emissions is one of the most effective ways to decrease overall greenhouse gas (GHG) emissions from engines over the next 10 years, complementing other efforts to reduce CO₂ emissions. From an international shipping perspective, the International Maritime Organisation (IMO) is considering methane emissions in the upcoming GHG regulations. At a regional level, the EU is implementing a set of methane-related measures in FuelEU Maritime (2025 onwards) and in EU Emission Trading System (EU ETS) (2026 onwards).

The effect of methane emissions will be introduced as a percentage of the mass of the fuel used by the engine. For EU regulation, four-stroke engines not certified with lower emission values will have to adhere to a default methane emission of 3.1% of fuel use. To provide flexibility in meeting the GHG intensity limits, the FuelEU Maritime regulation will not only impose costs if a vessel does not comply, it will also allow vessels to capture value from overcompliance through banking or pooling compliance surplus between reporting periods.

Launched in 2022, the Wärtsilä 25 engine platform offers a modular, upgradeable, and flexible design that helps operators to significantly reduce fuel consumption and emissions, improving the efficiency of vessels, and facilitating the adoption of sustainable fuels. With the NextDF technology, engine efficiency is further improved by up to 0.5 percentage points.

This is the second Wärtsilä dual-fuel engine to be made available with NextDF technology. In 2023, Wärtsilä introduced the new technology for its Wärtsilä 31DF engine. Due to the modular design of Wärtsilä’s engine platform, the NextDF feature can be retrofitted to existing Wärtsilä 31DF and Wärtsilä 25DF engines. The NextDF feature for the Wärtsilä 25DF engine will be available for delivery in the second half of 2025.