Wärtsilä broadens methane slip reduction technology to its 25DF engine
This latest innovation minimises methane slip to less than two percent across all load points, with emissions as low as 1.1 percent within a broad operating range. In addition, NextDF technology achieves lower nitrogen oxide (NOx) emissions than the standard Wärtsilä 25DF engine, which already complies with IMO Tier III emission standards.
As LNG remains a key transition fuel within the maritime sector, Wärtsilä’s efforts aim to address a common issue: methane slip, or unburned methane escaping into the atmosphere during combustion. By targeting methane emissions directly, Wärtsilä’s NextDF feature strengthens LNG’s position as a lower-emission fuel, addressing global and regional regulatory frameworks.
Internationally, the IMO is expected to factor methane emissions into upcoming greenhouse gas (GHG) regulations, while the EU is preparing to enforce methane-focused requirements under its FuelEU Maritime initiative in 2025 and the EU Emission Trading System (ETS) in 2026. The EU mandates a default methane emission limit of 3.1 percent of fuel use for non-certified four-stroke engines, but Wärtsilä’s NextDF technology positions operators to achieve emissions well below this threshold. For vessels exceeding these compliance levels, FuelEU Maritime will introduce banking and pooling mechanisms, allowing operators to monetise surplus compliance or cover shortfalls.
“Advancing dual-fuel technology to minimise methane slip will strengthen LNG’s viability as a marine fuel,” said Stefan Nysjö, vice president of power supply at Wärtsilä Marine. “Our focus on reducing methane slip and GHG emissions reflects Wärtsilä’s commitment to continuous product improvements, helping operators future-proof their fleets while achieving regulatory and financial advantages.”
Wärtsilä’s 25 engine platform, launched in 2022, is known for its modularity, flexibility, and adaptability for sustainable fuels. The addition of NextDF technology enhances the platform’s efficiency by up to 0.5 percentage points, further reducing fuel consumption and emissions. The Wärtsilä 25DF engine, now equipped with NextDF technology, delivers methane slip levels as low as 1.4 percent at specific loads and pushes these limits even lower, providing significant overcompliance benefits for operators navigating new EU regulations.
NextDF technology was initially launched for the Wärtsilä 31DF engine in 2023, and its modular design allows for retrofitting on existing Wärtsilä 31DF and 25DF engines. The NextDF feature for the Wärtsilä 25DF engine will be available for delivery beginning in the second half of 2025, offering ship operators an immediate path toward decarbonisation and operational savings in a rapidly evolving regulatory environment.
