World’s greenest passenger ferry now runs on wind-powered electricity and biogas

The Aurora Botnia, a passenger and cargo ferry operating between Vaasa, Finland, and Umeå, Sweden, has achieved carbon neutrality five years ahead of schedule by switching to wind-generated electricity and biogas, reports Finnish broadcaster Yle.

The vessel’s batteries were fully charged with wind power before departure, while its two large fuel tanks contain only biogas for its four engines. According to operator Wasaline, the ferry—dubbed the world’s greenest passenger ship—reached its carbon-neutral target in August 2025, well before its original 2030 deadline.

Since entering service in 2021, the 150-meter Aurora Botnia has undergone upgrades to reduce emissions nearly to zero. Last August, Wasaline, along with energy company Gasum and new owner Stena Line, agreed to use exclusively biofuels on the vessel. Additional batteries installed this year expanded its storage capacity to 12.6 megawatt-hours—the largest of any passenger-cargo ferry globally.

The ferry’s four Wärtsilä 31DF engines can run on liquefied natural gas (LNG), biodiesel, or biogas, with flexibility to optimize efficiency. Onboard monitors display real-time fuel consumption and battery levels, while its smokeless funnels—emitting only steam—highlight its emissions-free operation.

Each crossing between Finland and Sweden (roughly 100 km) is meticulously planned to balance power sources. In icy or windy conditions, engines assist, but the vessel often relies solely on electric power in port and archipelago areas. Captain Anders Andersson notes that wind direction and speed constantly influence decisions, such as whether to engage a second engine or complete the final leg on battery alone.

The ferry’s carbon-neutral status also benefits Stena Line financially under the EU’s emissions trading system, which since 2024 has required shipping companies to pay for CO₂ emissions. Excess credits from Aurora Botnia can offset costs for the operator’s other, fossil-fueled vessels.

Below deck, the engine room reflects the ship’s clean technology: quieter than traditional vessels and notably free of soot, a direct result of its zero-emission fuels.