Are electric motors the future of shipping?

The two-minute trip across the Rhine on the Mondorf ferry used to be accompanied by clouds of sooty smoke and the constant cough of a combustion motor. But since February, the ferry's chugging diesel engine has been replaced with one run entirely on electricity.

To power through its 14-hour day, the ship needs a 1,000 kilowatt (kWh)-hour battery — equivalent to about 14 electric car batteries. At night, the ferry recharges with renewable energy while docked at the pier.

Converting the 60-year-old ferry to run on renewable energy was possible thanks to federal funds, which covered up to 80% of the cost. "Without the subsidy, it would have been too expensive," said Elmar Miebach-Oedekoven, managing director of the shipbuilding company Lux Werft und Schifffahrt. His company has already converted some 20 passenger ships to electric propulsion, including several that operate along the Rhine in and around Bonn.

Compared with diesel engines, electric motors require less maintenance. As a result, said Miebach-Oedekoven, running the ferry on a battery will "probably be cheaper in the long run," even with Germany's high electricity prices. And that's not the only environmental advantage, added operations manager Ingo Schneider-Lux. An electric motor means "no flammable diesel on the ship, no risk of spills when refueling — the technology is simpler and safer."

Schneider-Lux told DW that the ferries and passenger ships plying the waters of Germany's lakes and rivers were increasingly going electric. That's also the case worldwide: A conservative estimate from the Maritime Battery Forum nonprofit in Norway shows that more than 1,000 ships are already operating with fully electric or hybrid engines, and at least 460 additional electric ships are under construction.

Norway leads the way in electric ships

Norway is the world leader when it comes to battery-powered ships. For the last decade, the government has introduced stricter regulations and supported the electric technology for ferries, cargo ships, fishing boats, cruise ships and maintenance ships for maritime industries, which in future will be able to recharge directly from offshore wind turbines.

It's all part of Norway's goal to drastically reduce CO2 emissions in the shipping industry by 2030. Starting next January, tourist ships and smaller ferries sailing in the western fjords will have to comply with new zero-emissions requirements. Today, more than 40% of the region's 199 ferries — a key transportation link along the 1,800-kilometer (1,100-mile) coastline — are already fully electric.

One of country's largest battery-powered ferries, with space for some 200 cars and 600 passengers, has been shuttling between two communities south of Oslo since 2020. And the world's largest battery-powered ship, a lightweight high-speed catamaran, is set to launch in May. It will transport 2,100 passengers and 225 cars across the wide, muddy waters of the Rio de la Plata between Argentina and Uruguay, a distance of some 50 kilometers.

Inland shipping turning to battery power

While electric motors are useful for shorter distances, longer journeys remain a challenge. That's why some electric ships also have a traditional engine on board, powered by diesel, liquefied natural gas (LNG) or biodiesel.

The hybrid vessel Saint-Malo, which has been making the 260-kilometer journey across the English Channel twice a day since February, primarily uses its battery along the coast and while in harbor, reducing emissions and noise pollution. For the rest of the trip, it relies on an LNG-powered motor.

But electric ships can cover much longer distances if they swap out batteries while en route. Two small e-freighters, which regularly sail the 300 kilometers along the Yangtze, China's longest river, between Nanjing and the port of Yangshan in Shanghai, are powered by 36 battery containers. They provide up to 57,000 kWh of power, and when depleted are switched for freshly charged batteries at the next stop.

That technology is also being used in two smaller barges in the Netherlands, at the port in Rotterdam. The battery exchange system, which takes only 15 minutes, was built in part with support from the European Union. The bloc's aim is to significantly reduce emissions from inland waterway shipping between the Netherlands, Belgium, France and Germany by mid-century.

Global shipping industry aims to cut all emissions by 2050

The maritime shipping sector is responsible for about 2.8% of the world's CO2 emissions; it's even higher in the EU, where shipping represents between 3 and 4% of the bloc's total emissions.

Making the switch to electric motors could help cut back those planet-heating gases, and significantly improve local air quality. It also makes economic sense: Battery-powered ships are already overtaking traditional barges on shorter routes, when all costs are factored in.

Roger Holm, president of Helsinki-based ship engine supplier Wartsila Marine, said the outlook for the electric shipping industry was positive. He told DW that demand for hybrid and fully electric engines was increasing every year, and had quadrupled since 2019.

NatPower Marine, a London-based company which develops charging infrastructure for ports, also sees room for growth. CEO Stefano Sommadossi told DW that the "groundbreaking innovations in battery technology" and hybrid propulsion systems are expected to give the industry a boost over the next 20 years. A big advantage of electric engines, he added, is their high efficiency, compared with other climate-friendly options like methanol and green hydrogen.

The International Maritime Organization aims to cut greenhouse gas emissions produced by shipping by 30% in the next five years, 80% by 2040 and eliminate them completely by mid-century.

Currently, the Asia-Pacific region is far ahead when it comes to electric shipbuilding, and Sommadossi expects it will continue to dominate the field. But Europe isn't far behind, he added, boosted in part by the EU's decarbonization goals.

This includes recent legislation that will require all European ports to install high-performance power connections by 2030, allowing all passenger, container and cruise ships to rely solely on local electricity while berthed, instead of running their engines.

Battery technology limited over long distances

But when it comes to long-distance travel, ship battery technology will likely remain limited.

While distances of up to 15,000 kilometers (9,300 miles) are technically possible to cover with climate-neutral propulsion — allowing a container ship to comfortably make the crossing from New York to Lisbon, for example — the 30,000 kilometer journey from Shanghai to Venice, Italy remains out of reach without a stop to swap batteries along the way.

For these longer maritime routes, biodegradable methanol fuel is the current favorite when it comes to environmentally friendly ship propulsion. Danish shipping giant Maersk launched its first methanol-powered container ship in 2024 — with the fuel produced in part by solar and wind energy in southern Denmark.

But according to industry experts, many more such plants will be needed to achieve climate-neutral shipping.