WASP is key to decarbonisation

1 April 2025

A new study by NGO Seas At Risk shows the significant economic and climate benefits of using wind-assisted propulsion for global shipping.

The study, ‘Wind First!’ shows that retrofitting sails to large, existing ships can save almost half a million US dollars in fuel costs and reduce fuel consumption and CO2 emissions by 12% annually.
This makes wind-assisted propulsion, which is readily available and scalable today, a crucial tool for meeting the 2030 target of 5% zero emissions and near-zero emissions energy in the IMO’s greenhouse gas strategy.

Preferred suction wings

According to the study, the use of wind-assisted propulsion and, in particular, suction wings, together with optimised weather routing, can significantly reduce greenhouse gas emissions and operational costs. Financial benefits include lower carbon tax, reduced EU ETS and improved energy efficiency rates, leading to further savings.

Three ship types were studied, each with different WASP configurations:

50,000 DWT MR tanker (2 or 4 suction wings, 24 m long)
80,000 DWT Panamax bulker (2 or 4 suction wings, 30m long)
125,000 DWT Post-Panamax container ship (14,000 TEU, 2 or 4 suction wings, 30m long)

Routes

The weather routing study examines the benefits of WASP on the three ships on three major return routes: Rotterdam <> Santos, Accra <> Shanghai and Mombasa <> Shanghai, using simulations over a 3-year period (2020-2023) with a departure frequency of one week. It is found that four suction wings consistently outperform two suction wings in terms of fuel savings, CO2 reduction and financial benefits for all ship types and routes.

The Rotterdam <> Shanghai route is the only route to which the EU ETS applies, but only on 50% of emissions because it is a route between the EU and a non-EU/EEA country. The Accra <> Shanghai route shows the highest fuel savings for all ships, especially bulk carriers and tankers, both of which are equipped with 4 suction wings. The Mombasa <>- Shanghai route shows modest fuel savings, with container ships benefiting the least from WASP.

CII classification, EU ETS and IMO carbon tax

Ships with WASP (both 2 and 4 suction wings) generally achieve better CII ratings (A and B) than those without sails, indicating improved carbon intensity. The IMO levy on greenhouse gas emissions from the shipping industry used in this study is USD 150 per 1 tonne of CO2e. The EU ETS applies only to routes calling at EU/EEA ports.

Therefore, Seas AT Risk only analysed the results for the Rotterdam<>Santos round trip, considering only 50% of the emissions. The highest EU ETS reduction in absolute terms is for the four-sucker container ship and amounts to €148,995. The EU ETS covers routes between EU/EEA ports, so only the Rotterdam<>Santos round trip (50% of emissions) was considered. The container ship with four suction wings achieved the highest EU ETS cost reduction: €148,995.

“Installing wind support in the global shipping fleet is a win-win-win for businesses, the economy and the planet – it delivers lower costs for the shipping industry, a smoother energy transition for global trade and an immediate reduction in emissions,” said Anaïs Rios, shipping policy officer, Seas At Risk.

Conclusions

The results of the statistical study demonstrate the significant potential of integrating wind-assisted propulsion with weather routing and speed optimisation to improve shipping efficiency and reduce environmental impact. In particular, the Weather Routing Results and Analysis section details the overall fuel benefits by route and vessel.

The 80,000 DWT bulk carrier on the Accra – Shanghai route with 4 suction wings produced the highest average relative savings.
The 125,000 DWT container ship, despite higher fuel consumption and service speed (16 knots), achieved the highest absolute fuel savings (1,301 tonnes) and CO2 reduction (4,051 tonnes) on the Accra – Shanghai route when 4 suction wings were installed, although these savings represented a lower average percentage gain of 4.76%.
The 50,000 DWT tanker also showed quite good performance, especially with 4 suction wings installed, with the highest average savings (8.7%) on the longest Accra – Shanghai route, and 7.14% of average benefits on the Rotterdam <> Santos route.
Of the three routes, the Accra – Shanghai route was most favourable for WASP benefits, while Rotterdam – Santos involved EU ETS costs, with the container ship achieving the highest average ETS reduction in absolute values (€148,995).
The Mombasa – Shanghai route showed lower savings, especially for the container ship, which was attributed to the shorter voyage duration that limited weather optimisation. The CII rating, IMO Carbon Levy and EU ETS sections present the economic and regulatory improvements due to the implementation of WASP. Financial incentives, including the IMO carbon levy ($150/tonne CO2) and EU ETS, further underlined the economic viability of WASP.
Studied ships equipped with 2 and 4 suction wings consistently achieved CII ratings of A and B, reflecting improved carbon intensity.
In conclusion, integrating WASP is a robust way to meet IMO’s decarbonisation targets, especially when combined with route optimisation. Prioritising a ship configuration with 4 WASPs on long routes maximises the benefits, although ship-specific factors (e.g. service speed, fuel base) need to be taken into account.

“Upcoming IMO talks are crucial for the decarbonisation of shipping and wind must play a central role in the solution. It is a proven, readily available and cost-effective technology that can help the global fleet meet IMO’s 2030 energy targets and will only become more valuable as fuel costs will quadruple by 2040 due to the move to e-fuels,” said Sian Prior, Shipping Policy Director, Seas At Risk, who concluded that scaling up wind support is really a no-brainer.

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