Nov-2023

Fuelling the decarbonisation of international shipping

The shipping industry’s transition to net zero is a sizeable challenge, but major progress is being made on the main driver: legislation.

Sebastiaan Bleuanus
Wärtsilä Netherlands BV

Article Summary

It has been an eventful year for those working on the decarbonisation of international shipping. Besides a flurry of technology developments and the world’s first demonstrations, we have seen significant progress on the main driver of shipping’s transition to net zero: legislation. The recently increased ambition level of the IMO (described elsewhere in this issue of Decarbonisation Technology) can be interpreted as a solid call to action for the industry. Besides progress at the IMO, the European Union’s council adopted the FuelEU Maritime package on July 25, 2023.  This package includes a raft of measures but critically also focuses on the carbon intensity of the fuels used in shipping and incentivising the uptake of renewable fuels of non-biological origin (RFNBOs).

Though the legislative fog on the decarbonisation of shipping has started to lift, a one-size-fits-all solution has not yet emerged, nor is one expected to materialise. With so many different ship types, operational profiles and regional differences, different solutions will be needed.
So how do we get this done as an industry, and what are some of the ways Wärtsilä is supporting the industry with decarbonisation?

Efficiency will be critical, both upstream and downstream
While shipping is already the world’s most efficient mode of large-scale transportation, further increases in the shipping system are still possible. Here, we need to distinguish between five steps for further increasing efficiency:

Transport needs optimisation. The inevitable cost increase for transporting items over long distances will lead to a rethink of the need for transport. Tied in with global tensions, we may see an increase in re-shoring, which brings about changes in the need for raw materials and finished products.

Transport system optimisation. Because a ship’s energy consumption per mile is highly dependent on her speed, being able to go slower and avoid waiting at anchorage before docking pays off. Every year, more than 2 million port calls are co-ordinated individually, and more than $18 billion worth of excess fuel is unnecessarily burned, with 160 million tonnes of CO₂ emissions. To help avoid this, port call optimisation techniques have been developed and introduced.

Ship optimisation. Having established the need and optimum speed to sail, a close look at the ship itself reveals that a large part of today’s global fleet is not being used in an optimum way. Often designed and sea-trialled for higher speeds than those used in practice (especially when taking a holistic approach to transport system optimisation), real-world vessel efficiency can be increased through hydrodynamic improvements by adding so-called energy saving devices, by lowering ship resistance through hull air lubrication, and even by adding sails to take advantage of the free fuel: wind. A notable example of this is the Pyxis Ocean bulk carrier that recently completed her maiden voyage from Shanghai to Paranagua in Brazil after being retrofitted with two wing sails, one of which was co-funded by the CHEK project (see opposite) developed by BAR Technologies (see Figure 1). Each sail is predicted to save 1.5 tonnes of fuel per day at sea.

Engine optimisation. Medium-speed four-stroke internal combustion engines used either as main or auxiliary engines are already reaching 50% efficiency, but further improvements are still to be had. Special attention should be paid to combustion efficiency in low-pressure gas-fuelled engines, as an increase in combustion efficiency directly translates into lower methane emissions. An example of technology development to reduce methane emissions and increase engine efficiency was recently demonstrated on board the Aurora Botnia RoPax ferry as part of the SeaTech project (see Figure 2). Aurora Botnia is a state-of-the-art ferry powered by four Wärtsilä 31DF dual fuel gas engines as part of a hybrid propulsion system. One of the installed engines was upgraded to reach sizeable emission reductions and ultra-high energy conversion efficiency by precisely controlling the fuel mixture at every operating point of the engine. The VTT Technical Research Centre of Finland conducted a measurement campaign on board to verify the results. Measurements were conducted on the upgraded engine and one of the non-modified Wärtsilä 31DF engines. Figure 3 illustrates the main results on measured methane emissions from both the non-modified engine (Main Engine #4, or ME4) and modified engine (Main Engine #3 or ME3) (Lehtoranta, Kuittinen, Vesala, & Koponen, 2023). The achieved emission reduction is quite clear and sizeable, ranging from a 50% reduction at the highest loads to up to 75% at lower loads.

Engine and fuel optimisation. Having gone through the first four optimisation steps, the remaining gap for the required emission level will have to be tackled by optimising the carbon intensity of the fuel burned on board. Where the preceding steps often result in increased vessel profitability, this last step will increase the operational cost of the vessel. However, this is about to change. With legislation under development that includes so-called ‘market-based measures’ – such as carbon taxes, fuel levies or subsidies on renewable fuels – the playing field starts to tilt towards the utilisation of renewable fuels. With this in mind, Wärtsilä is developing a portfolio of engines able to run on methanol, ammonia, and hydrogen. Working to a compressed timeline, the market introduction of these engines is scheduled for 2026. For ammonia, the market introduction is planned for this year, with first deliveries (to the marine market) next year, while our first methanol engines have already been released and delivered.