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Doesn’t a zero-emission ship exist?

Written by

Nick Blenkey

In Whole Life Analysis, There Is No Zero-Emission Ship, Says OSK ShipTech [Image copyright OSK ShipTech]

Danish naval architecture consultancy OSK-ShipTech claims that, in a cradle-to-grave life cycle analysis over a 20-year life cycle, there is in fact no such thing as an emission ship. zero.

OSK-ShipTech has been involved in the design of many recent large-scale RoPax ferries, a sector which has led the way in the implementation of alternative fuels and the transition to battery propulsion.

It is generally understood, the company says, that the smaller the “direct” emissions footprint of ship propulsion, the larger the “indirect” emissions footprint of ship construction.

Anders Ørgård, Chief Commercial Officer of OSK-ShipTech, says that while reducing direct CO2 emissions must remain a priority, shipowners cannot turn a blind eye to indirect contributors to CO2 emissions: in particular the manufacturing process of ‘a ship and all the components that compose it is made of.

A recent study by the consultancy found that for an all-electric RoPax ferry, powered by climate-friendly electricity, non-operational CO2 emissions could well exceed 55% of the total CO2 emissions produced in the over the vessel’s 20-year life cycle. This study provides food for thought for responsible shipowners and shows that a holistic life cycle approach is essential when considering new construction.

“Rather than focusing exclusively on emissions from operations, shipowners should perform a cradle-to-grave life cycle analysis,” says Ørgård. “A life cycle analysis offers the opportunity to develop a construction strategy, reducing emissions during construction and operation, thereby further optimizing the operational life of the vessel.”

The study follows controversy surrounding the idea of ​​sustainability and new guidelines from the Danish Consumer Ombudsman which were published in December 2021. These emphasize that statements such as “emission-free” and “climate neutral “, for example, must be fully documented throughout the product life cycle through the use of life cycle assessments and must be verified by experts. .


OSK-ShipTech’s study included a lifecycle assessment of the all-electric Fanølinjen ferry built in 2021 Cave; a 50-meter long double-ended RoPax vessel operating the 12-minute Esbjerg-Nordby shuttle service. Despite the short distance covered, Grotte actually sails 12 hours a day. The study is therefore representative of a large ro-pax ferry with an equivalent daily operating time of at least 12 hours.

The assessment, which covered the six stages of a ship’s life, from resource extraction and steel processing to ship recycling, was carried out in accordance with ISO 14040 and ISO 14044 standards.

For the sake of redundancy, and to allow long positioning journeys, most electric ferries are still fitted with diesel engines. Experience of operating all-electric ferries has shown that they run around 90-95% of the time on electricity. For this reason, they also need backup power from other power sources. According to publicly available data, the climate-friendly electricity used to power Grotte has an emissions intensity of 0.0187 kg CO2/kWh, compared to the 0.297 kg CO2/kWh of electricity produced from a typical mix of renewable and conventional energy sources (such as coal, wood chips and natural gas) available on the grid.

OSK-ShipTech has calculated that over its entire cradle-to-grave life, Grotte will produce 2,508 tonnes of CO2eq from the operation of the ship with 1,833 tonnes of CO2eq attributable to the manufacture of the ship. As the ship and its materials will be recycled during demolition, scrapping the ship will have a positive CO2-eq footprint of 1,124.54 tonnes.

The ton of CO2 equivalent of Cave’The operation of s still exceeds the ton CO2-eq of the ship’s construction by a good margin, according to Ørgård.

“Our analysis clearly shows that a zero-emission ship does not exist at all,” he says. “To put it simply, manufacturing-generated CO2 emissions can no longer be ignored, which can account for over 50% of the cradle-to-grave carbon footprint in some cases.”

Following this thorough life cycle assessment, OSK-ShipTech is ready to apply the knowledge gained in future new build projects, helping shipowners develop a construction strategy to significantly reduce CO2 emissions during construction processes.

“A life cycle analysis already starts at the design stage of the vessel,” says Ørgård, “thus allowing us to develop a construction strategy, which we can take into account, when calculating the total cost of ownership and the cost total cradle to grave CO2 load.

Since the steel structure accounts for nearly 40% of a ship’s construction carbon footprint, a strategy should be developed to focus on the hull and steel structure from the design stage.

“You also have to consider the country of construction,” says Ørgård. “In many countries, steel production is fueled by coal. As part of their construction strategy, shipowners should also consider where to build their ships and where to buy the steel.

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