He says “LNG is practical as there is a lot of LNG on the market. Shipowners should focus on intermediate steps they can take rather than waiting for zero emissions solutions.

“This will spoil the planet more. Why do this when if they choose LNG today, they could reduce their greenhouse gas emissions by 25%? Why not take this step and in 15-20 years reduce it further? They can ease this transition by going step-by-step rather than waiting. That is our message ꟷ small steps are more helpful than doing nothing.”

He points out that each vessel type and trading area will have its own fuel solution. “Everything above 5,000 TEU will probably move in the direction of LNG as an intermediate solution.”

However, for smaller feeder vessels, Mr Probst says hybrid battery propulsion could be used. DNV GL produced a joint presentation with MAN Energy Solutions in June about a potential 1,700-TEU container vessel using a hybrid battery solution.

But he says “If the vessel is 10,000 TEU a battery is not practical – the battery pack would be too big due to the power needed. A battery pack would not work on a container vessel much larger than feeder size due to the current size of battery packs.

However, he suggests that a combination of power could be used in the future – for example an 18,000-TEU vessel could use LNG propulsion alongside batteries.

He explains “Battery packs are an option because if an 18,000-TEU ship is in port for 14-24 hours, in that time the boil off gas from the LNG tank could be used.” He said this excess energy could be burned in the generator and stored in the battery, to be used for reefer units or to support onboard systems.

Introducing LNG retrofits

DNV GL is classing Hapag-Lloyd’s retrofit of 15,000-TEU Sajir to dual-fuel LNG propulsion – the largest container ship to undergo such a refit.

Speaking generally about container ship operators also considering LNG retrofits, Mr Probst says “They need to think about how fast they want to trade, how much generator capacity they need and then calculate the required LNG volume. You would always place the LNG tank in cargo hold, in a typical 40-ft bay area. This will be restricted by two bulkheads, but you can play a bit with the height of the tank. You can have a membrane or a type B tank. For 15,000 TEU, both have advantages and disadvantages and then you decide which type fits best in the cargo space and which fulfils the demand on LNG volume.”

The vessel was built for UASC and classed under DNV GL’s LNG-ready notation. Containership Excellence Centre director Mr Stute says “This vessel was LNG ready, so in the newbuilding stage open space was included that at a later stage could be utilised for a gas handling room and equipment. The vessel had a huge benefit as there is space to accommodate the equipment.”

Mr Stute comments on the steps taken when following the LNG-ready notation. “There needs to be an agreement between the buyer and shipyard about how far to take the preparation steps. This is a very individual specification and the reason why we have established several steps of LNG-ready class notation. Some are only preparing space for piping and others are preparing larger spaces for fuel handling and yet others are considering space for bunkering, there are different levels of space provided.”

Nevertheless, a pre-condition of this notation is that it must be possible to convert the main engine to LNG. Mr Probst says “This is mandatory because if the main engine cannot be converted it makes no sense as the main engine is the largest and most expensive equipment in the whole vessel – you would never take it out and put a new engine in.”

He points out that if a container ship operator wanted to build an LNG-powered vessel, it would take at least 2.5 years before delivery. But a conversion would only take about a year. “This is the fastest way to obtain an LNG-fuelled vessel under today’s market conditions” he says.