DEME chooses LNG over scrubbers

Cutter suction dredger Spartacus. Credit: DEME
Cutter suction dredger Spartacus. Credit: DEME

Dredging and marine engineering company DEME has decided that its newbuildings will have dual-fuel engines and run liquefied natural gas (LNG) where possible and on marine diesel oil when LNG is not available.

The announcement was made against the backdrop of the shipping industry’s ongoing struggles to decide which fuels and abatement techniques to use as the start date of the International Maritime Organization’s (IMO’s) forthcoming low-sulphur regulation draws near.

The company’s first two ships on dual-fuel engines, trailing suction hopper dredgers Minerva (ABC engines) and Scheldt River (Wärtsilä engines), are already in operation. In November, cutter suction dredger Spartacus will be launched at shipyard Royal IHC in the Netherlands, followed by offshore installation vessel Orion, which is being built in China by COSCO. Both vessels will take up work for the company at the end of 2019.

“There is a whole lot of uncertainty around the effectiveness of scrubbers and we didn’t want to live with that,” Bart Verboomen, managing director of the technical department for DEME, told IHS Markit sister title DPC.

Therefore, the company decided against the use of scrubbers as it is not convinced that the after-treatment of fuel exhausts is as effective as advertised or that it rids the environment of sulphur emissions and heavy metal residues.

This also includes doubts about the general energy efficiency of using low-sulphur heavy fuel oil. “A lot of people forget that the desulphurisation of the fuel costs a lot of energy,” said Jan Gabriël, department manager of the technical department of construction and conversion.

And speaking of high energy usage, due to the high load variations to which dredging engines are exposed, the company doesn’t believe that exhaust gas abatement devices will work correctly at all times. “While we believe this equipment might exist, a series of treatment systems dealing with severe variable load does not guarantee in all circumstances clean exhaust gases. We therefore chose ‘green’ at the input to be sure of clean at the output,” Verboomen said.

Another concern relates to silt deposition in the chimney. “Scrubbing results in a lot of fine soil particles to be dissolved in the seawater, which when sprayed through the nozzles of the scrubber, may clog them,” which would add to maintenance costs and uncertain functioning of the system, Verboomen said.

As such, the company has also called on the IMO to impose stricter regulations on the acidic discharge that enters the ocean due to open-loop scrubber treatments. “I do think that, in future, it could be entirely forbidden to use open-loop scrubbers for environmental protection reasons, so to say, save the bird but kill the fish,” he said, adding that these areas are just the working territory of the dredging vessel, reaffirming the company’s choice to invest in LNG.

Build bigger

Speaking about the LNG infrastructure needed to attract more operators to use liquified gas, Gabriël, referring to the situation in Europe, said, “We have hoped that the LNG infrastructure would be more advanced by now.” At the same time, he cited developments in China and Singapore, which have invested in LNG bunkering facilities, which Gabriël thinks will result in certain sectors of the global maritime industry also taking up LNG.

Apart from being able to run on natural gas as an environmentally friendly feature, Spartacus will boast a heat-recovery system that uses the waste heat from exhaust gases to produce electrical energy.

In addition to environmental innovations, the vessel will also be able to cut harder soils at advanced speeds. “With a total installed capacity of 44,180 kW, Spartacus will be able to cut harder soils at production levels that have not been possible before. This means that works can be taken on by the cutter dredger rather than relying on the use of dynamite and blasting,” the company stated in a press release.

DEME added, “Spartacus will be able to dredge in waters of up to 45 m,” compared with the 35 m depth that the company claims is presently the upper limit. “The dredger is also capable of operating in very remote locations with limited infrastructure, given its fuel autonomy, workshop, and accommodation capacity.”