Evidence is growing that scrubbers work well, save money and do not cause significant pollution, claims a ship operator that has used them for 10 years.

But even as they press the case for exhaust gas cleaning systems, scrubber proponents admit the bigger issue they now face is combating greenhouse gas (GHG) emissions.

Danish ferry operator DFDS presented new evidence from CE Delft that pollution from the use of open-loop scrubbers, which pump wash water into the sea, causes minimal pollution compared with pollution that land-based industries pump into the sea via rivers.

Quoting a CE Delft report, DFDS head of environment and sustainability Poul Woodall said a study modelling the use of open-loop scrubbers while ships were docked concluded that “surprisingly small” amounts of cadmium, copper, lead, mercury and zinc could be detected.

“It [the discharge of metals] of what a scrubber would generate is virtually beyond detection,” he said at a seminar hosted by DFDS, Belgium’s North Sea Port and the Clean Shipping Alliance 2020.

The findings were based on the equivalent of having 12 large boxships alongside for 12 hours per day, 365 days per year. The figures suggest metal discharges from scrubbers range from 0% to 0.4% of that from rivers into the North Sea and up to 0.6% in the Baltic Sea.

A scrubber control panel on a DFDS vessel Photo: Paul Berrill

By the end of this year, DFDS will have 27 ships fitted with scrubbers, and is aiming for 37 by the end of 2021. This will include six new 6,700-lane-metre ro-ros currently being built and delivered by CSC Jinling Shipyard.

Figures that Woodall has collated for DFDS vessels also show “scrubbers perform a lot better than the compliance level for SOx emissions”. He claimed they also outperform the levels of emissions that would have been made if its ships had operated on compliant fuels for the European emission control areas in which they were sailing.

In 10 years of use on the 15,990-dwt ro-ro Ficaria Seaways (built 2006), he calculates the scrubber has been operated for 56,000 hours in which 150,000 tonnes of fuel were burnt. He estimates that led to the emission of 29 tonnes of SOx whereas burning compliant fuels instead would have led to the emission of 1,721 tonnes.

But as the IMO was meeting to discuss how to meet its CO2 reduction targets last week, Woodall said: “Greenhouse gases are to me the overriding issue for us as an industry and as a planet.

“To achieve the 2050 ambition [of a 50% cut in emissions], we have to have ships on the water by the early 2030s on an alternative fuel that is not fossil-based. That is a huge task and today, apart from nuclear, there is no technology that can solve that problem.”

“Everything we do in this area [SOx emissions] is expensive, but wait until you have to face the greenhouse gas issue, because you haven’t seen anything yet.”

DFDS is testing a plug-and-play fixed-wing wind-propulsion system on two small bulkers. However, it believes there are still current operational steps that can be taken.

Low-hanging fruit

“There is much more potential in speed optimisation than speed limits,” Woodall said. “It is perhaps the last of the low-hanging fruit we have for reducing our greenhouse gas emissions.”

North Sea Port chief executive Daan Schalck outlined how earlier and better planning of vessel arrivals for DFDS coming into Ghent via its ship canal from the Scheldt river is making savings of 10% to 15% on fuel use and cutting 30,000 to 40,000 tonnes of CO2 emissions per year, by helping ships be able to sail into the dock without waiting time or having to speed up.

A hybrid scrubber on a DFDS ferry Photo: Paul Berrill

The port, which was formed through the merger of Ghent with the Dutch Zeeland Seaports of Vlissingen and Terneuzen in 2018, aims to expand the arrivals-planning scheme to all users, with the eventual hope of cutting CO2 emissions by 600,00 to 700,000 tonnes a year.

A second sea lock being built, which will open at the end of 2022, will boost efficiency and expand capacity to capesize vessels. Discounts on port fees will also be offered to companies that better plan their sailing arrivals.

“Climate change and digitalisation can go hand in hand and are strongly related to each other,” Schalck said.

Woodall added: “We have to raise our hand in the transport industry. We do pollute. It is important we recognise we have an issue we need to deal with. We have to make sure that tomorrow we are better than today.”