Open loop scrubbers help ship owners cheat emissions targets

open loop scrubbers
© iStock/brazzo

In the face of a 2020 deadline to reduce the air pollution produced by their ships, owners are saving money by installing open loop scrubbers rather than pay extra for cleaner fuel.

The deadline, imposed by the International Maritime Organization (IMO), compels vessels to use fuel with a sulphur content of 0.5 per cent rather than the 3.5 per cent standard currently in place. Because the fuel with a lower sulphur content is more expensive, between 2,300 and 4,500 ships – five to nine per cent of the full global shipping fleet – plan instead to install open loop scrubbers, which use seawater brought back on board to remove sulphur from ships’ exhaust gases.

An industry analysis showed that while the initial installation of open loop scrubbers is expensive, costing around $2 to $4 million per scrubber, ships would recoup the costs in fuel savings in the first year after fitting the device. Low sulphur fuel costs between $300 and $500 per tonne more than fuel with a higher sulphur content.

While open loop scrubbers do reduce the amount of sulphur produced in ship exhausts, the wastewater produced by their scrubbing process contains sulphuric acid constituents, polycyclic aromatic hydrocarbons and heavy metals; all of which are pumped back into the sea.

A statement from international shipping company Euronav said: “Promoters of this technology argue that the open oceans dilute wastewater, rendering it harmless. But the solution to pollution is not dilution. Like plastic contamination over the years, we don’t know what the cumulative effect of this wastewater [from open loop scrubbers] will be or how it will interact with existing seaborne pollutants, particularly in congested sea-lanes like the English Channel, Malacca Straits or Baltic Sea.”

At present pollution caused by dirty shipping fuel is responsible for 400,000 premature deaths and 14 million cases of childhood asthma per year. The full environmental and health implications of the increased marine pollution cause by the uptake of open loop scrubbers have yet to be disclosed.


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