Maritime & Trade Blog

Scrubbers gain favor as shipowners gird for SOx regulations




As enforcement of new emission regulations draws closer for the maritime industry, vessel operators are weighing their compliance options.

Beginning January 2015, the sulfur oxide (SOx) content of emissions from all vessels operating within emission control areas (ECAs), of which there are currently four—North America (including Hawaii), US Caribbean, North Sea, and Baltic Sea—will be required not to exceed 0.1%. The current 1% limit was set in 2010 under MARPOL Annex VI.

One option is to burn fuel with lower sulfur content, which is estimated to cost 70% more than the higher-sulfur fuel now used. For vessels already in service, however, the installation of "scrubbers," SOx abatement systems, appears to be an attractive second option. With scrubbers in place, vessels will be able to operate on higher-sulfur fuel and remain compliant under the emission regulations.

While scrubbing technology has been employed in power generation and other industries for a number of years, it is relatively new to the maritime sector. On ships, scrubbers work on the principle of spraying seawater as mist into the exhaust gases to neutralize the acids. In an open-loop scrubber, the wastewater is discharged overboard, where the natural alkalinity of the seawater neutralizes the acidic discharge. In a closed-loop scrubber, the washwater is mixed with a strong alkaline (caustic), which reacts with the acidic (sulfur) particles. The waste is then stored on board in sludge tanks for later disposal onshore.

Hybrid scrubbers provide flexibility for ships to switch between open and closed loop, permitting zero discharge where local regulations prevent such actions. In Europe, ferry operator DFDS Seaways has led the way in installing this technology. The Tor Ficaria (later renamed Ficaria Seaways) was installed with a hybrid system developed by Aalborg Industries (now part of Alfa-Laval) in May 2009, which laid the foundation for a large-scale fleet investment. Thus far, 11 of the company's vessels that service routes in the Baltic Sea and North Sea have been retrofitted with the system.

While DFDS' decision is driven largely by the fact that its operations are almost entirely within ECA zones, other owners have been mulling the decision to install scrubbers to provide operational flexibility. Carnival Corporation has committed to retrofit over 70 of its vessels with scrubbers. The cruise ship giant will install a proprietary "compact" scrubber unit on vessels in its Princess Cruises, Cunard, Aida Cruises, Costa Crociere, and Holland America brands. This will enable its fleet to transit in and out of ECA areas without having to switch fuels.

Retrofitting a vessel with a scrubber can be done reasonably quickly—as little as 10 days in some cases— as the units can be preassembled before installation on board. While scrubbers add weight to a vessel, their ability to allow ships to run on cheaper fuel, for now, appears to be making them the compliance option of choice for cost-conscious maritime operators.

Krispen Atkinson Principal Analyst, IHS Maritime & Trade 
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