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As it happens, seawater does a good job of scrubbing toxic chemicals from diesel engine exhaust. And therein lies the key to Royal Caribbean’s ambitious ongoing initiative to stay ahead of current and future emissions standards in places where it sails.
“It’s a part of our DNA to be above and beyond compliance, and to lead the way,” says Adam Goldstein, president and COO of Royal Caribbean Cruises Ltd. “We’re big into continuous improvement where we can see that there’s something quite materially important to our future welfare – like the control of sulfur emissions.”
Now underway and is scheduled for completion in 2017, the initiative includes the installation of so-called exhaust “scrubbers” on 13 Royal Caribbean International and six Celebrity Cruises ships. The work will be done on some ships during scheduled drydocks and on others while the ship is in service.
RCL officials prefer the more descriptive Advanced Emissions Purification (AEP) when speaking of the complex systems that are being retrofitted on 19 of its ships. The AEP systems being installed are manufactured by Wärtsilä of Finland and Alfa Laval of Sweden.
Sulphur dioxide is an airborne pollutant created when sulphur-containing fuel – including diesel – is burned. Although electricity generation and other land-based industries are the largest sources of this pollution, diesel-powered ships at sea have also identified for tighter emissions regulation around the world.
Burning specially distilled low-sulphur fuel is one option for reducing harmful emissions, but RCL decided that choice is iffy.
“We’re not guaranteed that it’s going to be available everywhere our ships will operate,” says Rich Pruitt, RCL VP of safety and environmental stewardship. “In choosing to use AEP systems, our ships will be totally emission-ready, so to speak, for any operation anywhere in the world.”
Put most simply, AEP works by spraying diesel exhaust with fine mist from a ring of water jets. As the mist combines with sulphur dioxide it creates sulphuric acid. In a happy coincidence, seawater is naturally alkaline so it neutralizes the sulphuric acid to a degree that meets strict water discharge standards after the wastewater is centrifuged to remove toxic particulates.
In some of the areas where RCL ships sail, alkaline levels in the seawater are too low to be effective. So the company opted for hybrid AEP systems allowing ships to switch as necessary between an “open loop” of untreated seawater to a “closed loop” system that boosts alkalinity with the addition of caustic soda.
The technology works. But fitting it into the confines of a cruise ship is a novel challenge.
“Having a marine installation for all this is very new,” says Harri Kulovaara, RCL’s executive VP, maritime. “And we are actually very happy to be leading the way in implementing this technology.”