Skip to content

2018 Cruise ship Air Questions

The Commercial Passenger Vessel Environmental Compliance Program (cruise ship program) has received an increased number of public complaints and questions regarding cruise ship air emissions in late 2017 and in 2018. The increase coincides with an increased in the number of ships operating Exhaust Gas Cleaning Systems (EGCS or Scrubbers). Public complaints include general air quality, smell of exhaust, and excess emissions from ships.

A  September 12 presentation on 2018 Cruise Ship related Air Quality is available as a powerpoint or pdf

Cruise ship Air Monitoring
DEC staff and a DEC contractor monitor the visible emissions (opacity) from vessel exhaust in Alaskan ports. Visible Emissions (VE) readers are trained and certified using EPA Reference Method 9. This method is used as an indicator of the particulate matter exiting the stack and requires VE readers to visually differentiate the opacity of the emissions.

Cruise ship Air Emissions State Requirements
All marine vessels, including cruise ships and state ferries, must comply with the State opacity standards in 18 AAC 50.070. The standard requires the opacity of the visible emissions to be no greater than 20 percent (excluding condensed water vapor), with limited time exemptions while maneuvering and while at berth or anchor.

Cruise ship Air Enforcement
The cruise ship program has an active enforcement program regarding air emissions. Annual reports are available which provide details on compliance actions each year.

Ambient Air Monitoring
The cruise ship program is working with Division of Air on plans for a potential future monitoring program. Ambient air was monitored in downtown Juneau for sulfur dioxide, nitrogen oxides, and PM 2.5 during 2000 and 2001. The pollutant levels were found in 2001 to be below federal and state health standards.

What are Exhaust Gas Cleaning Systems (EGCS or Scrubbers)?
Exhaust Gas Cleaning Systems are pollution control systems designed to remove pollutants from exhaust. Primarily, these systems are designed to extract sulfur oxides (SOx) from the exhaust. By installing these systems, vessels can be compliant with federal SOx emission regulations without using low-sulfur fuels. Exhaust Gas Cleaning Systems have been installed on many cruise ships operating in Alaska in the last three years.

Who regulates Exhaust Gas Cleaning Systems?
Ships are required to reduce their SOx emissions in certain waters in the world. These areas are called Emission Control Areas (ECA or SOx Emission Control Areas (SECA)). The North American Emission Control Area, under the International Convention for the Prevention of Pollution from Ships (MARPOL), came into effect in 2012, bringing in stricter controls on emissions of sulfur oxides. The SECA does not include the coast of Alaska west or north of Cook Inlet. From 2015, the allowable SOx emission in these areas cannot exceed 0.1 percent fuel sulfur (1,000 ppm). By 2020, a global 0.5 percent fuel sulfur limit will take effect. The US Environmental Protection Agency (EPA) regulates the ECA in the United States.

How do Exhaust Gas Cleaning Systems work?
Scrubbers are a form of pollution control equipment. Scrubbers use chemical or physical processes to remove pollutants from the exhaust gases. Open loop scrubbers use seawater and discharge the wash water. Closed loop scrubbers are an internally confined process using chemical reagents to selectively remove pollutants of concern. Reagents must be recharged or off-loaded as a waste stream and replaced. There can also be hybrid systems using more than one method. Scrubbers have limitations and must be adequately maintained, monitored, and operated in order to comply with a complex set of regulatory requirements. There may be trade-offs such as demands on shipboard resources and additional energy (fuel) use. The benefit for vessel operators of scrubbers is the use of fuel with higher sulfur content while maintaining compliance with the ECA.

How do Exhaust Gas Cleaning Systems change the exhaust appearance?
These systems add condensed water vapor (steam) to the exhaust by using large amounts of water in the scrubbing process. When steam is present within the plume as it emerges from the stack, opacity observations are made beyond the point at which the steam is no longer visible. Washwater may also cool the exhaust, reducing the ability of the exhaust to rise and dissipate compared to non-scrubber exhaust.