A study published by the International Council on Clean Transportation (ICCT) states that the International Maritime Organization (IMO) should prohibit the use of systems designed to reduce sulfur dioxide and other pollutants from ship emissions, often referred to as “scrubbers,” on newbuild ships and phase out scrubbers on existing ships.

The study, titled “air emissions and water pollution discharges from ships with scrubbers,” concludes that scrubbers are “not equivalently effective” at reducing air pollution compared to using lower sulphur fuels. Moreover, the report’s authors state that sulphur and other contaminants removed by the exhaust gas cleaning systems (EGCS) are routinely dumped overboard from the ships in the form of washwater.

The report notes that the IMO’s guidelines for scrubber discharges have not been strengthened since 2008 and they that ignore the cumulative effects of many ships operating and discharging washwater in heavily trafficked areas.

The study compares the air and water emission factors for ships using heavy fuel oil (HFO) with scrubbers and the emission factors associated with ships using marine gas oil (MGO) without scrubbers:

Particulate matter emissions are nearly 70% higher for ships using HFO with a scrubber as compared to ships using MGO. Black carbon emissions are as much as 81% higher for ships using HFO with a scrubber than ships using MGO.

A year ago, I discussed the harmful effects of scrubbers used throughout the cruise industry: Smoke and Mirrors: Cruise Line Scrubbers Turn Air Pollution Into Water Pollution. Carnival euphemistically calls its EGCS an “advanced air quality” system; Royal Caribbean calls its EGCS an “advanced emission purification” system. Whatever the name, the scrubbing systems turn toxic scrubber sludge collected from the ships’ emissions stacks into water pollution without materially reducing air pollution.

Smoke and Mirrors: Cruise Line Scrubbers Turn Air Pollution Into Water Pollution

Most travel and cruise writers shy away from covering this issue. In 2018, we discussed a situation where a Princess Cruises cruise ship appears to have piped scrubber sludge overboard while in the port of Ketchican. Port employees observed discharges coming from the Star Princess cruise ship in Ketchikan, Alaska and took photographs which showed darkened splotches in the water and lumpy black material floating near a piling.

Princess Cruises Discharges Scrubber Sludge in Alaskan Port

Princess claimed that the discharge was most likely naturally occurring “sea foam.”

Cruise lines have heavily invested in scrubbers so that they can continue to use low price but high sulphur fuel. The study points out that scrubbers have increased from 3 ships in 2008 to more than 4,300 in 2020. Expect a continued campaign of false and misleading information coming from Carnival, Royal Caribbean and the other cruise companies if and when they resume sailing.

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Photo Credit: Top – Star Princess Scrubber Sludge at Berth 4 in Ketchikan, Alaska – City of Ketchikan; middle – Carnival Freedom cruise ship – anonymous; bottom – Royal Caribbean’s Vision of the Seas cruise ship – AlaskanLibrarian’s Flickr photostream.