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Politicians urged to act as interactive map shows scale of global scrubber washwater discharges

The Washington DC-headquartered International Council on Clean Transportation (ICCT) has issued a first-of-its-kind 28-page report, along with an interactive map, looking at the global distribution of washwater pollution caused by ships using exhaust gas cleaning systems.

“The most popular type of scrubber, open loop, constantly discharges large amounts of washwater that is acidic and contains polycyclic aromatic hydrocarbons (PAHs), particulate matter, nitrates, nitrites, and heavy metals including nickel, lead, copper, and mercury, all of which are discharged to the aquatic environment where they can damage marine ecosystems and wildlife and worsen water quality,” the ICCT study states, something strongly denied by advocates of scrubber technology. Closed-loop scrubbers emit the same pollutants in lower volumes, but higher concentrations, the ICCT maintains.

The country with the highest concentration of washwater per sq km is Singapore


The study finds that approximately 3,600 ships with scrubbers will emit at least 10bn tonnes of washwater each year for the next several years, 80% of which is discharged within 200 nautical miles of shore. Putting the 10bn figure in context, the global shipping sector carries about 11bn tonnes of cargo per year. Actual discharges may be higher, as the ICCT said it used conservative estimates for washwater flow rates and the scrubber equipped fleet now stands at more than 4,300 ships.

The ICCT estimated scrubber washwater discharges from all ships that were expected to be using scrubbers by the end of 2020, the end of the first year of the global sulphur cap. For each ship, hourly washwater discharges were calculated as total energy demand per ship in megawatt hours multiplied by the scrubber washwater flow rate.

This study shows the consequences of regulating pollutants rather than pollution

The three countries with the highest expected washwater discharges are the United States, the United Kingdom, and Italy while the the country with the highest concentration of washwater per sq km is Singapore, five times higher than second placed Jordan. Even though the Southeast Asian republic has banned the use of open loop scrubbers in its waters, it is a victim of geography, being at the confluence of global trade. Between the northern tip of Sumatra and the start of the Singapore Strait, more than 180m tonnes of washwater enters this narrow area every year, according to ICCT data.


In terms of individual ports, cruise hubs dominate the top 10 ports by washwater discharge masses. Cruise ships represent only 4% of the scrubber-equipped fleet but account for 15% of scrubber washwater discharges. Cruise ships spend 25% of their time in ports, the study shows, and these vessels have the highest in-port energy consumption of any ship type; average power consumption for a scrubber-equipped cruise ship in port is 12 MW/h, compared with oil tankers, which consume, on average, 4 MW/h in port

Away from shore, scrubber discharges occur along major shipping routes. Some of these routes pass through protected areas, including the Great Barrier Reef, where about 32m tonnes of scrubber washwater is discharged annually, mainly from ships serving coal terminals in northeast Australia.

“Understanding how much washwater is expected to be discharged within territories, and where, could improve policymaking,” the study’s authors state.

The ICCT, long a thorn in the side of scrubber advocates, had many policy suggestions for governments, port authorities and international regulators. Among these, the Washington think tank urged the International Maritime Organization’s Marine Environment Protection Committee (MEPC) to pass a resolution calling on ships to immediately stop dumping scrubber discharge water in places that should be protected as well as mull a ban on scrubbers being installed on newbuilds and contemplate a phase-out timeline for existing exhaust gas cleaning systems.

“This study shows the consequences of regulating pollutants rather than pollution. In its effort to reduce sulpur dioxide emissions, the International Maritime Organization has created a global water pollution problem. Individual countries and ports now must decide whether to allow ships to continue to dump pollution in their waters, without compensation, or to ban the use of scrubbers in their waters,” commented Bryan Comer, marine program lead at the ICCT.


The Clean Shipping Alliance, a pro-scrubber lobby group, has repeatedly dismissed the toxic wastewater claims made by the ICCT and other organisations.

Mike Kaczmarek, chairman of the CSA, commented earlier this month: “Washwater from exhaust gas cleaning systems should not be interpreted as a form of marine pollution. These systems have been in use for decades and there is absolutely no evidence of any negative impact on marine life or sea water quality, neither in open waters nor in port environments.”

To access ICCT’s interactive map, showing scrubber discharge water near you, click here.

Sam Chambers

Starting out with the Informa Group in 2000 in Hong Kong, Sam Chambers became editor of Maritime Asia magazine as well as East Asia Editor for the world’s oldest newspaper, Lloyd’s List. In 2005 he pursued a freelance career and wrote for a variety of titles including taking on the role of Asia Editor at Seatrade magazine and China correspondent for Supply Chain Asia. His work has also appeared in The Economist, The New York Times, The Sunday Times and The International Herald Tribune.
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