Open-loop scrubbers, science and the Japan report

Greg Atkinson from Japan’s Eco Marine Power takes issue with the Japanese government’s approval of open-loop scrubbers.

“For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.” – Richard Feynman.

The ongoing debate about open-loop scrubbers often drifts towards being a clash of personalities and organisations (including lobby groups) whereas in my opinion we should be discussing in a rational manner, what adverse impact (if any) open-loop scrubbers may have on the marine environment. When it comes to shipping though quite often any discussion about science or technology is limited to people with no background in science or technology, telling us what their opinion is. Logical fallacies particularly variations of argumentum ad verecundiam (appeal to authority) are also utilised and we are supposedly expected to accept the claims of a person if they hold a senior position, or of an organisation because they are ‘trusted’, even without sufficient evidence to support what they claim is accurate. That however is not how the scientific method works or to quote Galileo Galilei, “In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.”

Views regarding open-loop scrubbers vary, but generally they follow two broad narratives. One is that they reduce emissions and don’t harm the marine environment, with the alternative or opposing narrative being that discharge water from scrubbers is basically pollution. Most parties involved in the debate agree though that scrubbers do reduce harmful airborne emissions including particulate matter. So in that respect they might be a step in the right direction.

My interest in this topic was begrudgingly renewed when I saw headlines recently in the shipping media heralding that Japan had basically declared open-loop scrubbers safe for the marine environment. One shipping publication (that I shall not name) even led its story with the headline ‘Japan tells IMO scrubbers are safe’. Around this time I also came across a very interesting post on LinkedIn by a Hong Kong-based doctoral student, Surinder Brrar, about the report behind these headlines. Mr Brrar was concerned enough after reading the views of the Japanese expert board for the environmental impact assessment of discharge water from scrubbers – to outline a number of his concerns about the report and the conclusions outlined in the associated presentation material. The full report is available via the Global Maritime Hub here.

Subsequently I obtained a copy of the aforementioned report that was prepared for Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and the presentation material entitled: Washwater discharge from open looped SOx scrubber system.

In the MLIT presentation it is stated that:

“Japan concluded that the discharge water with chemical substances such as SOx, PAHs and heavy metals can NOT cause unacceptable effects either on the marine organisms or on the seawater quality around Japan.”

That particular statement caught my attention as it is both vague (i.e. what is an unacceptable effect?) and in stark contrast to other reports that I had read.

For example in the published review paper: A New Perspective at the Ship-Air-Sea-Interface: The Environmental Impacts of Exhaust Gas Scrubber Discharge (2018) it is stated in the conclusions:

“[T]here is incomplete understanding of the impact of scrubber wash water discharge on marine chemistry, biodiversity, and biogeochemical processes. In particular, there is limited information on the amount and composition of wash water discharge and the associated marine biological impacts.”


“We conclude that despite the existing guidelines for levels of monitoring and compliance of scrubber wash water, there is still the risk for acidification, eutrophication, and accumulation of pollutants in the marine environment, especially in the coastal regions”.

My initial assumption was that the research that had been conducted in Japan would clearly support the conclusions outlined in the MLIT presentation. However, after reading the report by the expert board several times, I was unable to find clear evidence with the appropriate references to fully support those conclusions.

The report prepared for MLIT (or Japan report) is actually a collection of reports that were prepared by several universities, the National Maritime Research Institute (NMRI) and ClassNK. These individual reports are based on several studies regarding different aspects of open-loop scrubbers. For example one chapter is a theoretical study regarding the dilution rates of scrubber discharge water into the ocean using Computational Fluid Dynamics (CFD) analysis. But this analysis is limited to a theoretical panamax bulker operating at a constant speed of 12 knots and on a constant course. Dilution rates for different types of ships operating at slower speeds for example were not studied, nor was the dilution rate for a ship manoeuvring near an anchorage or berth. In addition the outlet for the discharge water was fixed at one metre below the waterline. No analysis was undertaken regarding situations when the outlet would be higher or lower as may be the case when the ship was unladen or laden for example. Another chapter was focused on the shore-based testing of just one open loop scrubber and no direct connection between the dilution rates and the shore based scrubber testing was established.

As I read through the report several more times I also found a number of statements that didn’t appear to be supported by the data and various assumptions appeared to limit the scope of what conclusions could be made. Therefore on May 16 I submitted to MLIT a six-page document in which I asked a number of questions and raised several concerns about the report including; why the dilution rate for only a ship operating at 12 knots was studied, why the sulphur content of the fuel used for scrubber testing was just 2.24%, and how could it be determined that scrubber discharge water would Not cause unacceptable effects either on the marine organisms or on the seawater quality? I also queried why no other studies from sources outside Japan related to scrubber discharge water were mentioned in the report. There was, for example, no literature review as would typically be found in a research paper.

On June 6 I received a document from MLIT that contained responses to my questions and concerns. MLIT confirmed that there were some phrasing errors in the English version of the report due to the translation from Japanese. They also commented that the English version of the paper had not been peer reviewed, although the Japanese version had been reviewed by a panel of experts. In addition MLIT stated that the report was not a “usual academic research paper” and that it had been prepared as a background paper to help the Japanese government with domestic policy.

The full list of questions and comments that I submitted to MLIT and their responses are carried at the end of this article.

Many of the responses to my questions I feel should have been included in the original report. For example regarding my question as to why the scrubber discharge outlet was set to one metre below the waterline, MLIT commented it was not possible to simulate (the dilution rates) in detail for all ship types and that some modelling and approximation was inevitable. I agree, but I would also suggest that if a study only considers one ship type, operating at only one speed with the outlet at only one position that this is a fairly significant limitation.

Regarding fixing the ship speed at 12 knots, MLIT responded that it is the maximum speed limit in the concerned areas in Japan. In addition they stated that when a ship decreases speed, then the volume of the plume will decrease.

Another limitation that would seem significant is that no discharge waste water was analysed from any ships fitted with scrubbers and samples were only taken from one type of scrubber tested ashore. MLIT explained that this was because no ships in Japan were fitted with open-loop scrubbers during the period when the research was conducted.

In my opinion that again is a fairly important limitation that would consequently reduce the scope of the conclusions that could be drawn. However on this and other points, MLIT does not agree.

In summary I would say the Japan report is a useful body of work in terms of helping us understand what impact scrubber discharge water might have on the marine environment. However I believe it was premature for the MLIT to declare in their presentation that waste water from scrubbers “can NOT cause unacceptable effects” and, “…. Japan is of the position that there would NOT be a scientific justification to prohibit the use of open looped scrubber, as long as the IMO’s discharge criteria were met”.

With those conclusions in mind I will quote directly from the last paragraph contained in MLIT’s response to my questions:

“[W]e do not agree to your comment that there are many important limiting factors/limitations in the study. We believe this study provides sufficiently reliable outcome based on best efforts within limited time and budget utilizing available information and technologies as of today.”

In conclusion please allow me to paraphrase a speech by Mark Antony from the immortal play Julius Caesar by William Shakespeare, I speak not to disprove what others spoke, but here I am to speak what I do know. In that context what I know is that the Japan report has been touted as research that settles the open loop scrubber debate. In reality though it is a report that has limitations and contains some assumptions. I also know there is research available including the example that I cited earlier, that suggests we don’t know enough yet about scrubber discharge water to declare it safe. But I must stress that I am not saying or implying that open-loop scrubbers will cause harm to the marine environment. That’s how it is in science sometimes, we just don’t have all the answers until further research is conducted and even then, there might be things we still don’t fully understand. So let’s hope that further research is conducted so that we get some more answers before shipping potentially scores an own goal and further damages its environmental reputation.


Review of Ministry of Land, Infrastructure, Transport and Tourism (MLIT) Ship Scrubber Report and Presentation. Review by Greg Atkinson: 16th May 2019. Responses from MLIT: 6th June 2019.


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  1. Bravo to Mr. Atkinson’s for his article and the objective approach he takes in the review. His quote of Richard P. Feynman (RPF) is on target. Feynman a winner of the Noble Prize in physics was a champion of science with a compulsive need to solve complicated challenges and an impatience with pretensions and hypocrisy of industry “experts” (see Challenger investigation). Two other Feynman’s quotes are favorites and apply to the CSA’s campaign for open the loop scrubbers already installed on over 200 ships at a quoted price of $5 million US per copy. “For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled,”RPF and the follow up “The first principle is that you must not fool yourself and you are the easiest person to fool.” Surely if Feynman were still alive his famous impatience with industry representative’s pretensions and hypocrisy regarding their selling pseudo science would have made him laugh at the scrubber tub thumpers approach. Thank you Mr. Atkinson for sharing your review. Nature will not be fooled. ActaNonVerba

  2. Thanks Jim. Another RPF quote I like is “It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.”

  3. While all aspects of marine environmental protection are important and the industry should, of course, consider emissions to air and emissions to sea in equal measure, but we should never lose sight of the reason why the global sulphur cap has been introduced in the first place: emissions of sulphur kill.
    Early this year, a study carried out by James Corbett, Professor of marine policy at the University of Delaware, estimated that the 1.2 million metric tonnes of particles emitted by ships to atmosphere each year is resulting in millions of cases of children suffering from asthma and attributing to more than half a million premature deaths a year from lung cancer and other cardiovascular diseases.
    Indeed, The New Scientist published a report way back in 2007 based on a number of independent studies carried out for the WHO found that small particles of less than 2.5 microns are responsible for about 0.8 million deaths each year of which 1.2% were premature. The New Scientist furthered the majority of these deaths were concentrated “in densely populated regions and ones that are close the major shipping lanes – mostly Europe, Asia and the Eastern US”.
    A more extensive report published in Nature in February 2018, offering projections following the implementation of the 2020 rules, stated: “Total premature mortality due to shipping in the 2020 Business as Usual (BAU) case is 403,300 per year…. Total avoided premature mortality in 2020 with implementation of the low-sulphur fuel standards is expected to be 266,300 per year…. Childhood asthma morbidity due to shipping declines by 54%, from 14 million children affected in the BAU case, to 6.4 million children in the 2020 Action case…. More than 97% of the adult mortality benefits from ship emissions reductions will be in Asia (80%), Africa (12%), and Latin America and the Caribbean (5%). More than 98% of the childhood morbidity benefits from ship emissions reductions also occur in Asia (54%), Africa (33%), and Latin America and the Caribbean (12%).”
    However, what is important here, is that burning low-sulphur fuel does not remove the problem but only reduces the impact of sulphur emissions on human health.
    In May this year, the Financial Times quoted the University of Southampton’s Dr Matthew Loxham, a specialist in air pollution, as saying: “With lower sulphur fuel you could have a greater number of particles even if their mass is reduced.” Smaller particles remaining in the air “will [still] have health consequences.”
    To a large extent the washwater debate is immaterial. You either want continue inhaling toxic shit or you don’t.
    The question we should really be asking is what is the best solution for our children, especially those living around ports and close to shipping lanes.

  4. Hi Patrick,
    surely the question should be : is removing a pollutant from the air and transferring it to the sea actually in the long-term best interests of our children? particularly as we don’t understand the long-term impact on the marine environment and the human food chain.

  5. Fully agree that removing the pollutant from the air is good. And there is no need to discharge the pollutant into the sea either because one can use the closed-loop scrubber where the pollutant is extracted on board and disposed to shore reception facilities. Since the technology already exists, why them so ships still use open-loop scrubber and discharge the pollutants into the sea. The simple answer is because open-loop scrubber is simpler and cheaper, as compared to a closed-loop or hybrid scrubber. Convenience and cost.

  6. In my article I mentioned how logical fallacies often enter the discussion regarding open loop scrubbers and then in the comments to my article – a false dichotomy appears. I did not write or suggest that nothing should be done about airborne emissions from ships, nor did I even touch upon the subject of closed loop scrubbers. Dare I suggest (and I will) that perhaps people would like cleaner air and cleaner oceans, therefore if solutions exist that can achieve this, then those are the solutions that should be encouraged.

  7. This article arouses curiosity but dissatisfies the desire for understanding. For example, “the 1.2 million metric tonnes of [Suphur] particles emitted by ships to atmosphere each year is resulting in millions of cases of children suffering from asthma and attributing to more than half a million premature deaths a year from lung cancer and other cardiovascular diseases.”

    Does that mean that the 10+ million tons of SO2 annually discharged to the atmosphere from coal fired power stations causes an additional tens of millions of asthma and 5+ million cancer and CVD deaths?

    These dire claims remind me of shrill statements made by the global warmist lobby [that warn] we should all by now be neck deep in seawater.

  8. That is incorrect, Evan. Many of the oil and coal fired power plants use scrubbers and discharge the washwaters into rivers and coastal seas since the effluent is within all the water standards, including the German Waste Water Ordinance, the EU Industrial Emissions Directive 2010/75/EU, and the EU Surface Water Standards Directive 2013/39/EU, and more…. So they don’t emit too much SOx.
    What’s good for land based application must surely be good for the maritime sector given recent research by CE Delft indicates that accumulated concentrations of exhaust gas cleaning systems’ wash water components are at very low levels and well below applicable regulatory limits.

  9. A quote from a literature review by Professor John Heywood and Dr. Emmanuel Kasseris of the Massachusetts Institute of Technology (MIT).

    “The first issue is the impact of scrubber effluent discharge on marine life and biogeochemical processes. This is especially concerning when discussing open-loop scrubbers which constitute the vast majority of installed EGCS. Scrubber effluent contains pollutants such as heavy metals and polyaromatic hydrocarbons (PAH),among others. It is also acidic, which can affect ocean chemistry and marine life. Although ocean dispersion modelling of scrubber effluent studies has been very limited, there is an almost complete consensus in the literature that there is cause for concern and justification for further scientific investigation.”

    The full document can be found via this link:

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