Sulfur Out, Scrubbers In

IMO 2020 marks the start of shipping’s journey toward sustainability. 

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Published Apr 17, 2020 11:47 PM by Mia Bennett

(Article originally published in Jan/Feb 2020 edition.)

When it comes to environmental pollutants, carbon dioxide is public enemy number one. Yet new regulations from the International Maritime Organization (IMO) target a different toxic molecule: sulfur dioxide. 

You might not be able to picture SO2, but you’d certainly recognize its smell: It’s that brief acrid tang of a struck match or, on a larger scale, the foreboding odor of an active volcano. The etymology of “sulphur” traces back to the Latin word for “burn,” betraying its combustive roots. 

Today, 99 percent of SO2 emissions comes from human activity, primarily burning fossil fuels. The release of large quantities of SO2 into the air causes environmental and human health problems like acid rain and lung disease. 

It’s little surprise, then, that the IMO is seeking to reduce SO2 emissions in the atmosphere, particularly as the shipping industry has been spewing out more and more of it. A 2013 study published in the journal Environmental Research Letters found that between 2000 and 2013, as the amount of cargo loaded worldwide rose 40 percent, SO2 emissions increased nearly 40 percent too.

IMO 2020

There’s legitimate hope for reversing this trend. Enacted on January 1, 2020, the IMO’s landmark initiative, referred to as IMO 2020, builds on various governments’ efforts since the 1970s to reduce air pollution, particularly in the U.S. Amendments to the Clean Air Act of 1990 – remarkably signed into law by a Republican President, George H.W. Bush – significantly decreased SO2 emissions from electric power plants and other industrial sources. 

The measures were so successful that between 1980 and 2018, average SO2 concentrations in the U.S. decreased 91 percent. 

Controlling mobile sources like ships, which contribute three percent of global air pollution, is a tougher target, requiring international coordination. That’s where the IMO comes in – though in the absence of a global policeman, the London-based organization ultimately has to rely on the willingness and ability of cooperating national governments to enforce its regulations. 

Outside of preexisting Emission Control Areas off the coasts of the U.S. and in the Baltic and North Seas, where the SO2 cap is just 0.1 percent, IMO 2020 sets the global maximum limit on sulfur content in marine fuels at a strict 0.5 percent, down more than 80 percent from the previous limit of 3.5 percent. Cutting ship emissions so drastically will undoubtedly help clear the air, preventing premature deaths from air pollution and acid rain. 

The High Cost of Compliance

While humans will be coughing – and dying – less thanks to IMO 2020, shipping lines will have to cough up significantly more money to meet the strict targets. A 2016 OECD report estimated that the container shipping industry may have to spend between $5 billion and $30 billion to get in line. The wide range is due to uncertainties regarding just how much very low sulfur fuel oil (VLSFO) will cost and whether it will even be available in adequate amounts. 

While only a few weeks have passed since IMO 2020 came into effect, the average cost of VLSFO has already risen. In Singapore, the world’s largest bunkering hub, it spiked from approximately $550 per metric ton in December 2019 to nearly $750 once the new year began. By mid-January, the spread between VLSFO and conventional heavy fuel oil (HFO) had reached $300/ton and was trending higher. For 8,000-TEU vessels relying on VLSFO, this can represent $23,000 in additional daily costs. 

It’s a pricey pill to swallow. It may also be in short supply in places like Iran, along India’s east coast, and in parts of Africa and South America. Furthermore, using VLSFO, especially when it’s created by blending fuels from various oil companies from different parts of the world, may present risks whose consequences are poorly understood. 

Tim Mournian, Chief Engineer for Marine Solutions-North America at Emerson, a Fortune 500 company, explains: “Heavy crude from one region must be treated with additives that are vastly different from the additives needed for light crude from a different global region. How these disparate fuels and additives will interact chemically remains to be seen, and there’s great concern about the impact on engines, fuel oil systems, controls and stack control devices.” 

Scrubbers: Ships’ Salve?

Fortunately, there’s an alternative to VLSFO – scrubbers, which are premised on the same basic technology encouraged by the Clean Air Act of 1990 to reduce emissions from power plants by literally “scrubbing” out noxious particles from their exhausts. 

On a ship, exhaust stack scrubbers use either sea or freshwater to remove exhaust gases before either discharging the washwater back into the ocean with open-loop systems or, in closed-loop systems, treating the washwater with caustic soda for discharge on land or far at sea. Typically, scrubbers need to be retrofitted onto ships with installations being expensive and occasionally technically challenging, especially when done at sea. 

Despite these hurdles, scrubber technology is attracting growing interest. Camilla Knappskog manages public relations and marketing for Norway’s Clean Marine, which provides exhaust gas cleaning systems to the shipping industry. She says, “Given current fuel spread predictions for 2020/2021, we’re seeing increased shipowner interest in our scrubber technology.”

Engineering firms are also designing a wider diversity of scrubbers to meet industry demands. Nick Confuorto, President & Chief Operating Officer of New Jersey-based CR Ocean Engineering, says that, to ensure his company’s scrubbers meet different installation needs, it’s introduced side-entry, U-shaped, and square designs. The firm is now working on over 150 projects on a range of vessels. 

Pacific Green Technologies is also busy installing scrubbers. The Delaware-based company has completed over 40 installations with another 100 in the pipeline. Chairman & CEO Scott Poulter says scrubbers not only remove SO2 from the exhaust gases of ships’ engines and boilers but up to 94 percent of harmful particulate matter as well – “something that can’t be achieved by switching to low-sulfur fuel.” 

Moreover, scrubbers can eliminate up to 60 percent of black carbon and a significant amount of polycyclic aromatic hydrocarbons. Responding to industry demand for lower-cost scrubbers that still comply with IMO 2020, Pacific Green has designed a highly efficient “naked scrubber” that provides a 15 percent reduction in weight, a 15 percent reduction in retrofit time, and lower risks during installation.  


They’re not without their detractors, however. In particular, the “open loop” variety has sparked concerns about whether air pollution is just being shifted down into the ocean. 

On the one hand, says CR Ocean’s Confuorto, “IMO has strict requirements on acid. They require that the pH of the discharge is 6.5 at four meters from discharge, and in the U.S. it has to be 6.0 pH. We meet both of those, so there’s really no issue with alkalinity or acidity from scrubbers’ discharge.” 

On the other hand, not everyone is convinced that all open-loop systems can meet these standards. In November 2019, for instance, the Malaysian government moved to ban the use of open-loop scrubbers in its waters, requiring instead that vessels use closed-loop systems or compliant fuels. 

Even in waters where open-loop scrubbers are permitted, many regulations still need to be met. New technologies are helping shipowners do just that. Emerson’s Mournian explains: “Controlling the various flows of exhaust gas, sea water, buffer chemicals and overboard discharge is possible using Valve Remote Control systems provided by Emerson Marine. The high torque and easy retrofitting of the actuators allows the circuits to maintain precise control of the scrubber systems while at sea and in port.”

“Future-Proofing” Shipping

Ultimately, ensuring a healthy environment requires the cooperation of international regulatory bodies, governments and industry. 

“We believe the key to cleaner air and reduced emissions is a close collaboration and continuous dialogue between different industries and relevant authorities,” states Clean Marine’s Knappskog, “plus a predictable policy framework.” While government policies may be volatile, they can – when done right – push companies to act in a way the market’s invisible hand may fail to do. Clean Marine sees IMO 2020 as a chance to solve even bigger environmental issues.
“Government policies play an important role of incentivizing investments into R&D, green technologies and future-proofing in a way that a self-regulated industry cannot do on its own,” Knappskog concludes. “We see the SOx and NOx focus of IMO 2020 to be the start of a journey that shall address climate challenge and transform shipping into a truly green and sustainable industry.” 

“Future-proofing” – anticipating forthcoming changes and building them into current technology – is a key concept promoted by Clean Marine and gaining wider traction in the shipping industry. At an IMO conference in 2017, Stefan Micallef, Director of the Marine Environment Division, gave a keynote lecture entitled, “Future-Proofing Your Fleet.” In his address, he called IMO a “catalyst for more efficient ships.” Both the private and public sectors, then, are integral to ensuring that shipping gets ahead of its own game. 

For that to really happen, it needs to break its procrastination habit. With this task, shipowners could use a little help. At the end of 2019, those that had delayed deciding between scrubbers or low-sulfur fuel found themselves either struggling to line up installations or purchasing VLSFO at very high cost when long-term contracts could have been signed much earlier. 

Nobody has a crystal ball, but regulatory efforts from bodies like the IMO that push the industry to integrate future-proofing into decision-making and design not only help bottom lines. They help protect the oceans for this generation and the next one too. – MarEx  

Dr. Mia Bennett is Assistant Professor of Geography at the University of Hong Kong. She is a frequent contributor to The Maritime Executive Magazine.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.