At LiqTech, our goal is to minimize the negative impacts made from living an improved lifestyle. With innovative clean technology, we reduce the harmful effects made by various polluting industries, including the marine industry, in line with current and emerging environmental regulations.

Shipping provides cheap and efficient long-distance transportation of goods and commodities with a low environmental footprint. Yearly, approximately 80 % of all global exports and imports by volume, equal to 11 billion tons of goods and commodities, are transported by ship. And according to the United Nations Conference on Trade and Development (UNCTAD), this number is even higher for most developing countries.

But although the shipping industry is effective, considered that it is cheap, can transport large volumes of goods and commodities, and has the smallest environmental footprint per ton within the whole cargo transportation industry, solutions are needed to obtain an even greener shipping industry.

The marine industry accounts for approximately 2.5 % of all global greenhouse gases (GHG). Insofar the industry was a country; it would rank as top 6 in relation to emission level. If no immediate actions are taken, the emissions from the marine industry are forecasted to skyrocket. It is estimated that emissions may increase by 50-250 % before 2050, neglecting the objectives of the SDGs.

Yearly, global shipping accounts for almost 940 million tons of CO2 emissions. To put that into context, the 15 largest marine cargo bulkers pollute just as much as all 760 million cars in the world. The marine industry primarily generates sulfur oxides (SOx), nitrogen oxides (NOx), particulate matter (PM), and carbon oxides (CO2). However, the industry also holds responsibility for oil spills, ballast water, and biocides.

And the marine industry’s environmental impact is notable. The emissions from one large cruise ship are equivalent to:

  • Sulfur oxides (SOx) = 376 million cars
  • Carbon dioxide (CO2) = 83,678 cars
  • Nitrogen oxides (NOx) = 421,153 cars
  • Black carbon = 1.05 million cars

Fortunately, there is significant untapped potential to reduce emissions from the marine industry. With the current omnipresent focus on sustainability and viable solutions, new imperative initiatives and regulations are implemented. And these have changed the marine industry and how cargo ships and vessels can operate radically. Let us dive into how it has changed the marine industry and what shipowners and shipyards can do to stay compliant now and in the future.

Read straight through everything worth knowing about the marine industry or jump to the section you want to read.

  1. What is the IMO 2020 sulfur cap?
  2. What are the IMO wash water discharge regulations?
  3. Where are open-loop scrubbers banned?
  4. How do I comply with the IMO 2020 sulfur cap?
  5. What are marine scrubbers?
  6. What are the differences between open-loop scrubbers and closed-loop scrubbers?
  7. How does a closed-loop scrubber work?
  8. Why use a closed-loop scrubber?
  9. What is open-loop to closed-loop conversion?
  10. What does a scrubber remove?
  11. What does a scrubber water treatment unit remove?
  12. What is the technology behind a scrubber water treatment unit?
  13. Endless opportunities for a sustainable shipping industry

1. What is the IMO 2020 sulfur cap?

The International Maritime Organization (IMO) is an international standard-setting authority under the United Nations, aiming to improve security, safety, and environmental performance within the shipping industry by implementing global regulatory frameworks. Thus, the IMO works to achieve the SDGs.

The sulfur cap is an international regulation that significantly lowers the allowed sulfur content in marine exhaust gases from the previously allowed 3.5 % to a new maximum of 0.5 %. The regulation entered into force on the 1st of January 2020, and it applies to all ships globally. Still, the IMO 2020 sulfur cap does not affect the Emission Control Areas (ECA), maintaining its 0.1 % sulfur content maximum.

Timeline of allowed sulfur content in marine exhaust gas:

IMO Sulfur Cap

The new international sulfur cap framework aims to reduce atmospheric pollution caused by the marine industry. The IMO expects to see a 77 % SOx reduction before 2025, benefitting human health, wildlife, and ecosystems. With this massive SOx reduction, the IMO estimates that more than 570,000 premature deaths can be prevented within the same timeframe. Moreover, the new SOx regulation can help prevent acid rain, which has harmful effects on forests, soils, and freshwaters, harms and kills insects and aquatic species, causes corrosion of steel structures such as bridges, and makes buildings decay.

If a ship does not abide by the IMO 2020 sulfur regulation, it may involve debunking, fines, or even imprisonment.

Click here to learn more about the IMO 202 sulfur cap.

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2. What are the IMO discharge limits on scrubber wash water?

A method to treat exhaust gas is by means of a scrubber, which is an exhaust gas cleaning system (EGCS). Yet, a scrubber generates wash water, which can contain harmful elements. To be allowed to discharge the wash water into the sea, the Exhaust Gas Cleaning System Guidelines demand several parameters to be met.

  1. pH (with temperature compensation)
    Discharged scrubber wash water must not be lower than pH 6.5. Moreover, it must not exceed a temperature of 60 ˚C.
  1. Polycyclic Aromatic Hydrocarbons (PAH)
    The limit for PAH is based on the concentration of phenanthrene equivalents in the wash water. To control the total amount of harmful PAH discharged into the sea, an upper limit of 50µg/l above that at scrubber wash water inlet is related to a 45t/MWh flow rate, equal to that of an open-loop scrubber.
  1. Turbidity
    Turbidity is an effective method to determine particulate matter (PM) removal performed by the water treatment unit. The turbidity may not exceed 25 formazin nephelometric units (FNU) or 25 nephelometric turbidity units (NTU).

With a water treatment unit, all parameters can easily be met. 

Click here to learn more about the scrubber wash water discharge limits.

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3. Where are open-loop scrubbers banned?

More countries and regions have adopted a ban on open-loop scrubbers as they discharge sulfuric wash water with a great emphasis on the marine industry's environmental performance. More than 120 pots worldwide have banned open-loop scrubbers. Likewise, the European Union’s environmental committee has voted to out-phase open-loop scrubbers, and the IMO is expected to follow. According to Safety4Sea, the following counties have implemented a ban on open-loop scrubbers:

  • Bahrain (within port limits)
  • Belgium (ports and inland waters)
  • Bermuda (territorial waters)
  • China (territorial waters)
  • Egypt (Suez Canal)
  • France (specific ports)
  • Germany (inland waters and ports bordering inland waters)
  • Gibraltar (local waters)
  • Ireland (within the ports of Cork, Dublin, and Waterford)
  • Lithuania (port waters)
  • Malaysia (territorial waters)
  • Norway (heritage fjords)
  • Pakistan (within port limits)
  • Panama (the Panama Canal)
  • Portugal (port waters)
  • Scotland (within the ports of Forth and Tay)
  • Singapore (within port limits)
  • Spain (within the port of Algeciras)
  • Sweden (within the port of Brofjorden)
  • UAE (within Fujairah and Abu Dhabi port limits)
  • USA (within Connecticut port waters and Californian waters)

Click here to learn more about open-loop scrubber bans.

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4. How do I comply with the IMO 2020 sulfur restrictions?

The marine industry has two options to comply with the IMO 2020 sulfur regulations.

Option 1: Switch to compliant fuel with reduced sulfur content or alternative fuel with no sulfur

Option 2: Implement a closed-loop scrubber and keep using heavy fuel oil (HFO)

A scrubber is an exhaust gas cleaning system (EGCS), which can control air pollution. It can reduce the sulfur content in marine exhaust gases by more than 98 %. Thus, a scrubber is a compliant solution, which can reduce SOx emissions from the previously allowed 3.5 % to less than 0.1 %, meaning that ships with a scrubber can also operate within the ECA.

Although both options ensure compliance, option 2 brings forward a competitive advantage. A scrubber is a cost-intensive investment. Still, it brings financial returns in the form of fuel cost savings, ensuring low OPEX. With a closed-loop scrubber, you can continue to operate on HFO, which is often much cheaper than low sulfur fuel. The price spread between the fuel types can easily be triple-digit per metric ton (mt). When the fuel price gap peaked on the 3rd of January, 2020, at $321.5/mt on a FOB Rotterdam barges basis, the return on investment for a scrubber was less than 6 months. 

Additionally, a study conducted by the research and analyst firm CE Delft on scrubbers and alternative fuels revealed that scrubbers have a significantly lower carbon footprint than alternative fuel options.

Thus, a scrubber ensures financial and sustainable growth. And the development is clear. More and more ships implement scrubber technology to operate compliantly, sustainably, and cost-effectively.

Marine scrubber installations

Click here to learn more about how to comply with the IMO 2020 sulfur regulation.

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5. What is a marine scrubber?

A scrubber is an exhaust gas cleaning system (EGCS), which can remove harmful matter such as sulfur oxides (SOx) and nitrogen oxides (NOx) from exhaust gases emitted by ships.

There are three kinds of scrubbers: Open-loop, closed-loop, and hybrid. Previously, open-loop scrubbers have been preferred due to low installation and operational costs. Yet, it discharges sulfuric wash water, causing ocean acidification. With more stringent environmental regulations such as the IMO 2020 and open-loop scrubber bans, the balance is starting to flip in favor of closed-loop scrubbers as this is an environmentally sound technology.

A closed-loop scrubber consists of three main components, which are 1) A scrubber tower, 2) A water treatment unit, and 3) A sludge handling facility.

1) In the scrubber tower, the exhaust is scrubbed with alkali-dosed freshwater. This will turn the SOx into sulfates, which are harmless to the environment.

2) The scrubber generates a bleed flow of polluted wash water. The WTU filters the bleed flow to remove polycyclic aromatic hydrocarbons (PAH), particulate matter (PM), oil, ash, and soot stemming from the combustion process, so no harmful elements end up in the oceans.

3) Sludge is retained for safe and sustainable onshore disposal. A filter press can dewater the sludge to ensure reduced sludge handling fees.

Open-Loop Scrubber Ban

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6. Open-loop VS. Closed-loop scrubbers

Open-loop scrubbers:

Open-loop scrubbers use seawater to scrub the exhaust gases. The sulfuric acid from the exhaust and remains from the combustion process, such as unburned fuel oil, soot particles, ash, polycyclic aromatic hydrocarbons (PAH), and heavy metals, are concentrated in the scrubber wash water. To comply with IMO scrubber wash water discharge limits, the open-loop scrubber takes in an extremely large amount of seawater to correct the pH and lower the temperature, turbidity, and concentrations of PAH. The scrubber wash water is then discharged overboard without any treatment. Thus, the scrubber wash water discharge limits are only obtained by large quantities of seawater. No type of treatment is applied to reduce the amounts of acidic elements. The acidic elements are merely moved from the atmosphere to the ocean, causing ocean acidification.

Open-Loop Scrubber Illustration - LiqTech Water

Closed-loop scrubbers:

Closed-loop scrubbers use alkali-dosed seawater to scrub the exhaust gases. The scrubber neutralizes the pH of the wash water with alkali to prevent ocean acidification. This process is the major environmental advantage. Afterward, a bleed-flow of wash water is treated by a water treatment unit to remove the remains from the combustion process, such as unburned fuel oil, soot particles, ash, and PAH. Clean water can be discharged without any damages done to the oceans. Sludge is stored onboard for safe and sustainable onshore disposal.

Closed-Loop Scrubber Illustration - LiqTech Water

Hybrid scrubbers:

Hybrid scrubbers are a combination of an open-loop scrubber and a closed-loop scrubber. It can operate in an open-loop mode where discharge is allowed while switching to a closed-loop mode where open-loop scrubbers are banned.

Click here to learn more about the differences between open-loop scrubbers, closed-loop scrubbers, and hybrid scrubbers.

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7. How does a closed-loop scrubber work?

The exhaust gas moves through the scrubber tower, where it is scrubbed with alkali-dosed seawater using various nozzles. This will turn the SOx into sulfates such as Na2SO4, which are harmless to the environment. At the top of the scrubber, a continuous emission monitoring system (CEMS) is placed to ensure constant IMO 2020 compliance.

Alkali is dosed into the scrubber’s process tank to neutralize the pH of the scrubber water and maintain high SOx removal efficiency. A small amount of the scrubber wash water is bled off to a water treatment unit (WTU). The WTU will remove remains from the combustion process, such as oil, ash, soot, particulate matter (PM), polycyclic aromatic hydrocarbons (PAH), and heavy metals. A water monitoring unit (WMU) is attached to continuously monitor and control pH, temperature, turbidity, and PAHs in relation to IMO regulations on scrubber water discharge.

Only clean water is discharged or reused. Sludge is stored onboard for safe and sustainable onshore disposal.

Click here to learn more about how a closed-loop scrubber works.

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8. Why use a closed-loop scrubber?

There are many reasons for ships to operate with a closed-loop scrubber, but three in particular.

  1. Compliance

A closed-loop scrubber delivers compliance with the IMO 2020 and local authorities as well as future environmental regulations.

  1. Financial gains

Implementing a closed-loop scrubber can bring about significant financial gains as it delivers financial returns in the form of fuel cost savings. As you can continue to operate on HFO, you are ensured low OPEX as HFO is typically much cheaper than low sulfur fuel. The price spread may easily be triple-digit per metric ton (mt). When the spread hits its peak, a scrubber has a return on investment in less than 6 months.

  1. A sustainable Outlook

The research and analyst firm CE Delft has concluded that a closed-loop scrubber has a lower carbon footprint than alternative fuel options. By installing or retrofitting to a closed-loop scrubber, your operation supports the SDGs as you take an active role in reducing world pollution. Reducing SOx, NOx, PAH, and PM will benefit the planet, people, and wildlife.

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9. What is open-loop to closed-loop scrubber conversion?

Today, many ships operate with a closed-loop scrubber. In fact, approximately 80 % of all scrubbers are open-loop due to their low installation and operational costs. However, with more and more open-loop scrubber bans, this is not a sustainable or viable solution.

Fortunately, it is possible to convert an open-loop scrubber into a closed-loop scrubber. By doing so, ships can continue to operate with the scrubber they have invested in while staying compliant with current and future regulations. The conversion is easy, and it will not cause too many obstructions to your operation.

Green shipping - LiqTech Water

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10. What does a scrubber remove?

A scrubber cleans exhaust gases to remove harmful elements, including:

Sulfur oxide (SOx)

More than 98 % of SOx is removed. SOx was the primary reason for the IMO to implement the sulfur cap. SOx can cause respiratory symptoms and lung diseases. Moreover, it can cause acid rain, damaging crops, forests, and aquatic species by acidifying the oceans.

Nitrogen oxide (NOx)

A scrubber can reduce NOx, leading to respiratory infections, asthma, and chronic lung diseases.

Particulate matter (PM)

A scrubber can reduce PM, which is an airborne substance, also referred to as particle pollution. When inhaled, it can enter the human lungs and bloodstream.

What Does a Closed-Loop Scrubber WTU Remove

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11.What does a water treatment unit remove?

A water treatment unit filters the scrubber bleed-flow to remove harmful matter, including remains from the combustion process, such as unburned fuel oil, soot particles, ash, and polynuclear aromatic hydrocarbons (PAH), and heavy metals.

Open-Loop Scrubber Conversion - LiqTech Water

Particulate matter (PM)

The scrubber does not remove all PM. Some are absorbed by the wash water, which is why efficient water treatment is needed. PM is an airborne substance consisting of hundreds of different hazardous particles. PM can be various components from the combustion process, such as fuel oil, soot, and ash. When people inhale PM, they can enter the lungs and bloodstream, constituting a large health risk. The smaller the PM, the larger the health risk.

Polynuclear aromatic hydrocarbons (PAH)

PAH exists naturally in coal, gasoline, and crude oil. Likewise, it is produced when oil is combusted. Large volumes of PAH can cause cataracts, kidney and liver damages, and jaundice. It may also cause eye irritation and harm breathing passages.

Heavy metals

With a coagulation module, heavy metals can also be removed. Heavy metals are a high-density chemical matter, which is dangerous to humans at high concentrations. Heavy metals can cause kidney failures, lung diseases, and lung cancer. Likewise, it can contaminate food chains.

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12. What is the technology behind a scrubber water treatment unit?

A scrubber water treatment system can use multiple technologies. Yet, with more than 20 years of research and development within the filtration industry, we have concluded ceramic membrane technology to make up an effective replacement of conventional liquid filtration technologies due to its reduced energy consumption, excellent environmental performance, and efficient separation capabilities.

The ceramic membranes are produced of the durable material silicon carbide (SiC). Silicon carbide is the second hardest material in the world, only surpassed by diamonds and the hardest man-made material ever produced. The ceramic silicon carbide membranes can operate in up to 800 ˚C, are chemically resistant, and have an unmatched flux.

Ceramic silicon carbide membrane for liquid filtration

Click here to learn more about the technology behind a scrubber wastewater system.

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13. The endless opportunities for a sustainable shipping industry

With the emergence of more advanced green technology, we can rapidly desulfurize and decarbonize polluting industries.

And for the marine industry, there are also many possibilities to reduce emissions and propel a greener future. Still, two opportunities seem absolutely apparent and easy to adapt to contribute and further the SDGs:

Solution 1) Closed-loop scrubbers

A closed-loop scrubber ensures compliance with the IMO 2020 as well as future stringent environmental regulations. Moreover, it delivers a long-term sustainable and cost-effective operation.

Solution 2) Seawater reverse osmosis (SWRO)

Water scarcity is a global severe problem, and therefore, we ought to protect current water supplies and identify new ones. Seawater reverse osmosis is a technology that converts seawater into potable water. Thus, ships can have clean water anywhere, anytime.

Click here to learn more about the endless opportunities for a sustainable shipping industry.

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