Ship Emission Compliances as per MARPOL 2020: Navigating the Waters of IMO 2020

The International Maritime Organization (IMO) introduced one of the most significant regulations in the shipping industry in 2020. The new regulations, commonly referred to as IMO 2020, mandate a drastic reduction in the sulfur content of marine fuels from 3.5% to 0.5% globally. This move is part of a broader effort to minimize the environmental impact of shipping, particularly regarding air pollution caused by sulfur oxides (SOx) emissions. In this blog, we will explore what IMO 2020 entails, the role of scrubber systems in compliance, and how alkaline chemicals like caustic soda are used in this context.

Understanding IMO 2020 and MARPOL 2020

The IMO 2020 regulations are part of the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI, aimed at reducing harmful emissions from ships. Sulfur oxides are significant contributors to air pollution, causing acid rain and posing health risks to humans and marine life. By limiting the sulfur content in marine fuels to 0.5%, the IMO aims to significantly reduce SOx emissions, thereby improving air quality and protecting the environment.

Compliance Strategies: Low-Sulfur Fuels and Scrubber Systems

Ship operators have several options to comply with IMO 2020 regulations:

Using Low-Sulfur Fuel Oil (LSFO): One of the simplest compliance methods is switching to low-sulfur fuel oil (LSFO) with a sulfur content of 0.5% or less. However, LSFO can be more expensive than traditional high-sulfur fuel oil (HSFO), and its availability may vary depending on the port.

Installing Exhaust Gas Cleaning Systems (Scrubbers): Scrubber systems allow ships to continue using high-sulfur fuel oil while still complying with IMO 2020 regulations. These systems work by removing sulfur oxides from the ship’s exhaust gases before they are released into the atmosphere. Scrubbers can be open-loop, closed-loop, or hybrid systems, depending on how they handle the washwater used to capture SOx emissions.

Alternative Fuels: Some operators are exploring the use of alternative fuels such as liquefied natural gas (LNG), which has inherently low sulfur content, or biofuels. However, these alternatives require significant modifications to existing ship engines and infrastructure.

Scrubber Systems: How They Work and the Role of Alkaline Chemicals

Scrubber systems are an effective way to reduce SOx emissions while allowing ships to use less expensive high-sulfur fuels. They work by spraying an alkaline solution into the exhaust gas stream, which reacts with sulfur oxides to form less harmful substances like sulfates. The scrubbed exhaust is then released into the atmosphere with a significantly lower sulfur content.

Types of Scrubber Systems

Open-Loop Scrubbers: These systems neutralize sulfur oxides by using seawater. The natural alkalinity of the seawater reacts with the SOx and forms sulfates, which the system then discharges back into the ocean. Open-loop systems provide a simple and cost-effective solution, but local regulations in some ports may limit the discharge of washwater.

Closed-Loop Scrubbers: These systems use a freshwater solution mixed with an alkaline substance, such as caustic soda (sodium hydroxide), to neutralize SOx. The washwater is then treated and recirculated, with minimal discharge. Closed-loop scrubbers are more complex and expensive but offer greater compliance flexibility in ports with stricter environmental regulations.

Hybrid Scrubbers: These systems can operate in both open and closed-loop modes, offering versatility depending on the ship’s location and local environmental regulations.

Using Alkaline Chemicals: The Case for Caustic Soda

In closed-loop and hybrid scrubber systems, alkaline chemicals are essential for neutralizing sulfur oxides. One of the most commonly used chemicals is caustic soda (sodium hydroxide). When added to the scrubber washwater, caustic soda reacts with SOx to form sodium sulfate, a non-toxic compound that can be safely disposed of.

Advantages of Using Caustic Soda

Effective Neutralization: Caustic soda is highly effective at neutralizing sulfur oxides, ensuring that exhaust gases meet the stringent sulfur limits set by IMO 2020.

Availability: Caustic soda is widely available at ports around the world, making it a convenient option for ships using scrubber systems.

Compatibility: Most scrubber system designs are compatible with it, and crews can easily store and handle it on board.

Caustic Soda Bunkering at Ports

To comply with IMO 2020, many ports now offer caustic soda bunkering services. Ships equipped with scrubbers can bunker caustic soda in various concentrations, depending on their scrubber system’s requirements. The process of caustic soda bunkering involves:

Delivery: Suppliers deliver caustic soda to ships in liquid form, typically at a concentration of 50%.

Storage: Ships store the chemical in dedicated tanks on board.

Usage: During operation, ships mix caustic soda with fresh water in the scrubber system to create an alkaline washwater solution.

Neutralization: The alkaline washwater reacts with the sulfur oxides in the exhaust gases, neutralizing them and reducing emissions.

Challenges and Considerations

While scrubber systems and caustic soda bunkering offer a viable solution for IMO 2020 compliance, there are some challenges and considerations:

Cost: Installing scrubbers can be a significant investment, and the ongoing cost of caustic soda bunkering can add to operational expenses.

Port Restrictions: Some ports have strict regulations regarding the discharge of washwater from scrubbers, particularly for open-loop systems. Ships may need to switch to closed-loop mode or use low-sulfur fuels in these areas.

Handling and Safety: Caustic soda is a highly corrosive chemical, so it requires careful handling. Workers must receive proper training and follow strict safety protocols to prevent accidents and injuries.

Conclusion

IMO 2020 represents a significant step forward in reducing the environmental impact of shipping. By mandating a global sulfur cap of 0.5% in marine fuels, the regulation aims to cut sulfur oxide emissions and improve air quality worldwide. Scrubber systems, coupled with the use of alkaline chemicals like caustic soda, provide a practical and effective means of achieving compliance while allowing ships to continue using high-sulfur fuels. As the industry navigates these new waters, careful planning and consideration of the available options will be key to successful compliance and a cleaner future for maritime transport.