Glossary

Deutsch: Emissionskontrolle / Español: Control de emisiones / Português: Controle de emissões / Français: Contrôle des émissions / Italiano: Controllo delle emissioni

Emissions control in the maritime sector refers to the systematic regulation and reduction of pollutants released by ships into the atmosphere and water. This field has gained critical importance due to the global shipping industry's significant contribution to air pollution, greenhouse gas emissions, and environmental degradation. Effective emissions control measures are essential to comply with international regulations, mitigate climate change impacts, and protect human health and marine ecosystems.

General Description

Maritime emissions control encompasses a range of technologies, operational practices, and regulatory frameworks designed to limit the release of harmful substances from ships. The primary pollutants targeted include sulfur oxides (SO_x), nitrogen oxides (NO_x), particulate matter (PM), volatile organic compounds (VOCs), and carbon dioxide (CO₂). These emissions arise primarily from the combustion of marine fuels, such as heavy fuel oil (HFO) and marine gas oil (MGO), as well as from auxiliary engines and onboard processes.

The International Maritime Organization (IMO), a specialized agency of the United Nations, plays a central role in establishing global standards for maritime emissions control. The IMO's MARPOL Annex VI, adopted in 1997 and entered into force in 2005, sets limits on SO_x and NO_x emissions from ships and designates Emission Control Areas (ECAs) where stricter regulations apply. These areas, such as the Baltic Sea, the North Sea, and coastal regions of North America, require ships to use low-sulfur fuels or employ exhaust gas cleaning systems (scrubbers) to reduce SO_x emissions to 0.10% m/m (mass by mass). Outside ECAs, the global sulfur cap was reduced to 0.50% m/m in 2020, down from the previous limit of 3.50% m/m.

In addition to SO_x and NO_x, maritime emissions control addresses CO₂ emissions through the IMO's Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII). These measures aim to improve the energy efficiency of ships and reduce their carbon footprint. The IMO has also adopted a strategy to reduce greenhouse gas (GHG) emissions from international shipping, targeting a 50% reduction in total annual GHG emissions by 2050 compared to 2008 levels, with a vision to phase out GHG emissions entirely as soon as possible within this century.

Technological solutions for emissions control include the use of alternative fuels, such as liquefied natural gas (LNG), methanol, hydrogen, and ammonia, which produce lower emissions compared to conventional marine fuels. Exhaust gas aftertreatment systems, such as selective catalytic reduction (SCR) for NO_x reduction and scrubbers for SO_x removal, are also widely employed. Operational measures, such as slow steaming (reducing ship speed to lower fuel consumption) and optimized voyage planning, further contribute to emissions reduction.

Technical Details

Maritime emissions control relies on a combination of regulatory, technological, and operational strategies. The following sections outline key technical aspects:

Fuel Quality and Alternatives: The sulfur content of marine fuels is a critical factor in SO_x emissions. Low-sulfur fuels, such as marine gas oil (MGO) and ultra-low-sulfur fuel oil (ULSFO), comply with the IMO's sulfur cap but are often more expensive than heavy fuel oil (HFO). LNG is a promising alternative fuel, as it emits virtually no SO_x and significantly less NO_x and CO₂ compared to conventional fuels. However, LNG infrastructure and onboard storage systems require substantial investment. Other alternative fuels, such as methanol and ammonia, are being explored for their potential to achieve near-zero emissions, though their widespread adoption is still in the early stages.

Exhaust Gas Cleaning Systems (Scrubbers): Scrubbers are used to remove SO_x from exhaust gases by spraying a fine mist of seawater or freshwater mixed with an alkaline substance (e.g., sodium hydroxide) into the exhaust stream. There are three main types of scrubbers: open-loop, closed-loop, and hybrid systems. Open-loop scrubbers discharge the washwater into the sea, while closed-loop systems treat and recirculate the washwater onboard. Hybrid systems can operate in either mode. Scrubbers enable ships to continue using high-sulfur fuels while complying with emissions regulations, but their environmental impact, particularly the discharge of washwater, has raised concerns about marine pollution.

Selective Catalytic Reduction (SCR): SCR systems reduce NO_x emissions by injecting a urea-based solution (e.g., AdBlue) into the exhaust gas stream. The solution reacts with NO_x in the presence of a catalyst, converting it into nitrogen (N₂) and water (H₂O). SCR systems are highly effective, achieving NO_x reductions of up to 90%, but they require careful maintenance to ensure optimal performance and avoid ammonia slip, which can lead to secondary emissions.

Energy Efficiency Measures: The IMO's EEXI and CII regulations mandate that ships improve their energy efficiency to reduce CO₂ emissions. The EEXI sets a minimum energy efficiency standard for existing ships, while the CII rates ships based on their carbon intensity, measured in grams of CO₂ emitted per cargo-carrying capacity and nautical mile. Ships that fail to meet the required CII rating must implement corrective measures, such as engine power limitation, hull optimization, or the adoption of alternative fuels.

Norms and Standards

Maritime emissions control is governed by a framework of international, regional, and national regulations. The most significant standards include:

• MARPOL Annex VI: Adopted by the IMO, this annex sets limits on SO_x and NO_x emissions from ships and establishes ECAs. It also includes provisions for energy efficiency and GHG emissions reduction (see IMO Resolution MEPC.304(72)).
• IMO 2020 Sulfur Cap: This regulation, implemented in January 2020, reduced the global sulfur limit for marine fuels from 3.50% m/m to 0.50% m/m, with stricter limits of 0.10% m/m in ECAs.
• NO_x Technical Code: This code, adopted under MARPOL Annex VI, sets tiered limits for NO_x emissions based on the engine's rated speed and the ship's construction date. Tier III limits, which apply in ECAs, require an 80% reduction in NO_x emissions compared to Tier I levels.
• EU MRV Regulation: The European Union's Monitoring, Reporting, and Verification (MRV) regulation requires ships calling at EU ports to monitor and report their CO₂ emissions and energy efficiency data. This regulation complements the IMO's CII and EEXI measures (see Regulation (EU) 2015/757).

Application Area

• Commercial Shipping: Emissions control measures are primarily applied to commercial vessels, including container ships, bulk carriers, tankers, and general cargo ships. These ships are subject to strict regulatory requirements due to their significant contribution to global maritime emissions.
• Passenger Ships: Cruise ships and ferries are also required to comply with emissions regulations, particularly in ECAs. Many passenger ships have adopted LNG as a fuel or installed scrubbers to meet SO_x limits, while SCR systems are used to reduce NO_x emissions.
• Offshore and Specialized Vessels: Offshore support vessels, dredgers, and other specialized ships must also adhere to emissions control regulations. These vessels often operate in sensitive marine environments, making emissions reduction a priority.
• Ports and Terminals: Ports play a critical role in enforcing emissions control measures, such as providing shore power (cold ironing) to reduce emissions from ships at berth. Many ports have implemented incentives for ships that use low-sulfur fuels or alternative energy sources.

Well Known Examples

• Maersk's Methanol-Powered Vessels: Maersk, one of the world's largest shipping companies, has ordered a series of methanol-powered container ships. These vessels are designed to operate on green methanol, a carbon-neutral fuel produced from renewable sources, and are expected to reduce CO₂ emissions by up to 100% compared to conventional fuels.
• Carnival Corporation's LNG-Powered Cruise Ships: Carnival Corporation has introduced several LNG-powered cruise ships, including the AIDAnova and Costa Smeralda. These ships emit virtually no SO_x and significantly less NO_x and CO₂ than conventional cruise ships, making them compliant with the strictest emissions regulations.
• Scrubber Installations on Tankers: Many tanker operators, such as Frontline and Euronav, have installed scrubbers on their vessels to comply with the IMO 2020 sulfur cap. These systems allow the ships to continue using high-sulfur fuels while meeting emissions limits, though the environmental impact of washwater discharge remains a topic of debate.
• Shore Power in the Port of Los Angeles: The Port of Los Angeles has implemented shore power infrastructure to allow ships to plug into the electrical grid while at berth, eliminating emissions from auxiliary engines. This initiative has significantly reduced air pollution in the surrounding community.

Risks and Challenges

• Compliance Costs: The implementation of emissions control measures, such as scrubbers, SCR systems, or alternative fuels, requires significant investment. Smaller shipping companies may struggle to afford these technologies, leading to potential market distortions or non-compliance.
• Fuel Availability and Infrastructure: The transition to low-sulfur fuels and alternative fuels, such as LNG or methanol, depends on the availability of these fuels at ports worldwide. Insufficient infrastructure can hinder the adoption of cleaner fuels, particularly in developing regions.
• Environmental Trade-offs: Some emissions control technologies, such as open-loop scrubbers, may reduce air pollution but introduce new environmental risks, such as the discharge of acidic washwater into the sea. The long-term impact of these discharges on marine ecosystems is not yet fully understood.
• Regulatory Complexity: The maritime industry is subject to a patchwork of international, regional, and national regulations, which can create confusion and compliance challenges. Harmonizing these regulations is essential to ensure a level playing field for all stakeholders.
• Operational Disruptions: The adoption of new technologies or fuels may require modifications to ship operations, such as increased maintenance or changes in voyage planning. These disruptions can affect the efficiency and profitability of shipping operations.
• GHG Emissions Reduction: While SO_x and NO_x emissions have been effectively regulated, reducing CO₂ and other GHG emissions remains a significant challenge. The maritime industry must accelerate the development and adoption of zero-carbon fuels and technologies to meet the IMO's 2050 GHG reduction targets.

Similar Terms

• Air Pollution Control: A broader term encompassing all measures to reduce air pollution from various sources, including industrial facilities, vehicles, and ships. Maritime emissions control is a subset of air pollution control focused specifically on the shipping industry.
• Exhaust Gas Treatment: Refers to technologies and processes used to clean exhaust gases from engines, including scrubbers, SCR systems, and particulate filters. This term is often used interchangeably with emissions control but is more specific to the technical aspects of reducing pollutants.
• Green Shipping: A holistic approach to reducing the environmental impact of shipping, including emissions control, energy efficiency, and sustainable operational practices. Green shipping encompasses emissions control but also addresses broader sustainability goals, such as waste management and biodiversity protection.
• Decarbonization: The process of reducing or eliminating carbon emissions from a sector or activity. In the maritime context, decarbonization refers to the transition to zero-carbon fuels and technologies to achieve the IMO's GHG reduction targets.

Summary

Maritime emissions control is a critical component of global efforts to reduce air pollution and mitigate climate change. Through a combination of regulatory frameworks, technological innovations, and operational measures, the shipping industry is working to limit the release of harmful pollutants such as SO_x, NO_x, and CO₂. Key strategies include the use of low-sulfur fuels, exhaust gas cleaning systems, alternative fuels, and energy efficiency improvements. While significant progress has been made, challenges such as compliance costs, fuel availability, and environmental trade-offs remain. The ongoing development of zero-carbon fuels and technologies will be essential to achieving the IMO's long-term GHG reduction goals and ensuring a sustainable future for the maritime sector.

--