Creating a Ship Energy Efficiency Management Plan (SEEMP): Sulfur Cap Regulation

Since 2005, several Emissions Control Areas (ECA) have been implemented around the world to regulate the amount of harmful emissions produced by sea-faring vessels. But ECAs aren’t the only way the International Maritime Organization has sought to limit the harmful impacts of international sea transportation.

Sulfur cap regulations and Ship Energy Efficiency Management Plants (SEEMPs) have also been instituted with the goal of reducing critical environmental pollutants.

Continue reading to learn how ECAs, SEEMPs, and sulfur cap regulations work and what the future may look like for maritime transport.

Creating a Ship Energy Efficiency Management Plan (SEEMP)

A Ship Energy Efficiency Management Plan (SEEMP) is a document that must be carried on all large marine vessels (400 gross tonnage and above) detailing the ship’s efforts and goals related to energy efficiency. While every large marine vessel is required to have an SEEMP, companies that operate several large vessels may also develop a more widespread energy management policy that encompasses all of their vessels.³¹

SEEMPs, while tailored to the specifications of each individual ship, must meet certain standards. An SEEMP can be broken down into three parts:³¹

Part I: This section of the SEEMP provides the ship’s baseline (current at the time of developing the SEEMP) energy consumption and outlines the steps that will be taken to improve efficiency. Efficiency improving domains that may be specified include:

• Speed optimization
• Weather routing
• Heat waste recovery
• Route planning
• Improved propulsion
• Automated engine management

Part II: This section of the SEEMP, applicable to internationally voyaging ships at 5,000 gross tonnage and above, describes how the ship will collect and report annual fuel consumption data to be remitted to their flag State.

Part III: This section of the SEEMP, newly implemented in 2023, applies to the same ships as Part II. It should detail the method of calculating and improving the ship’s carbon intensity.

This includes:

• Current and projected Carbon Intensity Indicator (CII)
• Self-evaluative process
• Corrective action plan, where necessary

Ships that have attained the Energy Efficiency Design Index (EEDI) and have an SEEMP on board are granted an International Energy Efficiency (IEE) certificate to be presented for inspections and audits.³¹

What Is Sulfur Cap Regulation?

Sulfur cap regulation is a global standard put into effect by the International Maritime Organization (IMO) in 2020. This regulation dictates that as of January 1, 2020, all maritime vessels worldwide have a fuel sulfur limit of .50%, or 5,000 parts per million (ppm).⁸

This is not as rigorous as the .10% restriction in Emission Control Areas, but it still represents a drastic decrease from the previous 8 years’ global sulfur cap weight of 3.50% (35,000 ppm) or the 4.50% allowable prior to 2012.¹⁵ Marine vessel owners/operators may also elect to employ an exhaust gas cleaning system (a “scrubber”) to remove sulfur oxides from the ship exhausts.²⁰

A study conducted by NASA found that the new global sulfur cap regulation coincided with a marked decrease in observable “ship tracks,” or pollution trails, compared to 17 years of satellite imagery.²¹

What Are Emissions Control Areas (ECA)?

Emissions control areas (ECAs) are areas of the sea where specific greenhouse gas (GHG) emissions from ships are more strictly regulated. Note that although there is significant overlap, ECAs differ from the Marine Protected Areas (MPAs), where human activity is restricted to protect marine habitats and ecosystems.

ECAs were established as part of the 1997 MARPOL protocol, under Annex VI, though the first regulations did not take effect until mid-2005.¹⁵

Prior to Annex VI, only pollution generated from oil, noxious bulk liquids, “harmful substances,” sewage, and garbage was regulated. With the institution of Annex VI, air pollution from ships, in the form of sulfur oxides (SOx) and nitrogen oxides (NOx), ozone-depleting substances (ODSs), particulate matter (PM), and volatile organic compounds (VOCs) came under regulatory control.

(Image: John Simmons³⁹)

Originally, Annex VI allowed the International Maritime Organization (IMO) to establish maximum levels of sulfur in fuel (and subsequent SOx emissions) and maximum allowable nitrogen oxide emissions for all maritime vessels globally.^6,23

It also permitted the creation of ECAs, where additional regulations could be implemented for strict monitoring and control, but according to the National Oceanic and Atmospheric Administration (NOAA), the original Annex VI regulations only allowed ECAs designated for SOx emissions. It wasn’t until the 2008 amendment that ECAs could be designated for NOx and PM pollution as well.²

Nowadays, an ECA that restricts only sulfur oxides may be referred to as a sulfur emissions control area (SECA), while one that regulates only nitrogen oxides is called a nitrogen emissions control area (NECA).¹¹ Most ECAs regulate both.

How Many Emissions Control Areas (ECAs) Are There and Where Are They Located?

Currently, there are four emissions control areas (ECA) established globally. The first to be established was the Baltic Sea ECA which went into force in 2005.

The North Sea ECA was adopted around that time and went into force the following year, in 2006.¹⁵

According to the NOAA, the North American ECA was adopted in 2011, a large area encompassing most of the Atlantic and Pacific coasts of the United States and Canada, including the waters around the state of Hawaii (See U.S. Emissions Control Areas).⁷ Two years after the North American ECA was adopted, the Caribbean Sea ECA entered into force, including the territory of Puerto Rico and the U.S. Virgin Islands.^2,11

What Are the Restrictions for Emissions Control Areas (ECAs)?

The restrictions for ECAs have been modified or updated several times since they were first established in the early 2000s. The current amendment requires that vessels traveling in Emissions Control Areas operate using fuel that has a sulfur content of .10% (1,000 parts per million [ppm]) or lower (mass by mass).¹¹

Alternately, according to the EPA, vessels may employ an exhaust gas cleaning system or equivalent method to remove sulfur oxides from the exhaust.²³

The NOx standards were rolled out in three tiers to accommodate the limitations of older marine vessels:^11,25

Tier 1: Standards apply to ships constructed between the years 2000 and 2010.

• Ships less than 130 rpm (rated engine speed): 17 g of NOx per kWh
• Ships between 130 and 1999 rpm: 45 RPM-0.20
• Ships greater than or equal to 2000 rpm: 9.8 g of NOx per kWh

Tier 2: Standards apply to ships constructed between the years 2011 and 2015.

• Ships less than 130 rpm (rated engine speed): 14.4 g of NOx per kWh
• Ships between 130 and 1999 rpm: 44 RPM-0.23
• Ships greater than or equal to 2000 rpm: 7.7 g of NOx per kWh

Tier 3: Standards apply to ships constructed since 2016.

• Ships less than 130 rpm (rated engine speed): 3.4 g of NOx per kWh
• Ships between 130 and 1999 rpm: 9 RPM-0.20
• Ships greater than or equal to 2000 rpm: 2.0 g of NOx per kWh

Examining NOx and SOx Emissions

The most common greenhouse gas emissions discussed in relation to the maritime transport industry are NOx and SOx emissions, but what are these problematic pollutants?

(Image: minka2507⁴¹)

NOx denotes nitrogen oxides and SOx denotes sulfur oxides. Read on to learn more about these harmful gases.

Nitrogen Oxides

According to the UCAR Center for Science Education, nitrogen oxides include the greenhouse gases: nitric oxide (NO) and nitrogen dioxide (NO₂).²⁶ These gases are extremely reactive and poisonous!

Nitric oxide (NO), not to be confused with nitrous oxide (N₂O), nitrous acid (HNO₂), or nitric acid (HNO₃), is a colorless but slightly odorous, flammable gas. It is produced during high-temperature fuel combustion, and released from the engine exhausts of gasoline and diesel-powered vehicles.

NO is also a byproduct of propane use and tobacco smoke. When released into the atmosphere, it combines with oxygen molecules to form its nitrogen dioxide (NO₂).³³

Nitrogen dioxide (NO₂) is a reddish brown gas that is the prominent feature of urban smog. It is the indicator molecule for nitrogen oxides as a whole.

NO₂ and NO can both interact with atmospheric molecules to produce acid rain, and exposure to elevated levels of atmospheric NO₂ can result in acute or chronic respiratory distress.³ The Clean Air Act (CAA) of 1970 established the National Ambient Air Quality Standard (NAAQS).

Current standards set NO₂ limits at 53 ppb (parts per billion) for the 1-year average.

Sulfur Oxides

According to the UCAR Center for Science Education, sulfur oxides are molecules made from atoms of oxygen and sulfur that are known to pollute the atmosphere and contribute to both particulate pollution and acid rain. There are several types of sulfur oxides, but the most important are sulfur dioxide (SO₂) and sulfur trioxide (SO₃).³³

Sulfur dioxide (SO₂) is considered the most dangerous of all SOx emissions, and is the indicator of SOx gases.

SO₂ is primarily produced during fossil fuel combustion, engine exhaust, and metal extraction, though small amounts are also produced naturally through volcanic activity. Inhalation can produce respiratory symptoms.⁹

The National Ambient Air Quality Standard (NAAQS) sets limits SO₂ to 75 ppb averaged over 1 hour and .5 ppm (parts per million) averaged over 3 hours (with additional stipulations).²⁴

Sulfur trioxide (SO₃) is a compound which can be either gas, liquid or solid. It is typically a colorless gas at room temperature or a white crystalline solid below room temperature.³⁴

It reacts with water to form sulfuric acid, a highly corrosive substance.³⁵

How Are Sox Emissions Being Limited?

SOx emissions are considered especially problematic by many experts due to their contribution to particulate matter (PM) pollution. There are several ways in which these dangerous emissions are being limited.

Firstly, the ECA regulations and global sulfur cap are making great strides towards the overall reduction of SOx emissions with strict guidelines for the permissible levels of sulfur in engine fuel. The development of alternative fuels and ultra low sulfur diesel (ULSD) has made these guidelines attainable.⁸

(Image: Mika Baumeister⁴²)

The use of engine exhaust cleaning systems (“scrubbers”) enables some vessels to stay below the allowable levels of SOx emissions, though it must be pointed out that the end result of using scrubbers is that the sulfur oxides are dumped into the water rather than released into the air, creating a cascade of problems for marine life.⁵

However, it is not just marine vessels that produce these harmful SOx emissions. Power plants are another big emitter of both SOx and NOx emissions.

According to the EPA, several rules and programs have been established in the U.S. with aims at reducing SOx, specifically sulfur dioxide (SO₂). These include:³²

• Clean Air Act (CAA) of 1970: Required the reduction of 10 million tons of SO₂ annually after 1980.
• Acid Rain Program (ARP): Caps the amount of SO₂ emitted by electric generating units (EGUs) in the United States to 8.95 million tons, around half the amount of 1980 levels.¹
• Clean Air Interstate Rule (CAIR): Began regulating SOx emissions generated in “upwind” states in 2010. It was replaced by CSAPR in 2015.
• Cross-State Air Pollution Rule (CSAPR): Established in 2015 to reduce the impact of “transported pollution” upon downwind states by controlling either SO₂, NOx, or both in the Eastern U.S. states. This program regulates over 2,000 EGUs in 27 states.³⁰

The annual SO₂ emissions for 2021 reported under CSAPR were 592,000 tons, 93% down from 2005. SO₂ emissions (2021) reported under ARP were 936,000 tons, 94% down from 1990, per the EPA.²⁹

How Is Marine Fuel Efficiency Measured?

Comparing air freight vs sea freight carbon footprint, two very large contributors to global GHG emissions, it becomes increasingly apparent that international governments have a lot of work to do in curbing these extreme levels of toxic emissions. The Department of Transportation publication on the decarbonization of maritime shipping reports that sea freight already accounts for 80% of international goods trade and is expected to grow significantly over the next few decades.

(Image: william william⁴³)

The U.S. DOT Maritime Administration projects that demand for marine fuel will double between 2020 and 2030.³⁷ So while changes to shipping fuels are being made, the industry continues to grow, offsetting many of the positive emissions trends.

This is why accurate measurement of marine fuel emissions and marine fuel efficiency are so important, as more efficient fuel should ideally result in lower emissions across the board. So how is marine fuel efficiency being measured and monitored?

Marine fuel efficiency measured in grams per kWh.¹⁰ As of 2023, all ships are mandated to calculate their Energy Efficiency Existing Ship Index (EEXI) and carbon intensity as a means of reducing overall carbon impact of ships.

The EEXI reflects energy efficiency improvements of a given ship compared to baseline numbers. It is required for ships weighing 400 gross tonnage (GT) and higher.

Ships are given a graded score (A-E, where A is the best).¹²

Combining the EEXI with Continuous Emission Monitoring Systems (CEMS) that constantly track the concentration of particulate matter and GHG emissions produced by marine vessels creates a more complete picture of an individual ship’s carbon impact.¹⁴

How Does Sulfur Cap Regulation Impact Marine Fuel Efficiency?

The Energy Information Administration (EIA) has examined the impact of fuel sulfur regulations on energy markets. The sulfur cap regulation has done more than simply reduce the amount of SOx emissions from marine fuel exhaust.

The shift away from residual oils (HFOs) to more refined and cleaner oils increases costs for ship operators. This has had the indirect effect of encouraging slow steaming, a more energy efficient method of sea transport.¹³

A study conducted by the EPA in 1987 found that lower sulfur fuels were also gentler on engines, reducing wear over time.¹⁷ Note, however, that this information is contested, as other sources report that decreased lubricity of low sulfur oils is hard on engines.²⁸

While low sulfur oils may have the potential to improve marine fuel efficiency, there are still several obstacles to be mounted before this is unequivocally demonstrated. The institution of the Energy Efficiency Existing Ship Index by the IMO in 2023 should provide necessary data to draw these conclusions.¹²

Recommended Boat Fuel for Large Marine Vessels

While smaller boats can typically run on gasoline, larger vessels require more power than gasoline is able to provide, which is why the biggest cargo ships and passenger ships have traditionally relied on diesel-powered engines powered by heavy fuel oils (HFOs) and intermediate fuel oils (IFOs).

The sulfur content in diesel fuels has long been an issue, with extremely high levels of sulfur oxides in HFOs and IFOs, and this problem is being recognized and actively addressed in recent years by the International Maritime Organization (IMO). Biofuels, liquefied natural gas (LNG), marine gas oil (MGO), very low sulfur fuel oil (VLSFO), low sulfur diesel (LSD) and now ultra low sulfur diesel (ULSD) are widely available as marine fuels (See NOAA “Fueling the Blue Economy”).¹⁹

Some large vessels, such as cruise ships are relying increasingly on liquefied natural gas (LNG) which has its own hidden cost: fugitive methane emissions.¹⁸ Additionally, many large vessels continue to use higher sulfur content fuels, relying on scrubbing systems to remove sulfur dioxide from the exhaust, but in turn releasing it with the ship’s waste water.

(Image: Dorian Mongel⁴⁰)

In other words, many proposed solutions carry their own weight in problems.

So what is the recommended boat fuel for large, ocean-going vessels? The Department of Energy (DOE) discusses various sustainable fuels for marine use, recognizing that international sea transport is responsible for 3% of the global carbon footprint.

Some of the best options, as outlined by the DOE, include biocrude oil, biodiesel, bio-LNG, and e-Methanol among others.³⁶ Ideally, research into the efficiency, availability, and safety of biofuels for marine use will continue as newer ships are manufactured with the capability of utilizing these options.

What Is the Carbon Footprint of Cruise Ships?

Although ships are a less mainstream form of international travel than they were in the past, ocean liners still traverse the world’s oceans, and cruise ships are an increasingly popular vacation option. The carbon footprint of cruise ships varies from vessel to vessel of course, but some sources estimate that a cruise ship generates 250 grams of CO₂e for every passenger aboard and for every kilometer traveled.^5,38

The average cruise ship with 3,000 passengers would generate 75,000 kg of CO₂e (750,000 g) for every kilometer, and if the cruise ship traveled only 80 kilometers per day, that would amount to around 6,000 metric tons (6 million kg)!²⁷

The maritime shipping industry is by far the largest route for international trade and commerce, and it is subsequently responsible for at least three percent of global greenhouse gas emissions. The industry continues to grow as the International Maritime Organization (IMO) works to control the emissions produced by large marine vessels.

Read this article to learn more about the harmful emissions produced by sea transport and the steps that are being taken to reduce the carbon footprint of this industry.

Find out how the IMO is using sulfur cap regulation, Emission Control Areas (ECAs), Ship Energy Efficiency Management Plans (SEEMP), and more to make maritime shipping a more sustainable industry.

Frequently Asked Questions About Ship Energy Efficiency Management Plan (SEEMP)