IMO 2020 – cutting sulphur oxide emissions

On 1 January 2020, a new limit on the sulphur content in the fuel oil used on board ships came into force, marking a significant milestone to improve air quality, preserve the environment and protect human health.

Known as “IMO 2020”, the rule limits the sulphur in the fuel oil used on board ships operating outside designated emission control areas to 0.50% m/m (mass by mass) - a significant reduction from the previous limit of 3.5%. Within specific designated emission control areas the limits were already stricter (0.10%). This new limit was made compulsory following an amendment to Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL).

The resulting reduction in sulphur oxide (SOx) emissions from ships is having major health and environmental benefits for the world, particularly for populations living close to ports and coasts. Sulphur oxides are harmful to human health, causing respiratory, cardiovascular and lung disease. Once released in the atmosphere, SOx  can lead to acid rain, which impacts crops, forests and aquatic species and contributes to the acidification of the oceans.

Before the entry into force of the new limit, most ships were using heavy fuel oil. Derived as a residue from crude oil distillation, heavy fuel oil had a much higher sulphur content which, following combustion in the engine, ended up in ships’ emissions. Now, the vast majority of ships are using very low sulphur fuel oil (VLSFO) to comply with the new limit, and no safety issues have to date been reported to IMO. 

Below you will find answers to some of the frequently asked questions about the sulphur limit.

IMO 2020 - five key changes

1. How significant is the reduction in sulphur oxides emissions? 

We have seen a substantial cut in the limit for sulphur content of fuel oil for ships operated outside designated emission control areas: from 3.50% m/m (mass by mass) to 0.50% m/m. 

There is an even stricter limit of 0.10% m/m in effect in emission control areas (ECAS) which have been established by IMO. The four ECAS are: the Baltic Sea area; the North Sea area; the North American area (covering designated coastal areas off the United States and Canada); and the United States Caribbean Sea area (around Puerto Rico and the United States Virgin Islands). 

In 2022, MEPC 79 adopted amendments to designate the entire Mediterranean Sea as an emission control area for Sulphur Oxides (SOx-ECA) and particulate matter, meaning that ships will have to comply with more stringent controls on sulphur oxide emissions. The amendments to MARPOL Annex VI are expected to enter into force on 1 May 2024, with the new sulphur limit taking effect from 1 May 2025. 

In 2024, MEPC 82 adopted amendments to MARPOL Annex VI for the designation of the Canadian Arctic Waters and the Norwegian Sea as emission control areas for Nitrogen Oxides (NOx), Sulphur Oxides (SOx) and particulate matter. These amendments will enter into force on 1 March 2026, taking effect from 1 March 2027.

2. What are the impacts of the new limit on human health? 

Simply put, limiting sulphur oxides emissions from ships reduces air pollution as well as particulate matter, which are tiny harmful particles which form when fuel is burnt. 

The new limit was forecast to lead to a 77% drop in overall sulphur oxide emissions from ships – a reduction equivalent to 8.5 million metric tonnes of SOx. Sulphur oxides are linked to asthma, pulmonary, cardiovascular and respiratory diseases. Reducing these harmful emissions will therefore improve the health of populations, especially those living near ports and coasts, and help prevent premature deaths.

A  study on the human health impacts of SOx emissions from ships, submitted to IMO’s Marine Environment Protection Committee (MEPC) in 2016 by Finland, estimated that by not reducing the SOx limit for ships from 2020, the air pollution from ships would contribute to more than 570,000 additional premature deaths worldwide between 2020-2025. 

IMO 2020 - A Breath of Fresh Air - download the infographic (PDF) by clicking on the image.

3. What must ships do to comply with the new IMO regulations? 

The IMO MARPOL regulations limit the sulphur content in fuel oil. This means ships must use fuel oil which is inherently low enough in sulphur, or install an appropriate exhaust "alternative” method, in order to meet IMO requirements. 

Refineries may blend fuel oil with a high (non-compliant) sulphur content with fuel oil with a sulphur content lower than the required sulphur content to achieve a compliant fuel oil. Additives may be added to enhance other properties, such as lubricity. 

Some ships limit the air pollutants by installing exhaust gas cleaning systems, also known as “scrubbers”. This is accepted by flag States as an alternative means to meet the sulphur limit requirement. These scrubbers are designed to remove sulphur oxides from the ship’s engine and boiler exhaust gases. A ship fitted with a scrubber can use heavy fuel oil, since the sulphur oxides emissions will be reduced to a level equivalent to the required fuel oil sulphur limit. By mid-July 2020, some 2,359 systems had formally been reported to IMO as an approved “equivalent method” by Administrations (flag States).  

Ships can have engines which use alternative fuels, which may contain low or zero sulphur, for example liquefied natural gas or biofuels. 

4. What is IMO doing to ensure compliance with the 0.50% limit? 

Monitoring compliance and enforcing the new limit falls under the remit of Governments and national authorities of Member States that are Parties to MARPOL Annex VI. Flag States (the State of registry of a ship) and port States have rights and responsibilities to enforce compliance. IMO has adopted 2019 Guidelines for port State control under MARPOL Annex VI Chapter 3 (download  here). 

Ahead of the entry into force of the new limit, on 1 January 2020, IMO worked with Member States as well as industry (including the shipping industry and the bunker supply and refining industry) to identify and mitigate transitional issues so that ships may meet the new requirement. 

This work included developing guidance and standardised forms for reporting fuel oil non availability if a ship cannot obtain compliant fuel oil, as well as considering verification and control issues. 

In October 2018, IMO's Marine Environment Protection Committee (MEPC) adopted a MARPOL amendment to prohibit the carriage of non-compliant fuel oil for combustion purposes for propulsion or operation on board a ship - unless the ship has an exhaust gas cleaning system ("scrubber") fitted. The amendment entered into force in March 2020 and is intended as an additional measure to support consistent implementation and compliance and provide a means for effective enforcement by States, particularly port State control.  

A set of guidelines for the consistent implementation of the MARPOL regulation was developed by IMO and issued by the MEPC. 

5. Are new fuels being used to meet the 2020 limit? 

Yes, new blends of fuel oil for ships have been developed. For example, a gas oil, with a very low sulphur content can be blended with heavy fuel oil to lower its sulphur content.  

Ships can also choose to switch to a different fuel altogether. Or they may continue to purchase heavy fuel oil, but install ”scrubbers” to reduce the output of SOx in order to levels that ensure compliance with the requirement. 

Of course, some ships were already using low sulphur fuel oil to meet the even more stringent limits of 0.10% m/m when trading in the established emission control areas (ECAS). So those fuel oil blends suitable for ECAS also meet the 0.50% m/m limit.  

6. Are low sulphur blend fuel oils safe? Can new low sulphur fuels cause problems for a ship’s engine? 

All fuel oil for combustion purposes on a ship must meet required fuel oil quality standards, as set out in IMO MARPOL Annex VI (regulation 18.3). For example, the fuel oil must not include any added substance or chemical waste that jeopardizes the safety of ships or adversely affects the performance of the machinery. 

Through 2020, and into 2021 to date, IMO has not received any reports of safety issues linked to VLSFO.  

Nonetheless, during 2020, an IMO correspondence group was established to consider fuel oil safety issues in general and consider the need for further mandatory requirements to ensure fuel oil supplied meets the required standards and required quality. The report of the group (MSC 102/6) is available on IMODOCS). The report will be discussed at the next IMO Maritime Safety Committee (MSC) session, MSC 103 in May 2021.

Prior to that meeting, the Sub-Committee on Prevention of Pollution from Ships (PPR 8, schedule to meet in remote session 22-26 March 2021) will further consider VLSFO fuel quality issues, including possible effects on black carbon emissions.

Guidance on best practice for fuel oil suppliers has also been issued. The Guidance is intended to assist fuel oil purchasers and users in assuring the quality of fuel oil delivered to and used on board ships, with respect to both compliance with the MARPOL requirements and the safe and efficient operation of the ship. The guidance pertains to aspects of the fuel oil purchase up to the loading of the purchased fuel oil on board.

Regulations in the International Convention for the Safety of Life at Sea (SOLAS) cover issues such as flashpoint (SOLAS regulation II- 2/4.2.1).

An International Standardization Organization (ISO) standard (ISO 8217) specifies the requirements for fuels for use in marine diesel engines and boilers.

ISO has issued a further standard: ISO/PAS 23263:2019 Petroleum products - Fuels (class F) - Considerations for fuel suppliers and users regarding marine fuel quality in view of the implementation of maximum 0.50 % sulphur in 2020. It addresses quality considerations that apply to marine fuels in view of the implementation of the sulphur 2020 limit and the range of marine fuels that will be placed on the market in response. It defines general requirements that apply to all 0.50% sulphur fuels and confirms the applicability of ISO 8217 for those fuels. It gives technical considerations which might apply to particular fuels for the following characteristics: kinematic viscosity; cold flow properties; stability; ignition characteristics; and catalyst fines. Additionally, it provides considerations on the compatibility between fuels and gives additional information on ISO 8217.

7. What did IMO do to help shipowners comply with the 0.50% sulphur limit?

To assist ship operators and owners to plan ahead for the 0.50% sulphur 2020 limit, the MEPC approved various guidance and guidelines. 

The 2019 Guidelines on consistent implementation of 0.50% sulphur limit under MARPOL Annex VI  adopted by resolution MEPC.320(74) are available here. 

These comprehensive guidelines include a template for a "Fuel Oil Non-Availability Report (FONAR)" set out in Appendix 1 and a "Technical review of identified possible potential safety implications associated with the use of 2020 compliant fuels" set out in appendix 2.

Guidance on ship implementation planning  (issued November 2018) can be downloaded  here.

The ship implementation planning guidance includes sections on: risk assessment and mitigation plan (impact of new fuels); fuel oil system modifications and tank cleaning (if needed); fuel oil capacity and segregation capability; procurement of compliant fuel; fuel oil changeover plan (conventional residual fuel oils to 0.50% sulphur compliant fuel oil); and documentation and reporting.

Guidance on best practice for fuel oil suppliers was also issued. The Guidance is intended to assist fuel oil purchasers and users in assuring the quality of fuel oil delivered to and used on board ships, with respect to both compliance with the MARPOL requirements and the safe and efficient operation of the ship. The guidance pertains to aspects of the fuel oil purchase up to the loading of the purchased fuel oil on board.

A full list of guidance and guidelines can be found on the  infographic. 

8. What is the "carriage ban" and how does it work? 

The carriage ban refers to the MARPOL amendment adopted in 2018 to prohibit the carriage of non-compliant fuel oil for combustion purposes for propulsion or operation on board a ship - unless the ship has an exhaust gas cleaning system ("scrubber") fitted. 

The amendment is intended as an additional measure to support consistent implementation and compliance and provides a means for effective enforcement by States, particularly port State control.  

The specific provision requires that fuel oil used on board ships shall not exceed 0.50% sulphur limit. The amended provision to prohibit the carriage of non-compliant fuel oil reads as follows: "The sulphur content of fuel oil used or carried for use on board a ship shall not exceed 0.50% m/m.” 

This MARPOL amendment entered into force on 1 March 2020. The full text of the MARPOL amendment can be downloaded here. 

As a result, carriage of fuel oil for use on board ships is now prohibited if the sulphur content exceeds 0.50%. 

Regulation 2.9 of MARPOL Annex VI provides the definition for 'fuel oil' - "Fuel oil means any fuel delivered to and intended for combustion purposes for propulsion or operation on board a ship, including gas, distillate and residual fuels." 

The provision does not apply to fuel oil being carried as cargo.  

9. Do small ships have to comply with the sulphur limit? 

Yes, the MARPOL regulations apply to all ships. Only larger ships of 400 gross tonnage and above engaged in voyages to ports or offshore terminals under the jurisdiction of other Parties have to obtain an International Air Pollution Prevention Certificate, issued by the ship’s flag State. But all sizes of ships must use fuel oil that meets the 0.50% limit since 1 January 2020. 

Some smaller ships were already using fuel oil that meets the limit, such as a marine distillate suitable for their engines. 

10. Does the sulphur limit only apply to ships on international voyages? 

The sulphur oxides regulation (MARPOL Annex VI, regulation 14) applies to all ships, whether they are on international voyages, between two or more countries; or domestic voyages, solely within the waters of a Party to the MARPOL Annex. 

11. Are all types of scrubbers allowed under IMO rules? 

Yes, so long as they achieve the same level of emissions reduction. 

Regulation 4 of MARPOL Annex VI allows for Administrations (flag States) to approve "equivalents" - any "fitting, material, appliance or apparatus to be fitted in a ship or other procedures, alternative fuel oils, or compliance methods used as an alternative to that required" - that enables the same standards of emission control to be met.

For reduction of sulphur oxide emissions, flag States have accepted and approved scrubbers - otherwise known as "Exhaust Gas Cleaning Systems" (EGCS) as meeting the requirements for sulphur oxide reduction. 

There is an important requirement in the same regulation on Equivalents, which says that in paragraph 4 "The Administration of a Party that allows the use of an equivalent …. shall endeavour not to impair or damage its environment, human health, property, or resources, or those of other States". 

IMO has adopted strict criteria for discharge of washwater from EGCS. Any residues generated by the EGC unit, usually in a closed-loop configuration, should be delivered ashore to adequate reception facilities. Such residues should not be discharged to the sea or incinerated on board.

Open-loop scrubbers add water to the exhaust gas which turns sulphur oxides (SOx) to sulphates/sulphuric acid, before returning washwater to the sea. The washwater must meet strict criteria, including a pH of no less than 6.5. There are also strict limits on discharge of PAHs (Polycyclic Aromatic Hydrocarbons) and nitrates. 

The guidelines, with the washwater criteria, (last revised and adopted in 2015), have been under review by the IMO Sub-Committee on Pollution Prevention and Response (PPR). The Sub-Committee finalized its work on revising the 2015 Guidelines in February 2020 and they will be submitted to MEPC 76 for adoption.

In May 2019, the Marine Environment Protection committee (MEPC)  asked the PPR Sub-Committee to look into "Evaluation and harmonization of rules and guidance on the discharge of liquid effluents from EGCS into waters, including conditions and areas". 

To assist the discussions, a report from a task team established by the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) was submitted. This report contains the conclusions of the task team in relation to the available evidence on the environmental effects of discharge water from EGCS, as well as recommendations on the data, tools and approaches that could be used as basis for conducting a risk assessment of the possible effects of discharges. 

Following discussion in a working group, the PPR Sub-Committee (February 2020) agreed to recommend to the MEPC that its future work should look at evaluation and harmonization of rules and guidance on the discharge of discharge water from EGCS into the aquatic environment, including conditions and areas. 

The scope of the work should include: 

• risk assessment (development of risk assessment guidelines for the evaluation of possible harmful effects of the discharge water from EGCS, taking into account existing methods and mathematical models); 
• impact assessment (to consider developing impact assessment guidelines); 
• delivery of EGCS residues (developing guidance on delivery of EGCS residues to port reception facilities, regarding volumes and composition of residues); 
• regulatory matters (including assessing state of technology for EGCS discharge water treatment and control, identifying possible regulatory measures, developing a database of local/regional restrictions/conditions on the discharge water from EGCS; 
• database of substances (establishing a database of substances identified in EGCS discharge water, covering physico-chemical data, ecotoxicological data and toxicological data, leading to relevant endpoints for risk assessment purposes).

The MEPC was invited to approve the planned scope of work and to consider involving GESAMP for scientific advice. 

In 2021, MEPC 77 adopted the updated Guidelines for exhaust gas cleaning systems (resolution MEPC.340(77)), which specify the criteria for the testing, survey, certification and verification of EGCS as well as discharge water quality criteria.

In April 2022, IMO's Sub-Committee on Prevention of Pollution (PPR 9) considered issues related to discharge from exhaust gas cleaning systems (EGCS). Subsequently, in June 2022, MEPC 78 approved:

12. Why have some ports already banned discharge of washwater? 

Some IMO Member States have taken a precautionary approach towards washwater discharge and have taken measures to limit or restrict discharge of washwater in their local ports and coastlines.

States have the right under  UNCLOS  to adopt their own laws and measures to reduce and control pollution of the marine environment from ships in their ports, internal waters and territorial seas. 

13. Where can I find out which ships have scrubbers or are using other equivalents? 

The IMO GISIS module on MARPOL annex VI includes a list of notifications received from IMO Member States in relation to Regulation 4.2 Equivalent compliance method. Please find the database  here.

14. Is a FONAR a waiver? 

 
No. 

The  2019 Guidelines on consistent implementation of 0.50% sulphur limit under MARPOL Annex VI  adopted by resolution MEPC.320(74) here clearly state (in APPENDIX 1):

• "3.1 A fuel oil non-availability report is not an exemption. According to regulation 18.2 of MARPOL Annex VI, it is the responsibility of the Party of the destination port, through its competent authority, to scrutinize the information provided and take action, as appropriate."

• "3.2 In the case of insufficiently supported and/or repeated claims of non-availability, the Party may require additional documentation and substantiation of fuel oil non-availability claims. The ship/operator may also be subject to more extensive inspections or examinations while in port."

• "3.3 Ships/operators are expected to take into account logistical conditions and/or terminal/port policies when planning bunkering, including but not limited to having to change berth or anchor within a port or terminal in order to obtain compliant fuel." 

• "3.4 Ships/operators are expected to prepare as far as reasonably practicable to be able to operate on compliant fuel oils. This could include, but is not limited to, fuel oils with different viscosity and different sulphur content not exceeding regulatory requirements (requiring different lube oils) as well as requiring heating and/or other treatment on board." 
  

How does shipping compare to other forms of transport in terms of air pollution? 

Ships do emit pollutants and other harmful emissions, but they have always been and remain the most sustainable way to transport commodities and goods.

When considering the emissions per tonne of cargo carried, per kilometre travelled, studies have shown that ships are by far the most energy-efficient form of transportation, compared with other modes such as aviation, road trucks and even railways.

Ships transport large quantities of vital goods across the world’s oceans – and seaborne trade continues to increase. In 2019, seaborne trade by volume reached 11.08 billion tons. In 2020,  during the COVID-19 pandemic, a fall of 4.1% was forecast, according to  UNCTAD - but shipping continued to move huge volumes of trade.

Meanwhile, ships are increasingly becoming even more energy efficient. IMO regulations on energy efficiency support the transition to ever greener and cleaner shipping. A ship which is more energy efficient burns less fuel so emits less air pollution. Click here to read more on the IMO Strategy on the reduction of GHG emissions from ships. 

Find out more

• Index of MEPC Resolutions and Guidelines related to MARPOL Annex VI - click here.

• For more detailed information on the sulphur 2020 limit and its implementation, please download the IMO Sulphur 2020 FAQ.
  

• IMO has published a compilation of all related guidance, best practices and so on, as a single IMO publication (hard copy and electronic formats). (IMO 2020 Consistent Implementation of MARPOL Annex VI, 2019 Edition I666E, Price £22, ISBN 978-92-801-17189) .

• IMO hosted (October 2019) a Symposium on IMO 2020 and Alternative Fuels to raise awareness and to take stock of the preparations for the IMO 2020 rule, and to discuss the role of alternative fuels in the decarbonization of international shipping. Presentations can be downloaded here.
  

• "Assessment of fuel oil availability" (2016) - The full study can be downloaded  here. 

• IMO 2020 ICS Guidance on compliance for shipping companies and crews
  

• Joint Industry Guidance on supply and use of 0.50% sulphur marine fuel

• INTERTANKO 2020 Practical Guide

• A Videotel training package is free to download and includes video information on the regulations and how to comply.
  

• CIMAC Guideline: Marine fuel handling in connection to stability and compatibility", issued by the International Council of Combustion Engines (CIMAC).