Sulphur 2020 – cutting sulphur oxide emissions

August 21, 2020 IMO

The main type of “bunker” oil for ships is heavy fuel oil, derived as a residue from crude oil distillation. Crude oil contains sulphur which, following combustion in the engine, ends up in ship emissions. Sulphur oxides (SOx) are known to be harmful to human health, causing respiratory symptoms and lung disease. In the atmosphere, SOx can lead to acid rain, which can harm crops, forests and aquatic species, and contributes to the acidification of the oceans.

Limiting SOemissions from ships will improve air quality and protects the environment.

IMO regulations to reduce sulphur oxides (SOx) emissions from ships first came into force in 2005, under Annex VI of the International Convention for the Prevention of Pollution from Ships (known as the MARPOL Convention). Since then, the limits on sulphur oxides have been progressively tightened.

From 1 January 2020, the limit for sulphur in fuel oil used on board ships operating outside designated emission control areas is reduced to 0.50% m/m (mass by mass). This will significantly reduce the amount of sulphur oxides emanating from ships and should have major health and environmental benefits for the world, particularly for populations living close to ports and coasts.

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

Watch the video: IMO 2020 – cleaner shipping for cleaner air (1.27 minutes)

IMO 2020 – five key changes


Limiting SOx emissions from ships will have a very positive impact on human health: how does that work?

Simply put, limiting sulphur oxides emissions from ships reduces air pollution and results in a cleaner environment. Reducing SOx also reduces particulate matter, tiny harmful particles which form when fuel is burnt.

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.

SOx graphic.JPG sox 2.JPG

So a reduction in the limit for sulphur in fuel oil used on board ships will have tangible health benefits, particularly for populations living close to ports and major shipping routes.

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

Why are ships already less harmful than other forms of transport?

​Ships do emit pollutants and other harmful emissions. But they also transport large quantities of vital goods across the world’s oceans – and seaborne trade continues to increase. In 2016, ships carried more than 10 billion tons of trade for the first time, according to UNCTAD.

So ships have always been the most sustainable way to transport commodities and goods. And ships increasingly becoming even more energy efficient. IMO regulations on energy efficiency support the demand for ever greener and cleaner shipping. A ship which is more energy efficient burns less fuel so emits less air pollution.

It has sometimes been quoted that just a few ships (all using fuel oil with maximum permitted sulphur content) emit as much harmful air pollutants as all the cars in the world (if the cars were all using the cleanest fuel available).

Not only is this the very worst case scenario, but this does not take into account the amount of cargo that is being carried by those ships and the relative efficiency. It is important to consider the amount of cargo carried and 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.

It is also relevant to remember that shipping responds to the demands of world trade. As world trade increases, more ship capacity will be needed.

Do small ships have to comply with the sulphur limit from 2020?

​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 have an International Air Pollution Prevention Certificate, issued by the ship’s flag State. But all sizes of ships will need to use fuel oil that meets the 0.50% limit from 1 January 2020.

Some smaller ships may already be using fuel oil that meets the limit, such as a marine distillate suitable for their engines. (Small ships operating in the already-designated emission control areas will be using fuel oil that meets the 0.10% limit in those emission control areas.)

How can ships carry so much cargo so efficiently?

Ships are the largest machines on the planet and the world’s largest diesel engines can be found on cargo ships. These engines can be as tall as a four-storey house, and as wide as three London buses. The largest marine diesel engines have more than 100,000 horsepower (in comparison, a mid-sized car may have up to 300 horsepower). But the largest container ships can carry more than 20,000 containers and the biggest bulk carriers can carry more than 300,000 tons of commodities, like iron ore.
So powerful engines are needed to propel a ship through the sea. And it is important to consider how much energy is used to carry each ton of cargo per kilometre.  When you look at the relative energy efficiency of different modes of transport, ships are by far the most energy efficient.
Ships can reduce air pollutants by being even more energy efficient, so they burn less fuel and therefore their emissions are lower.

Does the sulphur limit apply only 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.

What was the regulation on SOx in ships emissions and by how much has it improved?

​We have seen a substantial cut: to 0.50% m/m (mass by mass) from 3.50% m/m.

For ships operating outside designated emission control areas the previous limit for sulphur content of ships’ fuel oil was 3.50% m/m.

The limit is now 0.50% m/m, since1 January 2020.

There is an even stricter limit of 0.10% m/m in effect in emission control areas (ECAS) which have been established by IMO. This 0.10% m/m limit applies in the four established ECAS: 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).

(Countries bordering the Mediterranean Sea are currently considering the possibility of applying to designate the Mediterranean Sea or parts thereof as an ECA. Read more here.)

Fuel oil providers supply fuel oil which meets the 0.10% m/m limit (such as marine distillate and ultra low sulphur fuel oil blends) to ships which require this fuel to trade in the ECAs.

What must ships do to meet the new IMO regulations?

The IMO MARPOL regulations limit the sulphur content in fuel oil. So ships need to use fuel oil which is inherently low enough in sulphur, 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. So 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.

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

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, some flag States have accepted and approved scrubbers – otherwise known as “Exhaust Gas Cleaning Systems”, 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, where 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. Open-loop scrubbers return washwater to the sea. The washwater must meet strict criteria, so that discharge washwater should have 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 in 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 75 for adoption.

The Marine Environment Protection committee (MEPC) at its session in May 2019 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.

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.

Where can I find out which ships have EGCS 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. You can view the database here.

Consistent compliance with the 0.50% limit is vital. What is IMO doing about that?

​Monitoring, compliance and enforcement of the new limit falls to 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).

IMO has 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.

For example, developing guidance, developing standardised formats for reporting fuel oil non availability if a ship cannot obtain compliant fuel oil and considering verification and control issues.

The MEPC has issued guidance on ship implementation planning, part of a set of guidelines being developed by IMO for consistent implementation of the MARPOL regulation coming into effect from 1 January 2020.

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.

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

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.

How have ship operators and owners planned ahead for the 0.50% sulphur 2020 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.

See also outcome of MEPC 74 here.  A joint industry group has also developed its own guidance, which IMO has shared with its Member States and international organizations in a circular letter. You can view the Joint Industry Guidance on the Supply and Use of 0.50% Sulphur Marine Fuel here.

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 provide 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.”

So, carriage of fuel oil for use on board ships has been prohibited since 1 March 2020  – 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.

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

Is a FONAR a waiver?


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

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 have an equivalent means to meet 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. So those fuel oil blends suitable for ECAS,  also meet the 0.50% m/m limit in 2020.

A study commissioned by IMO into the “Assessment of fuel oil availability” concluded that the refinery sector has the capability to supply sufficient quantities of marine fuels with a sulphur content of 0.50% m/m or less and with a sulphur content of 0.10% m/m or less to meet demand for these products, while also meeting demand for non-marine fuels. The full study can be downloaded here.

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.

IMO has discussed how to identify any potential safety issues related to new blends of fuel oil as it is recognized that if these fuels are not managed appropriately, there could be compatibility and stability issues. 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.

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.



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