IMO 2020 Sulphur Limit and How It Applies
The legal basis of the rule that cut the global sulphur limit in ship fuel to 0.50%, how it applies by region, how it is enforced and its effect on climate.
IMO 2020 is the regulation that cut the global cap on sulphur in ship fuel from 3.50% to 0.50% by mass on 1 January 2020. It sits in Regulation 14 of MARPOL Annex VI and applies to all ships, on international and domestic voyages alike. Emission control areas (ECAs) keep a stricter 0.10% limit. To comply, a ship either uses compliant fuel or applies an approved equivalent method, usually a scrubber.
Legal Basis and History of the Limits
MARPOL Annex VI governs air pollution from ships. It was adopted in 1997 and entered into force on 19 May 2005. The stepped timetable in use today came from the 2008 revision, which left the start of the 0.50% global limit open as either 2020 or 2025, subject to a review of fuel availability. At its 70th session in October 2016, IMO's Marine Environment Protection Committee (MEPC) fixed the date at 1 January 2020 through resolution MEPC.280(70).[1][2]
| Date | Global limit (by mass) | ECA limit (by mass) |
|---|---|---|
| Before 1 July 2010 | 4.50% | 1.50% |
| 1 July 2010 | 4.50% | 1.00% |
| 1 January 2012 | 3.50% | 1.00% |
| 1 January 2015 | 3.50% | 0.10% |
| 1 January 2020 | 0.50% | 0.10% |
Source: IMO, MARPOL Annex VI Regulation 14.[2]
Why Sulphur Was Limited
Crude oil contains sulphur naturally, and much of it ends up in residual fuel at the refinery. When the fuel burns, sulphur turns into sulphur oxides (SOx). SOx harm the respiratory system, contribute to fine particle formation and are one of the causes of acid rain. Coastal areas and port cities on busy shipping routes feel these effects directly.
IMO projected that the new limit would cut SOx from ships by about 77%, or 8.5 million tonnes a year. A study submitted to MEPC by Finland in 2016 calculated that without the lower limit there would be more than 570,000 additional premature deaths worldwide between 2020 and 2025.[1] Sofiev and colleagues, writing in Nature Communications, estimated that low-sulphur fuels would reduce ship-related premature deaths by 34% and childhood asthma cases by 54%. The same study found that ships would still account for about 250,000 deaths and 6.4 million childhood asthma cases a year, even on these fuels.[3]
Limits by Region
The global limit applies in all waters outside ECAs. Inside a designated ECA the limit is 0.10%. These areas have grown considerably in recent years.
| Area | Sulphur limit | Limit applies from |
|---|---|---|
| All waters outside ECAs | 0.50% | 1 January 2020 |
| Baltic Sea, North Sea | 0.10% | 1 January 2015 |
| North America, US Caribbean | 0.10% | 1 January 2015 |
| Mediterranean | 0.10% | 1 May 2025 |
| Canadian Arctic waters, Norwegian Sea | 0.10% | 1 March 2027 |
| North-East Atlantic | 0.10% | 1 September 2028 |
Source: IMO; MEPC.361(79); decisions of MEPC 82 and MEPC 84.[1][4][5]
National and regional rules apply alongside these. EU Directive 2016/802 sets 0.10% for ships at berth or at anchor in Union ports. Ships due to stay under two hours according to published timetables, and ships that shut down their engines and use shore power, are outside this rule.[6]
The Mediterranean ECA ends in the Strait of Çanakkale, so the Sea of Marmara and the Bosphorus come under the 0.50% global limit.[4] Türkiye's national rule applies separately. Article 7 of its regulation on reducing the sulphur content of certain fuels bars fuel above 0.1% sulphur on ships at berth.[7] A letter from the Directorate General of Maritime Affairs dated 31 January 2020 also applies this limit to ships moored or anchored for more than two hours in inland waters and harbour master areas.[8]
Ways of Complying
Most ships meet the limit with compliant fuel: VLSFO outside ECAs and MGO or ULSFO inside them. The differences are compared in the guide to types of marine fuel.
The second route is the equivalent methods allowed by Regulation 4 of MARPOL Annex VI. The main one is the scrubber, which removes sulphur from the exhaust gas. With a system approved by the flag state, a ship can keep burning HSFO. Local restrictions on washwater discharge apply, however. Türkiye's Ministry of Environment and Urbanisation banned scrubber washwater discharge in its territorial waters in April 2021, so a ship with an open-loop system switches to compliant fuel in Turkish waters.[9]
The third route is fuels with almost no sulphur by nature, such as LNG on LNG propulsion ships, LPG and methanol.
Fuel Changeover and Record Keeping
A ship arriving at an ECA on a different fuel must complete the changeover before it enters. Regulation 14 requires a written procedure for this. After the changeover, the quantity of compliant fuel in the tanks and the date, time and position of the operation are recorded.[2] The time needed to flush the fuel line sets the starting point. A late start can leave high-sulphur fuel in the line when the ship crosses the boundary.
The Carriage Ban
Under the amendment adopted by resolution MEPC.305(73), in force since 1 March 2020, fuel used or carried for use on board may not exceed 0.50% sulphur. The rule was introduced to make enforcement easier, since non-compliant fuel in a ship's tanks is now a breach in itself. Ships with scrubbers and ships carrying fuel as cargo are exempt.[1]
Sample Types and Verification
Sulphur compliance is verified through three types of sample. The MARPOL delivered sample is taken during bunkering. The in-use sample comes from the fuel line, and the onboard sample from a tank. A tolerance is recognised only for the last two, because the MEPC.324(75) amendments take test method precision into account at this stage.[10]
| Sample type | Legal limit | Highest value treated as compliant |
|---|---|---|
| MARPOL delivered sample | 0.50% | 0.50% |
| In-use or onboard sample | 0.50% | 0.53% |
| MARPOL delivered sample, ECA | 0.10% | 0.10% |
| In-use or onboard sample, ECA | 0.10% | 0.11% |
Source: Steamship Mutual's summary of MARPOL Annex VI Appendix VI in practice.[10]
The same amendments require ships to have an in-use fuel sampling point. Ships with a keel laid on or after 1 April 2022 have it on delivery. Existing ships fit it by the first IAPP renewal survey after 1 April 2023.[10]
Fuel Non-Availability and FONAR
A ship that cannot find compliant fuel despite its best efforts files a fuel oil non-availability report (FONAR). The template is annexed to the MEPC.320(74) guidelines. IMO is clear that a FONAR is not an exemption. Under Regulation 18, the party of the port of destination reviews the report and takes the necessary action.[1] The ship is expected to document its attempts to buy fuel and its voyage plan.
Inspection and Enforcement
IMO does not set penalties. Enforcement falls to the flag and port states party to MARPOL. Port state control starts with documents: the bunker delivery note (BDN), record books, the changeover procedure and the International Air Pollution Prevention (IAPP) Certificate. If there are clear grounds, the inspection goes further and samples are taken.[10] When non-compliance is found, the port state acts within the framework of the MEPC.320(74) guidelines.
Effects on Fuel Quality
The main technical consequence of the limit was the spread of VLSFO. Fuel meeting 0.50% is a blend of different refinery streams. Two parcels can therefore differ in density, viscosity and chemistry, and sediment can form when they are mixed. The MEPC.320(74) guidelines devote a separate annex to safety implications.[1] In practice a new stem goes into an empty tank, and a compatibility test comes first if mixing is needed. The 2024 edition of ISO 8217 drew on this experience and added minimum viscosities for residual fuels.
Lubrication changed too, since the move to low-sulphur fuel affected the choice of base number for cylinder oils. Background is in the article on base oils and API groups.
An Unexpected Effect on Climate
The health benefit of the limit is clear, but there is a climate cost. Sulphur particles increase the formation of cloud droplets that reflect sunlight. When those particles fall, the cooling effect of ships on clouds falls with them. Sofiev and colleagues projected that low-sulphur fuels would reduce the cooling from ship aerosols by about 80%.[3]
A 2024 modelling study by Yoshioka and colleagues takes sulphur emissions from ships over open oceans to have fallen by about 80%. It finds a global radiative forcing of about 0.13 W/m² and expects an average of 0.04 °C of additional warming between 2020 and 2049. The authors note that the results rest on one climate model and that it is unclear whether the effect has yet emerged in observations.[11]
The Next Stage: Carbon Rules
The sulphur rules have largely settled, and the regulatory agenda has moved to carbon. In the EU, FuelEU Maritime and the emissions trading system for shipping are in force. IMO's Net-Zero Framework was approved in April 2025, and the session to adopt it was adjourned for a year in October 2025. As of 3 November 2026 it has not been adopted.[12] The effect of these rules on ship operations is covered in the article on marine fuel management.
The compliant fuels Bunkerist supplies are on the Fuel Oil and Gas Oil page.
Frequently asked questions
What is IMO 2020?
It is the MARPOL Annex VI rule that cut the global limit on sulphur in ship fuel from 3.50% to 0.50% on 1 January 2020.
Does IMO 2020 cover small ships?
Yes. Regulation 14 makes no distinction by ship size. The IAPP Certificate is required for ships of 400 GT and above on voyages to foreign ports.
Can a ship with a scrubber carry HSFO?
Yes. The carriage ban does not apply to ships with an approved scrubber. Where washwater discharge is banned, the ship switches to compliant fuel.
Does a FONAR prevent a penalty?
Not with certainty. A FONAR is not an exemption, and the state of the port of destination assesses the report and decides.
What sulphur limit applies in Istanbul?
The Sea of Marmara and the Straits are outside the ECA, so the MARPOL limit is 0.50%. Türkiye's 0.1% rule applies to ships at berth and to ships anchored for more than two hours.
Why was IMO 2020 introduced?
To cut sulphur oxides from ships, which harm the respiratory system, form fine particles and contribute to acid rain. IMO projected a cut of about 77%, or 8.5 million tonnes a year.
Which fuels meet IMO 2020?
VLSFO outside emission control areas and MGO or ULSFO inside them. LNG, LPG and methanol have almost no sulphur, and a ship with an approved scrubber can keep burning HSFO.
Sources
- International Maritime Organization (IMO). IMO 2020: Cutting Sulphur Oxide Emissions; MEPC.305(73); MEPC.320(74), 2019 Guidelines for Consistent Implementation of the 0.50% Sulphur Limit.
- International Maritime Organization (IMO). Sulphur Oxides (SOx) and Particulate Matter (PM), Regulation 14; MEPC.280(70), 2016.
- Sofiev, M. et al. Cleaner Fuels for Ships Provide Public Health Benefits with Climate Tradeoffs. Nature Communications, 9, 2018.
- International Maritime Organization (IMO). Resolution MEPC.361(79), Mediterranean Emission Control Area, 2022.
- International Maritime Organization (IMO). Meeting summaries of MEPC 82 and MEPC 84, 2024 and 2026.
- European Union. Directive (EU) 2016/802, Article 7.
- Republic of Türkiye. Regulation on Reducing the Sulphur Content of Certain Fuels (Bazı Akaryakıt Türlerindeki Kükürt Oranının Azaltılmasına İlişkin Yönetmelik), Official Gazette, 6 October 2009, No. 27368, Article 7.
- Istanbul and Marmara, Aegean, Mediterranean, Black Sea Regions Chamber of Shipping. Circular on Scrubber and Fuel Use in Turkish Territorial Waters, 3 February 2020.
- UK P&I Club. Discharge of Open-Loop Scrubbers Prohibited in Turkish Waters, 2021; Britannia P&I. Turkey: No Discharge of Scrubber System Washing Water, 2021.
- Steamship Mutual. How Will Compliance with MARPOL Annex VI Be Determined? (summarising MEPC.324(75) and MEPC.1/Circ.882).
- Yoshioka, M., Grosvenor, D. P., Booth, B. B. B., Morice, C. P., Carslaw, K. S. Warming Effects of Reduced Sulfur Emissions from Shipping. Atmospheric Chemistry and Physics, 24, 13681-13692, 2024.
- Carbon Brief. Q&A: How Countries Got the Global Net-Zero Shipping Deal Back on Track, 2026.
