Every captain fuelling in the Mediterranean has, at some point, been asked for the Bunker Delivery Note without quite knowing why it mattered. MARPOL Annex VI is the reason. It is the part of MARPOL that governs what comes out of the exhaust — not what goes overboard — and since May 2025 it applies more strictly across the entire Mediterranean than it did the season before.
This guide covers what Annex VI actually requires, what changed with the new Mediterranean Emission Control Area, and which parts of it apply to a yacht your size.
What MARPOL Annex VI Actually Regulates
MARPOL has six annexes, and it's easy to lump them together. Annex I covers oil pollution, Annex V covers garbage — both regulate what leaves the vessel into the water. Annex VI is different: it regulates air emissions from ships' exhaust — sulphur oxides (SOx), nitrogen oxides (NOx), ozone-depleting substances, and volatile organic compounds from cargo (not relevant to yachts), along with a separate chapter on carbon intensity.
For a yacht, the two provisions that matter day to day are Regulation 14 (sulphur limits, tied to fuel quality) and Regulation 13 (NOx limits, tied to engine certification). This article focuses on both — not on the ship's energy efficiency framework, which is a separate compliance track covered below.
If your vessel operates commercially and calls at ports covered by the Paris MOU, PSC officers can and do check fuel compliance alongside the more familiar SOLAS and STCW items. See our Port State Control guide for how these inspections work in practice.
The Global Sulphur Cap: 0.50% Since 2020
The headline change under Annex VI — the one most captains have heard of even if they don't work with the regulation text directly — is the IMO's 2020 sulphur cap. Since 1 January 2020, marine fuel burned anywhere in the world may not exceed 0.50% sulphur content by mass, down from the previous 3.50% limit. Carriage of non-compliant fuel for use as fuel was banned from 1 March 2020, closing the loophole of simply having the wrong fuel aboard without burning it.
For yachts, this is largely academic in the sense that most vessels already run on Marine Gas Oil (MGO), which typically comes in well under the 0.50% threshold as supplied. The practical requirement isn't chasing down cleaner fuel — it's being able to document what's aboard. A Bunker Delivery Note (BDN) records the sulphur content of each fuel delivery and should be retained for three years. When a PSC officer asks for it, "we always use MGO" is not a substitute for the paperwork.
Emission Control Areas: Where the Limit Drops to 0.10%
Inside a designated Emission Control Area (ECA), the sulphur limit is tighter: 0.10% m/m rather than the global 0.50%. Before 2025, there were four SOx ECAs: the Baltic Sea, the North Sea, the North American ECA, and the US Caribbean Sea ECA — all in force since the 2010s.
The Mediterranean SOx ECA — What Changed in 2025
At MEPC 79 in December 2022, the IMO adopted Resolution MEPC.361(79), designating the entire Mediterranean Sea as a SOx Emission Control Area. It entered into force on 1 May 2025. Inside the Med ECA — which covers the waters most charter and private yachts actually operate in — fuel sulphur content must not exceed 0.10% m/m, a fifth of the global limit.
This is not a future rule to plan around — it is already in force. If your vessel bunkers fuel that meets the 0.50% global standard but not the 0.10% ECA standard, and you're operating anywhere in the Mediterranean, you are out of compliance. Confirm with your fuel supplier that deliveries meet the ECA-grade specification, and keep the Bunker Delivery Notes to prove it.
Most yachts running on standard MGO are already compliant, since typical MGO sulphur content sits well below 0.10%. The exposure is greater for older vessels or unusual fuel arrangements where sulphur content wasn't a design consideration. When in doubt, ask the supplier for the sulphur content figure on the delivery note rather than assuming.
NOx Tier III and Keel-Laid Dates
Nitrogen oxide limits work differently from sulphur limits. Rather than a fuel-quality rule, NOx compliance under Regulation 13 is tied to engine design and certification, and it applies based on when the vessel was built, not when it's operating.
Ships whose keel was laid on or after 1 January 2016 and that operate in a designated NOx Emission Control Area (NECA) must meet the stricter Tier III NOx limits — roughly an 80% reduction from the Tier I baseline. The currently designated NOx ECAs are the North American Area and the US Caribbean Sea Area. Baltic and North Sea NOx requirements apply to newer-build vessels as well, though captains should confirm current applicability dates with their class society or flag administration rather than relying on a fixed date, since NOx ECA designations have continued to expand.
For most yachts, Tier III is a build-time consideration handled by the shipyard and class society at construction — not something a captain manages fuel-by-fuel the way sulphur compliance works. It matters most when chartering or delivering a newer vessel into North American waters.
Does This Apply to My Yacht? Certificates and Size Thresholds
This is where most confusion sits, because the rules apply differently to the fuel itself versus the paperwork proving compliance.
The sulphur limit applies to every vessel, regardless of size. There is no small-yacht carve-out from the 0.50% global cap or the 0.10% ECA limit. A 20-metre motor yacht burning fuel in the Mediterranean is bound by the same 0.10% limit as a 90-metre superyacht.
Certification is size-gated. Vessels of 400 gross tonnage (GT) and above on international voyages require an International Air Pollution Prevention (IAPP) Certificate, issued after survey by the flag administration or a recognised organisation. Most private and charter yachts sit well under 400 GT and are not formally IAPP-certified — but that doesn't exempt them from burning compliant fuel, it just means there's no separate certificate confirming it.
Engine certification is a separate threshold. An Engine International Air Pollution Prevention (EIAPP) Certificate applies to marine diesel engines rated above 130 kW output, independent of the vessel's overall tonnage. A yacht well under 400 GT can still carry engines that individually require EIAPP certification — check the engine's own documentation rather than assuming the vessel's tonnage settles the question.
When chartering or purchasing a yacht, ask specifically which Annex VI certificates the vessel holds and which fuel sulphur records exist for the current season — not just whether the vessel is "MARPOL compliant" in general terms. The two questions have different answers.
MARPOL Annex VI vs CII/EEXI — Different Rules, Same Annex
It's easy to conflate MARPOL Annex VI's exhaust emission rules with the IMO's newer carbon intensity framework, since both live inside the same Annex and both get shortened to acronyms in conversation. They are not the same compliance track.
Regulations 13 and 14 — covered in this article — govern what comes out of the exhaust in terms of SOx, NOx, and particulate matter, tied to fuel quality and engine design. The Carbon Intensity Indicator (CII) and Energy Efficiency Existing Ship Index (EEXI) sit in Chapter 4 of the same Annex and govern a vessel's overall carbon efficiency and energy performance — a measurement of CO2 output relative to work done, not exhaust gas composition. A vessel can be fully compliant on sulphur and NOx while still facing a poor CII rating, and vice versa. They require separate documentation, separate calculations, and in practice, separate conversations with class societies.
Compliant Fuel in Practice
For most captains, day-to-day Annex VI compliance comes down to a short list of habits rather than technical calculation:
- Confirm sulphur content on every bunkering. Ask the supplier for the figure, don't assume MGO is automatically compliant everywhere you'll operate.
- Retain Bunker Delivery Notes for three years. This is the document PSC officers ask for; keep it organised and accessible, not buried in a folder from two suppliers ago.
- Know your operating area's ECA status before departure. With the Mediterranean now an ECA in its entirety, this is less about route planning around an ECA boundary and more about confirming every fuel purchase meets the 0.10% standard by default.
- Log fuel changeovers if your vessel carries more than one grade. Vessels transiting between ECA and non-ECA waters on different fuel grades need a documented changeover procedure and log entry — a maintenance and voyage-planning habit best tracked in the same system used for engine hours and service records.
- Treat certificates as season-opening items. IAPP and EIAPP certificates, where the vessel holds them, should be reviewed at the same time as other season-opening documentation — not discovered as missing at a PSC inspection.
Consequences of Non-Compliance
Fuel sulphur violations are checked the same way other PSC deficiencies are found: documentation review, and in some ports, direct fuel sampling. A missing Bunker Delivery Note, a sulphur content above the applicable limit, or no evidence of a changeover procedure where one was required can result in a deficiency notation. In more serious cases — particularly repeat findings or evidence of deliberate non-compliance — detention is possible under the same framework that governs other MARPOL and SOLAS deficiencies.
The practical risk for most captains isn't a dramatic enforcement action. It's the accumulation of small paperwork gaps that turn a routine PSC call into a longer one, or that surface during an insurance or charter due-diligence review months later when nobody remembers which supplier delivered which grade of fuel.
Related Reading
- MARPOL Annex V: Garbage Management for Superyachts — the waste-discharge side of MARPOL, a separate compliance track from the exhaust rules above
- Port State Control Yacht Guide — how MARPOL findings surface during inspection
Frequently Asked Questions
Keeping Annex VI Manageable
MARPOL Annex VI compliance for a yacht isn't complicated in principle — burn fuel that meets the applicable sulphur limit, keep the paperwork that proves it, and know which certificates your vessel actually needs based on size and engine power. What makes it feel complicated is tracking it alongside everything else: maintenance intervals, crew certificates, insurance renewals, and now a Mediterranean ECA that applies to nearly every mile a Med-based yacht sails.
Keeping bunkering records, certificate expiry dates, and maintenance logs in one system — rather than scattered across paper receipts and a captain's memory — is what turns "we think we're compliant" into "we can show you the record" during a PSC call.
