A Rulebook That’s Simple on Paper
Under MARPOL Annex VI, the sulphur oxide (SOx) limit for ships operating outside Emission Control Areas is 0.50% m/m. Many vessels have met this requirement by installing Exhaust Gas Cleaning Systems (EGCS). An expensive, complex machinery designed to allow continued use of high sulphur fuel oil (HSFO) while remaining compliant.
On paper, it sounds straightforward: fit an EGCS, burn HSFO, stay within limits. At sea, another question has moved into the discussion. PPR 13 in February 2026 looked specifically at EGCS discharge water, including possible restrictions in Particularly Sensitive Sea Areas. The sulphur rule is moving towards what leaves the scrubber, and where it may be discharged.
At sea, it is not that clean.
EGCS is not just an emissions device. It is another operating condition the ship must manage across changing port rules, fuel requirements, engineering limits, and documentation pressure.
Local Rules, Global Confusion
The difficulty begins when local port regulations override what IMO rules otherwise allow.
In Fujairah and Oman, EGCS use is prohibited, forcing ships to change over to VLSFO or MGO before arrival. In Oman, proximity to territorial limits can require the switch even earlier. Inside the Persian Gulf, EGCS operation and washwater discharge may be permitted, until the next port changes the operating condition again.
For the ship, this creates a moving compliance target.
The same system that is accepted in one area may become unusable at the next port. The vessel remains technically equipped for compliance, but the crew still has to manage fuel changeover, documentation, timing, machinery limits, and the risk of getting the local interpretation wrong.
The Engineer’s Burden
The engineering burden does not remain hidden below deck. From the bridge, it is visible in timing, speed planning, port approach preparation, fuel readiness, and compliance documentation.
Fuel changeover is not a simple switch. It involves isolating and re-routing fuel lines, adjusting fuel temperatures gradually, monitoring purifier performance, checking compatibility, and avoiding filter clogging or asphaltene precipitation. During these transitions, fuel pump seal leakage remains a real risk, especially when viscosity and lubrication properties change abruptly.
Operating experience has added another concern. Gard’s scrubber claims from 2020 to 2025 show water ingress as the largest failure category, mainly from corrosion and leakage in overboard discharge piping. Around 75% of the failures occurred during passage. So the scrubber is also a sea connection, a corrosion point and, if things go badly wrong, a route for water into the engine room.
That is the real burden. The regulation may sit in MARPOL Annex VI, but the workload lands on the ship.
Decisions Made from Shore
From the bridge, the logic of these restrictions often appears inconsistent. Ports in open waters ban EGCS discharge, yet enclosed waters allow it.
From the bridge, these restrictions can still appear inconsistent. The same scrubber may be acceptable during one part of the voyage and restricted during another. But the environmental argument has also moved on. IMO is now looking more closely at EGCS discharge water itself. For the ship, whatever is eventually decided will still arrive in a familiar form: another position by which the operating mode has to change.
A Structural Problem at the Core
The larger issue is systemic. The IMO can regulate ships, but it cannot by itself create one global fuel supply reality across ports, terminals, bunker suppliers, and coastal states.
Instead of solving the problem upstream, the compliance burden lands downstream on the vessel. Ships install expensive equipment, carry multiple fuel strategies, manage local restrictions, and still face port-by-port uncertainty over whether the system may actually be used.
That is the contradiction at the heart of EGCS. The ship pays for the hardware, but permission to use it remains conditional.
The Real-World Consequences
- Financial Inefficiency: HSFO–VLSFO price advantage disappears where bans exist.
- Operational Risk: More fuel changeovers mean more chances of machinery problems, timing errors, and documentation gaps.
- Science vs Politics: Many bans lack published local environmental data.
- Crew Fatigue & Human Error: More changeovers mean higher risk of mistakes or machinery issues.
- No Unified Enforcement: Many restrictions are introduced without clearly published local environmental data.
The Question That Won’t Go Away
EGCS was accepted under MARPOL Annex VI as an equivalent way of meeting the sulphur limit. Ships invested in the equipment, crews learned to operate it, and companies built their fuel strategies around it.
Years later, the ship can still sail from one jurisdiction where open-loop operation is accepted into another where discharge is restricted.
Now the discussion is moving further towards the washwater itself, while operating experience is exposing corrosion, leakage, flooding and other failures in the system onboard.
This leaves the ship carrying both sides of the problem.
The Chief Engineer has to keep the equipment running safely. The Master has to know where it can be used. The company has to follow a growing map of local restrictions. And when that map changes, the machinery, fuel plan and operating procedure onboard have to change with it.
That is where I still have difficulty with the present arrangement.
If EGCS remains an accepted MARPOL compliance method, its use cannot be treated as a global solution on the certificate and a local uncertainty at every coastline. Ships need clear operating limits that can be planned before the voyage, understood onboard and applied without repeatedly shifting the technical burden back to the crew.
The environmental question around scrubber discharge deserves proper examination. So does the operational consequence of every restriction that follows from it.
Because in the end, IMO may write the rule and coastal States may draw the limits.
The ship still has to make it work.
Media Section
Sources
IMO 2020 sulphur limit.
IMO MEPC.340(77) EGCS Guidelines.
ClassNK regional EGCS restriction list.
Port of Fujairah open-loop scrubber restriction.
Revised on 13 August 2026 to reflect the latest developments. The original analysis remains unchanged.
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