Shipboard Waste Oil Incinerator: MARPOL, ORB, and Surveys

A waste oil incinerator burns engine room sludge, oily bilge water residues, and ship-generated garbage to reduce onboard waste volumes and comply with MARPOL Annex VI. This article is written for chief engineers and officers responsible for incinerator operation, ORB completion, and PSC readiness.

What does a waste oil incinerator do on a ship?

A shipboard incinerator burns sludge from fuel purifiers, oily bilge residues, and combustible garbage to reduce waste volume and avoid shore reception costs. It operates under MARPOL Annex VI Regulation 16, which defines what can be burned, at what temperature, and in what equipment.

Sludge accumulates from two primary sources. The fuel oil purifier generates the largest volume — a medium-speed four-stroke engine on a 10,000 DWT vessel produces 0.5–1.5% of daily fuel consumption as sludge. The bilge system contributes oily water residues that cannot be discharged under MARPOL Annex I.

Without a functioning incinerator, sludge accumulates in holding tanks. Once capacity is reached, the vessel must arrange shore reception — an increasingly expensive and logistically difficult operation in many ports.

What does MARPOL Annex VI Regulation 16 require for shipboard incinerators?

Regulation 16 divides requirements into two tiers. Regulations 16.1–16.4 apply to all ships. Regulations 16.6–16.9 apply specifically to incinerators installed on ships constructed on or after 1 January 2000, or units installed on existing ships from that date.

General requirements under 16.1–16.4:

• Regulation 16.1 — incineration only in equipment designed for that purpose. Burning sludge in the main boiler without flag state authorisation violates this requirement.
• Regulation 16.2 — certain materials are prohibited from incineration (see next section).
• Regulation 16.3 — incineration of PVC is prohibited unless the unit holds type approval under MEPC.59(33), MEPC.76(40), or MEPC.244(66).
• Regulation 16.4 — incineration of sewage sludge and sludge oil is prohibited within ports, harbours, or estuaries. This applies even to correctly type-approved equipment. The interaction between incinerator sludge and sewage treatment plant waste streams is a separate compliance question under MARPOL Annex IV.

Requirements specific to post-2000 units under 16.6–16.9:

• Regulation 16.6 — type approval required per the applicable IMO resolution. The approval certificate must be carried onboard.
• Regulation 16.7 — the manufacturer’s operating manual must be maintained onboard and available to crew.
• Regulation 16.8 — crew must be trained in correct incinerator operation. Training must be documented in the SMS.
• Regulation 16.9 — the incinerator must reach and maintain the temperature specified in the type approval certificate. For most approved units this is 850–1200°C in the primary chamber.

What materials are prohibited from incineration under MARPOL?

These materials must not enter the incinerator under any circumstances. Incineration of prohibited materials is a MARPOL violation regardless of the unit’s type approval status.

Prohibited materials under Regulation 16.2 and related MARPOL provisions:

• Cargo residues classified under MARPOL Annex I, II, and III, and contaminated packaging
• Polychlorinated biphenyls (PCBs)
• Garbage containing more than trace quantities of heavy metals — see garbage management on ships for the full MARPOL Annex V classification
• Refined petroleum products containing halogen compounds
• Sewage sludge and sludge oil not generated onboard the vessel
• Exhaust gas cleaning system (EGCS) residues — scrubber sludge must be landed ashore
• Pressurised containers and aerosols — explosion risk inside the furnace
• PVC, unless the unit holds specific MEPC.244(66) approval

The EGCS residue prohibition is operationally significant for scrubber-fitted vessels. Scrubber sludge cannot be incinerated and cannot be discharged overboard under MARPOL Annex VI. Fleet superintendents ordering scrubber installations must plan shore reception capacity for this waste stream from the outset.

How must incinerator use be recorded in the Oil Record Book?

Every incineration of sludge or oily residues must be entered in the Oil Record Book Part I under Code C — Disposal of Oil Residues (Sludge). Failure to maintain accurate ORB records is a MARPOL Annex I violation independent of whether the incineration itself was conducted correctly.

The ORB Code C entry must record:

• Date and position of incineration
• Quantity of sludge burned (cubic metres)
• Method of disposal: Code C for incineration
• Signature of the officer in charge

PSC officers cross-reference ORB Code C entries against the sludge tank sounding log. A discrepancy between reported incineration quantity and the reduction in sludge tank levels is treated as evidence of potential illegal overboard discharge — a detention-level deficiency under MARPOL Annex I.

The sludge tank sounding log and the incinerator running log must tell a consistent story. Cross-check both internally before any port arrival where port state control inspection is possible.

What do PSC officers check during an incinerator inspection?

PSC officers inspect the incinerator as part of MARPOL Annex VI and Annex I compliance checks. The inspection covers documentation, physical condition, and operational records.

Documentary checks:

• ORB Part I — Code C entries, frequency, quantities, officer signatures
• Type approval certificate — must be onboard and valid
• Operating manual — present and accessible to crew
• Training records — crew training under Regulation 16.8

Physical checks:

• Furnace condition — visible cracks in the refractory lining are a deficiency
• Thermocouple function — PSC may request a functional demonstration
• Prohibited materials — officers sometimes inspect sludge tank contents and garbage records
• Sludge tank sounding log — cross-referenced against ORB Code C

A common deficiency sequence: ORB shows 2 cubic metres incinerated over a 10-day passage; sludge tank sounding shows a 6 cubic metre reduction. The unexplained 4 cubic metres generates a deficiency and may trigger flag state notification by the PSC authority.

Deficiency codes for incinerator non-compliance fall under the 18.000 series (MARPOL Annex VI) and the 3.000 series (ISM Code) in the Paris MoU and Tokyo MoU systems. Both can be raised simultaneously. Ship detention is possible when the incinerator is non-operational and no approved alternative sludge management plan is in place.

What does a class surveyor examine during Annual Survey of the incinerator?

The incinerator is examined at Annual Survey under the vessel’s class rules. The survey covers safety, operational readiness, and compliance with the type approval certificate. The full context for this survey sits within the types of surveys carried out on ships.

Surveyors focus on four areas:

Refractory lining integrity — the furnace lining is inspected for cracks, spalling, and erosion. A cracked lining allows combustion gases to reach the steel shell — a fire hazard and a structural defect. Defects result in a Condition of Class requiring repair before the next survey.

Thermocouple calibration — incorrectly reading thermocouples allow the furnace to operate outside the type-approved temperature range. A unit operating below the minimum temperature does not achieve complete combustion — a MARPOL violation and a class deficiency simultaneously. Surveyors check calibration certificates.

Burner atomiser condition — the waste oil burner atomiser and swirler are wear items. A partially blocked atomiser produces incomplete combustion and elevated flue gas temperatures. Surveyors check the last cleaning record and may request a functional test.

Flue gas temperature records — the incinerator running log should show consistent flue gas exit temperatures within the design range. Repeated high readings indicate a fouled flue gas fan. Repeated low readings indicate incomplete combustion.

The incinerator room is classified as a fire-risk space under SOLAS Chapter II-2. Class verifies that the fixed fire-suppression system is operational and boundary construction meets the required fire rating.

What happens when the incinerator malfunctions or goes out of service?

A non-operational incinerator is a compliance event, not just a maintenance issue. The chief engineer notifies the master immediately. The master and DPA then assess whether flag state notification is required.

Flag state notification is required when:

• The incinerator is non-operational, and the vessel cannot comply with MARPOL Annex VI Regulation 16
• Sludge tank capacity is insufficient to hold accumulated waste until the next port
• The vessel intends to use the main boiler for sludge burning as an alternative

Notification goes to the flag state administration directly or through the Recognised Organisation (RO) acting on the flag state’s behalf. The RO then issues a dispensation — written authorisation to operate without a functioning incinerator for a defined period, subject to an approved alternative sludge management plan.

The alternative sludge management plan must specify one or more of:

• Shore reception — pre-arranged at the next port. Confirm availability before arrival.
• Increased storage — temporary use of additional tanks under flag state approval
• Vessel-to-vessel transfer — sludge transferred to another vessel, documented in both ORBs

The dispensation document must be carried onboard and presented to PSC if inspected while the incinerator is out of service. A vessel without a functioning incinerator and without a dispensation faces automatic deficiency under MARPOL Annex VI.

How is an incinerator room fire handled as an onboard drill scenario?

An incinerator room fire is one of the most frequently used scenarios in ship drills onboard merchant vessels. It is used because it combines multiple response decisions in a realistic engine room context: boundary cooling, CO2 activation, and ventilation management.

What is the drill scenario setup?

A general alarm is sounded for a fire in the incinerator room. The emergency team musters at the space boundary. The officer in charge confirms all personnel are clear of the space before any suppression action is taken.

What is the correct CO2 activation sequence?

1. Confirm all personnel clear of the incinerator room
2. Close all ventilation dampers serving the space
3. Close emergency fuel supply stops to the incinerator burners
4. Stop the flue gas fan via the emergency stop outside the space
5. Activate the CO2 fixed suppression system from the CO2 room
6. Maintain boundary cooling on surrounding bulkheads throughout
7. Do not re-enter for a minimum of 30 minutes after CO2 release

Should the flue gas fan be stopped or kept running during a fire?

Stop the flue gas fan before CO2 release. A running fan draws fresh air through the burner register, feeds oxygen to the fire, and disperses CO2 before it reaches suppression concentration. The fan emergency stop must be outside the space and clearly labelled.

Boundary cooling is a separate decision: hose teams must continue cooling adjacent bulkheads — particularly the boundary with the engine room — throughout the CO2 soak period. Stopping boundary cooling while CO2 is applied allows heat transfer through the bulkhead to continue.

Drill records must document the scenario, actions taken, time from alarm to CO2 activation, and deficiencies observed. PSC officers examine drill records under SOLAS Chapter III during port state control inspections.

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