Where Regulation 4 sits in the revised Annex V
The revised MARPOL Annex V adopted by Resolution MEPC.201(62) entered into force on 1 January 2013 and rebuilt the discharge regime around a single inversion: garbage discharge into the sea is prohibited by default, and any overboard disposal must point to a specific permission. The prohibition lives in Regulation 3. The permissions live in Regulations 4, 5, and 6. Regulation 4 is the one a deck officer applies on most blue-water voyages, because most voyages spend most of their time outside the eight designated special areas.
The numbering matters, and it is a frequent source of error. The consolidated layout runs: Regulation 1 Definitions; Regulation 2 Application; Regulation 3 General prohibition on discharge of garbage into the sea; Regulation 4 Discharge of garbage outside special areas; Regulation 5 Special requirements for the discharge of garbage from fixed or floating platforms; Regulation 6 Discharge of garbage within special areas; Regulation 7 Exceptions; Regulation 8 Reception facilities; Regulation 9 Port State control on operational requirements; Regulation 10 Placards, garbage management plans, and garbage record-keeping. Pre-2013 summaries, and a few that survive in circulation, label the general prohibition as Regulation 4 and slide everything down a number. The IMO consolidated text settles it: the general prohibition is Regulation 3, and “Discharge of garbage outside special areas” is Regulation 4.
Regulation 3 reads, in substance, that discharge of all garbage into the sea is prohibited except as provided otherwise in Regulations 4, 5, and 6. That single sentence carries the whole burden-of-proof structure. A master who logs an overboard discharge has to be able to name the paragraph that authorized it. There is no residual category of “probably fine.” If the discharge is not within Regulation 4 (outside special areas), Regulation 5 (platforms), or Regulation 6 (inside special areas), it is unlawful, and the Garbage Record Book entry stands as the contemporaneous admission.
Regulation 4 then opens the gate, narrowly. It allows discharge of exactly five things while the ship is en route and as far as practicable from the nearest land. This article takes the article-level overview in the Annex V garbage discharge regime and goes paragraph by paragraph through the conditions, the distance arithmetic, the comminution screen test, the en-route condition, the cleaning-agent allowance, and the animal-carcass language, with the compliance traps that surface in port State control.
Reading the structure of Regulation 4
Regulation 4 has four numbered paragraphs, and the first of those has four sub-items. Reading them in order is the discipline that keeps a discharge lawful.
Paragraph 4.1 sets the headline conditions and then lists the four permitted streams. The chapeau requires that discharge be made only while the ship is en route and as far as practicable from the nearest land, and then four sub-paragraphs attach a distance to each stream. Paragraph 4.1.1 is comminuted or ground food waste at 3 nautical miles or more. Paragraph 4.1.2 is food waste not comminuted or ground at 12 nautical miles or more. Paragraph 4.1.3 is cargo residues that cannot be recovered using commonly available unloading methods, at 12 nautical miles or more, where the residues are not classified as harmful to the marine environment. Paragraph 4.1.4 is animal carcasses, discharged as far from the nearest land as possible, considering the guidelines developed by the Organization.
Paragraph 4.2 is the cleaning-agents-and-additives allowance: those contained in hold wash water and in deck and external surface wash water may be discharged, provided they are not harmful to the marine environment. Paragraph 4.3 is the classification and declaration duty: solid bulk cargoes, other than grain, must be classified against Appendix I and the shipper must declare whether or not the residue is harmful to the marine environment. Paragraph 4.4 is the mixing rule: when garbage is mixed with or contaminated by substances carrying different discharge requirements, the more stringent requirement applies.
That is the whole regulation. Five permitted streams, one global condition (en route, as far as practicable from land), a classification duty for solid bulk cargo, and a tie-breaker for mixed waste. Nothing in Regulation 4 permits the discharge of plastics, domestic waste, cooking oil, operational waste, incinerator ash from products containing toxic residues, fishing gear, or e-waste; those categories are barred outside special areas as fully as inside.
The en-route condition and “as far as practicable from the nearest land”
The chapeau of Regulation 4.1 attaches two conditions to every permitted discharge: the ship must be en route, and the discharge must be made as far as practicable from the nearest land. Both qualifiers travel with the distance numbers; meeting the 3-nm or 12-nm minimum does not by itself authorize a discharge if the ship is stationary.
“En route” carries an operational meaning the convention does not spell out in a numeric definition, so the IMO implementation guidelines (the 2012 Guidelines under MEPC.219(63), as amended by MEPC.295(71)) interpret it as the ship being on a voyage and proceeding on a course such that the discharge is spread over as great an area of sea as is reasonable and practicable. The guidelines attach the often-quoted minimum speed of 4 knots to that interpretation. The convention text itself fixes the en-route requirement; the 4-knot figure is the guideline gloss on what “en route” means in practice. A ship making way at 4 knots over a track distributes a food-waste discharge across kilometers of wake, which is the dispersion-by-motion logic shared with the Annex I oily-water discharge rule and the Annex IV sewage discharge rule.
The practical consequence is sharp. A ship at anchor in an outer roads, drifting while waiting for a berth, or stopped for an engine repair cannot discharge food waste under Regulation 4, no matter how far the anchorage lies from land. A point release from a stationary hull builds a localized plume, the opposite of the spread the rule wants. This is one of the most common port State control findings: a Garbage Record Book entry showing a food-waste discharge at a position the inspector recognizes as a known anchorage, cross-checked against the deck log showing the ship at anchor at that time. The distance was fine; the en-route condition failed.
“As far as practicable from the nearest land” is a second, separate instruction. It is not a distance; it is a direction of travel. Where a ship has the sea room to be further out, the rule expects it to discharge further out, beyond the bare minimum. A ship that has crossed an ocean and is 200 nautical miles from the nearest land should not run in to exactly 3 nautical miles to discharge comminuted food waste; the practicable distance is the one it already has. The minima in 4.1.1 through 4.1.4 are floors, not targets. “Nearest land” itself is defined elsewhere in MARPOL by reference to the baseline from which the territorial sea is established, and it includes offshore islands and other features, so the nearest point of any land in any direction governs, not only the mainland coast.
Paragraph 4.1.1: comminuted food waste at 3 nautical miles
Regulation 4.1.1 permits the discharge of food waste outside special areas at a distance of not less than 3 nautical miles from the nearest land, provided the food waste has been comminuted or ground so that it is capable of passing through a screen with openings no greater than 25 millimeters. Three conditions stack here: the 3-nm distance, the comminution to the 25 mm particle size, and the chapeau’s en-route and as-far-as-practicable requirements.
The 25 mm screen test is the gating physical specification, and it is worth stating precisely because it is often paraphrased loosely. The waste must be capable of passing through a screen with openings no greater than 25 mm. That is a 25 mm maximum aperture, not a 25 mm particle. A galley macerator or comminutor reduces food waste to a slurry of particles small enough to fall through such a screen. The standard is a capability standard: the comminution equipment must produce output that would pass the screen, not that every discharge is physically sieved before it goes over the side. The output of a properly maintained galley macerator running on ordinary food waste meets the test; the operational risk is a worn or under-maintained unit that leaves coarse fragments, or a discharge of food waste that bypassed the macerator entirely.
The distance can be stated as a simple inequality the watch officer checks against the chart. With the distance to the nearest land and the ship’s speed:
The 3-nm figure tracks the historical 3-mile territorial-sea limit that many coastal States used before the 12-mile limit became the modern norm under UNCLOS. The drafters paired the shorter standoff with the comminution requirement because finely ground organic matter disperses quickly and undergoes aerobic breakdown in open water within hours to days, so the coastal-shelf habitats that the larger standoff protects are not exposed to settling of partly broken-down material. A ship without a working macerator does not get the 3-nm pathway; it falls to the 12-nm pathway under 4.1.2.
A note on what counts as food waste. The Annex V definition treats food waste as spoiled or unspoiled food substances such as fruit, vegetables, dairy products, poultry, meat products, and food scraps generated aboard ship. It does not include cooking oil, which the revised Annex V handles as its own category barred from sea discharge, and it does not include the packaging the food came in. A tray of galley scraps mixed with plastic film is governed by Regulation 4.4, not 4.1.1; the plastic contamination pulls the whole tray into the plastics prohibition.
Paragraph 4.1.2: non-comminuted food waste at 12 nautical miles
Regulation 4.1.2 permits the discharge of food waste that has not been comminuted or ground, outside special areas, at a distance of not less than 12 nautical miles from the nearest land, with the chapeau en-route and as-far-as-practicable conditions. The only difference from 4.1.1 is the comminution state and, consequently, the distance: 12 nautical miles instead of 3.
The 12-nm figure is the modern UNCLOS territorial-sea limit, and the longer standoff reflects the slower breakdown of larger food-waste particles. Whole or coarsely cut food waste, peelings, bones, and unmacerated scraps fall under 4.1.2 when no macerator is fitted or the macerator is out of service. The pathway exists for vessels that genuinely lack comminution capacity: small coasters, some fishing vessels, older general-cargo ships. Most modern installations include a galley macerator and operate primarily under the 3-nm 4.1.1 pathway, treating 4.1.2 as the fallback for a macerator failure during a long ocean transit.
The choice between 4.1.1 and 4.1.2 is the macerator. When the unit is working, food waste passes the 25 mm screen test and the ship can discharge from 3 nautical miles. When the unit is down, the ship must either hold the waste to 12 nautical miles or retain it for shore reception. The Garbage Record Book entry should make the basis clear: a 4.1.1 discharge logs the comminution; a 4.1.2 discharge at 4 nautical miles would be unlawful, and a port State control officer reading the position against the chart will flag it.
A second operational point about 4.1.2: it is the only food-waste route open to a ship whose macerator has failed and that does not want to retain the waste, but it is not available inside special areas. Inside a special area, food waste discharge requires comminution to the 25 mm standard regardless of distance, so a ship with a failed macerator inside a special area has no sea-discharge route for food waste at all and must retain it. That contrast between the outside-special-areas 4.1.2 pathway and its absence inside special areas is the single sharpest difference between Regulation 4 and Regulation 6.
Paragraph 4.1.3: cargo residues that cannot be recovered, not HME, at 12 nautical miles
Regulation 4.1.3 permits the discharge of cargo residues that cannot be recovered using commonly available methods for unloading, outside special areas, at a distance of not less than 12 nautical miles from the nearest land, where the cargo residues do not contain any substances classified as harmful to the marine environment. This is the bulk-carrier and general-cargo provision, and it carries three conditions beyond the chapeau: the residue must be genuinely unrecoverable by ordinary means, the distance must be 12 nautical miles or more, and the residue must not be HME.
The “cannot be recovered using commonly available methods for unloading” qualifier is doing real work. Cargo residue under Annex V is the material left after the cargo has been discharged by the normal grab, conveyor, suction, or auger methods that the loading terminal and the ship use. It is the swept material, the hold-bottom sweepings, the dust adhering to frames and hopper plating. It is not recoverable cargo that the master would prefer to flush to sea for convenience. A ship that has discharged 59,800 tonnes of a 60,000-tonne grain parcel and has a few tonnes of swept residue in the hold corners that the terminal grabs cannot lift is within 4.1.3; a ship dumping a few hundred tonnes of merchantable cargo it did not bother to discharge is not.
The HME gate is the chemistry test, and it is the central tightening that Resolution MEPC.277(70) brought to this paragraph when it entered into force on 1 March 2018. The discharge under 4.1.3 is allowed only where the residue does not contain substances classified harmful to the marine environment under Appendix I of Annex V. HME residues, the Category K residues in the Garbage Record Book Part II terminology, cannot be discharged under Regulation 4 at all; they go to a reception facility. The chemistry and the criteria for an HME determination, drawing on the UN GHS environmental hazard categories, are covered in depth in the dedicated article on HME cargo residues and e-waste; the point for Regulation 4 is that the residue’s HME status is the switch that opens or closes the 12-nm pathway.
The practical handling on a bulk carrier runs through the hold-washing sequence after the discharge port. Where the residue is non-HME and the cargo hold has been emptied of recoverable cargo, the wash water carrying the residue may be discharged under 4.1.3 once the ship is 12 nautical miles or more from land, en route. Where the residue is HME, the wash water and residue are retained for a reception facility. The decision is made before loading, on the strength of the shipper’s declaration, not improvised at the rail.
Paragraph 4.3: solid bulk cargo classification and the shipper’s declaration
Regulation 4.3 is the duty that makes 4.1.3 work. It requires that solid bulk cargoes, other than grain, be classified in accordance with the criteria in Appendix I of Annex V and that the shipper declare whether or not the residue is harmful to the marine environment. The classification is a pre-loading obligation, and it is the shipper’s, not the master’s.
The mechanism rides on the IMSBC Code declaration that the shipper must provide before loading a solid bulk cargo. The declaration carries the bulk cargo shipping name, the cargo group, the hazard data, and, since the 2018 amendments, the HME or not-HME determination against the Appendix I criteria. The master is entitled to rely on that declaration unless there is evident error or fraud; the legal burden of the HME determination rests on the shipper. The master’s downstream duty is to record the determination in the Garbage Record Book Part II when any residue discharge or retention occurs, referencing the declaration.
The grain carve-out in 4.3 reflects that grain cargoes, governed by the International Grain Code and the SOLAS grain rules, are treated as a known quantity for residue purposes and are generally non-HME; the classification duty targets the broad universe of mineral ores, concentrates, fertilizers, and industrial bulk materials whose environmental hazard varies with composition. Appendix I sets the criteria: a solid bulk material is HME if it meets thresholds for acute or chronic aquatic toxicity, certain carcinogenicity, mutagenicity, or reproductive-toxicity categories under GHS, specific target-organ toxicity on repeated exposure, persistence and bioaccumulation under synthetic-chemical criteria, or if it consists of or contains synthetic polymers, rubber, plastics, or plastic feedstock pellets. The plastics-pellet criterion is precautionary: pellets are HME regardless of their acute toxicity, on the marine-litter logic.
Where no declaration is provided, or the declaration is incomplete, the prudent and defensible course is to treat the residue as HME and retain it. The 4.1.3 discharge depends on a positive non-HME determination; absent that, the discharge is not authorized. A residue discharged under 4.1.3 on the assumption that it was non-HME, where the declaration later shows otherwise, is an unlawful discharge, and the Garbage Record Book entry recording it is the evidence.
Paragraph 4.1.4: animal carcasses
Regulation 4.1.4 permits the discharge of animal carcasses outside special areas, with the carcasses discharged as far from the nearest land as possible, taking account of the guidelines developed by the Organization. There is no fixed numeric minimum in the convention text for carcasses; the standard is the as-far-as-practicable instruction in a strengthened form, “as far from the nearest land as possible.”
The category is operationally relevant on livestock carriers, where animals can die during a voyage from illness, heat stress, or injury, and on any ship carrying live animals as cargo or for ship’s provisions. The Annex V definition of animal carcasses covers the bodies of animals carried on board as cargo that die or are euthanized during the voyage. The 2012 implementation guidelines, developed under MEPC.219(63), interpret “as far from the nearest land as possible” with reference to keeping carcasses away from coastlines, fishing grounds, and areas of likely human contact, and the working interpretation in practice is to discharge well offshore, often cited as at least 100 nautical miles where the ship’s route and schedule allow.
The guidelines also address the practical handling: carcasses should be discharged when the ship is en route, weighted or treated to ensure they sink rather than drift to a coast, and the discharge timed to avoid areas where the carcass could foul fishing gear or wash ashore. The discharge is logged in the Garbage Record Book. The alternative to sea discharge, retaining a decomposing carcass on a ship without dedicated freezer capacity, carries its own biosecurity and crew-health problems, which is why the convention permits sea discharge of carcasses outside special areas at all while barring it inside special areas under Regulation 6.
For livestock carriers operating regular trades, the carcass-handling procedure is set out in the ship’s garbage management plan and aligned with any additional requirements from the importing and exporting States’ animal-health authorities, which can be stricter than Annex V and can require carcasses to be retained for veterinary inspection or rendered rather than discharged.
Paragraph 4.2: cleaning agents and additives in wash water
Regulation 4.2 permits the discharge of cleaning agents or additives contained in cargo hold wash water, and in deck and external surface wash water, both outside and within special areas, provided the cleaning agents or additives are not harmful to the marine environment. This is the one Regulation 4 paragraph that reaches inside special areas as well, because the same allowance is carried into Regulation 6, and it is the provision that lets a ship wash holds and decks with detergents and additives and discharge the wash water at sea.
The condition is the “not harmful to the marine environment” qualifier, assessed against the IMO guidelines. The guidelines direct that cleaning agents and additives used be evaluated for their environmental hazard, and that products meeting the harmful criteria be substituted or their wash water retained. In practice, ships use proprietary hold-cleaning and deck-cleaning products whose safety data sheets and manufacturer declarations state whether the product is harmful to the marine environment under the relevant criteria. A product declared not harmful can be used and its wash water discharged; a product that is harmful requires retention of the wash water for a reception facility or substitution with a compliant product.
The distinction between the cleaning agent and the cargo residue it is washing is worth keeping straight. Regulation 4.2 addresses the cleaning agent and additive component of the wash water. The cargo residue component of the same wash water is governed by 4.1.3 and its HME test. So hold wash water after a non-HME cargo, cleaned with a not-harmful agent, can be discharged at 12 nautical miles or more under the combined operation of 4.1.3 (residue) and 4.2 (agent). Hold wash water after an HME cargo cannot be discharged regardless of the cleaning agent, because the residue side fails 4.1.3. And a harmful cleaning agent fails 4.2 regardless of the residue. Both components have to clear their respective tests.
For deck and external-surface wash water, the residue side is usually not a cargo-residue question but a matter of what is on the deck: paint scrapings, rust, oil traces, and operational debris that may have their own discharge constraints. Regulation 4.2 covers the cleaning agent in the wash water; the solids it carries are operational waste, which is barred from sea discharge, so a wash-down that mobilizes paint chips and scale is not cleanly within 4.2 even if the detergent is compliant. The practitioner reading is that 4.2 sanctions the discharge of compliant cleaning chemistry in wash water, not the discharge of the operational solids the wash water may carry.
Paragraph 4.4: mixed and contaminated garbage takes the stricter rule
Regulation 4.4 states that when garbage is mixed with or contaminated by other substances prohibited from discharge or having different discharge requirements, the more stringent requirements apply. This is the tie-breaker, and it is the reason segregation at source is the foundation of Annex V compliance rather than an optional housekeeping nicety.
The rule resolves the everyday reality that shipboard waste does not arrive in neat single-category streams. Food waste comes mixed with plastic packaging, plastic cutlery, and cling film. Cargo residue washes out with sweepings that may include dunnage and lashing debris. Domestic waste mixes paper, glass, and plastic. Whenever two streams with different discharge rules end up in the same receptacle, 4.4 says the stricter rule governs the mixture. Food waste mixed with plastic is treated as plastic: it cannot be discharged at sea at all, because plastics carry an absolute prohibition. Non-HME cargo residue contaminated with an HME substance is treated as HME and retained.
The operational consequence is direct: the value of the 4.1.1 3-nm food-waste pathway and the 4.1.3 cargo-residue pathway depends entirely on keeping those streams clean. A galley that scrapes plates into a bin that also takes plastic wrap has converted its food waste into plastic-contaminated waste that 4.4 bars from the macerator-and-discharge route. The defense to a port State control challenge that a food-waste discharge was actually a discharge of plastic-contaminated waste is the ship’s segregation procedure and the crew’s demonstrated familiarity with it, both documented in the garbage management plan.
This is why the inspection focus on Annex V is so heavily about segregation containers, their labeling, and crew interviews. A clean food-waste stream that has been comminuted and discharged at 4 nautical miles is lawful; the same discharge from a bin that the deck crew used for mixed waste is a plastics violation that 4.4 makes explicit.
Distance arithmetic and the “nearest land” reference
The two distance numbers in Regulation 4, 3 nautical miles and 12 nautical miles, are measured from the nearest land, and the measurement is the operational step where errors creep in. “Nearest land” in MARPOL is the nearest point of the land territory of a State, measured from the baseline from which the territorial sea of that State is established under international law, subject to the specific exceptions MARPOL lists for particular coasts. The practical reading is the nearest point of any land, in any direction, including offshore islands, low-tide elevations that count as baseline features, and, in the special-area context, ice shelves.
The trap is a complex coastline or an offshore island. A ship that is 14 nautical miles from the mainland coast but 9 nautical miles from a charted offshore island has not met the 12-nm test, because the island is the nearest land. The watch officer cannot reason from the mainland alone; the nearest point of land in any direction governs. The ECDIS-displayed coastline and island contours are the working reference, and the position recorded in the Garbage Record Book is the one a port State control officer will check against the chart after the fact.
The distances stack with the en-route and as-far-as-practicable conditions, never replacing them. A ship that has met 12 nautical miles but is stopped has not met Regulation 4. A ship that has met 3 nautical miles for comminuted food waste but could easily have discharged at 30 nautical miles, with no operational reason to discharge closer in, has arguably not discharged as far from land as practicable. The compliance posture that holds up is to discharge at the distance the ship already has, well beyond the minimum, while making way on the voyage.
For cargo residue under 4.1.3, the 12-nm measurement interacts with the post-discharge hold-washing schedule. A bulk carrier completing discharge in a port well inside a bay may need several hours of steaming to clear 12 nautical miles from all nearest land, including the bay’s headlands and any offshore islands, before the hold-wash water carrying non-HME residue can be discharged. The hold-cleaning plan should build that steaming time into the sequence so the wash does not begin while the ship is still inside the 12-nm contour.
What Regulation 4 does not permit
The fastest way to apply Regulation 4 correctly is to remember what it leaves out. Outside special areas, the following may not be discharged into the sea under Regulation 4 and are retained for a reception facility or, where fitted and appropriate, an approved incinerator: all plastics, including synthetic ropes, synthetic fishing nets, plastic bags, and incinerator ash from plastic products; domestic wastes such as paper, rags, glass, metal, bottles, and crockery; cooking oil; incinerator ash and clinker from products containing toxic residues or heavy metals; operational wastes such as cleaning rags, paint scrapings, and packaging that is not food-related; fishing gear; and e-waste such as discarded electronic equipment.
The plastics prohibition is the oldest and most absolute in Annex V, in force since the annex itself entered into force on 31 December 1988, and it admits no exception inside or outside special areas, at any distance, at any speed. Regulation 4 does nothing to soften it. Domestic waste and cooking oil are barred from sea discharge everywhere under the revised annex, so the only routes are shore reception or, for combustible domestic waste, approved incineration with the ash retained. Operational waste follows the same logic.
Incinerator ash sits in an awkward middle: ash and clinker from products that consist wholly of ordinary materials, with no heavy metals or toxic residues, can be discharged outside special areas at more than 12 nautical miles, but ash from a mixed garbage stream almost always carries trace heavy metals from glass, inks, treated paper, and the inevitable plastic fraction, so it fails the test in practice. The operational default on most ships is to retain all incinerator ash for shore disposal rather than try to prove a clean-ash discharge. That handling sits outside Regulation 4’s main food-waste-and-cargo-residue purpose and is covered in the Annex V garbage discharge overview.
The single rule that ties this together is Regulation 3 read with Regulation 4.4: discharge is prohibited unless expressly permitted, and a mixed stream takes the strictest rule in the mix. If a category is not in the 4.1.1 to 4.1.4 list, and not the cleaning-agent allowance of 4.2, it does not go over the side outside special areas.
How Regulation 4 differs from Regulations 5, 6, and 7
Regulation 4 is the outside-special-areas regime. Its three siblings cover the situations where it does not apply, and the boundaries between them are exactly where compliance decisions get made.
Regulation 5 is the platforms regime. It applies to fixed and floating platforms engaged in offshore exploration and exploitation, and to all ships when alongside or within 500 meters of such platforms. The platform rule is stricter than Regulation 4: it prohibits discharge of all garbage except comminuted food waste, and only at 12 nautical miles or more from the nearest land or platform, even though Regulation 4 would permit comminuted food waste at 3 nautical miles for an ordinary ship in the same water. A supply vessel working inside the 500-meter zone applies the platform rule; once clear of the zone it reverts to Regulation 4. The detail sits in the platforms article.
Regulation 6 is the within-special-areas regime, and it is the direct counterpart to Regulation 4. Inside a special area, discharge of all garbage is prohibited except food waste comminuted to the 25 mm standard, discharged at 12 nautical miles or more from the nearest land or ice shelf, en route. The two key contrasts with Regulation 4 are that the food-waste distance jumps from 3 nautical miles to 12 nautical miles, and that non-comminuted food waste, permitted at 12 nautical miles under Regulation 4.1.2 outside special areas, has no sea-discharge route inside a special area. Cargo residue discharge inside a special area is allowed only under tightly drawn conditions and only for non-HME residue. The full treatment is in the within-special-areas article.
Regulation 7 is the exceptions provision. It disapplies the Regulation 3 prohibition and the Regulation 4, 5, and 6 conditions in three narrow cases: discharge necessary for securing the safety of the ship and those on board or for saving life at sea; discharge resulting from accidental damage to the ship or its equipment, provided all reasonable precautions were taken before and after the damage; and accidental loss of fishing gear, provided all reasonable precautions were taken to prevent the loss. These are casualty and emergency defenses, not operational permissions, and they carry an evidentiary burden the master must be able to meet. The exceptions article works them in detail.
The mental model for the watch officer is a decision tree. Is the ship inside a special area? If yes, Regulation 6. Is the ship within 500 meters of a platform, or is it a platform? If yes, Regulation 5. Is this an emergency, casualty, or accidental gear loss? If yes, Regulation 7. Otherwise, Regulation 4, and only the five streams it permits, only en route, only as far from land as practicable.
Recording a Regulation 4 discharge in the Garbage Record Book
A Regulation 4 discharge is not complete until it is logged. The Garbage Record Book, required for ships of 400 GT and above and ships certified to carry 15 or more persons, records every discharge with the date and time, the ship’s position at the start of the operation, the garbage category, the estimated volume, and the signature of the officer in charge, with the master countersigning each completed page. Since the Part I and Part II split that took effect on 1 March 2018, food-waste and ordinary-garbage discharges go in Part I and cargo-residue discharges go in Part II.
The entry is the operational proof that the discharge was within Regulation 4. A food-waste discharge logged at a position 5 nautical miles from the nearest land, with the ship recorded as en route at 12 knots and the food waste comminuted, is a clean 4.1.1 entry. The same volume logged at a position the inspector identifies as an anchorage, with the deck log showing the ship at anchor, is an admission of an unlawful discharge. A cargo-residue discharge logged in Part II at 14 nautical miles, with the cargo’s non-HME determination referenced from the shipper’s declaration, is a clean 4.1.3 entry; the same discharge with no HME determination on file is a 4.1.3 entry that cannot be defended.
The position precision matters because the distance test is checked against it. The Garbage Record Book records latitude and longitude, and a port State control officer plots that position against the charted nearest land, including offshore islands, to confirm the 3-nm or 12-nm minimum was met. A position recorded loosely, or a position that plots inside the relevant contour, converts the ship’s own record into the evidence of the violation. The discipline is to record the position accurately and to be sure, before discharging, that the position clears the minimum from all nearest land.
The Garbage Record Book is retained on board for at least two years from the last entry and is one of the first documents a port State control officer asks for. The cross-checks an inspector runs, GRB against deck log, GRB against reception-facility receipts, GRB positions against the chart, are described in the placards, plans, and record-keeping article; the point for Regulation 4 is that the discharge and its record are a single act, and a permitted discharge with a defective record is treated as a suspect discharge.
Worked compliance scenarios
A few concrete cases show how the Regulation 4 conditions resolve in practice.
A container ship is on passage across the Pacific, 600 nautical miles from the nearest land, making 18 knots, with a working galley macerator. Galley food waste is comminuted to pass the 25 mm screen and discharged. This is a 4.1.1 discharge: the comminution test is met, the distance vastly exceeds the 3-nm minimum, the ship is en route, and the discharge is as far from land as practicable because the ship is mid-ocean. The GRB Part I entry records the position, time, category, and volume.
A general-cargo ship’s macerator fails 80 nautical miles from the nearest land while the ship is on passage at 11 knots. Non-comminuted food waste can still be discharged under 4.1.2 because the ship is more than 12 nautical miles out and en route; the comminution requirement of 4.1.1 does not apply to the 4.1.2 pathway. The GRB entry should reflect a 4.1.2 discharge of non-comminuted food waste. Had the same failure happened inside a special area, there would be no sea-discharge route and the waste would be retained.
A Panamax bulk carrier has discharged a non-HME grain cargo and is washing holds. The ship steams out of the loading bay and clears 12 nautical miles from the nearest land, including the bay’s headlands and a charted offshore islet, before beginning the hold wash. The wash water carries non-HME residue and a cleaning agent declared not harmful to the marine environment. This is a combined 4.1.3 and 4.2 discharge, lawful because the residue is non-HME and unrecoverable by ordinary means, the agent is compliant, the distance is met, and the ship is en route. The GRB Part II entry references the shipper’s non-HME declaration.
A livestock carrier loses three head of cattle to heat stress in the Indian Ocean, 250 nautical miles from the nearest land, on passage at 14 knots. The carcasses are discharged under 4.1.4, weighted to sink, as far from land as the route allows, with the GRB recording the discharge. The importing State’s animal-health rules are checked first; if they require retention for inspection, that stricter requirement governs and the carcasses are held.
A passenger ship at anchor in an outer roads 6 nautical miles from land discharges comminuted food waste, reasoning that the 3-nm distance is met. This is unlawful. The en-route condition of the 4.1 chapeau is not satisfied at anchor, and the distance test alone does not authorize the discharge. The lawful options are to retain the waste until the ship is under way and clear of the minimum, or to land it at a reception facility.
Limitations
This article states Regulation 4 as it stands in the consolidated Annex V adopted by Resolution MEPC.201(62) and amended by Resolution MEPC.277(70). Several limitations bind any specific application.
The 4-knot speed figure that practitioners attach to the en-route condition comes from the IMO implementation guidelines, not from the convention text of Regulation 4. Flag States and port States read the en-route requirement through those guidelines, and most treat 4 knots as the working floor and read the speed as speed over the ground, but the binding text fixes the en-route condition and the as-far-as-practicable condition, leaving the numeric speed to the guidelines. A practitioner relying on a precise speed threshold should check the relevant flag State’s implementation and the current guidelines text rather than treat 4 knots as a convention number.
The HME determination under 4.1.3 and 4.3 is the hardest part to get right, and it rests on the shipper’s declaration. The master is entitled to rely on the declaration absent evident error or fraud, but the declaration is a presumption, not an absolute defense. Where a declaration is unclear, missing, or contradicted by direct observation, such as a residue declared non-HME that visibly contains plastic feedstock pellets that are HME by the synthetic-polymer criterion, the defensible course is to treat the residue as HME and retain it. The detailed criteria sit in the HME cargo residues and e-waste article.
Distance measurement near complex coasts is a recurring source of inadvertent breach. “Nearest land” is the nearest point of any land in any direction, including offshore islands; a position that clears the mainland by a comfortable margin can still fail the test against a nearer island. The ECDIS contour is the operational reference, and the burden of getting the measurement right falls on the watch officer at the moment of discharge, not on a later reconstruction.
The cleaning-agent allowance in 4.2 turns on a “not harmful to the marine environment” determination assessed against IMO guidelines and the product’s own hazard data. The determination is product-specific and changes as formulations and the underlying guidelines change. A product compliant under one guideline version is not automatically compliant under a later one, and the ship’s stores should be checked against the current guidance rather than assumed compliant on the strength of past practice.
Finally, regional and national overlays can be stricter than Regulation 4. The EU Port Reception Facilities Directive 2019/883 adds delivery and notification rules in EU ports, animal-health authorities can require retention of carcasses that 4.1.4 would permit to be discharged, and some coastal States enforce their own waters more aggressively than the convention minima, with documented fines for food-waste discharges in their coastal zones. Regulation 4 is the floor of what is permitted at sea; the binding requirement in a given voyage can be tighter, and the master applies the stricter of the applicable rules.
See also
- MARPOL Annex V garbage discharge regime: the article-level overview of the whole Annex V discharge framework that this regulation-level article goes deeper than.
- MARPOL Annex V hub: the parent overview of Annex V scope, history, and structure.
- MARPOL Annex V Regulation 5 platforms: the stricter regime for fixed and floating platforms and ships within 500 meters.
- MARPOL Annex V Regulation 6 discharge within special areas: the within-special-areas counterpart, with the 12-nm food-waste rule and the special-area cargo-residue conditions.
- MARPOL Annex V Regulation 7 exceptions: the safety, accidental-damage, and gear-loss exceptions to the discharge prohibition.
- MARPOL Annex V Regulation 10 placards, GMP, and record-keeping: the documentary regime, including the Garbage Record Book entries that prove a Regulation 4 discharge.
- HME cargo residues and e-waste under Annex V: the chemistry of the HME determination that gates the 4.1.3 cargo-residue pathway.
- IMSBC Code: the solid bulk cargo code that carries the shipper’s classification and declaration required by Regulation 4.3.
- MARPOL Annex I Regulation 15 discharge control: the parallel oily-water discharge regime under the same en-route logic.
- MARPOL Annex IV Regulation 11 sewage discharge: the parallel sewage-discharge regime.
- MARPOL Convention: the overarching pollution-prevention framework.
- Port State control: the enforcement regime that inspects Annex V compliance.