Brown Coal Briquettes: IMSBC Code Schedule

Brown coal briquettes are compressed lignite fuel blocks regulated under the IMSBC Code as a Group B cargo. The coal-family hazard triad applies: self-heating toward spontaneous combustion, emission of absorbed methane from the cargo body, and accumulation of carbon monoxide and oxygen depletion in enclosed hold spaces. Temperature monitoring, carbon monoxide measurement, gas sampling, and surface-only ventilation are the core controls for the entire loaded voyage.

Brown coal (lignite) is the lowest-rank coal on the geological maturation sequence. Unlike the bituminous and sub-bituminous coals that dominate global seaborne trade at approximately 1.2 billion tonnes per year, lignite contains a higher proportion of moisture, oxygen-bearing functional groups, and residual organic compounds from incomplete coalification. In most producing countries the fuel is consumed at the mine mouth in dedicated power stations, because its low calorific value (typically 8 to 12 megajoules per kilogram on an as-received basis, versus 24 to 30 MJ/kg for steam coal) makes long-distance haulage uneconomical without processing.

Briquetting is the primary processing step that makes lignite export viable. Lignite is dried from typical mine-mouth moisture contents of 50 to 60 per cent down to approximately 10 to 15 per cent, then compressed in a roller press or extrusion press at elevated pressure without binder into uniform pillow or elongated-block shapes, usually 50 to 100 mm on the longest dimension. The process densifies the fuel, improves its calorific value per unit volume, reduces surface area relative to raw lump lignite, and cuts dust generation during handling. Despite the improved handling characteristics, the underlying chemical reactivity of the lignite feedstock is preserved in the briquette: the coal-family hazards of self-heating, methane release, and enclosed-space atmospheric hazards all follow the cargo onto the ship.

The IMSBC Code, adopted under SOLAS Chapter VI and mandatory from 1 January 2011 by Resolution MSC.268(85), classifies solid bulk cargoes into three groups based on principal hazard profile. Group B cargoes present a chemical hazard to the ship without meeting the liquefaction criteria for Group A. Brown coal briquettes sit firmly in Group B, sharing this classification with bituminous coal, petroleum coke, and other coal-family cargoes. Amendment 07-23 (Resolution MSC.539(107), mandatory from 1 January 2025) is the current mandatory edition governing the BROWN COAL BRIQUETTES schedule.

IMSBC schedule particulars

The IMSBC Code Appendix 1 lists BROWN COAL BRIQUETTES as a named entry with specific schedule particulars that define the cargo’s identity, hazard class, and physical parameters. The table below summarizes the primary schedule fields as they appear in the current mandatory edition of the Code.

Two features of this schedule deserve immediate attention. First, there is no loading-temperature criterion for brown coal briquettes equivalent to the 55-degree Celsius limit in the petroleum coke schedule. This does not mean temperature is irrelevant; it means the Code addresses temperature risk through monitoring and ventilation during the voyage rather than a pre-loading gate. Second, the briquetted form’s defined shape means an angle of repose is not applicable in the way it is for coal fines, and liquefaction testing is not required.

What the Group B classification means in practice

Group B means the cargo presents a chemical hazard, but not a liquefaction hazard. In practical shipboard terms for brown coal briquettes, this translates to three monitoring obligations that persist throughout the loaded voyage: temperature monitoring where practicable, CO monitoring at sealed sampling points in each hold, and methane and oxygen monitoring to characterize hold atmosphere before any entry. No flow-table or Proctor-Fagerberg moisture testing is needed for briquettes because liquefaction risk is absent.

The cargo may be carried in standard bulk carrier holds without special structural modifications beyond those required for all self-heating cargoes. The holds must be cleaned, dried, and fully watertight before loading, and all ignition sources including hot-work permits must be suspended for the entire operation from loading to discharge.

The cargo and the trade

Lignite geology and rank

Coal rank rises along a sequence from peat to lignite to sub-bituminous to bituminous to anthracite as burial depth and temperature increase over geological time. Lignite, or brown coal, occupies the low end of that sequence with carbon content typically between 60 and 75 per cent on a dry, ash-free basis, compared to 75 to 90 per cent for sub-bituminous coal and 85 to 95 per cent for bituminous coal. The lower carbon content goes with higher oxygen content in reactive functional groups, principally carboxyl (-COOH) and hydroxyl (-OH) moieties attached to the aromatic ring structure. These functional groups are the primary site of low-temperature oxidation that drives self-heating.

The large lignite deposits exploited for briquette production include the Rhenish (Rheinland) and Lusatian (Lausitz) fields in Germany, the Tiszaalpár and related fields in Hungary, fields in Poland (Bełchatów) and the Czech Republic, and the Latrobe Valley field in Victoria, Australia. German production is the largest in Europe, with the Rheinland field operated primarily by RWE Power AG producing the “Rheinische Braunkohlebriketts” familiar in European heating markets. The Latrobe Valley in Victoria holds one of the world’s largest known brown coal deposits at approximately 430 billion tonnes of recoverable resource, though the overwhelming majority is consumed domestically.

The briquetting process and why it matters for carriage

Raw mine-mouth lignite at 50 to 60 per cent moisture is essentially non-transportable by sea. It is too heavy per unit of heat delivered, too prone to spontaneous combustion from its very high reactive surface area, and too fragile to survive conveyor and shiploader handling without generating excessive fines. The briquetting process addresses each of these problems.

Drying removes moisture in large-scale drying drums or in modern processes using waste heat from the associated power station. The energy cost of drying is substantial, roughly 0.9 to 1.2 MJ of process energy per kilogram of moisture removed, and it is this step that makes briquetting economically justifiable only where low-cost process heat is available. After drying, the lignite is ground to a fine powder and then compressed under roller presses at typically 50 to 100 megapascals without any added binder; the natural bitumen and wax compounds in the lignite act as the binding agent.

The finished briquette has a bulk density of approximately 700 to 850 kilograms per cubic metre and a calorific value on an as-fired basis of 19 to 22 megajoules per kilogram, roughly double that of the original run-of-mine lignite. The surface area per unit mass is far lower than for loose lignite or coal fines because the small particles have been compacted into a dense solid. This reduced surface area is the key factor that makes briquettes less reactive than raw lignite, though not non-reactive.

Seaborne trade volumes and routes

Seaborne trade in brown coal briquettes is small compared to thermal coal or petroleum coke. Germany exports brown coal briquettes under the brand “Rheinische Braunkohlebriketts” primarily to the Netherlands, Belgium, Denmark, Poland, and other Northern and Central European markets. These are predominantly short-sea movements on coastal bulk carriers rather than ocean-going handysize or supramax voyages. Australian exports from the Latrobe Valley are limited by the economics of competing against domestically available black coal and liquefied natural gas.

The global seaborne trade volume for brown coal briquettes is in the low millions of tonnes per year, making this a niche cargo relative to the approximately 1.2 billion tonnes per year of all-grades coal trade. Vessel sizes typical for this cargo are smaller coastal bulk carriers and short-sea handysize vessels in the 5,000 to 35,000 DWT range on European routes. Supramax and panamax vessels handling brown coal briquettes are the exception rather than the rule, occurring primarily when large quantities move on trans-ocean routes to industrial users or when a consignment is consolidated with other bulk cargoes.

Receiving ports are concentrated in European Baltic and North Sea ports with established distribution networks for solid heating fuels: Rotterdam, Hamburg, Amsterdam, Antwerp, Gdańsk, and Copenhagen all receive brown coal briquettes at some frequency. The cargo moves through port storage to regional heating-fuel distributors and industrial users, primarily brick kilns, ceramics manufacturers, and district heating plants that have maintained solid-fuel infrastructure.

Self-heating and spontaneous combustion

The chemical mechanism

Self-heating in brown coal briquettes follows the same carbon oxidation pathway that applies across the coal family, but with a lower ignition temperature and faster oxidation rate than bituminous coal. This is a direct consequence of lignite’s chemical composition.

The lignite matrix contains a higher proportion of oxygen-containing functional groups than higher-rank coals. These groups, particularly carboxyl and hydroxyl moieties, react with atmospheric oxygen at lower temperatures than the aromatic ring structures dominant in bituminous coal. The initial oxidation step occurs at temperatures as low as 20 to 30 degrees Celsius; even at ambient temperature in a sealed cargo hold, a slowly self-heating mass of briquettes is generating a small exothermic heat flux. In a well-ventilated, low-density pile this heat dissipates safely. In a compacted bulk carrier hold with limited air exchange and the insulating mass of thousands of tonnes of cargo, the heat accumulates.

Brown coal briquettes have a higher tendency toward spontaneous combustion than bituminous coal. The comparative ignition temperatures illustrate this: the spontaneous ignition temperature of lignite is typically in the range of 130 to 200 degrees Celsius, versus 200 to 300 degrees Celsius for bituminous coal. This lower threshold means the cargo has less thermal margin from ambient conditions to the point at which open combustion can begin without an external ignition source.

Stages of self-heating progression

Self-heating in brown coal briquette cargoes progresses through identifiable stages, each with characteristic indicators in the monitoring data:

The first stage covers the temperature range from ambient up to approximately 50 degrees Celsius. Carbon monoxide production is low at this stage, typically below 20 parts per million in the headspace, and temperature rise is slow and may not be detectable against the normal thermal gradient in the hold. The reaction is primarily the oxidation of the most reactive surface functional groups.

The second stage, from approximately 50 to 80 degrees Celsius, produces measurably rising CO concentrations. The reaction rate has increased enough that CO accumulates faster than it disperses through the hold atmosphere. At this stage CO readings above 50 ppm should be treated as a serious warning, not a monitoring note. The cargo may also begin to emit a characteristic acrid odour detectable when sounding tubes are opened for sampling.

The third stage, above approximately 80 to 100 degrees Celsius, involves rapid carbon monoxide production, visible surface discoloration of the briquettes, and temperatures approaching the spontaneous ignition threshold. CO concentrations can reach hundreds of ppm in the hold headspace. The reaction is self-sustaining and can progress to open combustion if oxygen supply is maintained.

Above approximately 130 to 200 degrees Celsius, depending on the specific lignite source, the briquettes can ignite without any external ignition source. At this point the cargo is on fire internally and the firefighting response must be immediate.

Surface area and reactivity of the briquetted form

One practical question for cargo officers is how the reactivity of brown coal briquettes compares to raw lignite or coal fines. The briquetted form is measurably less reactive per unit mass than powdered or fine lignite because compression reduces the accessible surface area available for oxidation. A 75 mm briquette presents far less reactive surface area per kilogram than the same mass of 1-mm lignite powder.

This reduction in reactivity compared to fine lignite is why the IMSBC Code treats brown coal briquettes as a distinct schedule entry from coal in general. However, the reactivity reduction is relative, not absolute. Brown coal briquettes are still more reactive than bituminous coal briquettes or petroleum coke of comparable size. The improved handling characteristics of the briquetted form should not be misread as chemical inertness.

A cargo that has been partially broken during loading, creating a fraction of fine material, is more reactive than intact briquettes. Loading damage from excessive drop heights on the shiploader or from hold trimming with heavy equipment can produce significant fines. Pre-voyage hold inspection should note the proportion of broken briquettes and fines in the loaded cargo.

Methane emission hazard

Source and behavior in the hold

Lignite retains adsorbed methane in its pore structure from the geological environment in which it formed. The adsorption is weaker than in higher-rank coals because the pore structure of lignite is less ordered and the sorption capacity per unit mass is lower. As a result, brown coal briquettes release methane more rapidly than bituminous coal after the pressure and atmospheric conditions change, which means the initial methane evolution rate after loading is relatively high and then declines over the voyage.

Methane released from the cargo accumulates in the hold headspace. Methane is lighter than air (relative molecular mass 16 versus 29 for air) and tends to stratify in the upper headspace when the hold is sealed and still. The flammable range for methane in air is 5 to 15 per cent by volume (the lower and upper explosive limits). If methane concentrations reach this range in the headspace and an ignition source is present, a gas explosion can occur with potentially catastrophic consequences for the vessel’s structure.

For brown coal briquettes, the methane content of the source lignite is lower than for higher-rank bituminous coals, particularly coking coals that may carry several cubic metres of methane per tonne. Lignite methane content is typically in the range of 0.1 to 2 cubic metres per tonne (as-received basis, desorption at atmospheric pressure), compared to 4 to 15 cubic metres per tonne for gas-prone bituminous coals. The lower methane content of brown coal briquettes reduces but does not eliminate the methane explosion risk; even at the low end of this range, a 10,000-tonne cargo could release 1,000 cubic metres of methane into a hold headspace of roughly 1,000 to 3,000 cubic metres, readily producing headspace concentrations within the explosive range if ventilation is insufficient.

Monitoring requirements

The IMSBC Code requires methane monitoring throughout the voyage for brown coal briquettes. The standard practice, consistent with the broader coal monitoring protocol, is to measure methane concentration in the hold headspace at each sampling point at the start of the voyage and daily during the first several days when methane evolution is highest. As the cargo stabilizes and outgassing slows, the monitoring interval may be extended, but methane measurement should continue throughout the loaded passage.

Methane measuring instruments on bulk carriers are typically catalytic-bead (pellistor) detectors reading in percentage of lower explosive limit (%LEL) or percentage by volume. A reading of 100% LEL corresponds to the 5% by volume lower explosive limit. Any reading above 20% LEL warrants increased ventilation and increased monitoring frequency. Any reading above 50% LEL warrants sealing the hold to prevent ignition sources from entering and immediate consultation with the operator and P&I correspondent.

The instrument must be calibrated against reference gas at intervals specified by the manufacturer. Catalytic bead sensors can become poisoned by sulphur compounds and silicone vapors; a sensor that reads zero consistently across all holds despite methane being expected should be treated as suspect and replaced or cross-checked against an independent sensor.

Oxygen depletion and carbon monoxide in enclosed spaces

Dual-atmosphere hazard

Cargo hold spaces and any adjacent enclosed spaces (cofferdams, void spaces, pipe tunnels) associated with a brown coal briquette cargo present two independent atmospheric hazards: oxygen depletion through consumption by self-heating oxidation, and carbon monoxide accumulation as the product of that same oxidation. Either hazard alone is sufficient to be immediately life-threatening to personnel who enter without breathing apparatus; together they are doubly dangerous because CO can be at toxic concentrations before the oxygen deficiency is severe enough to be noticed through physiological symptoms.

SOLAS Regulation III/19 requires that enclosed spaces on ships be subject to atmosphere testing before any entry, and that the following criteria be met before entry without breathing apparatus: oxygen concentration between 19.5 and 23.5 per cent, flammable gas or vapor below 1 per cent LEL, and toxic contaminants below threshold limit values. For a hold containing brown coal briquettes that has been sealed, none of these conditions can be assumed without direct measurement.

Self-heating as an oxygen sink

Self-heating in brown coal briquettes consumes oxygen from the hold atmosphere according to the primary reaction:

and the partial oxidation pathway that produces carbon monoxide:

In a sealed hold with no ventilation, the oxygen concentration drops progressively as these reactions proceed. The rate of oxygen depletion is fastest in the early stages of the voyage when the cargo surface is most reactive and in warmer ambient conditions that accelerate the oxidation kinetics. A hold that is sealed in a tropical climate and opened after two weeks of ocean passage can have an oxygen concentration well below 19 per cent, which is the threshold at which cognitive impairment begins in a person without breathing apparatus.

The critical operational implication is that CO monitoring data alone does not confirm the hold is safe to enter. A hold could have elevated CO with near-normal oxygen, or it could have apparently moderate CO with severely depleted oxygen if most of the oxidation product has been CO2 (which does not register on a CO detector). The pre-entry atmosphere test must measure all three: oxygen, CO, and combustible gas, using calibrated instruments in that order before any person enters.

Carbon monoxide as the primary early-warning indicator

Among the three gas parameters, CO concentration is the most sensitive and most practically useful indicator of incipient self-heating during the voyage. CO starts accumulating at detectable concentrations in the hold headspace before bulk cargo temperature has risen measurably and before the overall oxygen content of the hold headspace has changed enough to be notable on routine monitoring.

The Coal: IMSBC Code Schedule article provides the primary threshold guidance that practitioners use informally across the coal family. CO readings below 50 ppm with a flat trend over successive days are generally treated as background. CO readings above 50 ppm with a rising trend warrant escalated monitoring frequency, informing the operator and P&I, and reviewing ventilation procedures. CO readings above 200 ppm, or any sharp upward step in readings, warrant emergency response: halt ventilation if it was through the cargo, seal the hold, prepare fixed firefighting systems, and contact the shipper, the operator, and the nearest Maritime Rescue Coordination Centre.

These thresholds are derived from the coal schedule and from industry practice; the IMSBC Code does not set explicit CO threshold values for the BROWN COAL BRIQUETTES entry specifically. Masters carrying brown coal briquettes should apply the coal family guidance as the closest applicable operational benchmark.

Ventilation policy

Surface ventilation: the prescribed method

The IMSBC Code prescribes surface ventilation for brown coal briquettes. Surface ventilation means airflow is applied to the headspace above the cargo, removing accumulated methane, CO, and other gases from the hold atmosphere without introducing fresh oxygen into the cargo body itself. The ventilation air passes in at one opening, sweeps the headspace, and exits at another, without passing through or around the briquette mass.

This is the opposite of through-ventilation, in which air is introduced from below the cargo (through the duct keel or lower ventilation ducts) and rises through the cargo body to exit at the top. Through-ventilation actively supplies oxygen to the entire cargo body at every level, accelerating self-heating throughout the mass rather than just at the surface. The IMSBC Code prohibits through-ventilation for brown coal briquettes precisely because it would feed the self-heating reaction.

In practical terms on a bulk carrier, surface ventilation is achieved by opening hatch covers to a controlled position, using hatch-mounted cowl ventilators, or operating mechanical fans that draw air across the cargo surface. The exact method depends on the vessel’s equipment and the weather conditions. In heavy sea states, with green water risk at the hatches, surface ventilation is not practicable, and the holds are fully sealed. During sealed periods, CO and methane monitoring takes on heightened importance because any self-heating that has started continues without the gas removal that surface ventilation provides.

Ventilation in relation to self-heating stage

The relationship between ventilation and self-heating is not straightforward. In the early, ambient-temperature stage of the voyage, light surface ventilation is beneficial: it removes methane from the headspace and prevents the headspace atmosphere from becoming anoxic at the surface. As the voyage progresses and if CO monitoring indicates the cargo is not self-heating, routine surface ventilation remains appropriate.

If CO monitoring shows a rising trend suggesting incipient self-heating, the ventilation decision becomes more nuanced. Surface ventilation that removes CO from the headspace while introducing limited oxygen to the surface layer may arrest early-stage self-heating if the rate of oxygen removal by the oxidizing cargo exceeds the rate of fresh oxygen supply. If the self-heating has progressed to the second or third stage (CO above 50 ppm with rising trend, cargo temperature above 60 to 80 degrees Celsius), the risk calculus shifts: continued ventilation, even surface ventilation, may supply enough oxygen at the cargo surface to sustain the reaction, while sealing cuts off oxygen and allows CO2 and CO concentrations in the hold to rise to levels that suppress the reaction.

The decision at this point is not made mechanically from a procedure table; it requires the master to assess the specific condition of the cargo, the CO and temperature trend data, the available firefighting resources on the vessel, and the time to the nearest port of refuge. P&I clubs provide 24-hour emergency advice lines specifically for situations of this type.

Temperature monitoring

Temperature monitoring of brown coal briquette cargoes throughout the voyage is required by the IMSBC Code where practicable. The same “where practicable” qualification that applies to coal applies to brown coal briquettes, acknowledging that most bulk carriers do not have permanently installed cargo temperature probes. Monitoring is done by lowering calibrated probes through sounding pipes or hatch openings to contact the cargo surface or upper cargo layers.

Industry practice and P&I guidance call for at minimum once-daily temperature measurement in each hold during the loaded voyage. Results are recorded in the cargo monitoring log and transmitted to the operator and charterer. More frequent measurement is warranted when CO readings are elevated, when ambient temperatures are high (particularly in tropical loading ports or on voyages through equatorial waters), or when the cargo has a history of self-heating incidents on previous voyages from the same origin.

The temperature measurement alone is less sensitive than CO as an early warning. The thermal mass of a full bulk carrier hold (potentially 5,000 to 15,000 tonnes of cargo) means that a small but active oxidation zone deep within the cargo can raise CO concentrations in the headspace to detectable levels well before the bulk temperature reading from a surface probe has risen by even one or two degrees. CO monitoring is therefore the primary screening parameter; temperature provides corroboration and a means of assessing the severity of a developing situation once CO has already indicated a problem.

Temperature probes lowered through sounding pipes measure surface or near-surface temperature, not deep cargo temperature. A bulk with active internal self-heating in the lower third of the hold will show normal or only slightly elevated surface temperature until the heat front has migrated upward. This spatial limitation of surface-probe monitoring is a recognized limitation of shipboard temperature measurement for self-heating cargoes and is not specific to brown coal briquettes.

Hold preparation before loading

Proper hold preparation before loading brown coal briquettes is a carriage requirement under the IMSBC Code and a direct risk-management measure. The following checks must be completed and documented before cargo is accepted:

General cleanliness and residue removal: all previous cargo residues must be removed, the hold swept and washed as needed, and all residue removed from frames, web frames, pipe tunnels, and bilge wells. Previous cargo contamination in a subsequent brown coal briquette cargo creates an unpredictable chemistry that can affect self-heating behavior, particularly if the previous cargo included oils, fertilizers, or other reactive materials.

Bilge well condition: bilge wells must be clean, free of oil or organic accumulation, and tested to confirm free drainage. Brown coal briquette fines can compact in and around bilge strums and reduce their effectiveness. The bilge system must be functional throughout the voyage because condensation from the cargo and any minor water ingress must be pumped out promptly.

Hatch cover integrity: hatch cover seals and closing mechanisms must be inspected and confirmed watertight or near-watertight. Water ingress into a brown coal briquette cargo during the voyage does not create liquefaction risk (the cargo is Group B), but water on a thermally active briquette cargo can accelerate surface reactions and produce steam that complicates atmosphere monitoring. The marine fire detection and fixed fire fighting systems article covers vessel-level fire system readiness, which should be verified before loading any self-heating cargo.

Hot-work suspension: all hot-work permits in cargo spaces, adjacent spaces, and on deck above cargo holds must be suspended before loading begins and remain suspended for the entire loaded voyage and throughout discharge. Any welding, cutting, grinding, or other hot work adjacent to loaded holds during the voyage requires the master’s direct authorization after a full risk assessment and atmosphere test; in practice, hot work adjacent to self-heating cargo should be avoided entirely.

Hold dryness: internal surfaces must be dry before loading. Wet holds introduce moisture into the briquette mass that can affect the oxidation kinetics and compromise the accuracy of atmosphere monitoring. If the hold has been washed, it must be dried thoroughly before cargo is loaded.

Cargo declaration receipt: the shipper’s cargo declaration must be received, reviewed, and found materially complete before any cargo is accepted for loading. SOLAS Chapter VI Regulation 2 gives the master the right to refuse loading where the declaration is absent or inadequate.

The cargo hold preparation standards article provides a systematic hold-preparation checklist and the pre-loading survey documentation expected by cargo surveyors and P&I clubs.

Cargo declaration and shipper responsibilities

The shipper of brown coal briquettes must provide a cargo declaration that meets the IMSBC Code requirements. Under the current mandatory edition, the declaration for BROWN COAL BRIQUETTES must include:

Cargo identification: the IMSBC schedule name BROWN COAL BRIQUETTES, identifying it clearly as the schedule entry being shipped.

IMSBC group: Group B. This is not optional or discretionary; the declaration must state the correct group.

Certification of self-heating status: the shipper must certify that the cargo is not liable to spontaneous combustion under normal conditions of carriage. This certification places legal responsibility on the shipper for the accuracy of the hazard characterization. A shipper who certifies a cargo as safe when it has already begun self-heating in storage, or when it has been improperly stored after briquetting, carries significant liability exposure.

Physical properties: bulk density, stowage factor, and moisture content for the specific consignment. These values affect hold loading plans and stability calculations and must be measured from representative samples, not simply taken from generic reference tables.

Specific hazard information: any characteristics of the specific consignment that deviate from the schedule standard, including elevated fines content from production or handling damage, elevated temperature from recent briquette pressing, or any other factor the shipper is aware of that could affect carriage safety.

Shipper’s signature and date: the declaration must be signed by an authorized representative of the shipper and dated.

The master who accepts loading without receiving a materially complete declaration may find that P&I coverage for any subsequent cargo claim is complicated by the absence of proper documentation. P&I clubs have documented cases where masters accepted coal-family cargoes on verbal assurances or informal emails and subsequently faced difficulty in claims resolution.

Loading operations

Brown coal briquettes are loaded by shore-based conveyor systems and shiploaders. The loading rate at terminals handling this cargo is typically lower than at major coal export terminals because the trade volumes are smaller and the terminal infrastructure is less specialized. European short-sea terminals may load at 200 to 800 tonnes per hour; purpose-built bulk handling ports can achieve higher rates.

Dust suppression is required at all transfer points: at the conveyor transfer stations, at the shiploader head, and at the point of cargo entry into the hold. Water misting at transfer points is the most common suppression method. The drop height from the shiploader to the cargo surface should be minimized to reduce both dust generation and mechanical impact that breaks briquettes and increases fines content.

Trimming within the hold is done with the shiploader arm or with bulldozers lowered into the hold to create a level, well-distributed cargo surface. Excessive mechanical compaction from bulldozer tracks can break briquettes; operators should use the minimum necessary compaction to achieve a stable, flat surface that allows secure hatch closure.

Masters and chief officers should be present during loading to observe the condition and color of the incoming cargo (fresh briquettes should be uniformly dark brown-black without visible discoloration or oxidation), assess the proportion of intact briquettes versus fines, and verify that the cargo temperature at the shiploader is not elevated compared to ambient. Hot steaming cargo arriving at the shiploader is a warning sign, though without the specific 55-degree loading-temperature criterion that applies to petroleum coke, the master must use professional judgment on whether to accept cargo that appears thermally active.

After completing loading and sealing the holds, the initial CO and methane baseline readings should be taken in each hold within 24 hours of completion to establish the voyage starting point for trend analysis.

Voyage monitoring: the monitoring log

The IMSBC Code requires monitoring throughout the loaded voyage. The monitoring log for a brown coal briquette cargo should record, for each hold at each monitoring interval:

• CO concentration in ppm from the headspace sampling tube
• Methane concentration in per cent by volume or per cent LEL from the headspace sampling tube
• Oxygen concentration in per cent by volume from the headspace sampling tube (particularly important before any enclosed space entry)
• Cargo temperature in degrees Celsius from the sounding pipe probe or surface contact thermometer
• Ventilation status: surface ventilation open or closed, weather conditions affecting ventilation
• Any observations on hold condition: condensation on hatch underside, odour on opening sampling tubes, visible surface discoloration

The log should record the instrument used, its calibration date, and the calibration reference gas or standard. An undocumented monitoring event provides no evidentiary value if a claim arises.

Frequency: at minimum once daily in each hold throughout the loaded voyage. Increase to twice daily or more frequently if any hold shows CO above 50 ppm or a rising trend.

Firefighting response

The priority: seal before flooding

If CO readings, temperature data, or other observations indicate that self-heating has progressed to or toward spontaneous combustion, the firefighting response for brown coal briquettes follows the same hierarchy as for all coal-family cargoes. The central principle is that open combustion in the interior of a bulk briquette cargo cannot be fought with water applied to the surface, and opening hatches to inspect or ventilate a burning cargo can convert a smouldering internal fire into an open surface fire that is near-impossible to suppress.

The response hierarchy is:

First: seal the hold. Close all hatch openings, ventilation cowls, and any access through which fresh air can reach the cargo space. Cutting off oxygen supply is the single most effective action against self-heating cargo and is achievable without any special equipment beyond what is already fitted to the vessel.

Second: activate fixed CO2 or inert-gas flooding if available and if the master judges that active combustion is occurring. CO2 flooding displaces oxygen in the hold headspace and suppresses combustion. It creates a toxic atmosphere in the hold that excludes personnel without breathing apparatus, which is appropriate because personnel should not be entering an actively burning cargo hold in any case. The marine fire detection and fixed fire fighting systems article covers CO2 and inert-gas fixed system design and the operational requirements for their use.

Third: do not apply water to the cargo surface where the fire is internal and smouldering. Water on a thermally active briquette mass generates steam that distributes heat within the cargo body and may reach and activate briquettes that have not yet reached their ignition temperature. Water applied at high rate to a sealed hold creates pressure that can force toxic gases out through any remaining gaps. The appropriate use of water in a cargo fire situation is to cool the external boundaries of the hold (deck plating, hatch coaming) if radiated heat is threatening adjacent compartments, not to enter the cargo hold.

Fourth: contact the operator, the P&I correspondent, the shipper, and the nearest Maritime Rescue Coordination Centre as the situation develops. Decisions about port of refuge, tug assistance, or cargo discharge may become necessary.

The critical error in cargo self-heating incidents is delayed recognition: treating slowly rising CO readings as a monitoring note rather than an early-warning signal and not escalating the response until the cargo is in advanced self-heating. IMSBC Code Section 9 covers emergency response procedures for bulk carriers in detail, and every vessel carrying Group B self-heating cargoes must have those procedures accessible and understood before departure.

Interaction with the SOLAS fire detection system

Brown coal briquette cargoes are covered by the cargo hold fire detection requirements under SOLAS Chapter II-2. Many bulk carriers are fitted with smoke detection in the cargo hold headspace or with CO detection systems at the hatch coaming level. Where such systems are fitted, they provide an independent, continuous monitoring signal that supplements the manual monitoring protocol.

However, shipboard fire detection systems fitted to bulk carriers are not uniformly effective for deep-seated self-heating in large briquette cargoes. A smoke or thermal detector at the headspace level will not register a self-heating zone deep within the lower third of the hold until the heat and gas generation has progressed substantially and the hold atmosphere reflects what is happening at depth. The manual CO and temperature monitoring protocol remains the primary detection system for this type of cargo.

Comparison with higher-rank coal and petroleum coke

Understanding where brown coal briquettes sit relative to other Group B cargo hazards is useful for masters and cargo officers who may carry multiple self-heating cargo types across different voyages.

Self-heating tendency: brown coal briquettes self-heat more readily than bituminous coal at equivalent air exposure, because of lignite’s lower ignition temperature (130 to 200 degrees Celsius versus 200 to 300 degrees Celsius for bituminous coal) and higher oxygen-functional-group content. However, the briquetted form is less reactive than raw lump or fine lignite because of the reduced surface area from compression.

Methane emission: the methane content of lignite is lower than that of gas-prone bituminous coals. High-volatile bituminous coals from Qinhuangdao-exported Chinese coal or Glencore-operated Australian coal operations can carry 4 to 15 cubic metres of methane per tonne; lignite typically carries 0.1 to 2 cubic metres per tonne. The methane explosion risk from brown coal briquettes is real but of a lower magnitude than from gas-prone steam coal.

Liquefaction: brown coal briquettes do not liquefy. They carry no Group A classification and require no TML or moisture-content testing for liquefaction assessment. Petroleum coke is also Group B only; coal with a fines fraction may be Group A and B combined. The absence of liquefaction risk simplifies the pre-loading certification burden for brown coal briquettes.

Loading-temperature criterion: petroleum coke has a 55-degree Celsius loading-temperature ceiling. Brown coal briquettes have no such explicit criterion in the IMSBC Code, though loading hot or partially oxidized cargo is obviously inadvisable.

CO monitoring: required for brown coal briquettes, bituminous coal, and petroleum coke alike, though the coal schedule provides the most explicit threshold guidance. The Coal: IMSBC Code Schedule article and the Petroleum Coke: IMSBC Code Schedule article provide the relevant comparators.

Hold cleaning after discharge: brown coal briquettes leave a lighter residue than petroleum coke. The oily adhesive character of petcoke residue makes it harder to remove than the drier brown coal dust. Both are more easily removed than coal tar or chemical residues.

IMSBC Code amendment history relevant to brown coal briquettes

The IMSBC Code was adopted by Resolution MSC.268(85) in 2008 and entered force on 1 January 2011, replacing the Bulk Cargo Code (BC Code) that had governed solid bulk cargo carriage since 1965. The brown coal briquettes schedule was included in the original IMSBC Code text and has been carried forward through successive amendments.

Amendment 02-13 (Resolution MSC.393(95), mandatory from 1 January 2015) strengthened the cargo declaration requirements across Group B schedules, introducing more explicit shipper certification obligations. Amendment 06-21 (Resolution MSC.500(105), mandatory from 1 January 2023) updated physical property data and refined the schedule text for several coal-family cargoes. Amendment 07-23 (Resolution MSC.539(107), mandatory from 1 January 2025) is the current mandatory edition and applies to all voyages from its effective date.

Masters should verify that the edition of the IMSBC Code carried on board is the current mandatory version. The Code is available through the IMO bookshop at imo.org. Outdated editions lack the amendments to schedule texts and emergency procedures that represent current Code obligations.

One point of confusion for practitioners should be addressed directly: Resolution MSC.501(105) is the 2022 amendment to the IMDG Code (the International Maritime Dangerous Goods Code, which governs packaged dangerous goods), not the IMSBC Code. The IMSBC amendment in the same MSC.105 session is MSC.500(105). These two resolutions are sometimes cited interchangeably in error in secondary literature. The BROWN COAL BRIQUETTES schedule is governed by the IMSBC Code, not the IMDG Code, and the relevant IMO resolution is MSC.500(105) for the 06-21 amendment cycle.

Interaction with other regulations

SOLAS Chapter VI: carriage of cargoes

SOLAS Chapter VI Regulation 2 requires the shipper to provide appropriate information about the cargo before loading, in sufficient time for the precautions that may be necessary for the proper stowage and safe carriage of the cargo to be put into effect. For brown coal briquettes, this is the cargo declaration. The regulation also requires the master to be informed of any characteristics of the cargo that are hazardous, and the master has the right to refuse a cargo for which adequate information has not been provided.

SOLAS Chapter VI Regulation 7 requires that solid bulk cargoes that may liquefy only be accepted for loading when the moisture content of the cargo is less than the transportable moisture limit at the time of loading. Brown coal briquettes are exempt from this provision because they are not liable to liquefy (Group B only), but the underlying SOLAS framework for cargo information requirements applies in full.

SOLAS Chapter XII: additional safety measures for bulk carriers

SOLAS Chapter XII applies to bulk carriers of 150 metres or more in length carrying solid bulk cargoes with a density of 1,000 kilograms per cubic metre or more. With a bulk density of approximately 700 to 850 kilograms per cubic metre, brown coal briquette cargoes fall below the 1,000 kg/m³ threshold on which Chapter XII applies specifically. The Chapter’s structural and stability requirements are therefore not triggered directly by brown coal briquette carriage, though the vessel’s flag state compliance with Chapter XII remains in force regardless of cargo type.

ISM Code obligations

The vessel’s Safety Management System under the ISM Code must include documented procedures for carrying Group B self-heating cargoes. The SMS procedures must address: review of the cargo declaration before loading; the monitoring protocol for CO, methane, oxygen, and temperature; the ventilation regime; and the emergency response steps for incipient self-heating or fire. A vessel whose SMS lacks documented Group B cargo procedures may face port state control findings, P&I club scrutiny of claims, and flag state compliance action.

The bulk carrier article covers the regulatory framework for bulk carrier operations, including SOLAS Chapter XII and the ISM Code’s application to cargo-related hazard management.

Limitations

This article reflects the IMSBC Code schedule for BROWN COAL BRIQUETTES through the current mandatory edition, Amendment 07-23 (Resolution MSC.539(107), mandatory from 1 January 2025). The IMSBC Code is amended on an approximately 18-month cycle; masters and operators must verify that the edition of the Code on board is current and that any mandatory amendments have been incorporated. The authoritative text is available through the IMO bookshop at imo.org; third-party reproductions may lag behind mandatory amendments.

Physical property values (bulk density, stowage factor, moisture content, methane content) are representative ranges covering the variability across different lignite sources and briquetting operations. The actual values for any specific cargo must be obtained from the shipper’s declaration and analysis certificates rather than from reference data. Briquettes produced from different lignite sources, including different German coalfields (Rheinland versus Lausitz) or different producing countries, can differ in reactivity and methane content.

The self-heating hazard characterization in this article is based on the IMSBC Code text and established coal-science principles. Individual cargo consignments may have different self-heating characteristics depending on briquette age since production (fresh briquettes from the press are more reactive than those that have had partial surface oxidation during storage), storage conditions prior to loading, handling damage during transport to the port, and the specific lignite source. A cargo that has been partially oxidized in shore storage may show lower initial reactivity on the first days of the voyage (the most reactive surface sites already consumed) but still present internal self-heating risk.

The CO monitoring thresholds cited in this article (50 ppm as an alert level, 200 ppm as an emergency threshold) are derived from the coal schedule and from P&I and industry guidance. The BROWN COAL BRIQUETTES schedule does not specify numerical CO action thresholds in the current Code text. Masters should confirm the applicable thresholds with their P&I club and operator before loading.

Professional judgment in applying the ventilation and monitoring procedures described here must account for vessel-specific factors, including hold geometry, ventilation equipment, instrument calibration status, weather conditions, voyage duration, and the condition of the specific cargo. This article is a reference for practitioners with the relevant maritime qualifications and experience; it does not substitute for the IMSBC Code itself, P&I club guidance, or competent technical advice from a marine surveyor or cargo specialist.

See also

• IMSBC Code
• IMSBC Group B Cargoes
• Coal: IMSBC Code Schedule and Carriage
• Petroleum Coke: IMSBC Code Schedule
• Biomass Pellets: IMSBC Code Schedule and Carriage
• Cargo Hold Preparation Standards
• Marine Cargo Hold Ventilation
• Marine Fire Detection and Fixed Fire Fighting Systems
• Bulk Carrier

Related calculators:

• IMSBC Coal (Lignite)
• Coal Self-Heating Indicator
• IMSBC Group A/B/C Classification
• IMSBC Coal (Bituminous)