Glance at 10th session of the IMO’s Sub-Committee on Pollution Prevention and Response (PPR 10)

The 10th session of the IMO’s Sub-Committee on Pollution Prevention and Response (PPR 10) was held in London from 24 to 28 April 2023. A wide range of topics was on the agenda, including biofouling, ballast water management, black carbon, sewage treatment and marine plastic litter. PPR 10 agreed on revised guidelines on biofouling to minimize the transfer of invasive aquatic species.

Amendments to the IBC Code

Three new products were assessed for inclusion in the MEPC.2/Circ.28. To fulfill the carriage requirements for a chemical tanker, the inclusion of these products will be made in the next Certificate of Fitness. Seven new cargo tank cleaning additives were included in Annex 10 of the next MEPC.2/Circ.28.

A proposal to amend the IBC Code to include ventilation as an alternative means to determine a safe tank atmosphere following the discharge of toxic products, for which there is no available toxic vapour detection equipment, was not supported. Instead, it was decided to retain this agenda item for ESPH 29 (October) to further consider the implication of the lack of toxic vapour detection equipment on the daily operation of a chemical tanker.


The revised “Guidelines for the control and management of ships’ biofouling to minimize the transfer of invasive aquatic species” were finalized by PPR 10 for adoption by the MEPC. The guidelines provide recommendations on in-water inspections with a focus on the quantitative assessment of biofouling using a biofouling rating number, as well as on observations of the anti-fouling system condition. The inspection frequency should be at least every 12 to 18 months depending on the availability of a performance monitoring system based on fuel consumption. It is recommended to use inspection organizations or competent personnel who can provide impartial inspections. Sample templates for inspection reports were provided with the guidelines.

If macrofouling is observed, cleaning with capture is recommended. Proactive cleaning of microfouling may be recommended without capture if performed in an area accepted by the relevant authority for this activity. During operation, a ship is recommended to monitor biofouling risk parameters. A description of ship-specific biofouling management and monitoring should be included in a biofouling management plan (BFMP). The plan should also include a contingency action plan, and any contingency actions taken should be recorded in a biofouling record book. Sample templates for the BFMP and record book were provided with the guidelines.

The suitability of cleaning methods for specific coating systems should be considered. Frequent cleaning or too abrasive methods may impact the effectiveness of a specific coating system, and it is therefore recommended that the manufacturers provide relevant guidance for the BFMP. However, it was agreed that in-water cleaning is a complex activity and international standards for the management of in-water cleaning may continue to be developed and published in a standalone document. Interested parties were invited to submit proposals to the next PPR.

Furthermore, it was agreed that comprehensive testing of cleaning systems or processes is necessary to understand the cleaning performance, capture efficiency, and any release of harmful waste substances. Test and verification guidelines may be developed at the next session, and interested parties were invited to submit proposals.

Air pollution

Use of multiple engine operational profiles (MEOP) for a marine diesel engine

PPR 10 agreed in general that MEOP could be allowed under certain circumstances. However, it was decided to defer the matter to PPR 11 allowing for more time to develop proposals. The MEPC was also asked to consider extending the output to cover definitions of terminology and application related to EIAPP test cycles and the related amendments to the NOx Technical Code.

Marine Diesel engine replacing a boiler

PPR 10 agreed on accepting marine diesel engines replacing steam systems as “replacement engines” under MARPOL Annex VI if complying with the introduced requirements for steam systems, as set in the updated guidelines with respect to non-identical replacement engines, is not required to meet the Tier III limit.

Black Carbon (BC)

PPR 10 further discussed draft guidelines for recommendatory goal-based control measures to reduce the impact of BC emissions from international shipping on the Arctic. The guidelines were not finalized, and a Correspondence Group was established to further develop the draft guidelines.

A list of possible BC control measures was discussed, including,

  • a mandatory switch to distillate or other low BC fuels,
  • a fuel standard,
  • BC Emission Control Areas,
  • engine certification, and
  • mandatory use of BC reduction technologies.

Interested parties were invited to submit further proposals to the next session.Not having a valid IHM certificate/SoC may be a reason for detention. However, failure to update the IHM is not a detainable deficiency. Such inconsistencies shall be rectified at the time of the next survey.

Sewage treatment and revision of MARPOL Annex IV

PPR 10 discussed independent testing facilities for type approval and performance of sewage treatment systems for existing ships, as well as a proposal to introduce a “zero discharge system” definition and exempt the use of such systems from the requirements in MARPOL Annex IV.

A Correspondence Group was tasked to further develop the draft amendments, including to review the scope of application to new and existing ships, but not to consider the proposal for a “zero discharge system” definition.

Standards for shipboard gasification of waste systems

The draft 2023 “Guidelines for thermal waste treatment devices” were finalized for adoption at MEPC 80. The guidelines are technology-neutral, goal-based, and may be applied to any thermal waste treatment device using, for example, gasification, hydrothermal carbonization, pyrolysis, plasma or other thermal means for the disposal of garbage generated on board as an alternative to conventional incinerators.

Review of the Integrated Bilge Water Treatment System guidelines and amendments to the IOPP certificate and Oil Record Book

As no concrete proposals on amendments to MARPOL Annex I, on how to reflect that forced evaporation of bilge water is an acceptable means of disposal, had been submitted, it was decided to defer this agenda item to PRR 11.

Measures to reduce risks of use and carriage of heavy fuel oil (HFO) as fuel by ships in Arctic waters

Due to the characteristics of some of the new residual VLSFOs, when spilled in cold water they can adversely affect the effectiveness of oil spill equipment due to their high pour-point. This can cause the spilt oil to solidify and form lumps, which are difficult to retrieve and hard for nature to break down.

These fuels may not fall under the current HFO definition, and PPR 10 discussed a proposal to include an upper pour-point limit in the HFO definition given in Regulation 43.2.1 in MARPOL Annex I. However, the proposal was not supported at this stage, and PPR 10 agreed to revisit the issue at PPR 12 in 2025 following the entry into force of the prohibition on use and carriage of HFO as fuel in Arctic waters on 1 July 2024.

The work on the draft “Guidelines on mitigation measures to reduce risks of use and carriage for use of HFO as fuel by ships in Arctic waters” was deferred to PPR 11.

Marine plastic litter

Plastic pellets

MARPOL Annexes III and V and the IMDG Code were identified as potential instruments that may form a legal basis to regulate maritime transport of plastic pellets. Interested delegations can submit concrete proposals on potential mandatory measures.

As a short-term measure to reduce the environmental risk associated with carriage of plastic pellets by sea in freight containers, a draft circular providing recommendations for such transport was developed. This includes recommendations on packaging, transport information and stowage. The circular will be submitted to the Sub-Committee on Carriage of Cargoes and Containers (CCC) for input before finalization at PPR 11, with a view to approval by MEPC 81 in April 2024.

Furthermore, it was a general agreement that plastic pellets should not be shipped in bulk and interested delegations were invited to submit relevant proposals on potential regulatory changes to prevent the shipment of plastic pellets in bulk.

Fishing gear

Concerning the reporting of lost or discharged fishing gear, it was agreed that consistent thresholds should be developed and that recreational vessels should be exempted from mandatory reporting. The work on amendments to MARPOL Annex V and associated guidelines on marking and reporting will continue at PPR 11 in 2024.

Unified Interpretations (UIs)

PPR 10 agreed on two UIs for approval by MEPC 80.

BDN in electronic format – Regulations 18.5 and 18.6 of MARPOL Annex VI

The UI enables having the Bunker Delivery Note (BDN) in an electronic format provided it contains all the required information and is protected from edits, modifications or revisions. Authentication should be possible by a verification method, for example tracking number, watermark, date and time stamp, QR code or GPS coordinates.

Ballast water D-2 standard in case of major conversion – form of the International Ballast Water Management Certificate and Regulations B-3.5 and B-3.10 of the BWM Convention

In the case of a major conversion, the ship should meet the ballast water D-2 standard from the date of completion of the major conversion. The date of the commencement of the major conversion should be listed as the “Date of construction” on the International Ballast Water Management Certificate.

Other business

Volatile Organic Compounds (VOCs)

PPR 10 agreed on a scope of work for the reduction of VOC emissions from ships. This includes considering how to involve terminals in the reduction of VOC emissions, and considering new and existing regulations and guidance documents on VOC, including the application of a revised Regulation 15 of MARPOL Annex VI.

Protocol for verification of ballast water compliance monitoring devices

PPR 10 agreed on a “Protocol for verification of ballast water compliance monitoring devices” (CMD) for approval at MEPC 80. This protocol describes how to verify the ability of a CMD to assess non-compliance with the D-2 standard of the BWM Convention. To satisfy a common level of quality when conducting commissioning testing using a CMD, PPR 10 encourages members states to verify the CMD by following this protocol.

Detection of 10–50 μm plankton in ballast water

PPR 10 encourages member states and organizations to conduct additional experiments on the neutral red staining method. This is a detailed analysis method using neutral red staining microscopy for the detection of 10–50 μm plankton.

Correspondence Groups established

The following Correspondence Groups were established and will report back to PPR 11 in 2024:

  • Correspondence Group on prevention of air pollution from ships addressing black carbon
  • Correspondence Group on amendments to MARPOL Annex IV and associated guidelines addressing sewage treatment
  • Correspondence Group on marine plastic litter from ships
  • Correspondence Group on the development of draft guidelines on the clean-up of plastic pellets from ship-source spills

As PPR is a sub-committee, all decisions concerning rules, regulations and dates are subject to further consideration and approval by the Marine Environment Protection Committee (MEPC).

Source: IMO Sub-Committee on pollution prevention and response (PPR 10) (

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