IMO Sub-committee on pollution prevention and response (PPR 12)
The 12th session of the IMO’s Sub-Committee on Pollution Prevention and Response (PPR 12) was held in London from 27 to 31 January 2025. PPR 12 finalized guidance on in-water cleaning of ships’ biofouling and guidelines on certification of Selective Catalytic Reduction systems. A wide range of other topics was on the agenda, including cargo tank cleaning procedures, carriage of biofuel blends, black carbon, discharge water from Exhaust Gas Cleaning Systems, sewage treatment and marine plastic litter.
Relevant for ship owners, managers well as manufacturers marine engines and sewage treatment plants.
Meeting highlights
- Finalized a circular on guidance on in-water cleaning of ships’ biofouling
- Revised guidelines on certification of Selective Catalytic Reduction (SCR) systems
- Agreed on an interim circular allowing bunker ships certified as oil tankers to carry biofuel blends containing up to 30% biofuel
- Discussed amendments to MARPOL Annex II on cargo tank stripping, tank washing operations, and prewash procedures
- Continued the revision of MARPOL Annex IV on sewage treatment
- Reviewed the Action Plan to address marine plastic litter from ships
Safety and pollution hazards of chemicals and preparation of amendments to the IBC Code
Carriage of biofuel blends on bunker ships
Currently, oil tankers are permitted to carry biofuel blends containing up to 25% biofuel, while blends exceeding this limit are restricted to transport on chemical tankers. PPR finalised an interim circular allowing conventional bunker ships certified as oil tankers under MARPOL Annex I to carry biofuel blends containing up to 30% biofuel. The circular is subject to approval by MEPC 83 in April.
Prewash requirements for FAME
Due to the physical properties of Fatty Acid Methyl Ester (FAME) and several pollution incidents in the North Sea resulting from tank cleaning after unloading of FAME, PPR 12 considered a proposal to add operational requirement 16.2.7 to the IBC Code entry for FAME. This would mandate a prewash after unloading FAME. The geographical area of concern will be as defined by Regulation 13.9 in MARPOL Annex II, extending from Gibraltar in the south, along the Norwegian coast, including the Baltic Sea, as well as the UK and Ireland. The ESPH Technical Group, reporting back to PPR 13 in 2026, was tasked with further consideration of this proposal.
Amendments to MARPOL Annex II
Concerning the amendments to MARPOL Annex II aimed at improving the effectiveness of cargo tank stripping, tank washing operations, and prewash procedures, PPR 12 agreed that the scope of work should be limited to persistent floaters with a high melting point and/or high viscosity, when assigned pollution category “Y” and special requirement 16.2.7 in the IBC Code. The geographical area of concern will be as defined by Regulation 13.9 in Annex II of MARPOL (see above).
Additionally, PPR 12 agreed that the work should focus on enhancing operational procedures. The ESPH Technical Group was tasked with developing these amendments, while MEPC was invited to extend the target completion year of the output to 2027.
Biofouling – development of guidance on matters relating to in-water cleaning
PPR 12 finalized a circular on guidance on in-water cleaning of ships’ biofouling, which is expected to be approved by MEPC 83 in April. The guidance includes voluntary procedures related to planning, documentation, reporting and inspection when conducting in-water cleaning. It also includes recommended practices for those jurisdictions that wish to approve cleaning operations or those that want to test and certify in-water cleaning systems (IWCS).
PPR 12 agreed that further work is needed to develop additional guidance on compatibility testing between the coating and IWCS, on methods to assess the minimum performance standard for IWCS and on how to conduct inspections. More topics may be relevant, as
MEPC 83 will consider a new output on the possible development of mandatory requirements for biofouling management.
Air pollution
Black carbon (BC)
PPR 12 reviewed the “polar fuels” concept based on five key characteristics for discussion: density, viscosity, carbon residue content, cetane index or number, and pour point. However, there was no consensus on recommending distillate fuels as “polar fuels”. ISO provided insights on defining a polar fuel standard and the impact of a proposed pour point requirement, concluding that a maximum 0°C pour point would have minimal global impact.
PPR 12 agreed to further work on the “polar fuels” concept at PPR 13, supported by scientific studies and BC measurement campaigns.
Discharge water from Exhaust Gas Cleaning Systems (EGCS)
PPR 12 discussed developing possible regulatory provisions on restrictions of discharge water from EGCS but noted that a global ban was outside the scope its work.
PPR 12 reviewed the terms of reference for the GESAMP Task Team on EGCS, with the aim of developing a methodology for emission factors to ensure a uniform evaluation of regional restriction areas. The draft terms were forwarded to MEPC 83 for approval, with an extension of the target completion year to 2026.
Certification of Selective Catalytic Reduction (SCR) systems
PPR 12 reviewed proposed amendments to the 2017 SCR Guidelines, aiming to remove ambiguities and ensure consistent application. It was determined that there is no urgent need for additional guidance on certifying SCR arrangements with multiple engines. PPR 12 specifically defined criteria for NOx measurement devices and established alternative requirements for transparent verification of the ageing and deterioration of catalyst reactors.
The 2025 SCR Guidelines were finalized and are expected to be adopted by MEPC 83 in April. These revised guidelines will not apply retroactively but will enhance the certification process for engines with newly installed SCR systems.
Sewage treatment and revision of MARPOL Annex IV
PPR 12 considered the progress on the draft revision of MARPOL Annex IV by the Correspondence Group. Due to the lack of consensus on whether new performance test requirements and indicative monitoring should be retroactively applied to existing sewage treatment plants, it was decided to revisit this issue at a later stage, closer to the completion of the amendments.
The Correspondence Group was re-established to continue working on the MARPOL amendments and related guidelines, with a particular focus on the new sewage record book and sewage management plan.
Given the remaining tasks and the agreed work plan, MEPC was requested to extend the target completion year to 2027.
Review of the IBTS guidelines and amendments to the IOPP certificate and Oil Record Book
PPR 12 considered two proposals to amend MARPOL Annex I, aiming to introduce requirements that would recognize forced evaporation of oily bilge water as an acceptable disposal method. However, due to mixed support for the proposals and time constraints, this agenda item was deferred to PPR 13.
Marine plastic litter
PPR 12 discussed proposals regarding the appropriate IMO instrument to regulate the transport of plastic pellets in freight containers. These included the IMDG Code, MARPOL Annex III or Annex V, a new annex to MARPOL, or a new code for plastic pellets. However, no clear preference was agreed on during this session.
PPR 12 decided to consider mandatory measures to reduce the environmental risks of plastic pellets transport at sea as a new action in the Action Plan to address marine plastic litter from ships.
Additionally, a new action for a ship-specific management plan for the gear and equipment used in fishing activities was included.
The actions in the 2025 Action Plan should be completed by 2030, subject to an assessment of their effectiveness.
Unified Interpretations (UIs)
PPR 12 discussed a proposal for a UI regarding the application of Regulation 12.3.2 of MARPOL Annex VI on Ozone Depleting Substances (ODS). The UI concerned systems initially installed using non-ODS before 1 January 2020, where the refrigerant was replaced with an ODS after that date.
It was generally understood that the replacing of refrigerants should be considered as a new installation. However, the criteria of the newly adopted policy for approving new UIs were not met. As a result, interested Member States and international organizations were invited to submit a proposal to the MEPC for a new output to amend MARPOL Annex VI.
Any other business
An issue brought up at MEPC 81, seeking clarification on the carriage of cargo oil in the slop tank(s) of an oil tanker, was deferred to PPR 13 due to the lack of comments.
PPR 12 revised the 2023 “Guidelines for the Development of the Inventory of Hazardous Materials”, clarifying the relevant threshold of cybutryne when samples are taken directly from the hull or from wet paint containers.
Correspondence Groups established
The following Correspondence Group was established and will report back to PPR 13 in 2026:
- Correspondence Group on Amendments to MARPOL Annex IV and Associated Guidelines (sewage)
Recommendations
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).
DNV recommends to note the guidance on in-water cleaning, which may be required by local jurisdictions, and the revised guidelines on SCR certification. We also recommend that our customers monitor the outcomes of MEPC 83 in April 2025 and the Correspondence Groups established.
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