IMO PPR 13
A snowy day in London viewed from the IMO. Photo - D. Smith
[Originally posted February 2026]
The 13th session of the IMO's Sub-Committee on Pollution Prevention and Response (PPR 13) is taking place this week at the International Maritime Organization (IMO) in London. Key agenda items include establishing a legally binding framework for biofouling management, reducing Arctic black carbon emissions, regulating exhaust gas cleaning systems (scrubbers) in sensitive areas, and updating NOx standards. The PPR Sub-Committee will submit a report detailing its discussions and recommendations to the IMO's Marine Environmental Protection Committee (MEPC) for final approval.
The PPR 13 agenda items have significant potential consequences for cruise and cargo ships alike. Here are some insights related to the PPR 13 agenda items this week:
1. In 2023 IMO published Guidelines for the control and management of ships' biofouling to minimize the transfer of invasive aquatic species (resolution MEPC.378(80)). Because an international framework for controlling biofouling does not exist, various states have adopted their own biofouling laws. Many of those countries are basing their requirements on the 2023 guidelines. The guidelines are based on a risk management approach that is designed to ensure that ship hulls and niche areas are cleaned to remove micro-fouling (slime layer) before it develops into macro-fouling. When ships remove macro-fouling while stationary in a port, invasive aquatic species can be released unless the fouling is captured during removal. Capture is easier said than done, however, ECOsubsea has developed an impressive approach for doing that. It is worth noting the EPA Vessel General Permit (VGP) under the Clean Water Act requires the use of capture with in-water cleaning when available and feasible.
2. Exhaust Gas Cleaning Systems (EGCS) are used to scrub Sulphur Dioxide (SO2) from exhaust gases when Heavy Fuel Oil containing elevated levels of Sulphur is used by a ship. MARPOL regulations limit the fuel Sulphur content. Compliance can be achieved by using cleaner Marine Gas Oil (MGO) however, it is a lot more expensive than HFO. Current MARPOL regulations allow the use of HFO if an equivalent amount of Sulphur is scrubbed out of the exhaust gas via an EGCS. There are two types of EGCS - Closed Loop & Open Loop. The closed loop systems keep the removed Sulphur onboard for offloading in a port. The open loop systems spray sea water into the exhaust gas to capture the SO2 with the wash water discharged back into the ocean. The primary concerns with open-loop EGCS center on the environmental impact of discharging wash-water into marine environments. Major potential issues include localized acidification (low pH), the release of heavy metals and polycyclic aromatic hydrocarbons (PAHs). Countries around the world are increasingly banning open-loop EGCS discharges. There are conflicting studies and arguments on both sides of this contentious debate.
Lloyd's Register (LR) and DNV both provided insightful summaries of PPR13 (See links below). Here are some key takeaways from those summaries:
LR indicates "Studies have shown that scrubber-equipped ships using high-Sulphur HFO emit higher particulate matter, black carbon, and CO₂ emissions than ships using compliant low‑sulphur fuels. Scrubbers reduce SOₓ but are not designed to effectively reduce particulate matter (PM), resulting in higher PM and Black Carbon emissions when compared to ships using no scrubbers and low‑sulphur fuels such as Marine Gas Oil (MGO). This therefore results in a regulatory gap and may undermine the air quality benefits intended by ECAs." This might explain some non-compliant opacity observations during the Alaska cruise season.
DNV reports "PPR 13 considered a proposal for the restriction of EGCS discharge within Particularly Sensitive Sea Areas (PSSAs). The Sub‑Committee concluded that, for any future PSSA designations, proposing member states should first undertake a risk assessment in accordance with the methodology set out in MEPC.1/Circ.899, and subsequently determine whether discharge restrictions are reasonable based on the assessment’s findings."
LR also noted that "97% of ships tested do not meet sewage effluent discharge standards despite using approved Sewage Treatment Plants (STP) (with poor performance or failure being common causes), regular maintenance of STP, monitoring of STP effluent and strengthening the STP type approval test process should help to improve the situation."
DNV noted "PPR 13 commenced discussion of a legally binding framework for the control and management of ships’ biofouling to minimize the transfer of invasive aquatic species. PPR 13 agreed that a new convention would be most suitable way forward and recommended this approach for consideration at MEPC 86 in 2027. The aim is to finalize a draft legal framework by 2029 for consideration by MEPC 89." In the meantime, it may be challenging to navigate the proliferation of domestic biofouling requirements that are mostly aligned with 2023 IMO Biofouling Guidelines.
https://www.lr.org/en/knowledge/regulatory-updates/imo-meetings-and-future-legislation/
