IMO sharpens plans to achieve zero plastic pollution from ships by 2030
[Originally published several weeks ago]
This is to encourage open dialog on the IMO ambition to achieve zero plastic waste discharges to sea from ships by 2030. That cannot happen unless microplastics in ship laundry water are addressed. Here is a potential path to that end.
Under international maritime law, cruise ship laundry water is classified as grey water. Grey water is not directly regulated under MARPOL; It is defined as drainage from dishwater, galley sink, shower, laundry, bath and washbasin drains. See IMO Resolution MEPC.227(64). Grey water is regulated under MARPOL as sewage when it is mixed with drainage from toilets & urinals. See Regulation 1.3 of MARPOL Annex IV.
While grey water is not directly regulated under MARPOL, the MARPOL Annex V prohibition on “the discharge into the sea of all plastics” must be considered when grey water contains microplastic. Laundry water may currently be discharged to the sea as grey water without onboard treatment, but ...
Research shows that laundry water from cruise ships is a significant source of microplastics. See: Folbert MEF, Corbin C and Löhr AJ (2022) Sources and Leakages of Microplastics in Cruise Ship Wastewater. Front. Mar. Sci. 9:900047. doi: 10.3389/fmars.2022.900047. Microplastics are generated as synthetic clothing is washed onboard. Heat and abrasive detergents promote the release of microplastics. Water-soluble polyvinyl alcohol (PVA/PVOH) laundry detergent pods may be an additional contributor to microplastic loading as the wash water cools to allow the PVA/PVOH to precipitate before discharge.
Here are some potential options (there may be others) to achieve compliance:
Option 1: Install filters to capture and remove microplastic from laundry wash water. On 11 March 2025 the TUI Group announced – “Marella Cruises and Cleaner Seas Group are rolling out an industry first initiative in microfibres captured in all laundry systems across the fleet of the five ships by September 2025 after a successful six-month trial on Marella Explorer which showed that 99% of microfibres were captured.” This treatment option presumably allows for the laundry wash water to be discharged either as grey water or via an AWWTS in compliance with MARPOL Annex V.
Option 2: Treat laundry wash water in an onboard Advanced Waste Water Treatment System (AWWTS) and land the sewage bio-residuals ashore. These combined sewage/grey water treatment systems can reportedly remove almost all of the microplastic before sewage permeate discharge under MARPOL Annex IV regulations. Nonetheless, the remaining “sewage sludge” or “bio-residuals” containing the captured microplastic may have to be offloaded to comply with MARPOL Annex V.
Note: Microplastics in shower products used by guests may also be a matter to consider within grey water.
Adequate MARPOL regulatory controls may already exist, but compliance is uncertain and new regulatory guidance or clarification may be needed to realize the 2030 IMO ambition.
