Closed-loop hull cleaning is a regulatory imperative

The shipping industry faces mounting regulatory pressure to mitigate the transfer of invasive species via hull biofouling. The global detrimental impacts of sea vomit (Didemnum vexillum) is just one stark example of the damage caused by unmanaged hull fouling. The solution is clear: closed-loop hull cleaning must become an industry standard, writes Abigail Robinson, Vice President of Sustainability at ECOsubsea, applauding the IMO’s recent decisive action to align regulations with operational best practices.

An urgent but under-regulated threat

The spread of invasive species via ship hulls is not a new concern for shipping and regulators. While most industry stakeholders recognise the risks posed by biofouling – from increased drag and fuel consumption to environmental degradation and potential regulatory penalties – there remains a significant regulatory gap. Unlike ballast water, which is now subject to international regulations, hull biofouling remains underregulated despite profound implications for both vessel performance and marine ecosystems.

In-water hull cleaning introduces additional pollution risks. Many antifouling coatings work by leaching heavy metal-based toxins to deter biofouling growth. These products are typically polymer based and a large source of micro-plastic pollution into the ocean over time. It is estimated that marine coatings release over 210,000 tons of micro-plastic annually in the EU alone. Hull cleaning exacerbates the problems as friction increases the release of both toxins and plastic. Even gentle, non-capture cleaning methods contribute to local contamination, exposing ports to heavy metals and micro-plastics due to the very nature of coating design.

Momentum builds for global action

In response, Norway recently proposed to the IMO’s Marine Environment Protection Committee (MEPC) that biofouling management and environmentally responsible cleaning should be made mandatory. Co-authored by Fiji, Finland, France, Peru and the Republic of Korea, the proposal gained a consensus to begin the process to creating a global regulatory instrument for biofouling management.

This step has significant implications and will ultimately result in reduced global invasion pressure from invasive species, as well as significant GHG reductions. However, the lag of regulatory consensus on appropriate management of risks associated with in-water cleaning will only hinder the journey to clean hulls, with great cost to the environment.

Risks of inadequate hull maintenance

Biofouling is more than an environmental issue – it is an operational, financial and compliance risk. Fouled hulls increase resistance, driving up fuel consumption and GHG emissions. As IMO and EU decarbonisation targets tighten, poor hull maintenance could make vessels non-compliant with energy efficiency and emissions regulations.

At the same time, ports are implementing their own biofouling controls. Ships with dirty hulls face delays, mandatory cleaning or even denial of entry, as already seen in New Zealand, for example, leading to increased operational disruption and added costs.

Best practice: The case for closed loop

Traditional in-water hull cleaning exacerbates the problem, releasing invasive species and pollutants directly into local waters. Closed-loop hull cleaning, by contrast, captures all biological material and debris, ensuring it is contained and brought to land where it is treated as contaminated industrial waste. On land, there would be strict legal consequences if it were not appropriately disposed of properly. In contrast, many ports still allow open-loop cleaning system to discharge that same waste into the ocean – without oversight or consequence.  This regulatory double standard is unacceptable.

ECOsubsea has developed a closed-loop system that enables vessel operators to reduce biosecurity and pollution risks while improving vessel performance. Clean hulls reduce drag, optimise fuel efficiency and reduce emissions – delivering both environmental and economic benefits.

The path to global compliance

The IMO’s decision to pursue mandatory biofouling management and environmentally sound cleaning is a necessary and overdue step and aligns with the broader push towards decarbonisation and ecosystem protection.

Some industry voices may cite cost concerns, but the price of inaction is higher. Hull fouling already leads to substantial fuel and emissions penalties. The ROI for proper hull maintenance is immediate. In fact, ECOsubsea’s 2024 customer data shows an average ROI of just 30 days. With our latest-generation “Pink Panther” ROV now operating in Singapore, the payback period is expected to shrink even further as vessels no longer lose money waiting to be cleaned.

Next steps for the industry

The time for voluntary action is over. Shipping companies must proactively adopt closed-loop cleaning before a patchwork of local rules forces costly compliance measures. Vessel operators are already facing growing pressure to demonstrate effective biofouling management, while the number of in-water cleaning options continues to shrink.

Supporting future-proof, closed-loop systems now is the only way to secure operational resilience and environmental integrity.

The IMO has a chance to deliver a globally harmonised, enforceable standard that protects the marine environmental while maintaining commercial viability. Making closed-loop cleaning mandatory is not only logical – but essential.

This is not just an environmental issue – it’s a business and regulatory imperative. The industry must give its full and unambiguous support.