The objective of the Clean Hull Initiative (CHI) is to increase the uptake of proactive in-water cleaning technology as a preventive biofouling management tool, including reducing barriers to its wider implementation.

Ships that operate with organisms attached to their hulls – called biofouling –  can pose a risk to the environment. In-water cleaning (IWC) can help mitigate these challenges when conducted in a safe and controlled manner.

Biofouling is currently the primary vector for the transfer of aquatic invasive species and represents a serious global biosecurity threat. The establishment of invasive species can cause severe and often irreversible ecological damage, disrupt fisheries and coastal industries, and result in economic costs amounting to billions of dollars worldwide. In addition, biofouling increases hull resistance and reduces propeller efficiency, leading to higher fuel consumption and at least 9 % increased greenhouse gas emissions from ships (source: IMO). This means that effective biofouling management could potentially save up to 80 million tonnes of CO₂-equivalent emissions annually.

The most common way of combating biofouling is through the use of antifouling coatings (paints) containing biocides. However, coatings alone cannot prevent all biofouling, and accumulated fouling must eventually be removed. Fouling removal can be conducted either in-water or in dry dock.

In-water cleaning can generally be classified as either proactive or reactive. Proactive in-water cleaning, sometimes referred to as hull grooming, is carried out on microfouling at the early stages of development and is performed at frequent intervals using gentle cleaning techniques that do not damage the coating. Reactive in-water cleaning is performed on macrofouling, which is more heavily attached to the hull and coating surface. Reactive cleaning carries a greater risk of coating damage and may result in the release of aquatic invasive species into the local marine environment. As opposed to proactive in-water cleaning, reactive cleaning of macrofouling should be performed using technology capable of capturing the organic material removed from the hull (Source: IMO).

Bellona believes that proactive in-water cleaning can significantly reduce the spread of aquatic invasive species through ships’ biofouling. By removing fouling before they leave port, ships can minimise the risk of transporting species from one port to another.

In recent years, a number of international guidance documents have been developed, including the IMO Biofouling Guidelines (2023) and the IMO Guidance for In-Water Cleaning of Ships (2023). There is currently no international convention specifically regulating in-water cleaning of biofouling, but there is an IMO convention on biofouling management on the way. Bellona works to ensure that this convention facilitates proactive in-water cleaning and clean hulls worldwide.

As awareness of biosecurity risks increases globally, some port authorities and coastal states are introducing their own preventive measures and regulatory requirements that visiting ships must comply with. The capacity and expertise of authorities to regulate in-water cleaning and assess ship biosecurity risks vary considerably. As a result, different jurisdictions often require different types of documentation, technologies, and operating procedures. This fragmented regulatory landscape creates uncertainty and operational challenges for shipowners and operators.

To address this challenge, Bellona and its industry partner Jotun established the Clean Hull Initiative (CHI), bringing together stakeholders from industry, the public sector, academia, and civil society to develop and propose an international standard for in-water cleaning through ISO. After three years of development under the leadership of one of Bellona’s own senior advisors, ISO 6319 was published in March 2026. CHI is now working to support its implementation and adoption globally.

ISO 6319 addresses how in-water cleaning operations should be documented and reported to ports and regulators. The standard is particularly valuable for authorities overseeing in-water cleaning activities, while also providing guidance for shipowners, operators, service providers, technology developers, classification societies, and other stakeholders involved in biofouling management.

We believe that biofouling in shipping is a challenge worth solving. Addressing this issue will reduce the transfer of invasive aquatic species, significantly lower greenhouse gas emissions from the global shipping fleet, improve energy efficiency, and generate fuel savings for shipowners and operators.

The solution

In-water cleaning technologies have now matured to a stage where proactive hull cleaning can be integrated into a ship’s biofouling management plan as a routine preventive measure. CHI supports the implementation and wider adoption of proactive in-water cleaning as a key biofouling management measure.

We are well aware of the complexity of achieving this vision and consider stakeholder collaboration essential. By facilitating dialogue and cooperation among stakeholders, CHI seeks to support practical, science-based, and internationally harmonised approaches to the management of biofouling through proactive in-water cleaning.

Contact

The Clean Hull Initiative (CHI) is led by Bellona Norway.

CHI Project Manager
Irene O. Tvedten
Senior Advisor, Maritime
irene.tvedten@bellona.no