By Anders W.B. Skilbred, Helle Ertsås Vines and Petter Korslund (Jotun)
Abstract
In-water hull cleaning has long been a routine port-side activity with no common rulebook. ISO 6319:2026 changes that. The first single global framework for conducting and documenting in-water cleaning of biofouling on ships, it sets requirements and best practice for planning, conducting, documenting and reporting cleaning across hull and niche areas, from biofilm to macrofouling, with or without capture. This paper argues that the standard’s real value goes beyond codifying practice: it lets the industry move from ad hoc, reactive interventions to systematic, documented and proactive hull performance management, in which early-stage fouling is removed before macrofouling develops. Robotic in-water cleaning, built on integrated monitoring, inspection and proactive cleaning, is a timely example of the always clean hull the standard enables. Placed in the wider context of invasive aquatic species risk, fuel efficiency, greenhouse gas reduction and port governance, ISO 6319 gives shipowners, ports, regulators and service providers a common objective: clean hulls, lower fuel consumption, lower emissions and lower biosecurity risk. Its value, however, will depend on disciplined application.
1. Introduction: From an old practice to a modern standard
Cleaning ships’ hulls in ports and anchorages is not new. Since the earliest days of commercial shipping, hull fouling has been recognised as a practical problem. Fouled surfaces increase drag, reduce speed, increase fuel consumption and can compromise manoeuvrability. Historically, the primary motivation for cleaning was operational and economic. A cleaner hull meant better speed, lower fuel use and fewer disputes over vessel performance. Environmental questions, including the release of fouling organisms, paint debris and biocides during cleaning, were secondary or absent from the discussion.
That context has changed. Biofouling is now recognised as a significant factor for invasive aquatic species transfer, while shipping is under increasing pressure to reduce greenhouse gas emissions and improve energy efficiency. The regulatory and scientific landscape has also evolved. The IMO Biofouling Guidelines, regional biosecurity regimes in Australia, New Zealand and California, the GloFouling Partnerships Project, and industry initiatives such as the Clean Hull Initiative have all contributed to a broader understanding that hull cleanliness is a matter of environmental protection, fuel efficiency and operational transparency.
The publication of ISO 6319:2026, Ships and marine technology – Marine environment protection – Conducting and documenting in-water cleaning of biofouling on ships, arrives at a critical point in this development. Its importance lies in converting a long-established practice into a standardised process. By specifying how in-water cleaning should be planned, conducted, documented and reported, the standard provides a common language for shipowners, cleaning service providers, coating manufacturers, inspection companies, ports and regulators. It does not remove the need for local permission or environmental assessment, but it gives stakeholders a consistent framework for evaluating whether cleaning is being carried out responsibly.
2. Why biofouling management matters
Biofouling begins with microbial films and progresses through slime, soft fouling and hard macrofouling such as barnacles, tubeworms and shell-forming organisms. Even early-stage fouling can create a measurable hydrodynamic penalty. As fouling develops, surface roughness increases, drag rises and the vessel requires more power to maintain speed. For ships operating on fossil fuels – as most ships do – this translates directly into higher fuel consumption and consequently increased carbon dioxide emissions.
The economic argument is therefore straightforward. Fuel is a major operating cost, and performance loss caused by fouling can affect both voyage economics and charter-party compliance. The scale is significant. Fuel can account for as much as 50-60% of a ship’s operating costs, according to the World Shipping Council, though the share varies with ship type and fuel prices. The IMO’s GloFouling study found that slime just 0.5 mm thick, covering half the hull, can raise a ship’s greenhouse gas emissions by 20 to 25%, and a light layer of barnacles or tubeworms by up to 55% on an average container ship, depending on ship characteristics and speed. Charter-party compliance is where these economics become contested. Many charters still rely on wording that is decades old and says little about hull condition. In a typical time charter the owner pays for hull maintenance while the charterer pays for fuel, so the party that would invest in a cleaner hull is not the one that saves the fuel. This split in incentives is a real obstacle for many in the industry, and it can only be tackled with proper monitoring of performance. ISO 6319 and ISO 19030 play complementary roles here: ISO 19030 measures hull and propeller performance, and ISO 6319 documents what was done to the hull and when. Since shipping was included in the EU Emissions Trading System from 2024 for voyages linked to the EU, carbon cost has added a further commercial incentive to keep hulls clean. Hull performance is no longer only a technical matter for coating specialists and operators; it is increasingly linked to emissions accounting, regulatory exposure and financial performance.
The environmental argument is equally important. Biofouling can transport organisms between ports, regions and ecosystems. If organisms survive transit, reproduce and establish in a new environment, they may become invasive aquatic species. The consequences can include ecological displacement, economic losses and long-term management costs. While ballast water has received substantial regulatory attention, several studies and policy reports have identified hull biofouling as a major, and in some cases dominant, pathway for marine species introductions.
3. The problem ISO 6319 helps solve
The central problem addressed by ISO 6319 is not that ships have lacked cleaning methods. The industry has many cleaning technologies, including diver-operated tools, remotely operated vehicles, robotic systems, brush-based equipment, water jets and systems with capture and filtration. The problem has been inconsistency. Cleaning practices have differed by port, provider, vessel type, fouling level, coating type and local environmental requirement. Documentation has also varied, making it difficult for authorities to compare cleaning requests, assess environmental risk or verify outcomes.
In this fragmented situation, ports may be reluctant to permit cleaning, even when cleaning could reduce future biosecurity and emissions risk. Shipowners may face uncertainty over whether cleaning will be accepted by authorities. Cleaning providers may use different performance claims and reporting formats. Coating manufacturers may have limited visibility on how cleaning affects coating integrity. Regulators may lack comparable data on fouling condition, cleaning method, capture efficiency, waste handling or post-cleaning effectiveness.
ISO 6319 creates a structured framework for these issues. It covers planning, preparation, execution, documentation and reporting. Importantly, it applies to external submerged surfaces, including hull and niche areas, and to all biofouling levels from biofilms to macrofouling. It recognises both cleaning with capture and cleaning without capture, reflecting the reality that different fouling stages and technologies require different management approaches. Its value is therefore practical: it helps convert a cleaning event into a traceable, auditable operation.
4. From reactive cleaning to proactive hull care
A key conceptual shift in modern biofouling management is the move from reactive cleaning to proactive hull care. Reactive cleaning occurs when fouling has already developed to a level where performance loss, biosecurity risk or coating damage may be significant. At that point, cleaning may require capture, generate more waste, create greater uncertainty about organism release and impose higher operational disruption.
Proactive cleaning has a different logic. It seeks to remove early-stage fouling before it becomes established macrofouling. If cleaning is carried out while the hull is at or near a microfouling condition, the biomass removed is lower, cleaning forces can be milder, coating damage risk can be reduced or even completely mitigated, and the probability of releasing mature organisms will be lower. Proactive cleaning therefore aligns naturally with the environmental intent behind ISO 6319 and the IMO Biofouling Guidelines.
It is therefore crucial to highlight the importance of fouling ratings, particularly the distinction between microfouling and macrofouling. This distinction is central. When a hull is kept at a low fouling rating, the operational and environmental consequences of cleaning are very different from cleaning after extensive macrofouling has developed. ISO 6319 gives the industry a way to document these differences and to make cleaning decisions more transparent.
5. Robotic in-water cleaning as an example of the new paradigm
Robotic in-water cleaning is well aligned with the direction set by ISO 6319 because it can be applied as part of a proactive biofouling management strategy rather than as a one-off reactive cleaning intervention. When combined with suitable coating systems, condition monitoring, inspection routines and documented cleaning procedures, robotic systems can support the objective of maintaining an always clean hull rather than periodically recovering from a fouled condition.
Robotic cleaning systems may be deployed in harbour, at anchor, or during suitable operational windows depending on local rules, vessel configuration and system design. Such systems are typically remotely operated or semi-autonomous and can be designed to remove early-stage fouling with controlled forces intended to limit coating damage. In proactive hull management, timing is critical. Fouling predictions, operational data, inspection findings and oceanographic conditions can be used to determine when cleaning should occur. The objective is not to wait until visible fouling becomes a performance or biosecurity problem, but to intervene before fouling develops into a mature community.
This is precisely where ISO 6319 can add value. A proactive solution becomes more credible when its inspections, cleaning events and outcomes are documented consistently. The standard can help structure records of pre-cleaning condition, cleaning method, operational parameters, coating compatibility, post-cleaning condition and reporting of effectiveness. For a system designed around repeated proactive interventions, standardised documentation is essential for demonstrating environmental performance and operational reliability over time.
6. Benefits for shipowners and operators
For shipowners and operators, ISO 6319 offers clarity. A standardised framework reduces uncertainty about what information should be available before, during and after cleaning. This can support better communication with ports, charterers, class societies, flag states and environmental authorities. It can also support internal governance by making hull cleaning part of a documented maintenance and performance management system.
When combined with proactive robotic in-water cleaning, the benefits become broader. A clean hull reduces drag and helps preserve speed and fuel performance. Lower fuel consumption reduces greenhouse gas emissions and, where carbon costs apply, reduces exposure to emissions pricing. A consistently clean hull can also help operators avoid last-minute cleaning before entering regions with strict biosecurity requirements. Instead of reacting to a port entry problem, the vessel can build a continuous record of hull condition and maintenance.
The commercial case is therefore not limited to fuel savings. It includes voyage reliability, reduced off-hire risk, better evidence for charter-party performance discussions, improved environmental reporting and stronger preparedness for future regulation. In a market where shipping companies are under pressure to demonstrate decarbonisation and biodiversity risk management – documented hull cleanliness is becoming a strategic asset.
7. Benefits for ports and regulators
Ports are central to the implementation of responsible in-water cleaning. Yet many ports have been cautious about allowing hull cleaning because of safety, berth availability, water quality concerns and uncertainty over environmental consequences. Without reliable documentation, ports may find it difficult to distinguish between low-risk proactive cleaning of microfouling and higher-risk reactive cleaning of macrofouling.
ISO 6319 can help ports make more consistent decisions. If cleaning requests include standardised information on fouling condition, vessel areas to be cleaned, technology used, capture arrangements, waste handling, coating compatibility and reporting, port authorities can evaluate requests more efficiently. Over time, standardised records can also support better policy development by creating comparable datasets on cleaning frequency, fouling levels, methods and outcomes.
For regulators, the standard provides a bridge between voluntary guidelines and future mandatory requirements. It does not itself create global regulation, but it gives authorities a recognised reference point. This is particularly important in a field where national and regional approaches are developing at different speeds. A common ISO framework reduces the risk of fragmented expectations and supports a more level playing field for shipowners and service providers.
8. Benefits for coating and cleaning technology development
In-water cleaning cannot be considered separately from coating technology. Cleaning that is too aggressive can damage antifouling coatings, shorten service life and increase release of coating particles or biocides. Cleaning that is too weak may fail to remove fouling effectively. The compatibility between coating and cleaning method is therefore fundamental.
Robotic in-water cleaning illustrates the importance of system design. The cleaning method, coating system, inspection regime and operational frequency need to be considered together. This integrated approach allows cleaning parameters, coating properties and fouling development to be assessed as part of a single management system. It also enables evidence to be generated on coating condition before and after cleaning, time to refouling, water quality and long-term hull performance.
ISO 6319 supports this type of development by encouraging consistent documentation of cleaning effectiveness and environmental performance. As more systems are tested and documented under comparable frameworks, the industry can move beyond broad claims and toward evidence-based selection of cleaning methods for specific coating systems, vessel types and operating profiles.
9. Biosecurity: reducing risk before it accumulates
Biosecurity risk is difficult to quantify because it depends not only on fouling level, but also on species identity, reproductive status, voyage history, environmental similarity between donor and recipient regions, and post-arrival conditions. A visual fouling score does not automatically reveal whether a hull is carrying high-risk organisms.
Nevertheless, preventing the accumulation of mature macrofouling is a rational risk-reduction strategy. Mature fouling communities are more likely to include a diversity of organisms, reproductive individuals and structures that are difficult to remove. Proactive cleaning of early-stage fouling can reduce the opportunity for these communities to develop. When documented according to a standardised framework, such cleaning can provide better evidence that a vessel is actively managing biofouling risk.
In this sense, the always clean hull concept is not only a fuel-saving strategy. It is also a biosecurity strategy. The objective is to prevent the vessel from becoming a biological transport platform in the first place. ISO 6319 strengthens this strategy by making the process visible, repeatable and reviewable.
10. Climate and performance: the clean hull as an emissions measure
Biofouling is often discussed as a biodiversity issue, but it is also a climate issue. Added drag leads to added fuel use and added fuel use leads to added greenhouse gas emissions. The link is direct and measurable through vessel performance monitoring. This makes hull cleanliness a practical decarbonisation lever available to the existing fleet.
Proactive robotic in-water cleaning positions hull cleanliness as a continuous performance state rather than a periodic maintenance outcome. When combined with physical in-water inspections and performance monitoring aligned with ISO 19030, such approaches can connect visual hull condition with operational performance data. This is significant because it allows hull management actions to be assessed not only as cleaning events, but as measurable contributors to fuel efficiency and emissions reduction.
ISO 6319 and ISO 19030 therefore play complementary roles. ISO 6319 supports documentation of cleaning operations, while ISO 19030 supports performance monitoring of hull and propeller performance. Together they can help owners demonstrate that hull management actions are not only being conducted responsibly but are delivering measurable operational benefits.
11. The remaining gaps
ISO 6319 is an important advance, but it does not close every knowledge gap. Further work is needed to link fouling ratings with actual invasive species risk, to improve methods for species identification and quantification, and to generate more comparable data on water quality impacts during different cleaning operations. There is also a need for continued research into niche areas, which are often more difficult to inspect and clean than flat hull surfaces but can be important reservoirs for fouling organisms.
Another gap concerns global implementation. A standard can define good practice, but ports and national authorities must decide how to use it. Some ports may adopt ISO 6319 as part of permitting processes; others may continue to prohibit or restrict cleaning. The pace of adoption will depend on regulatory confidence, local environmental priorities, infrastructure, stakeholder engagement and the availability of certified or demonstrably competent cleaning providers.
Finally, transparency will be essential. If shipowners, ports and regulators are to trust proactive cleaning, records must be credible. This includes documentation of cleaning frequency, fouling condition, coating condition, cleaning parameters, waste management where relevant, and post-cleaning inspection. ISO 6319 provides the framework, but its value will depend on disciplined application.
12. Conclusion:
ISO 6319 enables the always clean hull. For centuries, ships have been cleaned in port because fouling hurt performance. Today the same activity is also a climate, biodiversity, water-quality and port-governance issue, and ISO 6319:2026 gives the maritime sector a shared definition of what responsible in-water cleaning looks like.
The standard’s greatest contribution is to make a different approach possible. By requiring structured planning, documentation and reporting, it turns cleaning from a reactive, one-off intervention into a transparent, comparable and repeatable part of hull management, to the benefit of shipowners, ports, regulators and the marine environment. Robotic in-water cleaning shows it in practice: suitable coatings, onboard or readily available inspection and cleaning capability, predictive monitoring and documented procedures keep the hull clean rather than recovering from fouling, with lower emissions and reduced biosecurity risk.
ISO 6319 does not close every knowledge gap or remove the need for local permission, and its value will depend on disciplined application and credible records. But it marks the point at which in-water hull cleaning stops being an informal port activity and becomes a documented environmental management practice. The opportunity is clear: use the standard not merely to justify cleaning, but to make a continuously clean hull the normal operating condition.
