How Biofouling Impacts Vessel Efficiency — And How to Fix It

March 24, 2021 Maritime Safety News

The maritime shipping industry has set ambitious decarbonization targets over the next decade. Shrinking the shipping industry’s carbon footprint is going to take a range of innovative solutions and technologies — from simple solutions like more efficient route planning to more advanced options, such as hull design.

Biofouling presents a major threat to the industry’s progress toward decarbonization targets. Biofouling is the accumulation of microorganisms, plants, algae, or small animals on wet surfaces that have a mechanical function, causing structural or other functional deficiencies. Maritime shipping and logistics companies face challenges in vessel marine performance related to macrofouling — the attachment of larger organisms such as barnacles, soft corals, and seaweed.

[Read more: What is Biofouling and How Can We Stop It?]  

Here’s how biofouling is affecting the shipping industry and what marine logistics companies can do to prevent and combat biofouling.

How biofouling impacts vessel efficiency

Biofouling happens in two stages: microfouling and macrofouling. In macrofouling, heavier organisms such as barnacles and small coral colonies adhere to the submerged hull of a ship. These organisms can weigh up to 10 tons, significantly increasing the vessel’s drag.

“The costs of these hull-fouling stowaways are substantial: According to one study, the U.S. shipping industry spends more than $36 billion each year in added fuel costs to overcome the drag induced by clinging marine life or for anti-fouling paint that prevents that life from hitching a ride in the first place,” reported Science Magazine. “And that figure doesn’t include the cost to regularly scrape a hull smooth, which costs approximately $4.50 for every square foot of hull surface.”

Even minor microfouling can decrease vessel efficiency by 10 – 16%; macrofouling and result in loss of 86% of a vessel’s cruising speed, contributing to delays across the marine shipping industry.

These losses are only expected to increase due to climate change. A recent study found that warmer water creates the conditions for even more intense macrofouling. The median-projected scenario of a 3.5°C increase in water temperature causes marine organisms to grow twice as fast as they do at today’s surface temperatures. Not only did organisms grow more quickly — but they also formed a thicker layer.

Biofouling is expensive no matter how you measure it: in terms of time, energy (e.g., fuel), and actual dollars. Plus, cleaning and other antifouling measures are regular expenses that add up over time.

What is antifouling?

The IMO defines antifouling as “a coating, paint, surface treatment, surface or device that is used on a ship to control or prevent attachment of unwanted organisms”. Basically, antifouling is a measure that reduces the impact of biofouling on vessel efficiency.

Historically, ships used compounds like arsenic and lime to protect the hull of a ship against biofouling. Over time, however, those compounds leach into the water and can destroy marine ecosystems. The IMO now regulates the types of antifouling paint, compounds and methods that the shipping industry can use to prevent biofouling safely.

It’s also worth noting that antifouling differs from “fouling-release” tactics: “Fouling-release describes the force required to remove an organism that is already attached to a surface. These two terms have been used interchangeably in the literature; however they are truly different phenomena,” explained Science Direct.

As the demand for antifouling and fouling-release strategies grows, here are some of the most effective measures currently in use today.

6 Ways to combat biofouling to improve vessel efficiency

There are a number of preventative measures and fouling-release tactics that can help combat biofouling.

Preventative measures include:

  1. Using an electrolytic system: This system passes a current between two anodes usually made of copper and aluminum. The current produces copper ions that prevent marine organisms from settling on the hull, as well as prevents the surface from corroding, as rough surfaces are more susceptible to biofouling.
  2. Chemical dosing: This measure is used specifically for a ship’s piping method. It involves using an antifouling chemical such as ferrous chloride to coat the pipework with a protective layer that prevents corrosion.
  3. Using an ultrasonic system: One of the most effective antifouling measures, this method uses high-frequency electrical impulses to prevent marine growth from attaching to piping systems.
  4. Electro-chlorination: A mechanism on the ship uses chlorine to produce sodium hypochlorite, which is then used to prevent fouling. This method is slightly more risky than others and must be tested as chlorine can damage marine ecosystems.

These tactics often require machinery on board: for smaller vessels, these preventative measures may not be cost-effective or efficient. As a result, some ships use antifouling paint to try to prevent biofouling. These coatings work in a few different ways. Some repel organisms from the hull; others make the surface slippery so that organisms have trouble sticking. Hydrophobic foul-release coatings make it easier to clean organisms from the hull of a ship.

There are a number of boat hull cleaning practices to remove marine organisms off the hull of the boat while the boat is still in the water. “Conventional hull cleaning is conducted by divers using rotating-brush carts, or using ROVs equipped with rotating brushes or waterjets,” explained one expert. “Alternatively, preventive maintenance approaches have also been suggested, such as hull grooming on US Navy vessels, consisting of frequent and gentle wiping of the hull and continuous prevention methods, such as aeration or ultrasound transducers.”

Ancillary technology like Sofar Ocean’s Wayfinder platform provides data that can help schedule antifouling maintenance to improve vessel efficiency before macrofouling becomes a big problem.  By combining the most accurate weather data from the Sofar network with custom vessel performance curves, Wayfinder is able to predict when a vessel might be underperforming due to fouling of the prop or hull. Marine logistics companies can use this information to schedule the appropriate cleaning — optimizing operational efficiency, improving vessel maintenance, and limiting unnecessary delays caused by biofouling.

Combatting the impact of biofouling on vessel efficiency takes a multi-pronged approach that starts with data. Vessel-specific performance models can provide the feedback shipping companies need to understand the causes and effects of decreasing vessel performance. From there, the appropriate combination of antifouling and fouling-release tactics can be used to remove marine organisms safely.


Source: sofarocean


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