HOCHLEITNER - INSIGHTS #Anti-fouling

Innovative paint solution to help protect ships from marine biofouling

Tue, 08 Mar 2022 22:41:00 +0000

European researchers have pioneered an ecologically friendly and sustainable antifouling paint solution that is based neither on biocide emission nor low adhesion.

The EU-funded Low Emission Antifouling (LEAF) project has developed an environmentally- friendly and fully sustainable prototype paint to minimise the damage to cruising ships and static constructions from marine biofouling.

The presence of micro and macroscopic fouling organisms, such as barnacles, on a ship's hull can become a major challenge for seafarers. As they multiply, they build up calcium deposits under a boat's paint, which in turn interferes with smooth fluid flow and can decrease fuel efficiency by up to 40 %, as well as result in higher carbon emissions. This is a major problem in particular for larger vessels and marine constructions.

Traditionally, a biocide-based poison, such as copper oxide, has been applied to hull paint to kill any fouling organisms attached, with 90 % of the world's marine fleet being coated in such a copper-based antifouling system.

However, coating a ship's hull in such a substance significantly increases the risk of toxins being released into the surrounding water, killing other marine life. Additionally, low adhesion coatings suffer from drawbacks of low durability and associated high material and maintenance costs.

In order to significantly reduce ecological damage and provide a solution that is both sustainable and cost-efficient, the innovative approach taken by the LEAF project does not rely on the exposure and release of biocides into the water.

Instead, the prototype paint's antifouling effect is based on the direct contact of a fouling organism with biocide that resides within the coating itself. This will also have the additional benefit of providing longer service life and fewer maintenance costs.

Promising tests held across European waters

After less than three years of development and testing in both the lab and in the field, the LEAF project has recorded successful results over the sustainability and durability of the prototype paint. Highly promising tests have been conducted in Scandinavian, Mediterranean and Caribbean waters.

During a test that took place in Grado's Lagoon, Italy, the hull of a boat that had been launched two and a half months earlier was fully colonised by tubeworms, indicating a high fouling pressure. Additionally, the white paint on the engine anchoring structures was suffering from significant marine biofouling.

Following the application of the prototype LEAF paint, in the same warm waters of the lagoon, the result three weeks later showed that the boat had a high level of antifouling efficacy. The boat owner also confirmed that the LEAF paint performed substantially better than the commercial products that had been used in previous seasons.

Additionally, human exposure and aquatic risk assessments performed within the project have shown that the LEAF paint is likely to comply with the most stringent global regulation systems, such as the European Biocidal Products Regulation (BPR).

The LEAF team is now currently working with external partners on the next steps required to fully commercialise the new technology and successfully bring it to market for all interested end-users.

What is fouling

Sat, 26 Feb 2022 15:15:00 +0000

According to Marine Paint research, is defined as: A particular species adhering to and growing on a hull depends on the waters through which the vessel moves, the season, and how much time the vessel spends in port.
Bacteria, cyanobacteria, diatoms (unicellular algae), and protozoans (unicellular animals) are common species in the initial microfouling. Diatoms excrete large quantities of extracellular polymeric substances (EPS), which contribute to the sliminess of the surface.

Following the microfouling, a macrofouling community establishes itself, consisting of soft or hard foulers. Soft foulers include higher algae, such as the green algae Ulva intestinalis. Ulva releases spores which, on touching a surface, secrete an adhesive consisting of glycoproteins to ensure that the algae adhere to and grow on the surface. Other types of soft foulers are sea squirts, sea anemones or soft corals. Hard foulers include mussels, tubeworms and barnacles, all of which have highly developed abilities to adhere strongly to the surface.

Different types of chemical adhesives, all have the same function; to allow the species to attach itself strongly to the surface.
Consequently, the fouling on a ship’s hull becomes a unique ecosystem in itself, but one that creates major problems for both commercial shipping and leisure boating.
The legislative pressure to develop antifouling strategies with low environmental impact, has led to a substantial commitment from national and international authorities.

The International Maritime Organisation (IMO), agreed in 2001 on a convention to ban of tributyltin (TBT)-based paints, as it has been shown to have severe ecotoxicological effects.

As of 2003, it is forbidden to apply new TBT-containing coatings, and from 2008 there is a ban on the presence of such paints on ship hulls for those states that adhere to the convention.

55 states representing 78% of the world tonnage

When developing new antifouling agents it is of the utmost importance to rigorously anticipate and assess the risk of long-term effects on the environment.

Paints and coatings containing bactericidal agent nanoparticles combat marine fouling

Thu, 24 Feb 2022 22:57:00 +0000

Scientists have discovered that tiny vanadium pentoxide nanoparticles can inhibit the growth of barnacles, bacteria, and algae on surfaces in contact with water, such as ship hulls, sea buoys, or offshore platforms. Their experiments showed that steel plates to which a coating containing dispersed vanadium pentoxide particles had been applied could be exposed to seawater for weeks without the formation of deposits of barnacles, bacteria, and algae.

Scientists at Johannes Gutenberg University Mainz (JGU) in Germany have discovered that tiny vanadium pentoxide nanoparticles can inhibit the growth of barnacles, bacteria, and algae on surfaces in contact with water, such as ship hulls, sea buoys, or offshore platforms. Their experiments showed that steel plates to which a coating containing dispersed vanadium pentoxide particles had been applied could be exposed to seawater for weeks without the formation of deposits of barnacles, bacteria, and algae. In comparison, plates that were coated only with the ship's normal paint exhibited massive fouling after exposure to seawater for the same period of time. The discovery could lead to the development of new protective, antifouling coatings and paints that are less damaging to the environment than the ship coatings currently used.

Marine fouling is a problem that costs the shipping industry more than 200 billion dollars per year. The accumulation of organisms such as algae, mussels, and barnacles increases the objects' water resistance and, in consequence, fuel consumption. This means additional costs for shipping companies and, even worse, increased environmental damage due to extra CO2 emissions. Within only a few months, an underwater boat hull can be completely covered and overgrown with organisms. According to Lloyds, this means an increase in fuel consumption of up to 28 percent and about 250 million tons of additional CO2 emissions per year. While it is possible to counteract this effect to some extent by means of the use of antifouling paints, conventional biocides are less effective and can have adverse environmental consequences. In addition, microorganisms can develop resistance to them.

It was one of nature's own defense mechanisms that provided the inspiration for the approach now taken by the team of scientists working under Professor Dr. Wolfgang Tremel of the Institute of Inorganic Chemistry and Analytical Chemistry at JGU. Certain enzymes found in brown and red algae produce halogen compounds that have a biocidal potential. It is assumed that these are synthesized by the algae to protect them against microbial attack and predators. The chemists at Mainz University decided to mimic this process using vanadium pentoxide nanoparticles. According to their article published in Nature Nanotechnology, vanadium pentoxide (V2O5) nanoparticles have "an intrinsic biomimetic bromination activity […] which makes them a practical and cost-efficient alternative for conventional chemical biocides." Vanadium pentoxide functions as a catalyst so that hydrogen peroxide and bromide combine to form small quantities of hypobromous acid, which is highly toxic to many microorganisms and has a pronounced antibacterial effect. The required reactants are present in seawater: This already contains bromide ions, while small quantities of hydrogen peroxide are formed when it is exposed to sunlight.

The process has been demonstrated both under laboratory conditions and in natural seawater. It has only very minimal consequences for the environment because the effect is restricted to micro-surfaces. The metallic oxide is particularly potent when it is present in the form of nanoparticles because then, due to the larger surface area, there is an enhanced catalytic effect.

"Vanadium pentoxide nanoparticles, due to their poor solubility and the fact that they are embedded in the coating, are considerably less toxic to marine life than are the tin- and copper-based active substances used in the commercially available products," explains Wolfgang Tremel. In his view, ships' coatings based on vanadium pentoxide could be a practical and cost-effective alternative to conventional chemical biocides. "Here we have an environmentally-compatible component for a new generation of antifouling paints that employ the natural defense mechanism used by marine organisms."

Ron Wever, the team's Dutch cooperation partner from the University of Amsterdam, has been investigating such natural defense mechanisms for the last 15 years. He suggested adding the enzyme involved, i.e., vanadium haloperoxidase, to antifouling paints. The chemists in Mainz are now working together with Wever to develop vanadium pentoxide nanoparticles. "Vanadium pentoxide particles are considerably cheaper and also more stable than genetically produced enzymes," he adds.

A research group headed by Dr. Klaus Peter Jochum of the Max Planck Institute for Chemistry in Mainz has been conducting experiments to determine whether the use of vanadium pentoxide might have a negative effect on the environment. Using a highly sensitive ICP mass spectrometer, the scientists determined the concentration of vanadium in various samples of seawater that had been exposed to the coated material for different lengths of time. The results showed that levels were only slightly elevated above the normal average vanadium concentration in seawater. It can thus be concluded that only very tiny amounts of vanadium migrate from the coating into seawater and will thus have no negative impact on the environment.

Journal Reference:

Filipe Natalio, Rute André, Aloysius F. Hartog, Brigitte Stoll, Klaus Peter Jochum, Ron Wever, Wolfgang Tremel. Vanadium pentoxide nanoparticles mimic vanadium haloperoxidases and thwart biofilm formation. Nature Nanotechnology, 2012; DOI: 10.1038/NNANO.2012.91