How a coat of paint makes our vessels more sustainable

Barnacles, algae and other marine organisms have always been a huge problem for shipping. If these organisms build-up on a vessel’s hull, it’s known as fouling, and the impact can be huge. In the old days of wind and sail, fouling could be so bad a ship could hardly move. Thanks to modern propulsion systems, fouling no longer causes vessel immobility, but it does lead to increased emissions.

Why does fouling increase emissions?

Even with a perfectly clean hull, an advanced vessel, like one of our Ro-Ro vessels, use several tonnes of fuel a day. Just like a car, this combustion of fuel causes CO2 to be released into the atmosphere.

If fouling builds up on the vessel’s hull, it reduces the vessel’s hydrodynamics. This means more fuel is required to move the ship through the water, pushing up CO2 emissions. In a study by Marintek, it was estimated that fouling increases fuel consumption and emissions on an average vessel by around 15 per cent over a 60-month period. On a very large vessel, this causes several thousand extra tonnes of CO2 to be released into the atmosphere each year.

How do hull paints reduce emissions?

Modern hull paints are designed to stop fouling from building up on the vessel’s hull. The best is extremely effective, essentially keeping the hull entirely fouling free for 60 months or more.

Most work in one of three ways:
• Biocide release paints contains tiny amounts of biocide. This is slowly released as the paint degrades, dissuading marine organisms from attaching to the hull.
• Silicone paints give the hull a very smooth surface that fouling can’t hold onto.
• Silicon-hydrogel paints combine silicon with a special hydrogel surface that appears like water, essentially rendering it invisible to fouling organisms.

Whatever the mechanism, the outcome is essentially the same. The vessel’s hull remains smooth, which means less fuel is needed for it to sail.

What does this mean for Höegh Autoliners?

At Höegh Autoliners, we’re committed to reducing emissions from our operations. On our vessels, we take everything into account, including the paint on the hull.

On our fleet, hull paints are estimated to reduce fuel use by an average of 4% per vessel. Across a year of operation, this reduces our CO2 emissions by around 50,000 tonnes.

Of course, many other factors affect fuel consumption and emissions. You can see what else we’re doing to reduce emissions here.