Making Shipping Greener with Hairy Ships

How Shipping Pollutes

Global shipping may be cheap, but it releases more CO2 every year than Canada and Mexico combined. That’s because the fuel it burns, called “bunker fuel,” is dirty stuff. When burned, it coughs up sulfur oxides, nitrogen oxides, methane, and particulate matter—causing everything from smog to ocean acidification to respiratory issues.

Why Fouling is Such a Drag

If you leave anything in water long enough, stuff grows on it. So-called “fouling” starts with a slime layer, followed by algae, and finally barnacles and shells that stick to the hull.

Fouling makes the ship’s underside bumpy, increasing drag. More drag means the ship has to burn more fuel (and emit more pollution).

Copper: An Oldie But Baddie

In the 1800s, people covered their hulls in copper to prevent fouling. Even today, no one’s totally sure how it works. We still put copper (and other compounds) into the biocide paints that coat ship hulls. Unfortunately, they leach toxins into the water.

[Captions]

zinc pyrithione

chlorothalonil

dichlofluanid

A Hairy Ship is a Greener Ship

Scientists have designed a new way to prevent fouling, inspired by an aquatic plant. Dunk Salvinia underwater and then pull it out—it stays dry. But how?

All along the plant’s surface are hairy structures that, when you look super close, resemble little egg-beaters. Most of the egg-beater is coated with a hydrophobic wax that repels water. But the tips are uncoated and hydrophilic, meaning they grab onto water molecules. And water molecules grab onto each other because they’re polar.

The combined effect looks something like a giant tent, actually sheets of water held up by multiple egg-beater hairs. The trapped air under the tent keeps fouling at bay.

The synthetic version is made of silicone and designed with an adhesive back to go on a ship like a bumper sticker!

Sources:

• https://www.transportenvironment.org/challenges/ships/greenhouse-gases/
• https://www.sciencedirect.com/science/article/pii/B9780128050521000309
• https://www.sciencedirect.com/science/article/pii/S1352231017305563
• https://darchive.mblwhoilibrary.org/bitstream/handle/1912/191/chapter%2014.pdf
• https://www.jstor.org/stable/2593163
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291976/
• https://www.sciencedirect.com/science/article/abs/pii/S0029801816305315
• https://aircoat.eu/wp-content/uploads/2021/01/Small-Journal-Air-Spring-Effect.pdf
• https://www.ppgpmc.com/marine/featured-products/ppg-sigmaglide-1290
• https://www.khanacademy.org/science/ap-biology/chemistry-of-life/structure-of-water-and-hydrogenbonding/a/hydrogen-bonding-in-water