Sunday Science: Sharks and Green Chemistry?

When we look at nature, we see beauty and struggle, life and death. The battle for survival has been going on for hundreds of millions of years, and living things have developed all kinds of tools and techniques to survive in that time. We’ve only been on the block for a blip in geological time, and we’re playing catchup with nature in the manufacturing business.

Manufactured chemicals are present in almost all of the products we use, and many of these find their way into the environment and our bodies. Some are innocuous and break down harmlessly, but others may be toxic to living organisms and persist in the environment. On top of that, synthesising chemicals can be energy-intensive and create unwanted waste products.

The concept of ‘green’ chemistry has been developed in response to these problems. Green chemistry seeks, firstly, to minimise and prevent chemical hazards, then re-use and recycle chemicals, followed by treating them to make them less harmful and then disposing of them safely. By doing this, problems caused by industrial chemicals can be avoided or reduced throughout the production process.

An example of an application of green chemistry is in the shipping industry. Biofouling – when organisms such as barnacles and algae grow on submerged structures – can damage and degrade ships’ hulls. Not only that, but the extra drag and weight slows ships down, meaning they use more fuel and take longer to travel. Until recently, the solution to this was to apply organic tin compounds (organotins) to kill the organisms and clear the fouling.

Organotins are highly toxic, which makes them very effective! However, organotins accumulate in the environment, and ongoing research showed that the long-term impact of organotins was potentially severe, disrupting basic ocean ecosystems and causing damage to higher organisms such as otters and dolphins.

To deal with this problem, new methods to prevent biofouling are needed. One possible solution is the use of biomimicry, developed by the Office of Naval Research in the US. They studied the properties of shark skin and found that it naturally resists biofouling. If such a surface can be replicated on the hull of a ship, it can reduce biofouling without the use of toxic chemicals. The grooved, rough surface of shark skin appears to resist fouling in several ways:

“three factors appear to help prevent marine organisms from being able to adhere to (“foul”) shark skin: (1) the accelerated water flow at a shark’s surface reduces the contact time of fouling organisms, (2) the roughened nano-texture of shark skin both reduces the available surface area for adhering organisms and creates an unstable surface repellant to microbes, and (3) the dermal scales themselves perpetually realign or flex in response to changes in internal and external pressure as the shark moves through water, creating a “moving target” for fouling organisms.” – Biomimicking Sharks

Sleek, fast and anti-fouled.

While there are awards and incentives available for green chemistry research, its application is generally motivated by a sense of responsibility. Chemists recognise that their work has the potential to be damaging, to the health of humans and the environment. By applying the principles of green chemistry, they can minimise their impact while still creating useful new products and solutions for industries worldwide.