Scientists Turn Cashew Nut Shells Into Sunscreen

A team of international scientists found an environmentally friendly way to produce sunscreen from cashew nut shells.

“Green chemists” from the University of Witwatersrand in Johannesburg are working to produce useful compounds from wood and other fast-growing, non-edible plant waste.

Cashew nut shells contain oil compounds that can cause contact dermatitis (similar in severity to poison ivy). Which is why the delicious snack is not typically sold to consumers in its husk.

But instead of simply throwing them away, researchers are recycling the pods to help protect humans, livestock, and polymers from the Sun’s harmful rays.

As described in a paper published by the European Journal of Organic Chemistry, cashew shells produce aromatic compounds that show good UVA and UVB absorbance.

“Cashew nut shells are a waste product in the cashew-farming community, especially in Tanzania, so finding a useful, sustainable way to use these waste products can lead to completely new, environmentally friendly ways of doing things,” principal study author Charles de Koning, a professor at the Wits School of Chemistry, said in a statement.

While the atmosphere blocks about three-quarters of the Sun’s ultraviolet (UV) radiation, that last quarter can be damaging to most materials—from dyes and plastics to human and animal skin.

To mitigate UV injury, according to Wits University, organic and inorganic compounds are used as filters. Ideal options display a high UV absorption of UVA rays (from 315-400 nm) and UVB rays (from 280-315 nm).

But, aside from their petrochemical origin, a major drawback of current UV protection agents is their negative effect on aquatic ecosystems.

As a result, there is growing attention from regulatory bodies and stricter regulations are being enforced on the production of Sun-filtering products.

“We aimed to find a way to produce new UV absorbers from cashew nut shell liquid (CNSL) as a non-edible, bio-renewable carbon resource,” de Koning said.

The team—including colleagues from universities in Germany, Malawi, and Tanzania—has already filed a patent application to commercialize this process in South Africa.

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