The earliest sunglasses weren't made of glass, or even plastic, but rather were carved from wood. Fashioned by Alaskan Inuits, the first known pairs were goggle-like eye coverings with tiny slits to see from.
Modern sunglasses, whether of the cheap drugstore variety or the gold and diamond Dolce & Gabanna pair that go for $383,000, are generally constructed of plastic, some metal, and sometimes, glass.
Zeal of Boulder, Colorado decided to cut oil-based plastic out of the sunglasses equation.
First the company produced frames with what they call Z-resin, a plant-based material that uses castor oil for plastic production. Hearty, drought resistant castor beans are easy to grow and make plentiful oil - yes, that's the same stuff little kids used to have to ingest to keep them healthy. Zeal says the castor grown doesn't compete with food crops because no one eats castor beans and castor oil these days is in very low demand.
So Zeal makes sunglasses with the castor-based plastic.
In order to make completely fossil-fuel-free sunglasses, ZEAL had to figure out how to make lenses from a material that could maintain high optical standards. Called e-llume, the new ZEAL lenses have a non-petroleum-based bonder yet maintain a clarity value of 38 (Abbe).
Zeal's bio-based lenses block UVA, B, and C light as well as HEV (High Energy Visible) light.
If you look at it pound for pound, your sunglasses are pretty low on the footprint list (production of a pound of plastic bottles is equivalent to about a pound of CO2). In fact it is more likely that you getting to the sun will emit more CO2 than the manufacture of your sunglasses. But if you've been looking to eliminate fossil-fuel plastic from your purchasing habits, Zeal has a variety of frames that do the trick.