Eggshells: The Next Innovative Frontier to Bioplastics

(3BL Media/Justmeans) - Bioplastics is a booming business these days, especially in Europe, where the industry that brought us things like biogradable dishes and recyclable plastic is positioned to grow by more than 300 percent by 2018. Made from renewable sources like corn, vegetable starches and cooking oil, these "green" biobased polymers offer an ingenious replacement to petroleum products that take much longer to break down in landfills and are harder to recycle.

But as many scientists will tell you, not all biobased polymers are created equal. Thermoplastic polymers, which are made from food starch for example, work well as pharmaceutical capsules because of their digestibility. But they also break down easily when exposed to moisture and wouldn't work well as commercial packaging. Polylactic acid plastics (PLA) made of corn or sugar on the other hand, are sturdier and can sometimes be blended with conventional petroleum polymers to make things like cups and 3-D printing plastics. Adding bio-based substances to conventional plastic polymers helps reduce the amount of petroleum required in production.

But PLA polymers also tend to be much more brittle and don't always mix well with other polymers. Creating a bioplastic polymer that can produce a durable and plyable product like plastic wrap that doesn't easily break is often is a matter of creative ingenuity, as researchers at Tuskegee University Alabama, recently discovered.

Scientists in the Department of Materials Research and Engineering wanted to create a packaging material that could take the place of bulky plastic molds and cardboard and could be used to wrap, cushion and protect commercial products during transit. To do this, they turned to one of nature's oldest and most reliable packaging materials: the eggshell.

Amazingly light, durable during transport and ample in supply, eggshells serve as a ready-made, self-contained incubator for many species, from the duck-billed platypus to the barnyard chicken. The calcium carbonate in the eggshell allows for superb malleability during gestation and birth and yet can withstand wide temperature ranges both in and outside the nest.

The researchers found that by including the nanoparticles of eggshells into bioplastics, they could more easily blend different forms of polymers together. By grinding the eggshell down and then blasting it with sonic waves, they were able to convert the calcium carbonate shell into  nanoparticles (about 35,000 times smaller than the diameter of a human strand of hair).   This allowed them to mix the eggshell in very small portions into their concoction of bio- and petroleum-based polymers.

By adding just .5 percent eggshell nanoparticles to a mixture of polybutyrate adipate terephthalate (a petroleum product that is often used to make plastic bags, but isn't strong) with PLA, they were able to extend the elasticity of the polymer, much like that found in sturdy plastic wrap.

The end result said the researchers, is a product that can be used in place of conventional plastic bags and film, that is 700 percent more pliable than standard bioplastic blends and can even be used to replace foam and cardboard egg cartons.

The findings, which were presented at the 251st National Meeting of the American Chemical Society in March, couldn't have come at a better time. Recent studies show that the growing bio-based industry contributed 4 million jobs to the U.S. economy in 2013. According to a 2015 study conducted jointly by researchers at Duke University and North Carolina State University, biodegradable products also play an important role in helping to reduce the global dependancy on fossil fuel feedstock.  The analysts found that by using biobased products in place of conventional fossil fuel materials, the annual reduction in carbon emissions is equal to 200,000 cars being taken off the road.

It will be interesting to see if researchers can develop other ways to use the properties of the  eggshell as the bioplastics industry continues to expand its market.

Flickr/Caitlin Regan