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Scientists Combine Shellfish, Tree Cellulose to Make Biodegradable Plastic
Wrap

by Sadie Witkowski

   WASHINGTON --

   The use of packaging plastic continues to rise as the world's
   population grows. Environmentalists say compostable and biodegradable
   packaging is needed now more than ever, particularly when it comes to
   plastics used to protect our food. But now, a biodegradable film made
   from discarded shellfish and trees may fill that need. It's being
   developed by researchers at the Georgia Institute of Technology.

   Lead researcher Carson Meredith is interested in exploring alternatives
   to crude-oil-based plastics now being used. "Probably about eight years
   ago, we got involved in what's referred to as forest-based
   nanotechnology," he told VOA news. This is an emerging area "looking at
   using wood and other plant resources to extract high performance
   nano-crystalline materials made out of cellulose and using those in
   creating light-weight, high strength materials."

   Wood, clamshells, lobsters

   What that means, is that the same cellulose fibers found in woody
   plants used to make paper can also be used to replace plastic packaging
   material. Meredith's group found that by combining the plant cellulose
   with chitin, the hard material that makes up clamshells and the
   exoskeleton of lobsters, they could create a biodegradable coating.

   At the molecular level, chitin and cellulose are oppositely charged --
   meaning they are attracted to each other. The Georgia Tech scientists
   used this property when they sprayed very thin, alternating layers of
   the two materials onto a base.

   "In this case, we chose to use polylactic acid, or PLA, which is also
   derived from natural materials and is biodegradable," said Meredith.
   PLA is a plastic made from renewable sources such as corn starch or
   sugarcane. It can be a clear film like cellophane or shaped into
   disposable tableware.

   Plastics without crude oil

   There is a common misconception that all plastics are made using crude
   oil. Susan Selke, who directs the Center for Packing Innovation and
   Sustainability, explained that technically, the term plastic refers to
   "a long-chain carbon-based structure that is capable of being shaped
   through an application of heat and pressure." She continued, "PLA
   itself is classified as a compostable plastic. So if you put it into a
   municipal composting program that's organized to get to the elevated
   temperatures with lots of moisture, then what happens is that the PLA
   hydrolyzes. And once it's hydrolyzed, then it can biodegrade."

   So in the case of the new plastic film, Meredith and his co-authors
   used a clear flexible PLA base and applied alternating layers of chitin
   and cellulose nano-fibers that dry into a thin, but durable clear
   plastic like that used most commonly in grocery stores.

   Meredith notes his research shows that the chitin and cellulose
   "perform much better as two or three thin layers, than they would as
   independent materials of equivalent thickness."

   The new material is exceptionally good at keeping oxygen out, which
   would make it useful for food packaging. Meredith says they haven't
   formally tested it as a food packing material, but one of the
   attractions is that this would be a compostable packaging material that
   would be completely biodegradable.

   Green alternative

   Moving forward, Meredith hopes to see the new material put to use as a
   green alternative, although challenges remain. "I think the major
   challenge for commercializing this would be having a scalable supply
   chain of raw materials. Right now that largely doesn't exist,"he told
   VOA.

   Selke agrees, wondering how cost-effective the material might be. "It's
   going to have to compete with other kinds of materials that are
   designed to do the same kind of thing in improving the barrier."

   Although future obstacles remain, the new material has two key
   benefits. The plastic itself is completely composed of bio-materials,
   and is compostable, meaning it can break down without the harmful
   pollution associated with fossil fuel-based plastics.

   Sadie Witkowski is a PhD candidate in Psychology at Northwestern
   University where she studies sleep and memory. She is also the 2018
   AAAS Mass Media Fellow for Voice of America and is reporting this
   summer on science, medicine, and technology. She received her
   undergraduate degree from the University of Texas in Austin.