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.
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.