Trees and Crab Shells Could Replace Plastic and Keep Food Fresher

Plastic wrap could be replaced by a new material made from natural fibers, the latest in many steps to help the environment.

Researchers from the Georgia Institute of Technology revealed their new invention to replace plastic packaging film on Monday. According to research published in ACS Sustainable Chemistry and Engineering, the new compostable material uses trees and crab shells to re-create the flexible material that's used for so many products.

To create the material, the researchers derived chitin from crab shells. Chitin is a major component of the exoskeleton of crabs as well as insects and fungi. It is the second most popular natural biopolymer; the most popular, cellulose, comes from plants, and, in this case, trees.

Originally, the scientists worked with just cellulose.

"We had been looking at cellulose nanocrystals for several years and exploring ways to improve those for use in lightweight composites as well as food packaging, because of the huge market opportunity for renewable and compostable packaging, and how important food packaging overall is going to be as the population continues to grow," J. Carson Meredith, a professor at Georgia Tech and author on the study, said in a statement.

The researchers weren't looking at chitin as a packaging alternative until they noticed that it was positively charged, while cellulose is negatively charged. The scientists thought the two materials might work well together as alternating layers because of the interface their charges would form.

Captured king crabs in Repparfjord, Norway. Chitin, a natural biopolymer, is a major component of the exoskeleton of crabs as well as insects and fungi. STOYAN NENOV/REUTERS

The team decided to suspend chitin and cellulose nanofibers in water, then alternated spraying layers of the material onto a surface, leaving a transparent, flexible and strong crystalline material when the layers dried. The material was comparable to polyethylene terephthalate, or PET, which is used as the base for many plastic items, like drink bottles and plastic film.

However, PET isn't the best option, the scientists said.

"It's difficult for a gas molecule to penetrate a solid crystal, because it has to disrupt the crystal structure," Meredith explained. "Something like PET, on the other hand, has a significant amount of amorphous or noncrystalline content, so there are more paths easier for a small gas molecule to find its way through."

This means that the new creation could keep food fresher for longer, because fewer toxins would be able to penetrate it. In fact, the scientists found that compared to some forms of PET, their material had a 67 percent reduction in oxygen permeability. In addition, the shellfish food industry has a lot of chitin left over, so this would provide a way to sustainably use that material.

The material isn't perfect yet: Scientists need to find a way to mass-produce it and improve its success at blocking water vapor. But the invention could eventually be a sustainable and compostable alternative to plastic.