Crab Shells and Tree Fibers Create A Sustainable Plastic Alternative

Plastic is everywhere, from water bottles to the cellular devices we use every day, it has become a staple in the modern consumer’s life. However, 50 percent of the world’s plastic is just thrown away after a single use, which contributes to the growing 6.3 billion tonnes of plastic waste accumulated worldwide. This is why researchers from the Georgia Institute of Technology have developed a sustainable plastic alternative from crab shells and tree fibers.

This new material, which was described in the journal ACS Sustainable Chemistry and Engineering on July 23, is a product made from multiple layers of chitin from crab shells and cellulose from trees. Chitin is a fibrous substance that can be found in the exoskeletons of arthropods and in fungi, while cellulose is an insoluble substance found in plant cell walls.

“The main benchmark that we compare it to is PET, or polyethylene terephthalate, one of the most common petroleum-based materials in the transparent packaging you see in vending machines and soft drink bottles,” said J. Carson Meredith, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. “Our material showed up to a 67 percent reduction in oxygen permeability over some forms of PET, which means it could, in theory, keep foods fresher longer.”

In addition to potentially extending the lifespan of foods, this new innovation may be able to replace common single-use plastics and its production technique can easily be replicated in other labs. The researchers created this film by suspending nanofibres extracted from chitin and cellulose in water and then spraying these fibers onto a surface in alternating layers. The result of this process is a flexible, transparent and compostable film that is similar to the consistency of plastic packaging film.

“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,” Meredith said.

According to Meridith, chitin nanofibers carry a positive charge whereas cellulose nanocrystals are negatively charged. These opposing charges make it possible to create alternating layers of both substances. Both substances interface with each other’s charges to form a solid yet flexible plastic alternative that can prevent the oxidation of foods. Meridith claims that the crystalline structure of the film which prevents gases from passing through plays a key role in preserving the freshness of foods.

“It’s difficult for a gas molecule to penetrate a solid crystal because it has to disrupt the crystal structure,” Meredith said. “Something like PET, on the other hand, has a significant amount of amorphous or non-crystalline content, so there are more paths easier for a small gas molecule to find its way through.”

This makes the flexible packaging product good for the environment and it can complement efforts to reduce food waste. The materials needed to create the film are also easily accessible with chitin found in mass quantities as a byproduct from the shellfish industry and large quantities of cellulose can be sourced from byproducts from the paper industry.

However, more work needs to done. Manufacturing processes need to be developed in order to produce this film in bulk so that the material’s cost can be more comparable to the cost of plastic. In addition, methods to extract chitin are not as developed as methods to extract cellulose, which means that new extraction methods the maximize the production of chitin need to be developed as well. Meridith also claims that researchers need to work on the film’s ability to block water vapor.

Nevertheless, this new development speaks to the food industry’s efforts to reduce pollution and after full-scale development, it has the potential to become the new plastic film. As researchers continue to develop plastic-alternatives, this solution might evolve to become a substance that is comparable to hard plastic in the near future.