Plastic, once seen as a miracle material, has a dark side to it, because once it's released into the environment, either on purpose or by accident, it sticks around for a really long time, contributing to water contamination and ocean pollution, as well as harming wildlife. And while there are options for replacing some plastics with bioplastics (which are made from renewable and/or biodegradable materials), for the most part, those products require the production or harvesting of virgin biomass, such as trees or biomass crops, both of which have an environmental impact that isn't sustainable at our current rate of plastic consumption.
However, a new type of bioplastic is in the works, one which can be used to fabricate large and complex three-dimensional shapes, using traditional manufacturing techniques such as injection molding or casting. This new bioplastic is not only made from a waste resource, shrimp shells and wood 'flour', but it can also break down into benign, even helpful, components in the soil in about two weeks.Researchers at Harvard's Wyss Institute developed the new bioplastic from chitosan (a form of chitin, a natural polymer said to be the second most abundant organic material on Earth), derived from shrimp shells.
"There is an urgent need in many industries for sustainable materials that can be mass produced. Our scalable manufacturing method shows that chitosan, which is readily available and inexpensive, can serve as a viable bioplastic that could potentially be used instead of conventional plastics for numerous industrial applications." - Don Ingber, M.D., Ph.D., Professor of Bioengineering at Harvard School of Engineering and Applied Sciences
This newest bioplastic is the next version of a material the team developed a few years ago called "Shrilk" (made from chitin from shrimp shells and a silk protein), but in a bid to make the material easier to manufacture, and cheaper, they moved away from using silk protein in the mix.
One of the challenges they faced was fabricating the chitosan with a method that could preserve the natural integrity of its molecular structure, which would yield strong mechanical properties and be usable with large-scale manufacturing techniques.
"Depending on the fabrication method, you either get a chitosan material that is brittle and opaque, and therefore not usable, or tough and transparent, which is what we were after." - Javier Fernandez, Ph.D., Postdoctoral Fellow
The chitosan polymer they developed initially had a shrinkage problem that kept it from maintaining its shape after the molding process, but the team found that by adding wood 'flour' (a wood processing waste product) to the mix, the new bioplastic could be molded into a 3D form with "impressive precision."
The team's research was published last week in Macromolecular Materials & Engineering journal: Manufacturing of Large-Scale Functional Objects Using Biodegradable Chitosan Bioplastic
[Update: One reader had a question about the allergic potential for this bioplastic to those with shellfish allergies, and according to a response on Twitter, Javier Fernandez states that the "Allergy is to tropomyosin, protein destroyed during the extraction of chitin. Chitin is FDA approved for medical use.". Fernandez also stated that they make a version of the bioplastic without wood flour, with pictures and a video available here.]