When it comes to sustainable materials, plastics may not be the first option you think of. Bio-sourced materials have already made an impact, but new research is hoping to significantly expand that.
Packing peanuts are a great example of this topic. Polystyrene peanuts (and other Styrofoam™ products) have received a lot of negative attention for their slow degradation in the environment. That prompted the introduction of starch packing peanuts.
The benefit of the starch peanuts was their rapid disintegration in water. The downside is that they have a higher manufacturing cost and weigh more. There is no up-front cost benefit, and if it is not cost-competitive, companies are less likely to use it.
The main problem many biopolymers have is that they simply aren’t performing as well as traditional, synthetic polymers and tend to cost more. There are, however, some common biopolymers such as polylactic acid (PLA) which is used in a variety of applications such as cups, bottles and 3-D printing.
PLA has been a popular choice due its ability to be processed using manufacturing methods currently in use. To have a new material adopted into mass manufacturing, where it will have the broadest impact, it must be compatible with present industry.
A Harvard research group has made important advancements in achieving that balance between environmentally friendly and industrially friendly. They have found a way to make chitosan-based polymers perform and process more like synthetic versions. Chitosan is a form of chitin, the material responsible for the durability in insect and crustacean shells.
Whereas most biopolymers are derived from cellulose, the researchers propose to use chitin due its availability (it’s the second most abundant material on Earth) and tailorable properties. Although the material has been studied before, the ability to scale-up production and create a suitable material has been elusive.
The molecular structure of chitosan is sensitive to processing, and the properties are a result of both. By carefully controlling these factors, the biopolymer can be made tough enough to replace synthetic polymers, but is reported to fully degrade within two weeks after disposal.
A major source for the polymer feedstock is anticipated to be unwanted shrimp shells. These shells are currently thrown away, used in fertilizer or in small quantities in other products. The team hopes to use this resource as a sustainable supply for creating products.
The chitosan is mixed with wood flour to reduce shrinkage during molding, which allows for high-precision manufacture. If you’re worried about whether a chitosan cell phone will disintegrate if left in your pocket for a ride through the washing machine, it can be made suitable for use in water as well. How that affects biodegradation was not discussed.
Sustainability has become an imperative engineering task. Making eco-friendly materials that fit in contemporary manufacturing is not always an easy task, but it is one worth undertaking.
Image courtesy of Texas Fresh Seafood