A Professor Plastics Feature ArticleSee Other Articles
The term “bioplastics” seems to cause almost as much confusion as the term “biodegradable.” So what are bioplastics—and what, exactly, does the “bio” in bioplastics refer to?
Bio … bio … hmmm. The history of plastics? No. Biotechnology? No. The “bio” in bioplastics actually has more to do with that oft-dreaded high school class, biology. You know: having to do with life, living organisms, biological systems and the like.
Ok… biological organism and plastics. Since oil and natural gas originate from biological organisms, does that mean plastics derived from oil and natural gas are bioplastics? Well, not really—at least that’s not how the term is commonly used. So just what are bioplastics?
A Brief History of Bioplastics
Let’s step back in time for a bit of perspective. The very first plastics were (and still are) made by plants through their very own internal chemical synthesis. Rubber from a rubber tree, for example, is actually a plastic. Early synthetic or “manmade” plastics were largely an attempt to replicate existing materials, such as rubber, ivory, or tortoise shells.
One of the first synthetic plastics was made from cellulose, a substance made by plants and trees. In today’s vernacular, this plastic is deemed a bioplastic. That means its primary raw materials (feedstocks) originate from “biomass:” living or recently living and renewable bio-organisms. Biomass… bio-organisms … thus the term: bioplastics.
What are Bioplastics Today?
Early bioplastics were largely eclipsed by more efficient plastics. The raw materials for today’s plastics come from many places (some even use salt), but most plastics can be made from the hydrocarbons that are readily available in natural gas, oil and coal. Even though these resources are derived from living organisms, they are not alive, recently alive or renewable (biomass). So plastics made from natural gas, oil or coal are not considered bioplastics.
Interest in bioplastics and other “bio” products has been growing (get it?) due to concern about the use of finite resources, primarily natural gas and oil. Bioplastics are reemerging today as scientists develop more efficient ways to produce the necessary quantities of biomass, most often sugarcane, wheat and corn.
Bioplastics ≠ Biodegradable
Many people believe—incorrectly—that if something is derived from biomass then it must also be biodegradable. However, the use of “bio” feedstocks does not necessarily mean that the finished product, a plastic or otherwise, will be biodegradable.
For example, a bioplastic called polylactic acid (PLA) is made with plant feedstocks and is considered biodegradable in a commercial composting facility. But PET bioplastic made with plant feedstocks is not biodegradable. In other words, the “bio” in bioplastics does not mean biodegradable.
PET bioplastic is, however, recyclable just like PET made from natural gas and oil feedstocks—they are chemically the same.
Molecule = Molecule
This brings up another point of general confusion—the comparison between a molecule derived from natural gas/oil/coal and the same molecule derived from a “bio” source. Many people believe these two molecules surely must have different properties and behave differently in the environment. Well … In reality, identical chemical structures behave the same.
Here’s an example for plastics. One of the primary feedstocks for plastics is ethylene, produced in North America primarily from natural gas. (Ethylene derived plastics are used for all sorts of everyday products, from milk jugs to carpeting to fleece jackets.)
Ethylene also is created naturally by plants. Ever wonder why a banana ripens faster in a paper bag? The banana actually creates and emits ethylene gas, which helps speed the ripening process—placing the banana in the bag traps more ethylene gas.
Does the “bio” ethylene have different properties than the ethylene derived from natural gas? No. Ethylene is ethylene, regardless the source. Ethylene’s structure (C2H4) is always exactly the same… just like good old water’s structure (H20) is always the same.
Will plastics derived from different ethylene sources have different properties? No. The original source of the ethylene is irrelevant to plastics (and to bananas).
Do Bioplastics = Better?
But doesn’t “bio” mean better for the environment? That’s the subject of much discussion and debate today—as well as considerable research and development. Plastics already are derived from corn, wheat, sugarcane … even orange peels. Using biomass—particularly food plant sources—raises complex questions about the potential impacts on water use, recyclability, the effects of farming, greenhouse gas emissions, food supply, the cost of food and others important issues.
Whew! No wonder the term bioplastics seems confusing …