There is a great deal of confusion about the term “bioplastic”. Some believe that the definition of bioplastic means biodegradable plastic. Some people think that bioplastics will automatically "melt" when exposed to water. There is a tendency to lump many of the new green plastics under the same umbrella: bioplastics, biodegradables, etc. These leads to the media using a number of terms as if they were interchangeable: “eco-friendly”, “green”, “compostable”, “biodegradable”, “degradable”, “bioplastic”, etc. But these terms are very different when looking at them from a scientific perspective.
Bioplastics in a technical sense are simply plastics created from the use of a biological feedstock: the starch from corn, potatoes, grass, trees, or other living or once living material. Biodegradable plastics, on the other hand, are defined scientifically as “…when the degradation is the result of naturally-occurring micro-organisms such as bacteria, fungi and algae.” As it turns out, creating plastic from biological feedstock (“bioplastic”) could result in plastics that are biodegradable, compostable, or even non-biodegradable like the traditional plastics like we see on the market today!
Understanding that a bioplastic could be compostable, biodegradable, or non-biodegradable leads one to see where there could be so much confusion. Even some of the “experts” in this field are confused by the term “bioplastic” -which really doesn’t tell us much about the environmental health of the plastic material. It may sound very pleasant and cause consumers to imply certain characteristics, but it really is a confusing and possibly misleading term to use.
This leads us to another term that is usually implied by the use of the word “bioplastic” that creates a lot of confusion within the market, and that is the term “biodegradable plastic”. Many believe that the bioplastic derived from corn also known most popularly as PLA (poly-lactic Acid) is biodegradable. Although corn is a renewable feedstock for making PLA, it is not biodegradable or even compostable based on ASTM standard definitions. PLA will last for hundreds of years if you throw it out into the same environmental conditions as traditional plastics (including your back yard compost pile).
PLA, a common bioplastic, requires an initial mechanical/chemical breakdown before the polymer can be assimilated by microbes and thus biodegrade. This chemical breakdown happens as the result of being exposed to high temperatures (140 F which are readily found in professional composting facilities) for approximately 10 days. Thus PLA would be defined as “professional-compostable” and not necessarily “biodegradable” or “compostable”. PLA would need that specific professional compost environment in order to maximize its environmental benefit of the polymer. This process is also validated by scientific ASTM definitions and test methods.
This brings us to the category of plastics which start off with traditional resins, and add an additive that will render it degradable. If we go back to the definition of biodegradable, we can see that some additive technologies such as those which are called oxo-degradable or photo-degradables, are not by definition biodegradable, but would fall under the ASTM definition of a degradable plastic. The categories of degradable plastics are those plastics which weaken or break down as the result of being exposed to oxygen, light or some environmental condition.
The additives being used for degradables utilize compounds to chemically attach to the traditional polymer. When this altered polymer chemically reacts to the environmental condition (oxygen, UV, etc) they cause the polymer chain to break, which weakens the polymer and eventually causes it to crumble into smaller and smaller pieces. Although, there are ASTM definitions and testing methods that scientifically validate degradable plastics, there is very little data on whether these plastics do, by definition, biodegrade and be called biodegradable.
Our last category is those plastics which are deemed biodegradable per the ASTM definition, meaning that the plastic would need to break down naturally into biogases and biomass as the result of being exposed to a microbial environment, such as found in soil. These plastics could be from a renewable resource such as a bioplastic, or they could be from a traditional plastic resin using an organic additive turning them into biodegradable plastics.
Plastics which use an organic additive rendering them biodegradable as per ASTM’s definition, is what I can talk most specifically about. Our company was created with the environmental mission to address the plastic pollution issue, specifically around bottles. The organic additive acts more like filler in the plastic and does not chemically bind to the existing polymer. Because of this, the plastic with the additive maintains the same physical characteristic and properties as the traditional resin, thus giving us the stable packaging needed for the end product. As a side note, there have been a few noticeable improvements with some of the physical characteristics when using organic additives.
Traditional polymers are known as hydrocarbons, meaning they are mostly made up of carbon and hydrogen atoms. Normally this make-up is a very attractive energy source for microbes in that they seek the carbon atoms as their source of what you could call food. To make plastic durable, the polymer chains are elongated which makes for a very durable, and long lasting material. Because of the long chain polymer(s), microbes are no longer able to easily get at the source of carbon, resulting in polymers that last hundreds or thousands of years before microbes can assimilate it back into gases and biomass. Organic additives provide an easily accessible food source, allowing the microbes to colonize on the plastic. This results in a biofilm of microbes, secreting of enzymes that will break the entire polymer down back into CO2, CH4, water and biomass. As with the other types of polymers, the ASTM has standard test methods that validate biodegradation of not only the additive, but also the entire polymer.
So what does all this mean and how do we better understand the terms being used in the market? I believe that responsible companies should clearly identify the required environments that are necessary for their materials to maximize their environmental benefit. They must also take into consideration the customary disposal method for an end-of-life product. From an environmental perspective it is also important that any application using environmental improving plastics that consumers have access to dispose of that plastic in a way that provides the “green” benefit of the plastic. One type of plastic solution will NOT work for every application.
For example, PLA makes a great solution for utensils and other food packaging items where it would be very easy to develop infrastructures to ensure those materials ended up in professional composting facilities. However, PLA is a very bad solution for bottle applications in that it will impact not only recycling (that is for another post) but will most likely end up in landfills where PLA will last just as long as traditional plastics.
With responsible companies taking the lead to clearly identify their product and ensuring that the appropriate applications are used, consumers and businesses will begin to better understand the specifics behind the various benefits of “green plastics”. And, following the great example of the Green Plastics website, we should work towards educating consumers and legislators about those technologies.
ENSO Bottles, LLC