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      Biodegradation explained

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“Biodegradable Plastic”, what does it mean and why is there so much confusion about something that sounds easy to explain? The ASTM defines biodegradable plastics as “a degradable plastic in which the degradation results from the action of naturally occurring micro-organisms such as bacteria, fungi, and algae”. Sounds simple enough, so why all the confusion? The confusion really arises from two aspects. Confusion between the use of the term degradable vs biodegradable and the very loose use of the word biodegradable.

In the market place today there are three categories of plastics that biodegrade or degrade. Those technologies are PLA (Polylatic Acid), Oxo-degradable and a new technology called Microbiodegradable. Now that we know this, how do we know which ones biodegrade or degrade?

P

PLA PLASTIC:

PLA is a bioplastic made from starch; specifically it is being manufactured from starches derived from genetically modified corn (GMO food). This technology and supporting organizations such as BPI (Biodegradable Products Institute) claim that PLA biodegrades. However, this claim is confusing because they are using the term “biodegradable” extremely loosely.  PLA is a “compostable plastic” in that it goes through “degradation” to break down and is therefore not true “biodegradation”. PLA does not break down or biodegrade in a landfill and will only begin to “degrade” after being exposed to heat (specifically 60° C over a five day period).  This kind of environment can only be found in a commercial composting facility, NOT in the domestic composter in your garden. We find that many of the articles and organizations who support PLA are greatly contributing to the confusion by not using correct standards based definitions of that technology. Once PLA composts the remnant is CO2 and because professional composting facilities are not currently capturing the gas it is usually released into the atmosphere.

OXO-BIODEGRADABLE PLASTIC:

Next we have oxo-biodegradable, as the name implies this technology allows the product to degrade. This particular technology incorporates the use of an additive that begins to break the plastic chains only when exposed to oxygen, heat and moisture.  Although this technology is fairly upfront with the type of degradation taking place, the marketing materials suggest that once the pieces of plastic have broken down into small enough fragments there is a second stage that gives microbes the opportunity to finish the process through biodegradation.  This aspect may be true but it is extremely difficult to validate as the plastic fragments must have degraded to the microbe level.  There are varying reports as to what remains in the soil and air once an oxo-degradable product has degraded.  These range from heavy or low metals, salts, CO2 and. Because many of these products will degrade in a landfill the  CO2 gas will normally be captured and released into the atmosphere.

MICROBIODEGRADABLE PLASTIC:

Moving on to the final technology we have third generation microbiodegradation. This is the technology behind Biogreen Products. This technology is also in the form of an additive which is added to existing polymers. Biogreen Products use organic compounds to open the polymer chain and attractants stimulate microbial colonization on the plastic.  Because the polymer chain is open the micro organisms can use the carbon chain as a source of food and energy. This is happening at the atomic level and the remnants are CO2, CH4 and inert humus and because many of these products will degrade in a landfill the gases of CO2 and CH4 will be captured, released or burned. It is also important to note that this process activates with or without the presence of air, light or heat and will take place no matter how deep the plastic is buried. This type of plastic can also be recycled in the normal way.

CONCLUSIONS:

So there we have it in a nutshell. We now know the difference between the three, degradable, oxo-biodegradable and microbiodegradable.  It still leaves the bigger question as to which technology and method is better for the environment? This is another important question and requires further explanation, however you should always keep in mind the overall net impact to the environment.  When trying to answer this environmental question it is important to keep in mind the following criteria: using food to create plastics, pesticides that effect water, total water consumption, total fossil fuels used in processing, greenhouse gases emitted in processing and breaking down, the benefit of the product, does the biodegradation or degradation create any benefits such as clean energy? Is it sensible to use vast amounts of food to create plastic that could otherwise be used to feed the worlds’ hungry. Will the degradation take place deep in the landfill and are the products acceptable for commercial recycling.

many thanks for taking the time to read this article and I hope that you found it informative.

Kind Regards

Malcolm Brown

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