Many faces of Biodegradability

Biodegradability

The claim of biodegradability is often associated with environmentally-friendly products, but I often wonder what exactly does this mean?  The answer is not simple as there are many faces of biodegradability.

The US Environmental Protection Agency (EPA) defines as biodegradable those materials which can decompose under natural conditions. The American Society for Testing and Materials (ASTM), a leader in setting international standards, states that biodegradation is brought about by a biological activity, particularly enzymatic action, which can lead to chemical structural changes. The Federal Trade Commission (FTC), another US government agency, has drawn up guidelines on what legitimately qualifies as biodegradable materials.

Examples of biodegradable materials include fruits, vegetables, leaves, paper and seeds. Non-biodegradable materials, on the other hand, do not break down easily. These materials pose a threat to the surroundings since they simply pile up and take a long time to degrade. Materials that you see in landfills mostly comprise non-biodegradable materials such as plastics.

Can we certify biodegradability?

Going by the definitions listed above, most products are fundamentally biodegradable; the only difference being the amount of time it takes to break each one down. Depending on the time, biodegradation may be partial or total.

In the test recommended by the European Union (EU), a 10-day window is used to define ready biodegradability. Within this time, a readily biodegradable substance must reach at least 60% mineralisation based on CO2 production or O2 depletion, or 70% based on reduction in Chemical Oxygen Demand (COD). The 10-day window begins when biodegradation has reached 10% and must end within the 28-day test.

Many manufacturers show some biodegradation taking place for an x-period of time and then use the data to extrapolate. But you cannot extrapolate the biological degradation process as such an extrapolation is scientifically unsound.

The Biodegradable Plastic Institute (BPI) in the US conducted two separate sets of tests on the Aquamantra water bottle sold by Dana Point, a California-based company which uses an additive from Enso Bottles LLC. The first test showed that the degradation process plateaued after 60 days and the second showed no degradation at all after 45 days. The company then did a 30-day test and extrapolated that the material will biodegrade in four years. This could be misleading.

Another example is found in the August 2010 issue of Biocycle Magazine. It published a study initiated by the Environmental Services Department and performed at the Miramar Greenery Composting Facility. Here 105 different compostable products were evaluated. The majority of the products selected meet ASTM standards (either ASTM D6400 or D6868). All of the products tested were purchased in the market. However, more than half of the 105 products did not biodegrade greater than 25%. Fifteen items that were both ASTM and BPI certified showed almost no effects of biodegradation.

Independently assessed and disclosed biodegradation data is thus essential to assess the fate and behavior of substances in the environment.

Are Biodegradable products always benign?

Take the case of active cleaning chemical nonylphenol ethoxylate (NPE), which is made of carbon, hydrogen and oxygen. NPEs do biodegrade to a benzene ring type and other simpler structures. However, this class of chemicals is considered suspicious because NPE can be possible endocrine disruptors. This means NPE may mimic endocrine hormones and cause havoc with a woman’s reproductive system. So although biodegradable, NPE may by no means be environmentally-friendly.

End products of biodegradation: Are they always safe?

It gets more complicated when we think about products that contain complex chemicals. Pesticides such as DDT are hazardous and toxic in their own right and take a long time to biodegrade. More than their slow breakdown, the problem is that the breakdown products are even more toxic and dangerous than the original DDT! So biodegradation of such compounds can in fact complicate the matters!

While biodegradability is something we all should desire in green products, we must understand its limitations, especially the “fuzziness around its hallow”. Until such time that we come up with a better operating and communicable definition, biodegradability is like Hamlet asking – “To be or not to be!”

(This article is a modified version of the original peice published in Green Prospects Asia in Malaysia)

(picture sourced from https://www.google.co.in/search?q=biodegradability&biw=1536&bih=740&source=lnms&tbm=isch&sa=X&ei=yX8RVKi4M8uIuASPgYGYBA&sqi=2&ved=0CAYQ_AUoAQ#facrc=_&imgdii=_&imgrc=8XzpuTMamE-ykM%253A%3BMWo_YO9M5okGzM%3Bhttp%253A%252F%252Fwww.greenoptimistic.com%252Fwp-content%252Fuploads%252F2012%252F09%252Fbiodegradable-plastic.jpg%3Bhttp%253A%252F%252Fwww.greenoptimistic.com%252F2010%252F10%252F25%252Fbioplastics-pollution-study%252F%3B446%3B239)

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2 thoughts on “Many faces of Biodegradability

  1. We in Rajsthan has put complete ban on plastic carry bags. However, it is now felt that we should keep compostable/biodegradable plastic bags out of ban. What is your expert advice. In case we wish to do it,
    which standards/definition we should follow.

    Like

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