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Packaging Products – Biodegradable or Recyclability which is better?

Posted on 10/2/2012 1:41:13 PM By Jeff Timm
  

Occasionally in the ongoing bioplastic discussion one sees questions that go something like – “what is a better end-of-life scenario-biodegradation or recycling” and “is biodegradation the same as composting?”  Other similar questions abound. 

Let’s set the record straight with a few definitions.  First, the Society of the Plastic Industry (SPI), a leading plastic trade association, defines a bioplastic as “a plastic that is biodegradable, has biobased content or both.”   By design this is a pretty broad definition.  It covers plastic that does not degrade like a green polyethylene (G-PE) shampoo bottle that is made from sugarcane, but is very recyclable, as well as a plastic that does degrade like polylactic acid (PLA) snack food films that are made from biobased content material like corn designed to be used in food service operations that turn all the food waste and food packaging into composte.

The bioplastic dialogue usually pits these definition nuances against each other many times attaching a value as to which is better.  The real answer is neither one is better or worse.  Any competent packaging designer designs their product for the required end-of-life that is suitable for each specific packaging application.  For example, if the packaging product is to be used like in the above food service application example then a biodegradable product that could be composted according to the applicable ASTM standards would dictate the material of choice.  If the end-of-life packaging product disposal method customarily fits into a recycling stream then a biobased content non-biodegradable and non-compostable material selection is in order.  The key is to design using the right choice of packaging materials for the brand preferred end-of-life outcome and not to fit into some questionable marketing claim.

Biodegradation and compostability are not the same.  Think of it as compostability being a subset of biodegradation.  In other words, not all biodegradable plastics are compostable.  SPI defines biodegradation as “a plastic that undergoes biodegradation, a process in which the degradation results from the action of naturally-occurring micro-organisms such as bacteria, fungi, and algae, as per accepted industry standards.”   As of 2008, some of the accepted industry standard specifications are:  ASTM D6400, ASTM D6868, ASTM D7081 and EN 13432.

Compostability is defined by SPI as “a plastic that undergoes degradation by biological processes during composting to yield CO2, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leave no visible, distinguishable or toxic residue.” 

The key in the ASTM standards is the value assigned for end products including percent of the residue remaining, temperature and most importantly time.  The FTC enforcement against false and misleading biodegradation/composting marketing claims has focused in this area.

  • ASTM D6400- Standard specification for compostable plastics
    • <10% of original dry weight remains on 2mm sieve
    • 90% of organic carbon converted into CO2 after 180 days
  • ASTM D6868- Biodegradable plastics used as coating on paper and other substrates
    • 90% of organic carbon in substrates converted to CO2 within 180 days at 58°C
    • plastic coating must meet ASTM D6400
    • does not diminish the value or utility of the compost resulting from the composting process.

Note that ASTMD6400 stipulates that the compostable standard covers plastics and products made from plastics that are designed to be composted in municipal and industrial aerobic composting facilities.  Anaerobic digestion has a different standard.

My next blog will explore composting as one of the many end-of-life choices packaging designers have as a packaging design option.

References:
The Society of the Plastics Industry http://www.plasticsindustry.org/
ASTM International, formerly known as the American Society for Testing and Materials (ASTM) http://www.astm.org



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