Degradable Plastics

Degradable plastics are a complex and evolving area with new products entering the market place all the time. Demand is being driven by a consumer market which is looking for so called “greener” plastics using polymers that will degrade under specific conditions. However, bioplastics currently comprise less than 1% of the global plastics supply although this is expected to increase from 2% to 5% by 2012.

As companies start to introduce and market degradable plastics as a greener option there is also confusion over what plastic to use and whether the various claims about how those plastics break down in the environment are actually true.

In 2006 Plastics New Zealand took the initiative to provide industry led management to minimise the risk posed by the introduction of these new degradable and bio-based plastics into the New Zealand market. We recognised the potential for misinformation and misunderstanding without clear and concise labeling and guidelines to enable manufacturers, brand owners, retailers, local authorities and recycling operators to make balanced and informed decisions regarding degradable plastic products by taking a life cycle approach and understanding their environmental impact.

With the anticipated growth in products made from degradable plastics, these materials will inevitably enter both the recycling and composting systems in New Zealand and Australia and are potentially a contaminant in these systems.

Plastics New Zealand formed a working group comprising brand owners, raw material suppliers, manufacturers, recyclers, composting companies, community groups and independent experts. With assistance from the Ministry for the Environment, this group assessed the Australian model developed by PACIA and used their experience to develop guidelines relevant to New Zealand.

Those involved have committed to adopting the guidelines which provide agreed definitions and standards to help consumers, manufacturers and brand owners understand how degradable plastics will perform and the impact they will have on the environment.

As this new technology is constantly changing the document will be continually updated by a reference group as the need arises.

The Degradable Plastics Guide and Commitment document is an excellent example of a group of interested parties coming to an agreed understanding on the important issues surrounding these materials under the guidance and management of Plastics New Zealand. As an industry body they have shown that through their inclusive approach they can successfully manage voluntary initiatives to produce real and effective outcomes.

A copy of the Degradable Plastics Guide can be downloaded below :

Degradable Plastics Guide Degradable Plastics Guide


What do I need to consider?

If you are purchasing, or commissioning, a degradable plastics product make sure you consider:

  • how it is labelled;
  • how you expect it to be disposed of;
  • What recovery systems are in place eg. landfill, recycling, or composting
  • the infrastructure required; and most importantly
  • ensure that the product has been tested against internationally agreed standards that ensure your disposal options are appropriate and environmentally sustainable.
     

What are Degradable Plastics?

Degradable plastics broadly describes plastics which are designed to break down into smaller particle sizes to a specific extent within a given time and within a specific end environment. [See AS/NZS ISO 140 1: 000 – self-declared environmental claims]

Degradable plastics can be classified by both the materials they are made from and how they break down at the end of their life. New degradable plastics will continue to be introduced into the marketplace. Any classification needs to be able to accommodate changes in both inputs and outputs.

It is important to understand that biodegradable and non-biodegradable plastics can be made from biobased/renewable resource materials as well as from synthetic (petrochemicals – fossil fuel) resources.

At this stage degradable plastics fall into two distinct categories based on their compostability according to international standards.

i. first break down mechanically by chemical attack involving water, air (oxygen), and/or ultra violet light (sunlight), often with the help of additives which accelerate this chemical attack;

ii. as a result of this initial breakdown the product may ultimately be reduced to a small enough size for attack and digestion by microorganisms. Only this second step can be termed “biodegradation”.

  1. Plastics which are compostable according to international standards and are typically biologically degradable and so readily attacked and digested by microorganisms early on in their degradation process (within the timescales of the standards). Within this category are home compostable and commercial compostable options.
     
  2. Plastics that are NOT compostable according to international standards and typically take longer times to degrade. They are typically degraded by a longer multistep, sequential, process. For example, these plastics will;

Plastics which fall into the second category will eventually undergo biological degradation after mechanical degradation, but not within the time/temperature constraints required by current commercial composting systems and standards.

The term biodegradable is often misunderstood and misused. The term should only be used if it includes a reference to an international standard and/or the specific time, temperature, water, air exposure conditions required.

This approach links to the Australian system, where degradable plastics are classified by meeting specific standards relating to specific end environments, i.e.commercial compost, home compost, on soil, marine water and freshwater.

However the preferred end of life option for plastics is recycling so care needs to be taken that degradable plastics do not contaminate existing recycling streams.

End of life options for plastics, including degradable plastics, include:

  • recycling
  • compost
  • energy recovery
  • landfill (least desirable disposal option).


Biodegradable plastics:

Biodegradable plastic bags are not the answer to replacing non-degradable plastic bags in supermarkets and retails stores for the following reasons:

  • they do not decompose in properly managed landfills
  • they support the throwaway mindset and the use of landfills as an acceptable disposal method; and
  • they do not discourage over-use in the first place.
     

Definitions of bioplastics:

Compostable plastic: A plastic that undergoes biological degradation during the composting process (up to 2-3 months in a windrow) to yield carbon dioxide, water, inorganic compounds and biomass at a rate consistent with other known compostable materials and leaves no visually distinguishable or toxic residues.

Biodegradable plastic: A degradable plastic in which the degradation must result from the action of naturally occurring microorganisms over a period of time (up to 2-3 years in a landfill).

Degradable plastic: An oil based plastic containing a chemical additive that undergoes significant change in its chemical structure causing it to break down into smaller particles. The degradation process is triggered only when material is exposed to specific environmental conditions (such as UV, heat and moisture). Residues are not food matter for microorganisms and are not biodegradable or compostable


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