How does biodegradable plastic work and why is landfill biodegradable the best choice?

When it comes to biodegradable plastics, the three main choices are Oxo-Degradable (sometimes just called 'degradable'), Compostable, and now Landfill-Biodegradable (which is our choice).
The table below summarizes these technologies.

Plastic Property Landfill-Biodegradable Oxo-Degradable Compostable
100% biodegradable in landfills?

Yes

No No
100% recyclable with other mainstream plastics? Yes No No
Special storage conditions required? No Yes No
Shelf life / has expiration dates? No Yes No
Will degrade when exposed to sunlight or high heat No Yes No
Fragments into small pieces in air No Yes No
Biodegradation begins at time of disposal; not before Yes No Yes, in compost facility only
Will biodegrade in commercial and municipal composts Yes No Yes
Needs oxygen in order to biodegrade No Yes Yes


 

Landfill Biodegradable

Fieldtech Solutions uses a patented additive to make our disposable products landfill-biodegradable. This means that the plastics will decompose under typical landfill environmental conditions much faster than traditional plastics which have an indefinite life span.  Biodegradation of plastic is achieved by enabling microorganisms to metabolize (i.e. break down) the molecular structure of the plastic, which produces an humus-like material (organic matter that cannot break down any further) which is a natural plant fertilizer.  There are two different ways this is achieved in industry.
Landfill-Biodegradable Plastics are made by combining traditional plastic, which is petroleum-based, with an organic additive.  The biodegradation only begins when the plastic is exposed to a microbe rich environment such as in a landfill.   The additive attracts microbes to the plastic and they start to digest it.   As they do this, the enzymes the microbes secrete cause the plastic polymer molecules to break down into shorter chains, which the microbes can then begin to digest them too. The biodegradability of a plastic can be confirmed using the standard laboratory test ASTM D5511.    


Advantages of Landfill-Biodegradable plastics:

  • Currently approximately 90% of plastic waste goes to a landfill.  This then is where the product should be designed to biodegrade.
  • No change of consumers disposal habits is required, which has been shown to be a big problem in the past.
  • Products made with a landfill-biodegradable additive are mainstream recyclable.
  • There are no shelf life issues as the plastic will only biodegrade when disposed to a landfill

Compostable

Another type of biodegradable plastic often mentioned is known as 'Compostable'.  These are a type of plastic made from renewable sources rather than petroleum-based plastics and will quickly biodegrade in a commercial compost facility (not in a backyard compost or garden bed).  The more common types of bioplastics are:

    • Polylactic acid (PLA) produced from cane sugar or glucose
    • Starch-based
    • Cellulose-based

Although the manufacturing of bioplastic materials is reliant upon petroleum as an energy and materials source, it is generally regarded as a more sustainable activity (due to carbon sequestration) when compared to petroleum-based plastics.   Compostable plastics are bioplastics that biodegrade under commercial composting conditions as per ASTM 6400*.  Note that not all bioplastics are compostable.  FTS does not use compostable plastics.

* To meet ASTM 6400 standards, a plastic needs to exhibit 60% biodegradation within 180 days in commercial composting conditions.

Confusion exists over the term bioplastic.  Some people think that a bioplastic is automatically biodegradable.   This is not the case.  A bioplastic is a plastic made from plant materials.  There is no inference about its biodegradability.  Polyethylene plastic can be made from sugar cane, but it is no more biodegradable than polyethylene made from petroleum.

The other question regarding bioplastics is, should we really be using good arable land for growing crops destined for bioplastics when the world has a food shortage?


Limitations to compostable plastics

At the present time there are several limitations for compostable plastics that make them not a suitable choice for controlling plastic waste.

  • For a compostable plastic to biodegrade it has to be in a commercial compost facility with temperatures of 60 deg C, plenty of oxygen and good moisture levels.  If those conditions are not met, the compostable plastic will not biodegrade as the microorganisms need those conditions to live.
  • Due to their different composition, compostable plastics cannot be recycled in the mainstream.  Their materials have different properties and would contaminate other conventional plastics if they were mixed together.  If they cannot be delivered to a commercial compost facility, they need to go to landfill.
  • There is no separate recycle facilities that will sort out the compostable plastic from other plastic waste.  Which means by default a compostable plastic will generally go to a landfill where it will not biodegrade.
  • There are very few commercial compost facilities in Australia, making it very unlikely that a compostable plastic will ever be transported to one to biodegrade. 
  • When a compostable plastic biodegrades its gaseous by-product is CO2, which cannot be used for energy capture methods to generate green electricity (as opposed to the CH4 generated from landfill-biodegradable plastics).

Degradable (Oxy-Degradable)

Confusion also exists over the term 'Degradable' plastics.  A degradable plastic is a plastic with a metallic additive that sets off a slow chemical reaction and over 12-24 months will cause the plastic to fragment into little pieces.  This has nothing to do with biodegradation and microorganisms, and so instead of 1 piece of plastic we end up with hundreds or thousands of little pieces of plastic, which is a worse result for the environment.

Also, the reaction will only work in the presence of oxygen and sunlight.  So if a degradable plastic is buried in a landfill where there is no sunlight and very little oxygen, it will stay there like a conventional plastic not degrading.  Therefore for a degradable plastic to fragment down into little pieces it has to be up on top of the ground and there those little pieces will blow around and disperse into the environment.   FTS does not use degradable additives.


Frequently Asked Questions

  • How long will it take a plastic item to biodegrade? The biodegradation time of a product depends on a variety of factors.  These landfill-biodegradable additives will make plastic biodegrade up to 95% faster than conventional plastic.  The thicker the plastic section, the longer it will take to biodegrade. Membrane films are expected to degrade in 45 days or so. Thicker sections may take 1- 5 years. If the plastic is put into a dry landfill it will degrade slower than a more actively managed water moistened landfill. The main point to realise is whether it takes a few months or multiple years it does not really matter. What does matter is that after some limited time, the product will no longer be around.  We are no longer leaving our plastic waste for future generations to deal with.

  •  Why do ASTM Testing to verify biodegradability? With so many manufacturers and retailers offering ‘Green’ products it has become confusing to distinguish between what is a genuine biodegradable product, what is a compostable product, what is a degradable product and what are unsubstantiated claims. ASTM tests are tests recognised internationally as being the bench mark of verifications. The ASTM test D5511 is a test performed by an independent laboratory to verify claims of biodegradability in anaerobic conditions, with the aim to replicate conditions found in a typical landfill.

  • Is it better to recycle used plastic items? Yes we should recycle as much as possible. The EPA promotes reduce, reuse, recycle and composting (a form of biodegradation) as ways to reduce waste. However according to PACIA (Plastics and Chemicals Industries Association), only 19% of plastics are recycled in Australia, the rest end up in landfill. Therefore while some plastic items can be recycled, only a few of them ever make that journey. Most would still end up buried in a landfill. The math is simple to perform: One hundred percent of plastic items discarded into a landfill biodegrading or only 19 percent of plastic being recycled while the rest persists for hundreds of years. A report was recently published in the US stating that recycling only begins to have a positive environmental impact once rates of 50% or higher are achieved. This is why it is a better environmental solution to have both biodegradable and recyclable. It is going to take decades to get recycle rates up to the 80 – 90% range. Unless changes are made to switch to biodegradable products we will be continuing to contribute to the overwhelming global plastic pollution problem. Landfill biodegradable plastics are a solution we have available to us today. The plastic fully integrates into the existing recycling infrastructure; i.e. all treated plastic (landfill-biodegradable plastic) that ends up in landfills will naturally biodegrade to biogas and soil. Plus the methane can be used, and is being used at hundreds of landfills to create clean energy, which offsets the need to use additional fossil fuel for electricity.

  • Is there any toxic residue left after biodegradation? No. There is no toxic residue when the biodegradable plastic decomposes. Plastic such as polyethylene break down to CH4, C02 and organic matter.

  • When PVC biodegrades, what happens to the vinyl chloride? Will it leach into the groundwater? No definitely not. Once the polymer chain is broken during biodegradation, it allows oxygen to enter which will attach itself to the hydrogen and carbon creating H2O and CO2 or as we know it as water and carbon dioxide. The lone chlorine atom bonds to a hydrogen atom creating a very weak salt that does not have any adverse effect on the ecosystem.

  • Is the additive safe? Yes, the biodegradable plastic is very safe. In fact, food packaging film made with the additive is USFDA compliant for food contact applications. Our products which are designed for groundwater sampling have been tested to ensure they provide the same high sampling integrity as you would see with a non-biodegradable equivalent.

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