BPI

   
Facts about polythene film biodegradation
   
Plastic films are often criticised because they are seen as disposable products which, once disposed of, do not biodegrade. However recent advances in technology now allow the production of a range of plastic films which are degradable, biodegradable or compostable.
Polymers
Landfill

FACT: When placed into landfill sites some biodegradable materials release methane as they breakdown. Methane is 20 times more efficient as a greenhouse gas than CO2. For this reason, the European Landfill Directive requires substantial reductions in the amount of biodegradable matter entering landfill sites over the next few years.
 


Biodegradable films

  • Given enough time, all plastics will eventually biodegrade.
  • Additives are now available to accelerate degradation, biodegradation and compostability in ordinary plastics. Likewise a range of polymers are available, which by virtue of a shortened polymeric molecular chain, are also inherently biodegradable or compostable.
  • Degradable plastics fragment and break down under the influence of light and heat. Biodegradable plastics, by contrast, decompose when they come into contact with microbial activity. Degradable plastics can eventually biodegrade in the right circumstances - once they have fragmented sufficiently to be capable of being acted upon by microbial activity - but they will not do so as quickly as those materials termed "biodegradable".
  • Whilst plastics can be made to biodegrade with relative ease, a manufacturer must first consider a number of issues before incorporating this feature:

    -

    The primary purpose of plastic films is to protect and contain and as such, they have to be durable enough to perform this function. In contrast to this requirement, biodegradable plastic is designed to break down. Making a packaging material biodegradable therefore might solve a waste issue at the end of the material’s life but if this feature means the packaging is unable to properly protect a product and that product is spoilt, there may actually be a greater negative impact on the environment.
    In addition, the speed at which a biodegradable packaging breaks down is dependent on exposure to light, heat and oxygen. As this exposure could vary dramatically, the shelf-life of bio-degradable packaging cannot be precisely predicted.


  • Another important consideration is the fact that the use of biodegradable plastic could also hinder the ability to recycle large volumes of plastic packaging. Biodegradable plastics are technically recyclable but a recycler would not want to recycle them and use them as the basis for another product (such as a plastic wood-substitute) due to their deliberately finite lifespan. Clearly, this does not present a substantial problem where the biodegradable plastic is either clearly recognisable or exists only in a small amount. However if biodegradable plastics were to enter the waste stream for recycled materials in any significant volume this could seriously compromise our ability to recycle plastic into new products.
  • Litter is often cited as a reason to make plastics biodegradable but plastic bags actually only account for 0.06% of litter in the UK. It is clear that plastic bag pollution does cause more serious problems in developing countries and in these areas a biodegradable alternative could provide a significant solution to a waste disposal problem.
  • Disposing of biodegradable plastic bags presents problems of its own. If they are placed into landfill there is no guarantee they will breakdown quickly as typically this is an environment starved of light, heat and oxygen. Indeed there are instances of newsprint remaining legible when recovered from landfill after 40 years.
  • Biodegradable plastics can play an important role when they divert waste from landfill to composting or where they are designed to decompose naturally in the environment in which they have been used. Examples of this include plastic mulch films and crop covers.