8. Biodegradable plastics

Based on the nature of degradation the plastics are categorized into two main types such as
i. Degradable plastics and
ii. Compostable plastics
 
Biodegradable plastics:

The concept of biodegradable plastic was introduced in the year \(1980\). Microorganisms degrade the biodegradable plastics into carbon dioxide or methane, water and biomass under specific conditions.
 
Biodegradable plastics can be applied in various ranges, beneficial to humans, animals and the environment. These plastics are cheaper and are completely waterproof. These are useful in making single-use plastics. The compostable plastics are made from renewable sources such as seeds of avocado, corn, sugarcane and shrimp shells etc.
 
Degradable plastics:

  

The degradable plastics breakdown into tiny pieces known as microplastics.

 

The degradable plastics do not break down entirely in the environment, causing pollution.

 

It is found that microplastics in the ocean and soil is harmful to both humans and animals present on earth.
 
Plastic eating bacteria:
 
In the year \(2016\), scientists found that Ideonellasakaiens is \(201-F6\), a bacteria that could digest the plastic made of polyethylene terephthalate (PET).

 

 

This bacteria secretes the enzyme ‘PETase’, which breaks the plastic down into smaller molecules. The bacteria adhere to the PET film and break it down to terephthalic acid and ethylene glycol. This chemical which is reduced is then consumed by bacteria.

 
It will not be a feasible solution to the issue of the large quantities of non-recyclable low-grade
plastics which are polluting the environment. These bacteria’s take a longer time digesting a small amount of plastics.

 

 

This bacteria breaks only the PET plastics of resin code number \(1\). The other plastics that are complex in the recycling cannot be decomposed or degraded with this bacteria. The other resin code numbers from \(2\) to \(7\) are mostly non-degradable low-grade plastics that are complicated to recycle and causes severe impacts on the environment.