Biodegradable Plastics

Biodegradable vs Compostable

Biodegradable is not the same as compostable. Biodegradable means that an object can be biologically broken down.  Compostable means that the process will result in compost, or humus.

Biodegradable vs Bio-sourced vs Bioplastics

Bio-sourced means that the plastic is made of renewable raw materials. This means that it’s a non-fossil plastic (the plastic was not made using petroleum) ad thus made of plants, corn, algae, etc. Biodegradable refers to the end-of-life process and the fact that the plastic will usually break down or decompose by the action of living organisms such as bacteria. Petrol-based plastic is often enriched with biodegradable additives to enhance biodegradation. The word bioplastics is often used to refer to those two types of plastics: bio-sourced and biodegradable. However, not everyone agrees with this.

Types of Biodegradable Plastics

  • Aliphatic Polyesters
  • Polyanhydrides
  • Polyvinyl alcohol
  • Starch derivatives
  • Cellulose esters like cellulose acetate and nitrocellulose and their derivatives (celluloid).
  • Polyethylene terephthalate
  • Enhanced biodegradable plastic with additives

 

Biodegradable, bio-based polymers in various environments

biodegradable plastics

How does biodegradation work for plastics?

Biodegradation means that the molecule chains of certain polymers (plastics) will split. Some microorganisms such as bacteria or fungi will absorb macromolecules and use them to fuel their metabolic processes. The end products of this metabolism are then removed and incorporated into the natural product cycle. Biodegradation works in the same way, with microbes using macromolecules in plastic, which in turn causes it to degrade. Additive can be added to increase this microbial action.

Types of Biodegradable Plastics Additives

  • Oxo-degradable additives: are useful in litter environments where heat, light and air can force the plastic to break into diols (small pieces below 500 daltons). Bacteria and fungus produce a saliva like product that can dissolve the diol. It will take a long time and heat, air and light will be needed for the breakdown. This is unlikely to happen in a landfill. Oxo-degradable plastic additives require UV light to reduce the polymer chain prior to being placed into a landfill, without this step Oxo-degradable additives are essentially useless when disposed of in landfills.
  • Corn Based Plastics and BioResins are useful when placed into an industrial compost facilities. There are not many compost facilities. They require temperature of 140 degrees while most composting facilities operate at 110-150 degrees. It will be very hard for Bioresins to decompose in normal composting facilities. This is why they need industrial compost facilities. Most BioResins are made from organic materials such as corn, sugar and algae and result in different types of decomposition and decomposition timedecompose. Certain testing standards only refer to industrial composting and not commercial composting or home composting conditions.
  • Biodegradable Plastic Additives: Many biodegradable additive companies are tested for environments with no oxygen, like a landfill environment. Bioadditives are useful in these environments. Bioadditives allow the bacteria and fungus to dissolve the plastic layer by layer.

 

Difference between degradable and bio-degradable

TBA

Types of Composting

  • Industrial
  • Commercial
  • Home composting