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Biodegradability vs. Compostability - Complexities and Realities

Biodegradability and compostability are terms often confused and used interchangeably by both consumers and businesses. Both a biodegradable and compostable material will breakdown and decompose overtime. The issue here is how long the decomposition takes and by-product that is left behind and this is very much dependent on the composition of the material and the environment in which the decomposition occurs.

theusfarmbelDecomposing corn

Biodegradation occurs when microorganisms such as bacteria, fungi and algae convert materials into biomass, carbon dioxide and water.  The main material is non petroleum based in nature and usually made from plant or animal sources. Examples are paper, vegetable scraps and some forms of plastics made from ingredients such as corn starch. Decomposition can take place from as short as a day to as long as a year. Biodegradation can take place in both aerobic and anaerobic conditions.

Composting process is similar to the biodegradation process, except that   the biodegradation process is carried out in a composting facility, where conditions (water, humidity, temperature, and lighting) are optimally tuned to bring about a speedy biodegradation.

In both processes, both biodegradable and compostable materials will ‘disappear’ after some time and the non-toxic by-product become fertilizers known as humus (very dark soil) which can be used to boost the growth potential of another plant.

Complexities and Realities

  • Compostability and biodegradability are not based on the feedstock of the product. It’s literally based on the chemical signature that is, the way the plastics are put together. The final product and any inks or labels used, need to be tested and certified using international standards in their own right as being biodegradable. And consumers express greater confidence in conformance with standards that are independently assessed by a third party, i.e. a certification body.
  • For decomposition to occur without the production of the poisonous methane gas, both biodegradation and composting need oxygen.


  • Technically all materials are biodegradable, but a traditional plastic water bottle will take 450 years to decompose**. Something labelled as biodegradable can make its claim though a technicality in the very definition (saying that anything is biodegradable if you wait long enough isn’t a lie after all). This idea makes it difficult for consumers to know exactly how much they are helping the environment.
  • Processing may inhibit biodegradation. Biodegradable items may not break down in landfills if the industrial processing they went through convert them into forms unrecognisable by the microbes and enzymes that facilitate biodegradation.  One  example is pertoleum, which biodegrades easily and quickly in its original form - crude oil. But when it is processed into plastic, it is no longer biodegradable.
  • Biodegradable/greener plastic water bottles and shopping bags are in fact extremely durable and add to the plastic debris in the ocean, instead of being a solution to the ubiquitous problem of litter in the oceans. UN’s top environmental scientist warns in a UN 2016 report .
  • Many plastics labelled biodegradable, like shopping bags will only break down in temperatures of 50 degree C and that is not thew ocean. They are also not buoyant, hence sink and are not exposed to UV and beak down.


  • Given that it needs compositing facilities, where conditions (water, humidity, temperature, and lighting) are optimally tuned to bring about a speedy biodegradation, composting is a hopeless reach for most individuals that want to help the environment through responsible consumption of material, which makes this standard seem difficult and misplaced.
  • Bioplastics are not always truly compostable. You can have oil-based plastics thatare compostable and plant-based plastics that are not compostable.
  • Different compost facilities use different processes. Some have trouble even with bioplastics.
  • In some facilities, the plastic-coated packaging get separated and no visible plastic is left in the compost, while others are concerned that the nearly invisible tiny fragments of plastic will ultimately ends up contaminating the environment.
  • Screening out the compostable items means extra steps and costs.
  • A product is either 100% compostable or it is not as most composting facilities cannot separate the biomass from the plastic effectively.
  • You need to know what your local composting facility does and does not accept.
  • If compostable plastics do not end up in the composting facility, then there is nothing green about them. In fact they end up in landfills and produce methane emissions.
  • To confuse matters further, many compostable plastics are made to look like real plastics and end up in the recycling bin where they cause problems for the plastic recycling process.
  • Most coffee cups and to-go food containers may look/claim to be recyclable and compostable. But they are lined with very thin plastic to hold food and drink. This plastic coating breaks down into tiny plastic fragments which do not disappear. Consequently, they contaminate the finished compost as well as the soil where that compost is used. Worms and insects will ingest them in the soil; and when they get washed out with the rain, they feed into rivers, lakes, and oceans and impact marine ecosystems.
  • PLA (Polylactic acid (PLA), a plastic substitute made from fermented plant starch (usually corn) is quickly becoming a popular alternative to traditional petroleum-based plastics.) biodegrades slowly unless subjected to industrial composting. PLA may well break down into its constituent parts (carbon dioxide and water) within three months in a “controlled composting environment,” that is, an industrial composting facility heated to 140 degrees Fahrenheit and fed a steady diet of digestive microbes. But it will take far longer in a compost bin, or in a landfill packed so tightly that no light and little oxygen are available to assist in the process. Indeed, analysts estimate that a PLA bottle could take anywhere from 100 to 1,000 years to decompose in a landfill. Recyclers Can’t Mix PLA and Other Plastics.



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