January 31

Why plastic is not biodegradable


why plastic is not biodegradablePlastics as we all know, are one of the most widely used materials on this planet. Available in different sizes, shapes, and structures, plastic has become essential in our daily lives. However, many of us are also aware of the damage plastic brings to the environment. One of the main reasons why plastic is such a huge pollutant is because of its lack of biodegradability. Here is why plastic is not biodegradable.

The Confusion

Plastic is a product of petroleum; a fossil fuel that was naturally produced by breaking down animal matter buried over millions of years. The slow process turns these fossils into three major components; gas, coal, and oil (or petroleum). The process is done by microorganisms that slowly decompose the matter into fossil fuels. However, some people think that since the matter is decomposed into oil, the plastic also made from oil should be decomposed over time, right? Wrong. There are two things that need to be clarified here:

  • The way plastic is manufactured into petroleum actually alters the structure of the petroleum itself which is unknown to the microorganisms. We’ll see how this happens later in the post.
  • Plastic is “technically” biodegradable, that is, if you leave it untouched for the next few centuries! The light, as well as a few adaptive microorganisms, are able to eventually break down the material. However, not only does it take a colossal amount of time, but also risks releasing toxic chemicals into the atmosphere over the years.

To understand why plastic is not biodegradable, we are going to use three widely used types of plastic; polypropylene, polystyrene, and PETE. Each of these contain unique properties that make them resistant to decomposing.


Plastics are often made from a type of petroleum chemical called propylene. This chemical is then heated up to a certain degree that it starts to link with other carbon links around it, forming what is called polypropylene. This material, also known as PP, is used to make a number of different products from puncture-resistant bags to ketchup bottles. PP is recyclable, marked with the number 5 on the list of plastic recycling numbers. However, although recyclable, polypropylene is not biodegradable because the unnatural links made by heating the propylene are no longer known to the microorganisms responsible for breaking down organic matter.


Probably one of the most widely used packaging material of them all, polystyrene is a lightweight, versatile plastic that is used in almost every household or industry. Known famously as styrofoam, polystyrene is also widely used to insulate a number of items such as drink holders and even in the frames of double glassed windows. Unlike polypropylene, polystyrene is made from a process known as suspension polymerization. In this process, benzene and ethylene are combined to form styrene. This is then polymerized by adding water as well as mucilage, forming a lightweight, stable structure called polystyrene.

Not only is polystyrene non-biodegradable, but is also non-recyclable. The non-biodegradability is due to the material being resistant to the photons provided by light sources necessary for breaking down the compound (known as photolysis). However, the inability of being recycled is due to two primary reasons

  • Firstly, polystyrene is very lightweight (almost 95 percent air in some cases), and recycling it is tedious and quite costly, so companies try to cut costs and produce new styrofoam instead because it seems much more economical for them.
  • Second, polystyrene is porous, which traps particles of food and other liquids. This is very hard to clean off, therefore the option of recycling no longer remains valid.

Since it is no longer recyclable and not biodegradable, polystyrene is one of the most dangerous plastics to be produced, as the only way to get rid of them is through incineration, releasing tons of harmful chemicals into the atmosphere.

Polyethylene Terephthalate (PETE)

Pretty much the most popular plastic in the world, PETE is used to make almost any container you would find in your household. This brings us to another reason why plastic is not biodegradable, which is because in most cases there is little effort on sustainability and more on cutting costs. PETE helps manufacturers create cheap, yet strong containers that would help keep contain their food without the risk of spillage or leaching. Although this plastic is considered to be recyclable, only 20 percent of it is actually recycled, whereas the rest is incinerated, releasing harmful gases into the air.

The biodegradability of PETE is the worst of all three plastics on this list. This is because PETE is extremely durable, and at the same time it is also resistant to photolysis. This makes PETE almost impossible to break down and can take the longest when it comes to naturally decomposing compared to all other types of plastic (which already take several centuries to decompose).

Key Takeaways

Still confused why plastic is not biodegradable? If you weren’t able to grasp how these three contribute to the non-biodegradability, here is a table of key takeaways that will help you better understand through each type of plastic mentioned above

PlasticWhy it is not biodegradable
PolypropyleneStrong inorganic bonds
PolystyreneResistant to photolysis
PETEResistant to photolysis and strong inorganic bonds

What’s Next?

Since plastics are non-biodegradable, and many of them are also non-recyclable, they pose a huge threat to the environment. Plastic is the greatest pollutant on Earth, affecting land, sea, and even the air with plastic bags being on top of the list, killing thousands of animals both on land and sea each year (Find out more on how plastic bags harm the environment).

However, things don’t seem all dull for the future. With the increase in technology, people are now more aware of environmental hazards plastic brings along, and are now starting to look for alternatives that have a smaller carbon footprint. Going eco friendly doesn’t have to be expensive, which is why companies have also started making environmentally safe alternatives to plastic.

From large structures such as furniture to even the simplest of products such as garbage bags (check out the best biodegradable garbage bags available), eco friendly alternatives to plastic are now readily available at economical prices. All it takes is a simple google search. The question is, are you ready to switch?


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