How Long Does It Take For Plastic To Break Down

How Long Does It Take For Plastic To Break Down

If any one invention can be classified both as boon and bane, it is plastic.

This may come as a surprise to you that we, humans, have been using naturally-occurring polymers or “plastics” like animal horn, amber, latex from tree sap, cellulose, tortoiseshell, tar, and shellac for thousands of years.

However, the history of plastics took a sharp turn when Alexander Parkes introduced man-made plastic “Parkesine” to the world at the London International Exhibition in 1862. Though the concept did not find many takers initially, the discovery of celluloid by John Wesley Hyatt led to patenting of the first fully synthetic plastic by Leo Baekeland in 1907. No need to add that there has been no looking back since then.

However, polyethylene, the plastics as we know it today, gained popularity in the 1960s with the invention of petroleum-derived cellophane sack. It revolutionized packaging in an unimaginable way. It has changed our lives for the better in incredible ways. 

There ends the “blessing” bit of the story of plastic. Now, comes the horror part of the plastic chronicles. The worst aspect about it is that we were not even aware of the havoc it was wreaking in the environment until too late. And the story is still ongoing with no end in sight.

The main grudge against plastics is the time it takes to decompose and the greenhouse gas emissions it generates. The environmental impact of plastic waste is too significant to ignore despite the multiple benefits it offers.

Let’s begin at the beginning and try to understand why plastics are considered enemy no.1 across the world. Read on to learn answers to questions like how long does plastic last and how long for plastic to decompose.

Longevity of plastics: Blessing and curse

The structure of plastics is such that their chemical composition stays without change for centuries. This is an advantage if you want the object to last for a long time. However, when the same object is discarded after use as waste, if it is not decomposing within a short period, say 5, 10, or 20 years, it gives rise to plastic pollution. 

Every day millions of tons of plastic are being discarded as waste worldwide. When the discarded plastic doesn’t decompose fast enough and more gets added with each passing day, we would soon run out of space on this earth for plastic waste. The land and the oceans will soon get drowned under the plastic pile.

This is what is happening to us now. Besides the growing mound of physical plastic waste, plastics also give rise to greenhouse gas emissions. The greenhouse gas emissions are considered the hidden or invisible cost of enjoying the benefits of plastics. 

Plastics are made from a variety of raw materials like crude oil, natural gas, coal, and cellulose. In the first stage, these are refined to form ethane and propane, which undergoes a heating process called “cracking” to turn them into ethylene and propylene. Polymerization of these two products creates different polymers.

All the steps leading to the production of plastics from extraction and distillation to cracking and polymerization are all energy-intensive processes and hence generate enormous amounts of greenhouse gas emissions. The carbon footprint of plastics doesn’t end with their production.

In an effort at plastic waste management, most countries resort to incineration. Even the recycling of plastics gives rise to greenhouse gas emissions. For more on this topic, see our article on How Does Recycling Plastic Help the Environment.

From cradle to grave and beyond, plastics continue to cause harm to the environment in diverse ways.

How Long Does It Take for Plastic to Decompose? 

Not all plastics are the same and hence the rate of decomposition is varied among the numerous forms of plastics. Plastics can be classified into 7 categories based on polymer types as follows.

  1. Polyethylene terephthalate (PET or PETE)
  2. High-density polyethylene (HDPE or PE-HD)
  3. Polyvinyl chloride (PVC or V)
  4. Low-density polyethylene (LDPE or PE-LD),
  5. Polypropylene (PP)
  6. Polystyrene (PS)
  7. Polyurethane (PUR)

Depending on the type of plastic used in manufacturing the product, its decomposition rate also differs. This is how long some of the common plastic items take to decompose. 

  • Single-use plastic bag – 20 years
  • Sanitary pads and tampons – 25 years
  • Takeaway coffee cup – 30 years
  • Plastic straw – 200 years
  • Six-pack holders – 400 years
  • Plastic bottle – 450 years
  • Plastic cups – 450 years
  • Disposable diaper – 500 years
  • Toothbrush – 500 years
  • Polyurethane seat cushions – 500 years
  • Styrofoam – 500 years
  • Fishing line – 600 years

The plastic decomposition time given here is an estimation as it has never been tested before or verified in real-life scenarios. A vital factor that can aid in the faster decomposition of plastic products is exposure to sunlight. Plastics tend to absorb the ultraviolet rays from the sun and it helps in breaking down its molecules. This process called photo degeneration is made use of in landfills to accelerate the process of decomposition.

Why is it difficult for plastics to decompose?

Although plastic is made from natural resources like crude oil or natural gas, it is a synthetic substance not occurring as such in nature. The polymerization process used to create polymers is the reason why plastics are hard to decompose. 

During this process, small molecules called monomers to join together chemically to create long chain-like or 3-dimensional network molecules called polymers. This is unlike the molecular bonds of organic matter found in nature. 

The strength and complexity of the chemical bonding in polymers make it extra difficult to break. The involvement of energy can accelerate the decomposition process.

The decomposition of plastics also creates an altogether new problem. As it breaks down, plastics tend to leach toxic substances into the ground. This can lead to contamination of land as well as water bodies near it. 

The problem of microplastics

Another issue to tackle during plastic decomposition is microplastics. As plastic products undergo decomposition, the bigger pieces break down into smaller ones. Small pieces of plastics less than 5mm long are termed microplastics. 

Microplastics are also manufactured for various applications such as tires, road markings, marine coatings, plastic pellets, personal care products, and synthetic fabrics like polyester, nylon, and acrylic. 

Microplastics are present in the air we breathe and in the food we eat. It is present in large quantities in the oceans, making life difficult for marine creatures. The toxins leached from microplastics into the soil end up polluting the land and water. 

What can we do about the plastic problem? 

The easiest and simplest solution would be to stop using plastics. However, this is both impractical and inconceivable. Plastics have become an integral part of our lives that it is unthinkable to completely eliminate its use. We need to come up with a strategy to manage plastic pollution.

The 3 Rs – Reduce, Reuse, Recycle are considered the best way to deal with the growing mound of plastic waste. Reduce its use by restricting it to essential purposes. Reuse plastic products as long as possible. Recycle it into usable products. The world countries have been promoting this for a few decades now and the idea is not as easy to implement when it was conceived. 

Less than 10% of discarded plastics are recycled in the US, the rest ending up in landfills. The situation is slightly better in many European countries but the quantity of plastics dumped in landfills is growing at an alarming pace.

Here are some more suggestions for you as an individual to contain the problem created by plastic waste.

  • Avoid single-use plastics.
  • Stop buying water in a disposable plastic bottle.
  • Say no to personal care products containing microbeads.
  • Limit ordering food from outside. Cook at home more often.
  • Use everything you buy to the utmost. Try to buy from second-hand stores.
  • Take your own bags when you go shopping. Avoid plastic bags.
  • Buy food items in larger quantities to reduce plastic packaging.
  • Put filters on your washing machine.
  • Avoid manufacturers using too much plastic packaging.
  • Follow the rules of recycling properly.
  • Participate in the cleanup of your neighborhood.
  • Support legislation to limit the use of plastics.
  • Offer your unconditional support to organizations working to solve plastic pollution.

Plastic waste is expected to grow by 20% in a decade. The only way forward is the responsible use of plastics and good waste management. 

Alternatives to using plastics

One of the practical suggestions proposed is to replace traditional plastic with biodegradable plastic. These offer the same uses as plastic but would be easier and faster to decompose.

Here are some eco-friendly alternatives to plastics.

Starch-based polymers: 

Starch is added to aliphatic polyesters like PLA, PCL, and polyvinyl alcohol to make fully biodegradable plastics.

Polylactic acid (PLA) polyesters: 

This is an aliphatic polyester made from lactic acid produced from the fermentation of starch during wet milling of corn, wheat, or sugarcane.

Polyhydroxyalkanoate (PHA) polyesters: 

When the sugar in corn, molasses, or active sludge is fed to certain types of bacteria, it creates a compostable plastic that will break down in about 20 days.

Polycaprolactone (PCL) polyesters: 

This is a synthetic aliphatic polyester that decomposes completely in 6 weeks. 

Liquid wood: 

This biopolymer displays all the properties of traditional plastic, except for the fact that they are biodegradable.

Research is ongoing to make thermoplastics biodegradable with plastic additives or prodegradant concentrates (PDCs) like cobalt stearate or manganese stearate. They actively promote oxidation to render plastic brittle and break them into smaller fragments. Microorganisms do the rest of the job by disintegrating them completely without any harmful residues.

The new products being developed in the biodegradable plastics scene are from milk proteins and grape waste. Casein, the primary milk protein is converted into a biodegradable material that is as stiff and compressible as polystyrene.

Grape waste after extraction of juice is used to develop a biodegradable material that can replace vinyl leather. It also can be made into fabric. In the future, grape waste may find use in automobiles and furniture.

Bottom line

It is evident that plastic does not decompose quickly. While some types of plastics can break down in a few years, most take centuries. The amount of plastic in our oceans is a major issue that requires attention. We need to take action now to prevent future damage. 

Plastic waste poses a major problem, as the world’s plastic production is expected to quadruple by 2050. We must find ways to reduce our reliance on plastic and recycle what we do use. Let’s work together to make a difference!

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