Different types of plastic, and different plastic items and products can take different lengths of time to break down and degrade.
In this guide, we outline how long different plastic items take to break down.
We also outline various factors that might impact the break down of plastic.
The guide below compliments our separate guide on how long it takes different materials and everyday items to break down/decompose.
Summary – The Breakdown & Degradation Of Plastic
How Long Plastic Takes To Break Down
Different plastic items have different estimated times to break down into micro-plastics
In landfills, plastic bags might take between 10 to 1000 years years to break down, whilst a disposable diaper might take between 250 to 500 years. It’s dependent on the landfill conditions though
In the ocean, a plastic bag might take as little as 20 years to break down, whilst fishing line may take 500 years or more.
Plastics in the ocean may break down faster than plastics on land or in landfills
Some newer biodegradable plastics can break down in a matter of months in the right conditions, which is much faster than traditional plastics
What Happens To Plastic When It Breaks Down
There’s some debate as to what happens to all micro-plastics and nano plastics, with different theories being that they settle as deep sea sediment, they wash up on oceanfronts and are buried there, they get into soil and freshwater (or drinking water) sources, and humans and wildlife ingest them.
Bigger bits of plastic may also end up as waste pollution somewhere like on land, on beaches, or floating around in freshwater sources or the ocean
Where Plastic Breaks Down
Most plastic currently ends up in landfills, or somewhere in the environment like on land, on beaches, in rivers and lakes, or the ocean
These are areas where plastic commonly breaks down
Although, consumer products like some synthetic plastic fibre based textiles may release microplastics when washed. Other products may break down whilst in use too
Factors That Can Impact How Plastic Breaks Down
– The plastic itself matters i.e. the chemistry and makeup of the plastic.
Many plastics are non-degradable – which explains why some plastics made decades ago still exist as plastic waste today.
Other plastics may have a makeup that allows them to break down easier. There are newer plastics such as bio plastics that can break down quicker than petroleum based plastics under specific conditions
– The conditions of the environment that the plastic waste breaks down in
For example, different landfills have different conditions
A landfill site will also have different conditions to the ocean
The ocean’s unique conditions for example mean that plastics usually break down quicker here than when in landfill (where there may be a lack of light and physical weathering for example) – although some sources contradict this
– Other factors
UV (from the Sun) is a key factor in photo degradation of plastic
Physical weathering (from water, physical objects, and so on) is also a key factor in plastic breaking down
How Long Plastic Takes To Break Down & Degrade In Landfills
Different landfills can have different conditions, and this can impact the break down of the plastic items in them.
But, some general break down rates for plastic in landfills might be …
… plastic items can take up to 1000 years to decompose in landfills
… plastic bags we use in our everyday life take 10-1000 years to decompose
Foamed Plastic Cups [can take up to] 50 years
… plastic bottles can take 450 years or more
… disposable diapers take approximately 250-500 years to decompose in landfills
How Long Plastic Takes To Break Down In The Ocean, Or The Environment
In The Ocean
The average estimated decomposition times of typical [plastic] marine debris items [are]:
Fishing line – 600 years
Disposable diaper – 450 years
Plastic bottle – 450 years
Plastic beverage holder (6 rings) – 400 years
Foamed buoy – 50 years
Styrofoam cup – 50 years
Plastic bag – 20 years
The lifecycle of plastics in the ocean are:
Plastic toothbrush – 500 years
Disposable diaper (need to be exposed to oxygen and sunlight in order to decompose, and they don’t decompose well in landfill) – 500 years
Coffee pod – 500 years
Plastic cup – 450 years
Plastic water bottle – 450 years
6 pack plastic rings – 400 years
Plastic straw – 200 years
Coffee cup (plastic liner on the inside) – 30 years
Plastic bag – 20 years
Estimated time taken to biodegrade (in years):
Fishing line – 600 years
6 pack beer holder – 450 years
Plastic bottles – 450 years
Nappy – 450 years
Straw – 200 years
Foamed plastic cup – 50 years
– telegraph.co.uk (citing NOAA/Woods Hole Sea Grant)
On Land & In Freshwater Sources
We will provide data in this area if we find any on the breakdown rates of plastic on land, on beaches, or in freshwater sources like rivers and lakes
Currently, we don’t have any data.
How Long Plastic Bags Take To Break Down
From the above estimates, anywhere from 20 years in the ocean, up to 1000 years in landfill.
How Long Plastic Bottles Take To Break Down
From the above estimates, 450 years.
How Long Plastic Straws Take To Break Down
From the above estimates, 200 years.
How Long Biodegradable Plastics & Bioplastics Take To Break Down
It depends on the plastic – you have to read the product description to see how long it takes to break down, and the conditions it needs to do this (these plastics usually need specific conditions).
[Separate to traditional plastic, there are two more common types of biodegradable plastic, and they are] plant-based hydro-biodegradable plastic and petroleum-based oxo-biodegradable plastic
… polylactic acid (PLA), a plastic made from corn … decomposes into water and carbon dioxide in 47 to 90 days — four times faster than a PET-based bag floating in the ocean.
But conditions have to be just right to achieve these kinds of results.
PLA breaks down most efficiently in commercial composting facilities at high temperatures.
When buried in a landfill, a plastic bag made from corn may remain intact just as long as a plastic bag made from oil or natural gas.
Note the difference between the phrase ‘degrade’ which means to simply break down, and ‘biodegrade’, which more commonly refers to the break down of material organically or naturally.
How Plastic Breaks Down
Traditional plastic breaks down via photo degradation.
Materials can slowly break down through photodegradation [through exposure to UV radiation] (ourworldindata.org). This breaks the bonds in the plastic material (science.howstuffworks.com)
[Most fossil fuel based plastic does not biodegrade like organic matter i.e. it does not break down via bacteria]
[Most fossil fuel based plastics break down via photodegradation]
Factors That Can Impact The Break Down Or Degradation Of Plastic
Some factors that can impact how quickly plastic breaks down are:
– The plastic chemistry or the type of plastic product
– The level of mechanical abrasion on the plastic
– How saline the environment is
– Cool or warm environments [warm ocean water can speed up the break down of plastic – science.howstuffworks.com]
– Rain and other environmental conditions
Ocean vs Landfill Break Down Rates For Plastic
Ourworldindata.org suggests that the marine environment has factors which lead to quicker breakdown of plastic:
It’s important to note that within the marine environment, plastics can more readily break down into smaller particles: exposure to ultraviolet (UV) radiation, and consistent mechanical abrasion from wave action can cause larger particles to break down.
Wikipedia.org has some conflicting information on ocean break down rates:
Polymer degradation takes much longer as a result of saline environments and the cooling effect of the sea. These factors contribute to the persistence of plastic debris in certain environments.
Recent studies have shown that plastics in the ocean decompose faster than was once thought, due to exposure to sun, rain, and other environmental conditions
7. Hannah Ritchie and Max Roser (2019) – “Plastic Pollution”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/plastic-pollution’ [Online Resource]