Can plastic decompose or biodegrade? How long does it take?

Topics Discussed

Biodegrade =

To decompose as a result of biological action, especially by microorganisms.

Decompose =

To separate or break something down into components; to disintegrate or fragment.

Source: WikiDiff.

Some research suggests that is can take up to 1,000 years for one single-use plastic item to decompose. However, as a result of many conflicting environmental factors that contribute to the rate at which plastic decomposes, many studies contradict each other due to inconsistent variables and difficult testing conditions.

One thing that we know for sure is that plastic absolutely damages the environment and it’s surrounding organisms and eco-systems. Plastic is categorised together with many other waste-types as a material that takes a very long time to decompose.

The general consensus made by scientists is that polystyrene (plastic) remains for a very long time, if not forever in the environment. Opposing research argues that the persistence of polystyrene in the environment may be shorter and less complicated than first thought. 

Despite the ambiguity, the environmental damage caused as a result of plastic pollution is undeniable, highlighting the importance of eco-friendly products.

Since plastic materials come in so many different forms, there are differences in the time it can take for different plastic materials to decompose, if at all.

Here are some examples of common single-use plastic items with regard to the time it takes them to decompose (rates may vary depending on the material and environmental conditions):

– Single-use plastic bags (high-density polyethylene):
Can take up to 100 years before they decompose (different environmental factors contribute to the speed at which decomposing occurs).

– Single-use plastic straws :
Can take up to 500 years to decompose.

– Single-use plastic bottles (polyethylene terephthalate):
Can between 450 – 1,000 years to decompose – Plastic straws can take up to 500 years to decompose.

– Single-use plastic utensils:
Can take up to 1,000 years to decompose.

Most plastic items are made from a chemical composition called polyethylene terephthalate (Polyester/PET), a synthetic aromatic hydrocarbon polymer, which when heated, releases toxic chemicals into the atmosphere.

Polyethylene can decompose if exposed to ultraviolet sunlight radiation. This is a process known as photo-degradation.

Vice Media covered ‘the journey of a plastic bottle‘, providing an insight into a plastic bottles journey to the bottom of the ocean.

Environmental Influences:

Exposure to the sun is an example of an environmental factor that can change the rate at with decomposition occurs.

One study found that “plastic most commonly used in water and soda bottles can release antimony and bisphenol (A BPA industrial chemical).”

plastics inability to efficiently decompose

The above graphic highlights plastics inability to efficiently decompose.
Image Source/Credit: Small Business

In comparison to organic materials such as paper/plant-based products, plastics decompose extremely slowly (if at all).

There is no single answer to how long it takes plastic to decompose, due to the varying environmental conditions and exposures discussed above.

The environmental damage caused as a result of single-use plastics highlights the importance of eco-friendly waste-disposal.

Scientists continue to research new solutions to help solve the problem of plastic waste, as we discuss in the next section.

Can plastic biodegrade? How long does it take?


“To decay naturally and in a way that is not harmful”, according to The Cambridge Dictionary.

Most conventional plastics do not biodegrade, regardless of environmental conditions.

Some plastics do however biodegrade very slowly if exposed to air, water and light.

Biodegradable plastics can be categorised as: 

– Plant-based hydro-biodegradable plastic
– Petroleum-based oxo-biodegradable plastic

Further examples include: 

– Cellulose-based plastics
– Bacteria-based plastics
– Starch-based plastics
– Soy-based plastics

Most plastics derive from petroleum; the result of more than two million years of once-living decayed organisms. If petroleum comes from from biomaterials, why can’t it biodegrade?

This is because many plastics also originate from propylene, a petroleum-based chemical component. When combined and heated with a catalyst, chemical units join together, forming extremely compact carbon-bonds, hence the resilient capabilities of conventional plastic.

In biodegradable plastics, chemicals are added to help them break-down when exposed to conditions such as air, sunlight and water.

Biodegradable plastic is a controversial topic, since some research has reported that these plastics don’t in-fact biodegrade as efficiently as once thought.

Research from scientists at Michigan State University revealed that plastic-bag materials (polyethylene) and plastic-bottle materials (polyethylene terephthalate) showed little to no signs of degradation after scientists replicated natural conditions over a period of 2-3 years.

There are also bioplastics (corn-based bioplastic). Since there are only 42 commercial composting facilities in the US which are currently capable of processing these bioplastics, there is a lot of adoption still needed, despite positive early signs.

A quick way to differentiate biodegradable and non biodegradable materials is to question if it can be broken down naturally by microorganisms. If not, then it cannot biodegrade.

There are three ways that something can biodegrade:

Chemical alteration of the property of the substance

Environmentally Acceptable:
Biodegradation of the undesirable properties of the compound

The complete breakdown of a compound into either fully oxidised or reduced simply molecules

Biodegradation is nature’s recycling system. Microorganisms eat waste and convert it into nutrients. Since microorganisms can’t eat plastic, the plastic bags that you throw away take centuries before heat and ultraviolet sunlight radiation break them down.

The most common type of plastic is polyethylene, a petroleum-based polymer that, not surprisingly, cannot biodegrade.

Plastics impacts on the ocean and marine-life

Each second, it is estimated that around 500 pounds of plastic waste makes its way into the oceans.

These harmful plastics are referred to as microplastics. Microplastics are small plastic pieces (<5mm long) which can damage ocean and marine life.

Microplastics in the ocean:

Tiny particles consisting of dead animals and plants (also referred to as ‘marine snow’) found in the deep-sea, rain down to the depths of the ocean.

It is these particles that feed the vast majority of the deep-sea creatures. Within these particles, microplastics are found.

These microplastics can often be as small as the width of a human-hair and therefore easily consumed by creatures as tiny as a tadpole. Scientists have found microplastics at every level of the ocean. The most common type of microplastic that they find is polyethylene terephthalate (PET).

Single-use plastic waste can be transported into a nearby ocean via wind and river currents. After breaking down, the plastic materials become microplastics.

Animals in the deep-sea see these tiny particles and ingest them along with their food, unaware of the toxic side-affects. This endangers the whole marine food-chain as smaller creatures are consumed by larger creatures, and the cycle continues.

The term ‘plastic-soup’ was coined as an analogy of the tiny plastic particles found in the ocean. It can take just one plastic bottle more than five times the average human life expectancy before it decomposes (if at all).

It is thought that the United Kingdom alone disposes of approximately 35 million plastic bottles per year, which also highlights the cultural shift in mentality that is necessary in the fight against plastic pollution.

Here you can read more about the problem with plastic pollution.

How should you dispose of plastic, if you have to?

In general, we should try to avoid using any plastic materials.

There are currently no natural processes in place that allow non biodegradable plastic to be absorbed back into the biological cycle. Most plastics are made from oil and do not biodegrade, making single-use plastics very difficult to dispose of.

Conventional plastics cannot be composted in the same way that organic materials are, hence why plastics take centuries, if ever, to disappear. Another option cold be to consider precycling, i.e. identifying alternative use-cases for items that you’d normally dispose of.

Find creative ways (perhaps with your kids) to reuse ‘hard-to-recycle’ items and turn them into something that can be used!

For more inspiration, check out the 20 Creative Ways to Reuse and Recycle Plastic Bottles, by BudgetDumpster.

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