Today we live in what many are referring to as a ‘disposable society’. A world in which we buy things almost every day with the intention of using them once and throwing them away. In America alone, the average citizen produces 4.4 pounds of waste, in various forms, every single day https://archive.epa.gov/epawaste/nonhaz/municipal/web/html/. And according to the World Bank around 34% of all waste generated in the world is from high-income countries. http://datatopics.worldbank.org/what-a-waste/trends_in_solid_waste_management.html
But there has become somewhat of a disconnect between what happens to these items once they are placed in a trash can. The garbage truck takes the items away and they are out of sight and therefore out of mind. Although in many developed countries recycling is more common, still 37% of our waste ends up in landfills. http://datatopics.worldbank.org/what-a-waste/trends_in_solid_waste_management.html
Well, I’m here to bring home the reality of how long these items actually last once thrown away. In this article, I have scoured the web and scientific literature to try and find some answers. Many of the figures here are simply ‘best estimates’ because nobody has yet had the time, or patience, to sit down and wait hundreds or potentially thousands of years to time how long some of these items take to fully decompose!
It is also worth mentioning that a lot of the materials on the list will actually never decompose. This is because they are not made of organic material and so organisms in the soil have no interest in breaking them down. For those items, I am referring to how long it takes for them to break down into small enough parts to be virtually gone and not distinguishable as the original item.
The figures here vary significantly depending on the conditions the items are in. In the open air exposed to oxygen, rain and other elements an object will decompose or degrade much faster. Landfills are actually designed to prevent things decomposing, packed in with no light, water or oxygen means these sites are inhospitable for microbes and other organisms which are required for decomposition. This has led to people discovering intact lettuce leaves buried in landfill for over 20 years!
Plastic bags: 500-1000 years
If you look around the room you are currently in, the chances are there is a lot of plastic. Plastic seems to be everywhere and in virtually everything today. It’s sometimes hard to imagine it has only been around for about 50 years.
Even the very first plastic bags ever produced still haven’t broken down fully. This means that we don’t have any first-hand data to draw upon for this and any figures are based on scientist’s best estimates.
One way that scientists can try and model the decomposition rate of a long-lasting item is through something called a ‘respirometry test’. This is where a waste sample is placed in a container with microbe-rich compost and left for several days. As the microbes begin to break down the item carbon dioxide (CO2) is produced and the level of CO2 produced in a certain time gives an indication of how fast the item will decompose.
When this method is attempted with a plastic bag made from high-density polyethylene, no CO2 is produced because the microbes do not consider the plastic food and therefore do not break it down.
So really the answer here should be never. But scientists do believe a plastic bag would eventually break down to be virtually unrecognizable but only if exposed to sunlight in a process called ‘photodegradation’, where photons in sunlight break down the plastic into smaller molecules. This is where the figure of 500-1000 years comes from, nobody can be certain but it is ‘a very long time’.
Plastic bottles: 450 years or more
Our collective plastic bottle habit has got out of control. We are now at the point where we use a million bottles a minute globally. They contribute massively to the amount of plastic waste that ends up in the oceans, being the fourth most collected item on beach cleans by the Ocean Conservancy.
Plastic bottles are typically made of a plastic called polyethylene terephthalate (PET). This is a material that can be recycled, although only 31% of plastic bottles in the US are recycled, meaning many end up in landfills, or elsewhere in the environment.
Similar to high-density polyethylene plastic bags, PET is created from crude oil and does not decompose in the same way as organic matter such as food. So once again the only way PET plastic bottles break down is by photodegradation. This is why plastic bottles are estimated to take 450 years or more to break down. And even then it wouldn’t have completely disappeared it would just exist as tiny pieces of microplastic.
There is some hope on the horizon for the decomposition of plastic bottles. A student in America recently discovered a bacteria capable of breaking down PET. But this is still in very early stages of development so until then, probably best to avoid them.
Plastic Straws: 200 years or more
Plastic straws have received a lot of negative press over recent years, mainly because for many people they are an unnecessary luxury. In the US alone, 500 million plastic straws are still used each day.
Plastic straws are made from the polypropylene (PP) which can be recycled, but it rarely is, with most people just disposing of them in the nearest general garbage bin. If they don’t end up in landfill, they can end up in the same place as much of our other plastic waste, in rivers and eventually oceans, where they pose a threat to marine life.
Once again, because they are made of a type of plastic, they do not decompose. Therefore, plastic straws are estimated to take around 200 years to photodegrade. This is less than plastic bottles and bags simply because of the smaller size.
Plastic Cutlery: 200 years or more
Plastic cutlery and utensils have become almost as ubiquitous as plastic straws. They have been around since the 1950s and are made from a mixture of polypropylene and polystyrene.
It is estimated that plastic cutlery such as plastic forks, knives and spoons would take over 200 years to break down. This is in optimum conditions exposed to high amounts of sunlight so it can photodegrade. Unfortunately, these items often end up buried in a landfill where in theory they could last forever!
Milk Cartons: 5 years or more
Despite looking like they are made of cardboard, a milk carton also contains a layer of plastic, which is most commonly polyethylene.
As the layer of plastic is only thin, although it will never decompose, it will break down into smaller pieces much faster and would be virtually unrecognizable in around 5 years.
Writing Paper: 6 weeks
Paper is a material much closer to something you might find in nature than plastics. Paper has been around in one form or another since over 2000 years ago when it was made from the fibers of a tree mixed with water.
Modern-day paper is slightly different but still consists mainly of wood pulp mixed with water. White paper is bleached to remove the color of the lignin but it is still mostly wood.
Because it is made of organic material, the paper does actually decompose, woo! Estimates across the web vary from 2 to 6 weeks but where I can in this article I am going to carry out the experiment for myself to give you some real-world data.
I placed a piece of paper in my garden compost heap and it took around 6 weeks for paper to fully decompose.
Biodegradable plastic bags: 3 months or more
Recently a report was published in the Environmental Science and Technology journal following a study that started in 2015 by researchers at the University of Plymouth. The study monitored various biodegradable and compostable plastic bags in a variety of different conditions to see how long they took to decompose.
A bag placed in seawater fully degraded in 3 months, in 9 months bags left in the open air had broken down into smaller pieces (although technically had not fully decomposed) but a bag buried in soil was still able to hold groceries when it was dug up after 27 months!
Critics of the study pointed out that even these ‘biodegradable’ bags must be sent to a specialist recycling facility to be taken care of correctly. But this led to the question of whether the labeling of these products was misleading consumers.
Napper, Imogen E., and Richard C. Thompson. “Environmental deterioration of biodegradable, oxo-biodegradable, compostable, and conventional plastic carrier bags in the sea, soil, and open-air over a 3-year period.” Environmental science & technology (2019).
Paper bag: 6 to 8 weeks
I could write an entire article on the myth that paper bags are much better for the environment than plastic bags. The fact is, if you look at the entire life cycle of making one they use more energy, emit more greenhouse gases, use more raw materials and cause more water pollution. So they definitely aren’t the perfect solution to plastic waste.
One benefit they do have though, is that they degrade. A paper bag in the right conditions can decompose in around 6 to 8 weeks.
Newspaper: 6 weeks
As with everything mentioned on this list the length of time take to decompose depends on the conditions. There are stories of newspapers being dug up from landfills that are still legible after 40 years in the ground! That is because a landfill is not simply a big compost heap, items are buried and left there without being disturbed which means they stay dry, in the dark and with no oxygen. This does a remarkable job of preserving pretty much anything.
In a garden soil with regular aeration and exposure to organisms that can break down the newspaper, it will decompose in a similar time to normal paper in around 6 weeks.
Rubber tires: 50 to 80 years
Rubber tires have increased in number dramatically over the past few decades as people desire the latest model of car, van or lorry. Although recycling of these items has dramatically improved, with 95% in the EU re-used for a variety of things, many still end up in landfill. This is an issue because they take up a lot of space (despite being mostly air) and make great homes for rodents such as rats.
Glass: 1 million years or more
Glass is one of the most stable materials humans have managed to create. Contrary to plastic, we do have some long(ish) term first-hand data for this, with glass artifacts having been discovered from around 15,000 years ago in Egypt.
Glass does not decompose but it does very slowly break apart into smaller fragments, but modern glass is made to be even more stable and the chances are if not recycled, the glass will last pretty much forever.
This has led many people to speculate that glass would take a million years or more to fully break down.
Aluminium Cans: 200 years or more
Aluminum cans are one of the most recycled items. With a recycling rate of 67% in the USA. This is a good job because the process of mining and extracting the metal ore required to make aluminum in the first place is an environmentally damaging process which requires huge amounts of energy.
But as we know, many cans end up either in landfill or in other places where they are left for a long time.
One of the main reasons aluminum is so widely used is because, like plastic, it has the property of being durable and lasting a long time. This means you can store all sorts of liquids in the cans, store them in a cellar for several years and never worry about them disappearing or starting to break down and start leaking.
So if aluminum doesn’t decompose, what would happen to it over time?
Well, it might eventually ‘corrode’. The cans are covered in a protective layer of aluminum oxide which usually prevents this from happening, but all it takes is for the can to get a scratch or crumple and the protective barrier is breached.
Once this happens oxidizing chemicals such as chlorine and sulfides in the air or water begin to corrode the aluminum underneath. This would cause the can to slowly disintegrate over time into smaller and smaller pieces. They would remain in the environment but the can as you knew it would be gone.
Even with the right conditions to make that happen it is estimated an aluminum can would take over 200 years to break down fully.
Tin Cans: 50 years or more
Tin cans are virtually never made from tin, due to tin being relatively expensive. Most cans are actually made from aluminum (see above) or steel.
As with aluminum, because steel is a metal it will not decompose and breaks down via the process of oxidation, where elements in the air and water corrode the metal causing it to rust and break down into smaller and smaller pieces over time.
Most people on the web seem to estimate a tin can will fully break down in around 50 years, but this would be in optimum conditions and the reality is it could be much longer.
Electronic Items: 500 years or more
Electronic waste or ‘E-waste’ as it is now known is an ever increasing environmental issue around the world as more people get access to more electronic items at cheaper and cheaper costs.
It is tricky to put a timescale on how long a particular item will take to break down because there are a lot of variables in terms of composition, but most will contain plastic and heavy metals and many will contain glass.
So in total electronic items are unlikely to fully break down in less than 500 years or more.
Batteries: 100 years or more
Batteries are composed of a variety of materials from the steel metal casing to other substances such as potassium hydroxide and manganese dioxide inside. Other types of battery such as rechargeable models contain heavy metals such as cadmium.
We’ve already discussed that steel will take at least 50 years to break down in optimum conditions but with all the other parts involved it is estimated batteries would take at least 100 years to fully break down.
Polyester Clothing: 200 years or more
Polyester is actually the term used for a category of materials all derived from petroleum and terephthalic acid. This gives polyester clothing many similar properties to plastics, at least when talking about how easily they break down.
Even in the right conditions, polyester clothing will likely take over 200 years to fully break down.
Wool Clothing: 6 months to 1 year
Wool is a naturally occurring material, harvested from wild animals rather than created synthetically like polyester. It is made from keratin, the same protein found in our skin. This means it stands a much better chance of decomposing in a reasonable timeframe.
Cotton clothing: 6 months to 1 year
Similar to wool, cotton is a naturally occurring material, but this time it comes from plants rather than animals. Because it is made from organic matter it will break down in a similar way under the right conditions.
Under the correct conditions, cotton clothing should decompose in 6 months to 1 year.
Silk clothing: 6 months to 1 year
Real silk is also made from natural material, using the cocoons of silkworms. For this reason, it will also biodegrade in a reasonable time under the right conditions. It is estimated silk takes 6 months to a year to biodegrade fully.
Diapers: 500 years or more
Disposable diapers are made from a variety of materials, cellulose, polypropylene, polyethylene and other plastics, as well as adhesives and fragrances to mask bad smells.
According to the US Environmental Protection Agency, 20 billion disposable diapers are used each year!
With that combination of thick plastics, diapers will likely take 500 years or more to degrade.
Cigarette Butts: 10 years
Cigarette ‘butts’ contain a filter which is made from a material called cellulose acetate giving them an almost cottony texture. But don’t be fooled, this material is really a type of tightly woven plastic.
Due to there small size and the way the material is put together, cigarette butts will break down quicker than many other plastics but it can still take a long time. Estimates suggest a cigarette butt will take up to 10 years to fully break down.
Wood: 1 to 20 years
I’m sure you are all aware that wood is a naturally occurring material and therefore will biodegrade. The rate at which it does decompose depends on the type of wood and the conditions. Some tree species such as spruce which falls naturally in a forest can take up to 100 years to fully rot due to certain resins in the bark.
Wooden furniture, which is often covered in paints that slow down the decomposition process can take over 10 years to decompose.
Banana Peel: 6 weeks or more
A banana peel is organic material and will decompose. But as with everything mentioned, this depends on conditions. In the right conditions and composted correctly a banana skin will fully decompose in just 6 weeks. However, on the side of a road in cold weather, banana skins have known to not fully decompose for up to 2 years!
As a species, we have created some remarkable materials such as plastics which are incredibly useful due to the fact they are durable and last a long time. But as you can see from this article, this positive property of these materials also creates environmental issues. The key seems to be to stick to materials that occur naturally because they will break down in a natural way too once eventually disposed of.
Of course, it isn’t that simple. If recycling methods keep advancing and circular economy techniques come into play many of these materials can be re-used an indefinite amount of time. There are even companies popping up that are mining old landfill sites to recover these buried materials and re-use them once again (as it is cheaper and less damaging than mining more materials). These materials are not going anywhere and so the best option we have for now is finding a way to extend the lifespan on them so fewer end up in landfill causing problems.
Keep coming back to this page over the next few years for updates as I run my own tests on some of these materials to see how long they really take to decompose or break down.