We all know what plastic is, and we all use it. There is no getting away from this man-made material. In many ways, we have become reliant on plastic, for our packaging, to store food, toys, plastic chairs, and dozens of more applications. However, as environmental concerns grow it's useful to take a look at the life cycle of plastic. Where does it come from, and what happens to it when we discard it?
We now know that plastic is causing problems for the environment. From animals ingesting it to depleting finite natural resources1. There’s little doubt that switching to more sustainable and eco-friendly alternatives will prove vastly better for the planet.
Despite this, due to plastics' cost, durability and ubiquity, the demand is still there. Further, the majority of us still get through a great deal of disposable plastic yearly, all contributing to mountains of plastic waste that has to be dealt with.
We use it largely because alternatives are less convenient or simply not yet widely available. And because consumer demand, although shifting, has yet to absolutely require manufacturers and retailers to change their ways. As such, despite the environmental costs, our supermarket aisles are still full of the stuff.
We can all make a difference to how much plastic waste we generate, however, by consciously looking for alternatives when we’re buying goods. Simply making the choice to use eco-friendly straws or consider plastic alternatives such as bamboo all help. You can choose to say no to plastic bottles and when buying presents choose plastic-free. It's not just at home either consider steps you can take to reduce plastic waste in the office.
Meanwhile, let's take a deeper dive into the lifecycle of plastic to better understand both where it comes from and where it goes at the end of its useful life.
Known as a man-made polymer, the life cycle of plastic begins when we make new plastic materials using a number of resources mostly derived from crude oil. We can create the polymer from a number of oil-based compounds, which we can then manufacture into many shapes and variants. Across the world, we’ve created a huge volume of plastic. To date, estimates suggest that we have produced 8300 million metric tons of plastic8.
When you consider where we use plastic, we can see just how versatile it is. From plastic water bottles to car dashboards and plastic bags, it is certainly a flexible material.
While we all know about plastic and use it, you might not know its back story. In terms of the materials that we use regularly, we could still consider plastic as being new.
Plastic’s history dates back to 1907, making it just over 100 years old. Leo Hendrik Baekeland invented plastic in 1907, then known as Bakelite. At the time, unlike many plastics today, it was not possible to melt them.
Therefore, it was a great electrical insulator, and its early uses included items such as telephones and cameras. A couple of years later, in 1909, it became known as plastic.
Since plastic has made it possible for us to make advances in many different areas. From flight to medical advances with the creation of self-disinfecting plastics through to electronic devices. Innovative uses of plastic in medicine even help prevent infection5.
A wonder material in some ways, since plastics' invention, it has played a key role in the growth in mass consumerism, providing a number of benefits that we now take for granted. For example, a cucumber shrink-wrapped in the supermarket will last up to three times longer than its unwrapped counterpart. Accordingly, allowing supermarkets the world over to extend the shelf life of the cucumber alongside many other products. The result helps to provide often cheaper goods and a wider variety.
As such, plastic plays an important role in the supply chain of many goods. Helping food last longer also helps reduce food waste. As with any argument, there are two sides to the story.
We need raw materials such as oil and natural gas to make plastic6. The production involves taking some of the components of crude oil or natural gas and treating them. The trade calls this process the cracking process.
Following this process, manufacturers convert the components into hydrocarbon monomers. This can include ethylene and propylene. To create additional monomers, further processing can help to create vinyl chloride, styrene, and ethylene glycol.
The next step in the life cycle of plastic uses a process of chemical bonding. The monomers are bonded into chains that are known as polymers. By creating a combination of monomers, it is then possible to manufacture a wide range of plastics that have varying characteristics and properties.
When we consider the way in which we use plastic, it is clear to see that it has many characteristics. We use it in plastic packaging, we use it to protect items in transport, and we use it to make window frames. It is a material that we can find in an almost endless number of applications. Despite this, we can put the different types of plastic into two groups known as thermoplastics and thermosets.
Most of the plastics we know are thermoplastic. Therefore, once it has been made, we can heat it and reform it as many times as we wish3. Its ability to be reformed is crucial in the life cycle of plastic as it helps the recycling process and enables us to reduce the amount of plastic that we manufacture. In turn, helping to reduce waste at the end of plastic's life cycle, CO2 emissions, and our reliance on natural resources.
The other main type of plastic, thermosets, cannot be reheated. Therefore, it cannot be reused and is almost impossible to recycle.
After the production of plastics in their basic form, it is possible to alter them depending on how they will be used.
At this point, a wide range of plastics have additives blended with them. These additives change plastics' mechanical, chemical and physical properties.
Improvements in additives now make plastic more adaptable9. This can make them heat-resistant, bacteria-resistant, or add color. They can also alter the surface appearance, which in turn allows the plastic to have a huge variety of applications.
In those plastics that need a high level of flexibility or workability, we use plasticizers. This will help to create plastics such as flexible tubing or plastic wrapping. Plasticizers have been known to come with health risks, but new approaches do help to avoid these risks.
Plastic products take many different forms. Depending on how we use it, we require different manufacturing methods. There are four main ways of manufacturing goods from plastic, and we use these to create the end plastic products that most consumers use.
This method involves the use of plastic pellets. These pallets get added to an extruder and melted using heat from the mechanical work and the hot wall of the machine. The molten plastic then gets pushed through an opening in order to create the shape of the desired product. Manufacturers make plastic bags using the extrusion process.
Plastic pellets get fed into a heating chamber. Once softened, they then get placed in a cooled mold to become a solid state before the mold opens up to eject the product. A range of containers gets made using this method, including butter containers and yogurt pots.
We use this method alongside extrusion or injection molding. It consists of blowing the semi-molten plastic into a cooled mold, where it stretches and presses on the outer edge of the mold. We use this to create hollow plastic products such as milk bottles.
Here we place plastic granules in a closed mold in a machine that rotates on two axes. Factories then heat the granules while the mold rotates, evenly distributing the plastic around the mold to create a coating. The resulting part then cools before being ejected. We use this process to create large toys or plastic furniture.
Plastic is a material that is important to us, regardless of how we look at it. Its versatility means that we have many uses for it, but why has it become so widely used?
The truth is that plastic is a cost-effective material, especially thermoplastic composites. As such, the low costs enable manufacturers to keep up with consumer demand.
We can create a huge range of products and items from this flexible and adaptable material. Its ability to form many shapes and sizes makes it ideal for use in a range of industries. It essentially provides a quick and simple solution.
In some ways, the life of plastic is never-ending. It is a material that takes up to 100s of years to degrade, and we can recycle certain plastics. We can melt and reform thermoplastic almost indefinitely in some instances. However, in most cases, we can only recycle plastics several times before they become less usable.
However, our reliance on plastic is causing a number of problems. With over 300 million tonnes produced each year, our reliance is growing. This has meant that plastic has become a waste and environmental problem as well as a health problem due to the toxicity of some types of plastic10.
At this point in the life cycle of plastic, most recycled plastic gets down-cycled. And almost all food-grade plastics. This means recycled plastics result in a lesser grade. From here, we can make plastic bins for picnic tables, for example, rather than other food packaging use. However, it is also common to see textiles made from recycled bottles as well as toys.
When it comes to recycling thermoplastics, it is a process that requires thorough sorting. Often, it is not possible to mix different types of plastics.
This is down to the way in which the different properties will separate during the process. If contaminated with different types of plastic the resulting material is unusable as it is too soft. Therefore sorting prior to recycling becomes particularly important.
To make it easier to recycle, we sort plastic into categories. We do this by using plastic identification codes. The different plastics then get taken to the correct recycling facility, where they get ground into tiny pieces before being washed, dried, and heated. At this point, recycling facilities melt the result into pellets or transform them into the desired material.
The plastic life cycle then begins all over again.
Despite efforts to increase plastic recycling, much of the plastic that we make is not recycled. Estimates suggest that we actually recycle as little as 9% of waste plastic. Of the rest, 12% is incinerated, and the remainder ends up in landfills or the natural environment.
Neither of the last two options is optimal for the environment. Incineration releases C02 impacting climate change.
And landfills do not present a safe end to the life of plastic. Birds scavenge landfills ingesting plastic. Loose plastic blows out of landfills and can eventually find its way into our waterways.
The result is that up to 12 million tonnes of plastic enter the ocean every year. Once plastic reaches the natural environment the results can be devastating. Research shows that up to 700 species of marine life are affected by plastic7. And another study found that up to 1 million people die each year in the developed world due to diseases resulting from plastic waste4.
And because plastic takes 100s of years to break down it will still be around far longer than our lifetimes. Due to the different types of plastics having different compositions, quite how long they stay with us varies.
For example, a paper coffee cup lined with plastic breaks down in around 30 years. On the other hand, 6 plastic rings commonly found attaching beer cans together will break down in around 400 years. Disposable nappies and glass bottles are around 450 years.
Ultimately if we don't recycle plastic into new goods or incinerate plastic waste it lasts in landfills and the environment for a very long time.
Further, plastic doesn’t biodegrade, rather it breaks down into smaller plastic particles called microplastics. As such, even when plastic breaks down, these small particles will still be found in nature or awash in our Oceans. Researchers have even found microplastics in our water and glaciers2.
Related: for a deeper dive, read our article on the environmental impact of plastic water bottles.
Therefore, we all have a duty to make sure that we reduce the amount of plastic that we use. To help reduce plastics' environmental impact we should all do our bit to prevent the manufacture of new plastics in the first place. Simply reducing or eliminating entirely our use of plastics, if we were all to do so, would have a huge impact. And we can all start by changing what we buy and choosing plastic-free wherever we can.
Now is the time for us all to make a conscious effort to make a change. It is our responsibility to reuse plastic where possible.
We must all make sure we recycle and do our best to champion and implement the 4R principles of Refuse, Reduce, Reuse and Recycle. This way, we can help to make the world a better place. As it stands, plastic is killing wildlife, we are using natural resources and generating harmful greenhouse gases.
Plastic has helped us to achieve many things, and it has enhanced our lives. Despite this, the mountains of plastic waste in nature are a problem that we simply cannot ignore.
|David W. Laist, Overview of the biological effects of lost and discarded plastic debris in the marine environment, Marine Pollution Bulletin, Volume 18, Issue 6, Supplement B, 1987, Pages 319-326, ISSN 0025-326X, https://doi.org/10.1016/S0025-326X(87)80019-X.|
|First evidence of microplastic contamination in the supraglacial debris of an Alpine glacier. Roberto Sergio Azzoni, Roberto Ambrosini, Francesca Pittino, Guglielmina Diolaiuti, Andrea Franzetti, and Marco Parolini. Department of Environmental Science and Policy, University of Milan|
|Grigore, M.E. Methods of Recycling, Properties and Applications of Recycled Thermoplastic Polymers. Recycling 2017, 2, 24.|
|Williams, M.; Gower, R. and Green, J. with Whitebread, E.; Lenkiewicz, Z. and Schröder, P. (2019) No Time to Waste: Tackling the Plastic Pollution Crisis Before it’s Too Late, London: Tearfund|
|Kingston, D., Seal, D., & Hill, I. (1986). Self-disinfecting plastics for intravenous catheters and prosthetic inserts. Journal of Hygiene, 96(2), 185-198. doi:10.1017/S0022172400065955|
|Environmental impacts of conventional plastic and bio-based carrier bags. Khoo, H.H., Tan, R.B.H. & Chng, K.W.L. Int J Life Cycle Assess (2010) 15: 284. https://doi.org/10.1007/s11367-010-0162-9|
|José G.B Derraik, The pollution of the marine environment by plastic debris: a review, Marine Pollution Bulletin, Volume 44, Issue 9, 2002, Pages 842-852, ISSN 0025-326X, https://doi.org/10.1016/S0025-326X(02)00220-5|
|Production, use, and fate of all plastics ever made. Roland Geyer, Jenna R. Jambeck and Kara Lavender Law, Science Advances 19 Jul 2017: Vol. 3, no. 7, e1700782, DOI: 10.1126/sciadv.1700782|
|Rudolf Pfaendner, How will additives shape the future of plastics?, Polymer Degradation and Stability, Volume 91, Issue 9, 2006, Pages 2249-2256, ISSN 0141-3910, https://doi.org/10.1016/j.polymdegradstab.2005.10.017|
|Rinku Verma, K.S. Vinoda, M. Papireddy, A.N.S. Gowda, Toxic Pollutants from Plastic Waste- A Review, Procedia Environmental Sciences, Volume 35, 2016, Pages 701-708, ISSN 1878-0296, https://doi.org/10.1016/j.proenv.2016.07.069|