Plastic is not something that we can just use and then forget about. What happens to our plastic waste is a problem for our environment, on a scale which we cannot ignore. Plastic waste affects Earth's ecosystems and has a profound negative impact on the environment, wildlife and people.
Approximately 80% of the litter in the seas comes from the land6. One of the direct ways that plastic ends up in our waterways and oceans is through littering. Sadly, many people picnic and enjoy time outdoors without following countryside codes. They leave lots of plastic bottles, bags and containers behind when they go back home.
Whether you leave plastic items behind on a beach, beside a river, or in other environments, much of that litter will ultimately blow into the waterways and make its way into the oceans. And become what we know as ocean plastic.
Both in the seas and oceans and while it is on land, plastic litter has a huge impact on wildlife. Wildlife gets entangled in larger pieces of plastic, which can kill or injure them. Many creatures also eat plastics – causing internal injury and even death. We can also implicate floating plastics in the spread of invasive marine species, pathogens and bacteria, which disrupt ocean ecosystems.
But it is when the plastic litter begins to break down into ever smaller and smaller pieces that the most pervasive and worrying problems arise. Micro-plastics enter food chains and cause huge environmental disruption and a huge range of health problems in animals. Including (potentially) people, though we do not yet fully understand the health effects of micro-plastic ingestion.
The plastic we litter ends up as microplastics in oceans, but it does not just stay there. We can now find it in every single ecosystem on Earth, from the Arctic to the Antarctic and even in the human body. It leaves the oceans through food chains, and also through bubble burst ejection, cast back up onto land in sea sprays.
We are yet to determine all the negative effects of microplastics that come from land-derived litter. But it is very clear that leaving even one piece of plastic behind can have profoundly harmful impacts.
Another major source of plastic pollution is the plastic that we flush down the drain. Many people (often unknowingly) send plastic down the drains. Wet wipes and other larger plastic pieces contribute to the creation of 'fatbergs' that block sewage systems.
While other plastics like the plastic sticks from Q-tips cotton buds pass straight through treatment plant filters and end up in our oceans and on our beaches. Again, most insidious of all is the micro-plastics. Synthetic clothing releases micro-plastics every time we wash them, (as well as when we wear them).
Sometimes, the slurry from sewage treatment plants is used as a fertilizer on farm fields. But recent exposés have proposed that this slurry contains all sorts of harmful contaminants, including microplastics. And often regulation in this area leaves a lot to be desired. This means that consumers of agricultural produce are often unaware of the fact that plastic waste could contaminate the food they eat.
Throwing plastic in general waste for collection can be just as harmful as littering, or flushing plastic waste down the drain. Where plastic waste ends up (if the system does not separate it from other waste streams) will depend on where you live, and the practices in your area. The problem is that there is usually little transparency when it comes to waste management. It can be difficult to determine exactly where the household waste you generate ends up.
A high proportion of general waste globally ends up in a landfill. The landfill may be in your own country, or for some developed countries, abroad. Of course, where people take plastic waste abroad, there will be carbon costs and pollutants associated with transportation to contend with.
Landfill sites should contain waste and prevent it from entering wider environments. Unfortunately, poor management (especially in developing nations where much waste from the developed world ends up) means that plastic waste often blows away. Or the wind sweeps it off landfill sites and pollutes the wider environment.
But even well-managed landfill sites have negative environmental impacts. When plastic waste ends up in landfill, it can contribute to leachate. Where plastics are not handled correctly, certain types of plastic— such as polyvinyl chloride; PVC— can leach chemicals such as additives and plasticiser compounds into the surrounding land and waters5.
Another common practice is to incinerate or burn plastic waste. This produces CO2 and other greenhouse gases that contribute to our climate emergency. However, sometimes, we use the energy derived by burning plastics to heat and power homes and businesses.
Whether or not this waste to energy solution can result in a net reduction in greenhouse gas emissions depends on several factors. Including the efficiency of the incineration process, and the mix of the energy sources it is replacing. Where the energy mix contains a high proportion of fossil fuel sources, burning plastic for energy can reduce emissions. But in many countries — most across Europe for example — where incineration efficiency is low and the energy mix is lower-carbon, this does result in higher greenhouse gas emissions overall3.
Even where incineration does lead to a net reduction in CO2 emissions, it is far from an ideal solution. This is because incineration of plastic waste worsens air pollution, and can release a range of harmful particulates into the air4. Incomplete combustion of Polyethylene (PE), Polypropylene (PP) and Polystyrene (PS) can release carbon monoxide (CO) and noxious emissions, while polyvinyl chloride (PVC) can produce dioxins.
Modern facilities for incineration in the developed world have largely managed to introduce regulations and filtration to catch pollutants. But in developing nations, open incineration is still common and causes huge pollution problems. And containment for even modern facilities is still sometimes a contentious area and one of concern.
That said, incineration is still sometimes said to be better than landfill in our fight against global warming. And is the best currently available solution to deal with non-recyclable plastics on a large scale. And interestingly, certain studies have found that when we take all factors into account, it can be a more environmentally friendly solution even than some forms of recycling. This highlights the complexities in the issues of plastic waste and shows that we must take everything into account.
Where possible, it is of course generally best to try to recycle whatever plastic we can. But it is important to recognise that recycling alone is not enough. Or even better refuse, reduce, reuse, and recycle.
Of course, we cannot recycle some of the plastic waste we generate globally each year at all. And even when we can recycle plastic waste, it is not always actually recycled at all. Often, recycling simply isn't economically viable for authorities and businesses. When oil prices are low, it can be cheaper to make new raw plastics (e.g plastic packaging) than to recycle, which poses a major problem economically.
Another problem is that consumers do not always clean their mixed plastics and sort them as they should. This can also lead to reduced rates of recycling – even when consumers believe that they are doing the right thing.
The environmental benefits of recycling plastics are clear. For example, recycled PET plastic production reduces emissions compared to virgin production by 32%. And recent examples have shown that results can be even better.
But the issue is not always as clear-cut as some people believe. Researchers have also made many assumptions. Based on the idea that each tonne of recycled plastic can replace one ton of raw, virgin material.
But this is not always possible. Recycling processes cannot always deliver a like-for-like product. It very much depends on which plastics we are talking about, and which recycling processes regions use.
Most plastics go through a mechanical recycling process.
Unfortunately, we can only recycle these plastics mechanically once or twice before they are down-cycled. This means that the recycling plant demotes them to lesser valued materials. Those things are then themselves often not recyclable at the end of their useful lives. This often means that recycling does not prevent plastic waste from ending up in landfill or being incinerated – it only delays it.
Chemical recycling involves breaking plastic polymers down into their crude components. This, in theory, means that we can recycle certain plastics endlessly rather than being downgraded. We can utilize state-of-the-art techniques such as chemolysis, pyrolysis, fluid catalytic cracking, hydrogen techniques and gasification. All to break down plastics to make fuels for reuse1.
But chemical recycling does not necessarily bring environmental benefits. Though chemical processes are more tolerant of contamination2, and they yield polymers that are identical to the originals, eliminating downcycling, they can often be polluting, and result in higher greenhouse gas emissions. How environmentally friendly the process will very much depend on the exact processes used, how energy-efficient they are, and the type of energy used.
It is clear that of all the options currently commercially available, chemical recycling is usually the best option. But to solve the problem of plastic waste – refusing, reducing and reusing also have to be key parts of the picture. To tackle the plastic waste issue, we need to find ways to break our reliance on the product once and for all.
|Kim Ragaert, Laurens Delva, Kevin Van Geem, Mechanical and chemical recycling of solid plastic waste, Waste Management, Volume 69, 2017, Pages 24-58, ISSN 0956-053X, https://doi.org/10.1016/j.wasman.2017.07.044|
|C&EN, 2019: Plastic has a problem; is chemical recycling the solution?|
|Ola, E., Göran, F. (2009). Plastic waste as a fuel - CO2-neutral or not? https://doi.org/10.1039/B908135F|
|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|
|Our World in Data: FAQs on Plastics|
|European Commission (Environment): Our Oceans, Seas and Coasts. Descriptor 10: Marine Litter|