Plastics have only been around for a little over a century, yet they’ve become part of almost every aspect of our lives. From children’s toys to food packaging, plastic materials are a ubiquitous part of 21st-century life. In fact, in roughly 70 years, there has been 8.3 billion metric tons of plastic produced, with around 6.3 billion metric tons of that becoming waste.
And only 9% of that waste has been recycled.
There’s a variety of reasons for this, and while our plastic waste continues to grow, advances in technology and changes to the way we consume are helping to make it more efficient and effective.
Why is plastic recycling important and what are the challenges faced by the industry?
Plastic recycling is extremely important, both as a method to deal with our existing waste and as a component of both circular economy and zero-waste systems that aim to reduce waste generation and increase sustainability. There are social, environmental, and economic consequences surrounding our current waste generation and disposal habits, and whether that is the issue of microplastics or an estimated $2.5 trillion in damage and lost resources to fisheries, aquaculture, recreational activities, and global wellbeing, the impact is no longer in doubt.
However, meeting the challenges posed by plastics is not simple, and there exists a lack of awareness surrounding the plastic waste problem. Despite the fact that potential issues were first flagged in the 1960s, historically, there has been a lot of pushback against implementing real change—mainly from the plastics industry itself. Recently, the tide seems to be turning on this issue as more people look for sustainable options and educate themselves about why plastic recycling is important.
Today, as both consumers and businesses look to recycle more materials, there is a lack of knowledge on how to do it effectively. This creates issues in the form of contamination, either by mixing non-recyclable plastics with recyclable plastics or trying to recycle plastics soiled by things like adhesives, chemicals, and food remnants that further impedes the recycling process. Both of these problems can lead to plastics being sent to the landfill rather than recycled.
Another complication is found within the products themselves. While some goods, like water bottles and other drink bottles, are frequently made from a single, common plastic (such as PETE) allowing them to be easily recycled, many others are designed to use a mix of plastics, which can cause serious issues in our current plastic recycling process. What’s more, many products are a mix of plastics and non-plastics such as wood or metal. Sadly, these products won’t even go near a recycling center.
That said, the process for the recycling of plastic has seen a massive improvement in recent years and can be broken down into six basic steps.
The plastic recycling process steps
The first step in the mechanical recycling process is the collection of post-consumer materials from homes, businesses, and institutions. This can be done by either local government or private companies, with the latter often a popular option for businesses.
Another option is taking plastics to communal collection points such as designated recycling bins or facilities. This may be as simple as a bottle bank on a street corner or as complex as a local waste site with large areas for various recyclable and non-recyclable municipal solid waste (MSW).
The next step in the plastic recycling process is sorting. There are several different types of plastic (see below), which need to be separated from each other by recyclers. Further to that, plastics might be sorted by other properties such as color, thickness, and use. This is done by machines at the recycling plant and is an important step to increase the efficiency of plants and avoid the contamination of end products.
Washing is a crucial step in the plastic recycling process since it removes some of the impurities that can impede the operation, or completely ruin a batch of recycled plastic. The impurities targeted in this step commonly include things such as product labels and adhesives as well as dirt and food residue. While plastic is often washed at this stage, it is important to remember that this doesn’t take away from the importance of ensuring plastics are as free from impurities as possible before disposal and collection.
The plastic is then fed into shredders, which break it down into much smaller pieces. These smaller pieces, unlike formed plastic products, can be processed in the next stages for reuse. Additionally, the resized plastic pieces can be used for other applications without further processing, such as an additive within asphalt or simply sold as a raw material.
Breaking down the plastic into smaller pieces also allows for any remaining impurities to be found. This is especially true of contaminants such as metal, which may not have been removed by washing but can be easily collected with a magnet at this stage.
Here, the plastic pieces are tested for their class and quality. First, they are segregated based on density, which is tested by floating the particles of plastic in a container of water. This is followed by a test for what is known as the “air classification”, which determines the thickness of the plastic pieces. It is done by placing the shredded plastic into a wind tunnel, with thinner pieces floating while larger/thicker pieces stay at the bottom.
This final plastic recycling process step is where the particles of shredded plastic are transformed into a usable product for manufactures. The shredded plastic is melted and crushed together to form pellets. It is worth noting that it is not always possible to compound all types, classification, and qualities of plastic at a single plant, so different grades of plastic are sometimes sent to other recycling facilities for this final step.
The different types of plastic
There are numerous types of plastic, and when trying to familiarize yourself with the plastic recycling process and avoid contamination, there are seven categories to remember. Chances are you have seen these symbols on products, and while they look like the “recycling symbol”, they actually indicate resin type, with some representing material that is not recyclable at all.
Number 1: PETE (or PET) – Polyethylene Terephthalate
One of the most common types of plastic you are likely to come across – this is the resin used for the manufacture of products such as food containers and plastic bottles for water or soft drinks. PETE (sometimes referred to as PET) is widely recycled.
Number 2: HDPE – High-Density Polyethylene
More rigid than PETE, this type of plastic is used in what will appear to be “sturdier” products such as detergent bottles, food and drink storage, bottle caps, some thicker shopping bags, and non-single-use plastic products like toys, helmets, and piping. Again, this type of plastic is widely recycled.
Number 3: PVC – Polyvinyl Chloride
PVC is considered one of the most versatile and common plastic types and is used for applications such as water and waste pipes (due to it being very resistant to chemical and biological damage), flooring, signage, furniture, and more. While there are some methods developed to recycle PVC, it is not common and rarely found in general plastic collections. This is in large part due to the toxicity of PVC when processed.
Number 4: LDPE – Low-Density Polyethylene
While not as strong as HDPE, this low-density plastic is highly resilient and used across a wide range of products such as containers, playground fixtures, and plastic trash bags. This resin-type is recyclable, but many products can be excluded (such as plastic bags) since they pose the risk of clogging machinery and are deemed not worthwhile to recycle.
Number 5: PP – Polypropylene
Commonly used in injection molding, this plastic can be found in products from bottle caps to surgical tools and clothing. While PP is recyclable, it is often rejected by processing centers due to the problems it poses, making the rate at which it is recycled far lower than other plastics.
Number 6: PS – Polystyrene
This plastic is frequently used as disposable plastic containers for food, as insulated containers, and in packaging materials. Despite its abundance, PS is rarely recycled due to it not being cost-effective (in its most common form, expanded polystyrene or styrofoam, is 95% air) and requires more energy than it saves to recycle.
Number 7: Other
This category encompasses everything else, which can include combinations of any of the previous six as well as other lesser-used plastics. This classification also includes non-petrochemical plastics such as new plastics, polymers, and bioplastics. As such, anything marked with a number 7 is generally not included in the plastic recycling process but may have other waste solutions.
As it stands today, the plastics recycling process faces many challenges, and unlike glass and aluminum, plastics are not infinitely recyclable, meaning that with each subsequent processing, the recycled material degrades and is a lesser quality than virgin materials.
However, don’t miss the broader perspective. Today’s recycling process for plastic is leagues ahead of what it was just a few decades ago, with recycling rates growing, and continuing to grow, significantly. Innovations like chemical recycling are occurring to keep more plastics in the recycling loop for longer. What’s more, there are a growing number of alternatives to plastic items hitting the market.
As individuals and businesses increasingly engage with the plastic recycling process, we are likely to see it continue to improve. Along with the shift towards new products and plastic alternatives, this signifies a slow but steady movement in the right direction.
The plastic recycling process is likely to receive a huge boost as we become more conscientious in the way we use resources and manufacture products. In fact, while waste management concepts such as the circular economy and zero waste are broadly aligned with a move away from single-use plastics, recycling will remain a part of the waste management process for the foreseeable future, allowing us to gradually move away from unnecessary plastics and increase the recyclability of those that remain necessary.