Plastic has become essential to modern life. It’s durable and offers a level of versatility that makes it indispensable across multiple industries. However, with this type of convenience comes at least some costs. In the case of plastics, it’s the environmental impact of plastic disposal that weighs heavily on the industry. Recycling plastic is critical to reducing plastic pollution, as well as conserving resources and reducing the overall environmental impacts. Understanding the lifecycle of recycled plastics is the first key step to appreciating how the plastic industry can promote improved sustainability.
Six Steps of the Plastic Recycling Process
The plastic recycling process can be generally broken down into six major steps. Each of these steps is important in the efficient, safe, and sustainable recycling process.
Step 1: Collection and Sorting
The very first step in the life cycle of recycled plastics is the collection, followed by sorting. In this step, the plastic industry relies on individuals, homes, businesses, and industrial facilities, to take initiative in participating in recycling programs. In the case of businesses and industrial plants, this may also include following specified regulations relating to the handling of used plastics.
Without widespread participation, plastic ends up being disposed of and becoming a burden on landfills and the environment. Most communities have some level of a recycling program in place, whether it is a regular pick-up service, such as curbside recycling, or drop-off centers. Recycling initiatives, such as paid-deposit schemes on plastic beverage bottles are another example of community recycling programs, although these are generally adopted on a state level.
Once plastics have been collected, they go through a sorting process. This is a critical step, ensuring that only the right materials are sent off for recycling. Some facilities still use manual sorting, but advanced sorting technologies are quickly becoming the norm. Density-based separation is one example of a sorting technique used.
With this, the density of recycled materials is measured through a fluid density check, vibration screens, and other mechanisms. With this process, materials that aren’t plastics are recognized and swept away. New technology, such as AI optic separation is also streamlining the process by immediately identifying different types of plastic and non-plastic materials for separation.
The separation stage is important because different types of plastics each feature unique chemical properties. Because of this, not all plastics are compatible for being combined during processing. This is why resin identification codes, which are numbers located in a small triangle of arrows, are used on plastics to distinguish them by type.
Step 2: Washing and Shredding
After collection and sorting, the next important step in the recycling process is cleaning and shredding. During cleaning, contaminants, like adhesives, dirt, and food residue are washed from the plastics. The value of this is that clean plastics create higher-quality recycled materials. Every contaminant that is left on plastics poses a threat of compromising the recycling process.
After cleaning, plastics are then shredded, or broken down into smaller parts. This could be in the form of actual shreds, or even smaller particles such as small flakes or pellets. This step simplifies the handling processes that are involved in preparing recycled plastics for the next stage of production.
From a production standpoint, shredding plastics also increases the overall surface area, which makes it easier to remove any residual contaminants during future processing.
Step 3: How Different Types of Plastics are Processed
At this point, recycled plastics begin processing. This is where it’s important to differentiate between the various types of plastics, their characteristics, and required processes.
#1. Polyethylene Terephthalate (PETE or PET)
This type of plastic is most commonly used in the production of beverage bottles and food packaging. It is currently one of the most frequently recycled plastics. PETE plastics go through the standard sorting, cleaning, and shredding processes, where they are often recycled into new bottles and food packing. PET plastics are also sometimes recycled into fibers for clothing and carpets. Of all plastics, PET plastics require less energy resources in the recycling process.
PET may be melted to create new plastic resin. They may also go through a process of depolymerization. This is a chemical process that takes each polymer chain of the plastic and breaks it apart into smaller molecules.
# 2. High-Density Polyethylene (HDPE)
This is the plastic most often used in the production of milk jugs, detergent bottles, and plastic bags. It’s a highly durable plastic and has the advantage of being easy to recycle. Most curbside and drop-off recycling centers accept HDPE.
The process of recycling HDPE is relatively straightforward. After the initial stages, HDPE is typically melted and reformed. In addition to being used to make new bottles, HDPE is often used in making pipes and plastic lumber.
#3, 4, 5 & 6 (PP, PS, LDPE, and PVC)
These are important plastics but less common than PET and HDPE. Polypropylene (PP) is most frequently used in the production of food service containers, such as yogurt containers, and also straws. PP may also be used in the production of automotive parts. The challenge with PP is that it currently has a relatively low market demand, which creates some barriers to recycling.
Polystyrene (PS) is commonly known as Styrofoam. Today, PS is most commonly used in making disposable cups or food containers. Overall, PS has a low recycling weight. It offers little in durability, meaning it often is broken or carried away or otherwise damaged and disposed of, rarely being recycled. Due to the nature of PS, it can also make it more difficult to sanitize. There are certain facilities that process PS recycling, but the process mostly involves compacting PS into bricks where it can later be used for insulation.
Grocery bags and plastic food wraps are made of low-density polyethylene (LDPE). While historically difficult to recycle, new efforts are being put into LDPE recycling efforts and processes.
Last is PVC, which is used in products such as pipes and vinyl flooring. PVS produces toxic byproducts that are released during recycling, which creates both a health and environmental risk. Current advancements are being considered to help mitigate these risks.
Step 4: Melting and Repurposing
Now that we have a general idea of the different types of plastics, we can move on to the stage of melting and repurposing. This is the process of taking cleaned and shredded plastics and forming them into new products. This can happen through processes such as extrusion, where melted plastics are forced into a die to create uniform shapes, such as sheets of plastic or piping. There is also the process of injection molding, where melted material is injected into molds. This is the common method for creating recycled goods such as toys or plastic containers.
Step 5: Quality Control
Recycled plastics are required to undergo stick quality testing to ensure their safety and usability. During quality control, a number of characteristics are measured. This includes the overall strength and function, along with purity and chemical stability.
Step 6: Distribution
Upon certification, newly recycled plastics can then be distributed to manufacturers, who then take these plastics and make a wide range of recycled products.
Benefits of Plastic Recycling
There are many benefits to recycling plastics, both for environmental impact and economic value. For example, recycling plastic significantly reduces the need for new plastic production. This, in turn, cuts down on fossil fuel consumption and greenhouse gas emissions. The recycling of plastics is also critical to diverting plastic waste from landfills and the earth’s water sources. Recycling helps to reduce overall pollution and the extremely damaging effects on wildlife.
For manufacturers, the use of recycled plastics can have significant economic value. Recycled materials are valuable raw materials that come at a lower cost than new plastics. This saves manufacturers money and also contributes to a circular economy. In addition, there are also energy savings to be considered. Using recycled plastic uses less energy resources than new plastics from raw materials, which saves manufacturers additional money.
Challenges in the Plastic Recycling Process
Of course, there are some challenges with the process of recycling plastic. One of the most significant is the risk of contamination. This isn’t just about contaminants left on the plastic, but rather different types of plastics inadvertently being combined in the recycling process. This can lead to poorer quality of recycled materials.
There is also limited market demand for certain types of recycled plastics. This brings into question the economic viability of low-demand plastic recycling programs. We’re also seeing more complex plastic products. These are plastic products made with mixed materials or multiple players of plastic, which makes them more challenging and costly to process.
Looking Forward: The Importance of Plastic Recycling
The lifecycle of recycled plastic shows us the importance of proper waste management and recycling processes in preserving both the environment and resources. While some plastic recycling processes face hurdles, others have been fine-tuned for optimal efficiency and output. There is ongoing investment in recycling technology that is driving the future of the industry. By understanding how different types of plastics are recycled, we can make better-informed choices and help contribute to a more sustainable future.
