Chloe Zhang
Plastic is an essential part of many products we use daily, and it can help us cut carbon emissions. However, it is not always easy to recycle. The process of recycling plastic varies depending on the type of plastic and the method of recycling. Mechanical recycling involves washing, grinding, and melting plastic, while chemical recycling breaks down plastic into monomers to form new polymers. The resin type and colour of plastic also play a role in determining its recyclability. While many commonly used plastics can theoretically be recycled, the reality is that only a small percentage of plastics are actually recycled. This is due to a range of economical, environmental, and technical factors. Additionally, the infrastructure for collecting, recycling, and reusing plastic waste is not fully developed worldwide.
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What You'll Learn
Plastic resin codes and their recyclability
The plastic resin codes, also known as the Resin Identification Code (RIC), are a set of symbols that appear on plastic products to identify the type of plastic resin used to make the product. They were first introduced in 1988 by the US Society of the Plastics Industry (SPI) as the "Voluntary Plastic Container Coding System". The purpose of the original SPI code was to "provide a consistent national system to facilitate the recycling of post-consumer plastics". The RIC system has since been adopted by many communities implementing recycling programs to assist in sorting plastics. The numbers attributed to plastics range from 1 to 7, with 7 being "other". The lower the resin code, the more likely the plastic type is to be easily recyclable.
The RIC system has undergone some changes over the years. In 2008, ASTM International took over the administration of the RIC system and issued a new standard, ASTM D7611, which changed the graphic marking symbol from the "chasing arrows" of the Recycling Symbol to a solid triangle. The RIC symbols are often mistaken for the Recycling Symbol due to their resemblance. The Recycling Symbol, designed in 1970, was meant to inform people that a product was recyclable. However, the RIC does not address the recyclability of the product, and consumers may assume that products with similar symbols are recyclable, leading to confusion.
- PET or PETE (polyethylene terephthalate): This plastic is commonly used for single-use bottled beverages as it is inexpensive, lightweight, and easy to recycle. It is widely accepted for recycling in most areas.
- HDPE (high-density polyethylene): HDPE is another widely recycled plastic worldwide and is known for its durability and resistance to most solvents. It is commonly used for cleaning or personal care products and milk bottles. It can be recycled multiple times, making it valuable.
- LDPE (low-density polyethylene): LDPE is not often recycled through curbside programs, but some communities may accept it. Plastic shopping bags made from LDPE can often be returned to stores for recycling.
- PVC (polyvinyl chloride): PVC is a durable plastic that is resistant to sunlight, water, and other harsh conditions. It is commonly used for plumbing pipes, window frames, and other construction materials. Its recyclability may vary depending on the area.
- #7 plastics: This category includes polycarbonate, a clear, hard plastic that has raised concerns due to its potential hormone-disrupting properties. It is advisable to avoid using plastic containers marked with #7, especially when microwaving food or beverages. #7 also includes PLA (polylactic acid), a commercially compostable plastic made from natural materials such as corn starch, sugarcane, or tapioca.
It is important to note that the recyclability of plastic products is not solely determined by the resin code. Other factors, such as colour, can also impact recyclability. Clear or natural plastic is generally the most valuable and easiest to recycle. Additionally, the availability of recycling programs and the acceptance of specific plastic resins can vary depending on the region. It is always a good idea to check with local recycling facilities or guidelines to understand what types of plastics they can accept.
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Mechanical recycling and its limitations
Mechanical recycling is a multi-stage process of sorting, cleaning, shredding, and melting waste plastic into tiny particles to be reused. It is commonly used to recycle PE and HDPE, with typical end products including plastic bottles, carrier bags, and cosmetics bottles. This method is cheap, large-scale, solvent-free, and applicable to many polymers.
However, mechanical recycling has several limitations. Firstly, it changes the molecular structure of the plastic, reducing its material integrity and overall quality. This degradation of the polymeric chain occurs each time the plastic is melted and processed, limiting the number of times the plastic can be recycled. As a result, recycled plastic often needs to be mixed with virgin plastic to create new products. Additionally, mechanical recycling does not remove the toxins used in the original production of the plastic.
Another challenge is the sorting and separation of plastics, which is necessary for effective recycling. It is virtually impossible to separate plastics entirely, so the recycled plastic may have slightly altered properties compared to the original. Thin bags or films, for example, can clog machines if not separated properly, and therefore may not be accepted in kerbside collections.
Furthermore, mechanical recycling, like all recycling processes, releases emissions and is known to be a heavy polluter. While recycling can conserve limited natural resources and energy by reducing the need for raw materials, the process itself requires a significant amount of energy and produces greenhouse gas emissions.
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Chemical recycling and its benefits
Plastic is incredibly hard to recycle. It can take up to 1000 years for some types of plastic to biodegrade, and during this time, it takes up landfill space and pollutes the environment. Plastic production relies on non-renewable resources, and the process requires a lot of energy and produces greenhouse gas emissions. While mechanical recycling is the most common form of recycling plastic, chemical recycling is another method that can be used to address the growing problem of plastic waste.
Chemical recycling, also known as feedstock recycling, is an advanced form of recycling technology that breaks down plastics into monomers to form new polymers that can be reused. This process can be used on contaminated plastics and does not require additional space for storing plastic waste, reducing the area of existing landfills. It can also be used to process plastic waste that is already partially decomposed, such as rubbish that contaminates oceans, seas, lakes, and rivers.
There are three primary types of chemical recycling: pyrolysis, gasification, and solvolysis. Pyrolysis involves heating recycled plastic without oxygen in a reactor, which breaks apart the molecules. This process produces a naphtha-like liquid called pyrolysis oil, gases that can be circulated to create heat, and waxes that can be sold. Solvolysis is being used by PureCycle Technologies to improve the circularity of polypropylene. The output from chemical recycling can be used in food contact and other critical applications, and it can also produce high-quality raw materials that decrease the demand for fossil fuels and other natural resources.
Chemical recycling has the potential to reduce the amount of plastic that ends up in landfills and the release of harmful chemicals into the environment. It can also contribute to reducing the carbon footprint left by humans and improving the natural environment. As recycling technologies continue to advance, it is important to explore alternatives to landfill and view plastic waste as a valuable resource that can be reused and recycled.
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The environmental impact of plastic production
Plastic is everywhere, from food packaging to healthcare, construction materials, furniture, and textiles. However, it is also detrimental to the environment. The production, use, and disposal of plastics have significant health and environmental impacts at every stage of their life cycle.
Firstly, plastic is derived from fossil fuels, including natural gas and crude oil, and contains chemicals that are known endocrine disruptors, threatening human health. The extraction and production of these fossil fuels have severe environmental and health risks, including damage to sensory organs, effects on the respiratory, nervous, and gastrointestinal systems, and the impairment of organs such as the liver and brain. Additionally, the infrastructure required to transport raw materials, such as pipelines, can release hundreds of toxins during pumping or piping, further contributing to environmental pollution.
Secondly, the manufacturing process of plastics involves incorporating additives such as colorants, lubricants, plasticizers, and flame retardants. These additives, along with other chemicals present in plastic products, can leach into the surrounding environment, contaminating air, water, and food sources. Microplastics, which are tiny pieces of broken-down plastic, are now found practically everywhere on Earth, including in the air, waterways, agricultural soils, rivers, and oceans. The ingestion of these microplastics by animals and humans can lead to severe health issues, including chronic inflammation, cardiovascular diseases, diabetes, neurodegenerative diseases, and cancer.
Thirdly, the disposal of plastics poses a significant challenge. Plastic does not easily biodegrade, with some types taking between 500-1000 years to break down naturally. This means that discarded plastic items remain in the environment for generations, polluting ecosystems and contributing to the growing waste management issue. While recycling is an option, only about 9% of all the plastic ever produced has been recycled, with the rest either still in use or disposed of in landfills or the environment, including the oceans. The low recycling rate is partly due to economic and technical reasons, as well as the varying recyclability of different plastic types. Some plastics, such as thermoset plastics, contain irreversible chemical bonds and cannot be recycled, while others, like thin bags or films, can clog recycling machines if not separated properly.
Finally, the production and use of plastics contribute to climate change. The plastic industry relies on non-renewable resources and energy-intensive processes, resulting in greenhouse gas emissions. By 2050, emissions from plastic production could reach concerning levels, contributing significantly to global warming.
To reduce the environmental impact of plastic production, it is essential to minimize the use of single-use plastics, improve recycling technologies and infrastructure, and explore sustainable alternatives, such as bioplastics produced from renewable feedstocks or recycled materials.
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The future of bioplastics
The world has produced over nine billion tons of plastic since the 1950s, with 165 million tons polluting our oceans and almost 9 million more tons entering the oceans each year. The plastic industry depends on non-renewable resources, with more than 90% of global plastic production consisting of primary plastics made from petroleum products. This reliance requires a huge amount of energy and produces greenhouse gas emissions.
Bioplastics, which are typically plastics manufactured from bio-based polymers, could be the solution to this plastic pollution. They have a reduced use of fossil fuel resources, a smaller carbon footprint, and faster decomposition. They are also less toxic and do not contain bisphenol A (BPA), a hormone disruptor often found in traditional plastics.
However, bioplastics are not without their challenges. They are not yet widely recycled, and if they were to scale up significantly, they could create pressure on agricultural lands and water supplies. Additionally, there is a lack of consumer awareness and acceptance due to misunderstandings and misconceptions about their use.
Bioplastics have the potential to contribute to more sustainable commercial plastic life cycles as part of a circular economy, where virgin polymers are made from renewable or recycled raw materials. With continued research and development, bioplastics can play a significant role in reducing plastic pollution and creating a more sustainable future.
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Frequently asked questions
The colour of plastic does not determine its recyclability. Instead, the resin type is the deciding factor. Plastics are sorted according to their resin type, either manually or using mechanised automated processes, or even by colour. The lower the resin code, the more likely the plastic type is to be easily recyclable.
Incredibly hard-to-recycle plastics include crisp packets, salad bags, plastic wrap, bioplastics, composite plastic, plastic-coated wrapping paper, and polycarbonate.
Plastic recycling is difficult due to the lack of a complete infrastructure for collecting, recycling, and reusing plastic waste. There are also limits to the kinds of plastic that can be recycled with traditional mechanical methods.
Recycling plastic can conserve limited natural resources and energy. It can also help cut carbon emissions.
