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From Waste to Resource The Evolution of Recycling Techniques in a Circular Economy
Vinodhini Harish
20 Nov 2024
INTRODUCTION:
Plastic waste management remains a great concern across the globe, there are millions of tons of waste accumulated annually and the conventional recycling methods don’t suffice. There are plenty of challenges in the segment such as mixed plastic streams, contamination, and limited recyclability of certain materials. Therefore, the demand for innovative techniques has emerged to overcome these barriers. Some cutting-edge solutions such as molecular recycling, enzymatic processes, and advanced sorting technologies appear to be the most promising solutions to elevate the efficiency and quality of the recycling systems. In this article, we have highlighted these technologies for industries to adopt as the recycling landscape is rapidly evolving. Let’s begin.
REGIONAL GROWTH AND HOTSPOTS
Rising demand in the automotive and packaging industries has contributed the most to the recycled polymer market share in North America. North American market growth is expected to be higher than that in Europe and Asia Pacific.
Similarly, in the Middle East and Africa, the key growth factors for the growing demand are construction and food packaging applications. In this region, food packaging will be the primary application for recycled plastic and the rise in demand for lightweight yet sustainable food packaging shall expand the use of this polymer over conventional ones in the territory.
Latin America is all set to get a glimpse of considerable growth in the market during the forecast period. The increasing number of packaging product manufacturers, coupled with increased consumption of plastics due to the ban placed on single-use plastic products, have surged the recycled plastics market growth in the region.
The global recycled plastics market is valued at USD 69.4 billion in 2023 and is expected to reach USD 120 billion by 2030 with an 8.1% CAGR—the market.
SHIFTING PREFERENCES TOWARDS RECYCLED PLASTICS PACKAGING AND STRICT GOVERNMENT REGULATIONS:
According to National Geographic, only 9% of the world’s plastic waste is recycled and the rest ends up in landfills, and rivers or is dumped improperly. Thus, the plastic waste problem is growing into a big problem for governments across the globe.
Some countries like Germany, the UK, Italy and France have adopted and embraced a circular economy that focuses on reducing plastic waste by incorporating reusing the materials. Companies in Australia, Japan, and Mexico are producing water bottles that are made from recycled plastics. These efforts are helping the recycled plastics market to grow. Additionally, the COVID-19 pandemic has been a stronger push for adaptation of disposable packaging and the mass population is now focused on sustainability during the crisis, especially in food packaging and the practice continues.
Realization of the importance of preserving valuable natural resources and reducing the strain on ecosystems associated with extraction processes. Plastic waste is a major environmental concern and recycling helps in reducing the usage of virgin materials for plastic production. On the other hand, recycling practices require minimal energy compared to the production of plastics from raw materials. This leads to energy savings and, the reduction of greenhouse gases. Furthermore, most of the plastics utilized for various purposes are non-biodegradable and thus recycling is the only efficient solution to decrease the burden of polymers present in the environment.
The initiatives created by some countries like China, Europe, Brazil and India and restrictions for single-use plastics are boosting recycling promotions.
COMPARISON OF QUALITY-RICH RECYCLED PLASTICS IN THE MARKET:
Polyethylene Terephthalate (PET):
Polyethylene Terephthalate (PET) is transparent, lightweight and strong, and has high resistance to moisture and chemicals. Therefore, they are utilized for beverage bottles, food packaging and textiles. It possesses excellent recyclability and there is only minimal quality loss even after multiple cycles. Therefore, they are utilized to produce high-quality recycled PET that is used in bottles, fibres and packaging. However, recycling efficiency is affected due to labels, dyes and caps.
High-Density Polyethylene (HDPE):
High-density polyethylene is strong, rigid and resistant to chemicals, and it is opaque with excellent durability. Therefore they are utilized in milk jugs, detergent bottles, piping and plastic lumbers. They are capable of retaining their original strength and durability, therefore they are commonly used in non-food applications due to contamination concerns. Due to their nature and quality, they are used very rarely in food-grade applications, even if used they require appropriate and vigorous cleaning methods.
Polypropylene (PP):
Polypropylene is flexible, lightweight, and resistant to heat and chemicals. Therefore, they are well utilized in food packaging and containers, automotive parts and textiles. It suffers low recovery rates as recycling them is more complex compared to PET or HDPE. Therefore, they have lower market demand compared to PET and HDPE.
Low-Density polyethylene:
Low-density polyethylene possesses physical properties like soft, flexible, and transparent. They perform excellently well as moisture barriers however comparatively less durable than HDPE. Thus they are used in plastic bags, shrink wraps, and squeezable bottles. Recycling LDPE is quite complex due to thin-film contamination and poor recovery rates. Therefore recycled LDPE is often downgraded and utilized for non-critical applications such as bin liners, construction films and so on.
Other plastics:
Other plastics such as polystyrene, and PVC are rigid and flexible, however, they are utilized in specialized applications such as insulation, pipes and food containers.
Recycling is limited due to high contamination risks and lack of facilities. Therefore quality of recycled materials is poor, leading to limited reuse options.
ADVANCED RECYCLING TECHNIQUES:
Like every industry drawing towards efficient and sustainable solutions, the polymer recycling industry is also moving towards it while managing plastic waste. The advancements in technologies are creating revolutions and gaining significant attention from investors and industries. Some of the advanced recycling techniques include:
- Chemical recycling enhancements:
Researchers are developing methods to break down hard-to-recycle plastics like polyethylene and polypropylene using chemicals like hydrogen, and catalysts such as ruthenium. The processes create new monomers while minimizing byproducts, this makes them more energy-efficient and scalable for many industrial applications.
Breaking down of polyethylene and polypropylene is a difficult task and it is done by the chemical processing. The process begins with melting the plastic in a steel tank and then Gaseous hydrogen is introduced into the molten plastic.
The crucial step involves adding a powdered catalyst that contains metals such as ruthenium. The catalyst is selected carefully so that the researchers can increase the efficiency of the chemical reaction. Therefore, the formation of molecules with specific chain lengths is formed while minimizing byproducts such as methane or propane.
In the production process, the key challenge arises while stirring the molten plastic in the steel tank in a way to ensures the catalyst powder and hydrogen get mixed through. By carrying out experiments and computer simulations, the research team found that the plastic gets stirred in the best possible way when an impeller with blades parallel to the axis is used.
The efficiency is well-achieved when the blades are set parallel to the axis than a propeller with angled blades or a turbine-shaped stirrer. The results are favourable as it gets more even mixing and fewer flow vortices. The stirring speed is also crucial and should be close to 1000 revolutions per minute.
- Molecular recycling:
The molecular recycling approach involves processes like depolymerization and conversion. The depolymerization process involves breaking down plastics like PET into monomers that can be reused to produce virgin-quality materials. This innovative solution addresses the limitations of traditional mechanical recycling by targeting the chemical structure of plastics.
The process involves breaking down polymers into their fundamental building blocks and allowing for the production of materials with properties comparable to virgin plastics. Therefore it involves two primary processes in molecular recycling:
- Depolymerization and conversion.
Depolymerization involves breaking down polymer chains of plastics such as polyethylene terephthalate (PET) into monomers. These monomers are purified and then repolymerized into new plastics.
The process is found to be very effective for polyesters and nylons, as it enables closed-loop recycling, which is when the same material is reused repeatedly without the degradation of quality.
In this process, high-purity monomers are produced and are virtually indistinguishable from virgin materials. It helps in reducing the dependency on fossil fuels or raw materials. The process tackles contamination issues more effectively than mechanical recycling.
For example: Carbiosuses enzymatic depolymerization for PET and it employs enzymes to selectively break down the polymers at mild temperatures.
The demand for high-quality recycled plastics in the packaging, textiles and automotive industries is driving the investment in molecular recycling technologies. These methods have expanded the recycling possibilities for the polymers that were previously considered non-recyclable such as multi-layer and contaminated plastics.
- Biological solutions in plastic recycling:
The biological solutions in plastic recycling are a groundbreaking approach to recycling that leverages enzymes and microorganisms to break down polymers like PET into their fundamental components. This approach is considered the most efficient and eco-friendly alternative to traditional recycling techniques.
The technique involves specific enzymes that are often derived from bacteria or fungi that are used to catalyze the breakdown of plastic polymers into their monomers. For example, PET can be decomposed into terephthalic acid (TPA) and ethylene glycol (EG) which can be repurposed to create new plastic products.
A leader in the field, Carbios, has developed enzymes capable of degrading 90% of PET waste within hours under optimized conditions. The process operates at milder temperatures which significantly reduces energy consumption compared to conventional chemical recycling.
Enzymatic recycling is well-suited for PET used for bottles, textiles, food packing and other critical applications. This approach efficiently handles coloured and complex plastic waste that is challenging for mechanical recycling.
The approach is well received in the industry as it uses only biodegradable catalysts and eliminates the need for harsh chemicals or extreme conditions. Likewise, the process enables the recovery of monomers with the highest rate of purity and facilitates the production of recycled materials with properties that are equivale to virgin plastics. The approach requires less energy and makes it more sustainable.
Biological solutions are poised to revolutionize plastic recycling as they address the shortcomings of traditional methods. With continued advancements, the enzymatic recycling process has the potential to significantly reduce plastic waste, conserve resources and foster a circular economy.
- Advanced sorting technologies:
Advanced sorting technologies include Near-infrared (NIR) spectroscopy and AI-driven robotic systems, which transform the efficiency and accuracy of the plastic recycling processes. The innovations address one of the critical bottlenecks: effectively separating various plastic types to reduce contamination and improve the quality of recycled materials.
NIR spectroscopy identifies the materials that are based on their unique spectral signatures in the near-infrared wavelength range. When the plastics pass through the NIR sensors, they get detected by the reflected light and the polymer types such as PET, HDPE, and PP are determined.
Sorting plastics by type and colour even when they are mixed or contaminated is done effectively. Especially distinguishing between food-grade and non-food-grade plastics enables the researchers to segregate them with precision for precise recycling streams.
NIR systems are capable of processing large volumes of waste in real time. It is non-destructive and thereby doesn’t alter the materials and preserves the integrity for recycling. It is also effective for a wide range of polymer types and combinations.
However, it faces the challenge when it involves black plastics and multi-material items that may not reflect NIR light effectively. The expansion of NIR technology includes the new systems from TOMRA sorting solutions that incorporate NIR and UV-VIS sensors to detect even complex and opaque plastics. In recent times recent advancements include hyperspectral imaging that addresses the difficulty of sorting the black plastics which is considered as a persistent challenge for NIR technology.
CLOSING THOUGHTS:
The recycling techniques are getting better and reshaping the way the world tackles plastic waste, thereby turning the challenges into opportunities for sustainability. The advancements are enhancing efficiency, reducing contamination, and producing high-quality recycled polymers, hence paving the way for a more circular and environmentally friendly economy. Industries, governments and consumers work together to embrace the technologies and the future of recycling looks more promising than ever.
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