While it takes hundreds of years to decompose and if it decomposes to an extent, polystyrene foam is effectively not biodegradable. But by recycling and reprocessing this material, we can significantly reduce environmental pollution and the overall carbon footprint by reducing volume of waste sent to landfills.
Scientific researches have introduced bioplastics and biodegradable plastics as an alternate to fossil based plastics to mitigate the environmental effects of conventional plastic products. Please read here.
Types of Polystyrene
Currently there are four types of polystyrene being used in the market.
General Purpose Polystyrene (GPPS)
This is a thermoplastic polymer which can be softened through heating, moulded into shape and then left to cool and harden. Its ability to be rigid makes it a popular choice for polystyrene packaging for food, cosmetic packaging, medical devices and toys.
High Impact Polystyrene (HIPS)
High-impact polystyrene is a thermoplastic polymer made from a combination of polystyrene and rubber. By including rubber, we get tough and impact-resistant plastic widely used in packaging, car parts, toys and kitchen appliances.
Extruded Polystyrene (XPS)
Polystyrene granules mixed with special additives and foaming agents at a specific temperature and pressure produce expanded polystyrene. Due to its high thermal and moisture resistance, XPS is most commonly used for insulating buildings.
Expanded Polystyrene (EPS)
EPS is created from solid beads of polystyrene containing a small amount of expansion gas. The beads expand when heated and can be molded to form large foam blocks and customized into different shapes. EPS is composed of 98% air, being incredibly light and has low thermal conductivity. While it is also tough, it is a popular choice for packaging.
From protecting food to keeping products cool and delivering new appliances, expanded polystyrene provides good packaging solutions.
Health Impacts of Polystyrene Wastes
Most chemical recycling facilities, more technically called “plastics-to-fuel” facilities do not make reusable material, from more specifically polystyrene, for new products but instead convert petroleum based foam into fuel. This fuel is typically combusted, contributing to climate pollution and poor air quality.
Although, the cost of production of expanded polystyrene foam is lower but their human and environmental impact like other plastics is very high. Polystyrene is not biodegrade and so is hazardous to wildlife for longer periods as well.
By breaking down into smaller and smaller pieces, plastic foam enters the natural environment and animals often mistake it for food leaving impacts to their life. Because polystyrene foam floats, it can travel all across the world through waterways and harm animals all over the globe.
More Dangerous Impacts of Polystyrene Waste
Polystyrene foam also affects the health of people because of its chemical composition. Studies have shown the possibility of presence of human carcinogen in polystyrene, having potential to leach into food and drinks causing cancer. Breathing in polystyrene production can lead to permanent nervous system damage.
However, finding ways to reuse waste polystyrene is essential to prevent it from causing environmental harm.
How to Recycle Polystyrene
Polystyrene is mostly chemically recycled using heat, but repeated heat treatments degrade the material, causing it to lose strength and flexibility. This process requires specialized facilities, therefore, most recycling plants do not accept polystyrene, and because of its volume and high transport costs, a very little polystyrene is recycled at present.
The process of chemical recycling, called Pyrolysis, involves exposing a material to very high temperatures (more than 450°C) in an oxygen-free chamber where the polystyrene breaks down into parts known as monomers, which can then be purified and subsequently reconstituted into virgin polystyrene.
The process involves a pyrolysis reactor, heat exchanger, and a pair of distillation columns, which separate out the parts of polystyrene into 'monomer grade' styrene, the part which can be reformed into polystyrene and 'light' and 'heavy' petroleum-like by-products, which can be reused in other ways.
This process normally generates 60% yield, meaning that if 1kg of waste polystyrene is processed, a 600 grams of pure monomer grade styrene would be left available to generate new polystyrene.
This process also highlights the environmental benefits, noting that the cost to decrease the amount of carbon emissions through the implementation of this process is approximately $1.5 per ton of CO2 which is relatively lower than many other recycling processes.
Another method called polystyrene pelleting process involves several steps to convert polystyrene into usable pallets. Initially polystyrene waste is cleaned and shredded into smaller pieces for easy processing. The shredded pieces are melted at a desired temperature converting it to thick foam substance.
The melted EPS is then poured into molds designed for pallets by using injection molding or extrusion methods. The pallets are then cooled and removed from the molds can then be reused or recycled for making recycled and even more stronger polystyrene products.
Another efficient electrochemical process, called Iron-based electrocatalysis, operated using solar energy, decomposes polystyrene while generating eco-friendly hydrogen. This new electrocatalytic process, which can easily be scaled to an industrial level, combines efficient plastic recycling with decentralized, green hydrogen production.
Limitations of Recycling Polystyrene
According to reports, the recycling rate for post-consumer and post-commercial polystyrene in the United States is around 29% in 2022 and is expected to rise upto 50% by 2030. This value is still quite low as compared to many other solid wastes.
The major reason building this gap is that polystyrene takes up more storage space and costs more to transport and yet yields only a small amount of polystyrene for re-use or remolding. Polystyrene recycling accounts for only 2% of the volume of uncompacted EPS foams. This provides little incentive for recyclers to consider EPS recycling.
On the other hand, products that have been used to hold or store food needs to be thoroughly cleaned for hygienic reasons, which adds the cost as well. For the same reasons, these products are not recycled to produce the same food containers but rather are used for non-food plastic products.
The manufacture of food containers, therefore, always prefer new polystyrene. Therefore, currently it is more economical for manufacturers to produce new EPS foam products than to recycle it.
Benefits of Polystyrene Recycling
Recycling polystyrene offers several significant benefits:
Environmental Impact: Recycling polystyrene reduces the volume of waste sent to landfills, where it can take hundreds of years to decompose. By reprocessing this material, we can significantly reduce environmental pollution and the overall carbon footprint.
Economic Value: Improvements in recycling technologies can make it economically viable to recycle polystyrene. The production of high-value chemicals from recycled polystyrene can provide new revenue streams and reduce the dependency on virgin materials.
Sustainability and Circular Economy: Establishing a circular economy for polystyrene not only helps in managing waste more effectively but also ensures a sustainable supply of materials for the future.
However scientists suggest a massive awareness campaigns to change consumer habits to minimize use of polystyrene products specially used in food related uses.
Similarly in United States, The Virginia General Assembly passed legislation in 2021 that will ban the use of Expanded Polystyrene (EPS) by food vendors by 2028. The legislation also discourages the sale and use of EPS products and the encourages the promotion of alternatives to EPS.
Very informative and helpful in understanding the importance of keeping environment clean and use of resources
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