Expanded polystyrene (also known as EPS foam, polystyrene or Styrofoam) is a popular plastic for the packaging of food items, electric and electronic goods, furniture and more due to its excellent insulating and protective properties, as well as a being a production material in its own right for such items as disposable cups, trays, cutlery and cartons.
However useful the material may be, municipalities and organisations are facing a growing problem in disposing of polystyrene packaging and products. Being large and bulky, polystyrene takes up significant space in bins, meaning that they become full more quickly and therefore need to be emptied more often. Furthermore, polystyrene is lightweight compared to its volume, occupying lots of precious landfill space and liable to be blown around, causing a nuisance in the surrounding areas.
Although some companies have a recycling policy, most polystyrene still finds its way into landfill sites around the world. Conservative estimates indicate that in my area of particular interest, the Middle East, hundreds of thousands of tons of waste polystyrene is produced and sent to landfills each year. Its widespread use in Europe means that here, too, large amounts are being disposed of.
Glum on styrene
While it is estimated that EPS foam products account for less than 1% of the total weight of landfill materials, the fraction of landfill space it takes up is much higher. Furthermore, it is essentially non-biodegradable, taking hundreds – perhaps thousands – of years to decompose. Even after disposal in landfill, EPS can easily be carried by the wind to litter streets or pollute water bodies. To make things worse, when EPS foam breaks apart the small polystyrene components can be eaten by animals which may cause choking or intestinal blockage.
EPS foam also makes up a significant component of marine litter, and can be consumed by fish once it has broken down into small pieces in the ocean. When marine animals higher up the food chain eat the fish, the contaminant becomes ever more concentrated. This poses a potential health hazard for humans, given our spot at the top of the food chain: styrene, the plastic monomer used in manufacturing EPS, has been classified by the US National Institutes of Health (NIH) and the International Agency for Research on Cancer (IARC) as a possible human carcinogen. On top of these problems, styrene is derived from either petroleum or natural gas, both non-renewable resources which are rapidly being depleted, creating environmental sustainability problems for EPS.
The foam front
There seems to be a common misconception that polystyrene is non-recyclable. Being a thermoplastic, it can actually be melted and moulded into many different plastic items. At present, the recycling of polystyrene (or EPS foam) basically follows the following process:
- Segregation – EPS foam products are separated from other wastes and then sorted.
- Compaction – The segregated EPS foam products are fed to a compactor in order to reduce material volume. Some compactor systems have a compaction ratio of up to 50:1, meaning that volume can be reduced by up to 98%.
- Shredding – Larger pieces are shredded into flakes. Packaging “peanuts” – small EPS foam pieces used to cushion fragile items – normally skip this step and are fed directly to the pelletising machine.
- Melting/Extrusion – The flakes are forced through pelletising extruders where they are heated and melted before being allowed to cool in order to solidify. The resulting material can then be used, through reheating and melting, to produce clothes hangers, picture frames, DVD cases and numerous other plastic products.
Although the Alliance of Foam Packaging Recyclers have reported that the recycling rate for post-consumer and post-commercial EPS in the United States rose to 28% in 2010 from around 20% in 2008, this is still lower than for most solid wastes. According to USEPA, car batteries, steel cans and glass containers have recycling rates of 96.2%, 70.6% and 34.2% respectively. Because it is light weight and bulky, EPS foam recycling incurs storage and transport costs that are high in proportion to the eventual material yield of material for re-use or re-molding – in fact, polystyrene accounts for only 2% of the volume of uncompacted EPS foams. This provides little incentive for potential reprocessors to consider EPS recycling.
For reasons of hygiene, products that have been used to hold or store food must be thoroughly cleaned before processing, which further compounds the costs. For the same reasons, these products cannot be recycled back into food containers, but rather are used for producing non-food plastic products. The manufacture of food containers, therefore, always requires new polystyrene. At present, it is more economical to produce EPS foam products from primary material than to recycle it, and manufacturers would rather have the higher quality, fresh polystyrene than the recycled material.
The cost of transporting bulky polystyrene waste can discourage potential recyclers, but organisations that receive a large amount of EPS foam (especially in the way of packaging) can invest in a compactor that will reduce the volume of the material. Reprocessors will pay more for the compacted product, so the investment can be recovered relatively easily.
Technical breakthroughs have also been made in studies concerning EPS recycling, although most of these are still at the research or pilot stage. Research has found that the bacteria Pseudomonas putida is able to convert polystyrene into a more biodegradable plastic, and the process of polystyrene depolymerisation – converting polystyrene back to its styrene monomer – is also gaining ground.
Meanwhile, at the individual level, we can start reducing our polystyrene consumption by opting to use products that can be reused, taking such measures as bringing our own coffee mugs and food containers to stores that serve their food and drinks in EPS foam. A small change in our lifestyles can make a big difference for the environment, especially whilst the adoption of recycling remains in its infancy.
We are grateful to EcoMENA for the opportunity to reproduce this article, a version of which first appeared here. EcoMENA is a website focused on raising awareness of renewable energy, sustainability, waste management, environment protection, energy efficiency and resource conservation in the Middle East and North Africa (MENA) region.