Expanded polystyrene

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Expanded polystyrene

Expanded Polystyrene Resin Code.png

Documentation Status: Draft

Description Foamed polymer
Material Class Hard Plastic
Constituent monomers Polystyrene, styrene
Similar materials
Common Sources E-commerce packaging, Food containers, construction insulation
Cost new
Value unprocessed
Value processed
Processing Tools Shredders, Mealworms
Recycled Products Fertiliser, EPS bricks, Beanbags, Insulation, Molds, DIY evaporative cooler
Closest source
Nearest Processer

Expanded Polystyrene is a material that consists of hollow spherical balls of Polystyrene. EPS, also known colloquially by the brandname Styrofoam. It is generally not recyclable through domestic kerbside recycling schemes. It is most commonly used in food packaging, E-commerce, and as an insulating material. EPS is comprised of up to 98% air by volume.[1] In Australia about 45,000 tonnes of EPS is created and consumed per year. Approximately 40% of that total is produced for single-use or short term packaging.[2]

The Australian Packaging Covenant report that only 29.7% of EPS is recycled domestically.[3] This is especially problematic as Polystyrene takes hundreds of years to biodegrade, and EPS waste constitutes a large amount of landfill volume. There are however a large number of methods documented for repurposing and recycling EPS at home or in the community.


EPS can be torn, maintains it's shape when flexed, except when cracked under force, is very lightweight, and it is usually clearly visible that it is composed of small balls melted together. Some will be familiar with these balls from the interior of beanbags. Most EPS used in packaging is white, with a minority in other colours. It is rarely marked, but when it is, it often has resin identifier 2, for Polystyrene. This is despite the fact that EPS and solid PS may go into different recycling streams.


In some cases, people may mistake Polyurethane foam for EPS. This is a different base polymer, produced with open cells. That is; unlike EPS which is made up of closed balls, there is holes throughout this foam. The material can also be flexed far more than EPS, and does not crack under stress.


While Polystyrene is not being effectively recycled in the Australian domestic context, it is preferable to reduce the use of it in the community. Encouraging the use of reusable or more readily recyclable containers at takeaway restaurants, and the reuse of other forms of packaging in E-commerce should help reduce the burden on current recycling systems. Woolcool is an alternative insulative packaging material that according to Planet Ark is sustainable and suitable for tasks where EPS is used to keep products cool.[4]

A chunk of EPS


EPS food containers are not well suited to reuse compared to other plastics as they are nearly impossible to clean, and often deform after a single use. Some building insulation may be possible to reuse, and packaging for electronics can be kept in order to safely transport those electronics again.


As EPS is a thermoplastic, it may be possible to repair products that utilise it, by heating it and joining new pieces to the existing structure. Plastic welding may also be of use, as well as application of non-expanded Polystyrene coatings, as these should bond well to EPS.


Some EPS products are suitable for repurposing in a variety of ways. Containers that can cover something completely can be used to insulate it from the environment. Packaging like this could be used as an ice box or esky, or even in the construction of a DIY evaporative cooler.


While the fact that Polystyrene does not degrade rapidly in the environment means that certain recycling processes are impossible, it also means that products made with recovered EPS will not have degraded polymers, unlike with some other plastic recycling processes.[5]

Toxic contaminants[edit]

A major problem with the use of Expanded Polystyrene is the historical use of toxic fire retardants such as Hexachlorobenzene and Hexabromocyclododecane, now banned under the Stockholm Convention. These materials were prevalent in EPS used in insulating building materials, and as a result of recycling processes ended up in food packaging[6][7]. While the Australian government is still in the process of implementing this ban[8], the only viable pipeline for recycling Expanded Polystyrene is in to building materials, instead of food packaging unless it can be verified that the material was produced from sources which comply with the convention.

Mold making[edit]

A common use for EPS in both DIY[9] and industrial processes, is as a Lost-foam mold for various secondary manufacturing processes such as forging. The material is easy to work with, due to it's light weight, and the fact that it melts easily either with applied heat, or solvents.

At home or in your community[edit]


Day 2 of the Mealworm colony.

In 2015, Stanford University, along with a team of Chinese researchers announced the surprising discovery that mealworms not only eat EPS, but that they produce viable fertiliser in the process and remain healthy throughout.[10] Further research conducted by the same team determined that the ideal amount of EPS, as food, measured by weight is around 10% of the mealworm's diet, and that mealworms fed a diet of EPS consume it at a faster rate in subsequent generations.[11] The recycling experiments at Recycling research at home, undertaken in order to prepare for the publishing of Recyclopaedia confirmed that these findings were easy to recreate in a domestic setting with minimal effort. Where HBCD exists in the EPS the mealworms eat, the worms excrete the chemicals within 48 hours of eating it, making the mealworm a non-toxic food for agricultural animals and pets such as chickens and lizards.[12]

EPS Bricks[edit]

A variety of tutorials exist online showing a variety of methods for producing lightweight, sturdy bricks out of EPS and concrete. These methods likely result in a product that cannot be recycled easily when it's no longer needed. These bricks should be suitable for insulation. The following links are to unverified methods:

  1. https://www.youtube.com/watch?v=pJ-5nFkOJAU
  2. https://www.youtube.com/watch?v=e4n1-25z1mM
  3. https://www.instructables.com/id/Styrofoam-Concrete/

Precious Plastics[edit]

As part of the development of the v4 tools for the Open Source Precious Plastics project, a substantial amount of research into processing EPS was undertaken, documented in this thread. Key points from this discussion:

  1. Polystyrene degrades when exposed to prolonged heat.
  2. Melting EPS into solid PS may be too energy intensive to be justified.
  3. Compressing EPS to a denser foam under heat is possible.
  4. Cutting EPS into new shapes using a hot wire cutter is easy.

Industrial / government processes[edit]

Various industrial processes for recycling EPS

Many logistics chains compact EPS to improve the efficiency of logistics prior to the main recycling process. Cold compaction can reduce volume of EPS by up to 98%. Thermal densification can reduce volumes even further, but can result in the release of noxious vapours.[13] Recycling uncompacted EPS in industrial processes seems to either be via specialised shredding equipment, such as those sold by EnStyro or via it's use as a fuel source. There is a high probability of EPS releasing toxic byproducts when burned.

Cleanaway offers a commercial recycling program for businesses who produce large amounts of EPS waste[14].

Recycling domestic EPS waste with government[edit]

Depending on the local government area in Australia, council run waste transfer stations or tips may charge fees for disposing of EPS. For example, Stonnington City charges fees and does not specify that the material is recycled[15], while the neighbouring council of Glen Eira accepts clean, white EPS for free, with limits on quantity[16]. Glen Eira's Monash facility achieves the required efficiency to recycle EPS without charging fees via the utilisation of a extrusion machine that produces briquettes on site.[17] In Mount Gambier, the council is equipped with tooling which allows them to remove the air from EPS, allowing people like local entrepreneur Brad Scott to produce parts out of non-expanded Polystyrene through molding techniques.[18]

Methods in development[edit]

  • Conversion of plastics, including EPS, into methane to be used as an energy source has been the subject of a number of research projects.[19]
  • A method to produce water filters out of EPS has been developed by Valerii Orlov, Serhii Martynov & Serhii Kunytskiy[20]
  • Fraunhofer claims to have proprietary technology ready to break down various plastics including PS, while also removing contaminants.[21]

External links[edit]

Video about mealworms eating EPS

  1. https://recyclingnearyou.com.au/polystyrene/
  2. https://mwrrg.vic.gov.au/waste/recycling/polystyrene/
  3. https://www.packagingcovenant.org.au/documents/item/1070
  4. https://planetark.org/ourpartners/planetprotector.cfm
  5. https://www.foamex.com.au/about-us/news/entry/polystyrene-recycling-what-you-can-do
  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6104644/
  7. https://www.researchgate.net/publication/323205754_Hexabromocyclododecane_in_polystyrene_packaging_A_downside_of_recycling
  8. https://www.environment.gov.au/protection/chemicals-management/pops
  9. https://www.ehow.com/how_10057651_make-polystyrene-molds.html
  10. https://news.stanford.edu/pr/2015/pr-worms-digest-plastics-092915.html
  11. https://www.sciencedirect.com/science/article/pii/S0045653517317022
  12. https://pubs.acs.org/doi/10.1021/acs.est.9b06501#
  13. http://www.styrotek.com/lorem-ipsum-dolar-sit-amet/
  14. https://www.cleanaway.com.au/sustainable-future/is-polystyrene-recyclable/
  15. https://www.stonnington.vic.gov.au/Live/Waste-and-Recycling/Stonnington-Waste-Transfer-Station
  16. https://www.gleneira.vic.gov.au/services/rubbish-and-recycling/rubbish-or-recyclable-our-a-z-guide/polystyrene
  17. https://mwrrg.vic.gov.au/projects/the-metro-fund/metro-fund-round-three/city-of-monash-diverting-polystyrene-from-landfill/
  18. https://www.abc.net.au/news/2021-07-30/upcycle-expanded-polystyrene-into-food-safe-bowls-in-robe-sa/100314906
  19. https://www.plasticsnews.com/article/20180419/NEWS/180419880/scientist-seeks-investment-to-convert-plastics-to-biogas
  20. https://www.degruyter.com/downloadpdf/j/jwld.2016.31.issue-1/jwld-2016-0042/jwld-2016-0042.pdf
  21. https://www.ivv.fraunhofer.de/en/recycling-environment/recycling-plastics.html#creasolv