What to do with expanded polystyrene

While most of the precious plastic types listed as process able are already recyclable in Sydney Australia by the local Council collections, and a good news is NSW will follow South Australia’s lead to give a nominal refund for plastic drink bottles from July this year to reduce the amount of litter, I have two problems that would be great for the Forum to suggest solutions on.

One of them is plastic shopping bags that come in a variety of materials and are not welcome in the recycle bins.

The second is that expanded polystyrene – the light, white plastic often used to protect equipment or furniture from shipping damage – is also not among the materials accepted for recycling either in the bins or in the recycling depos, because of its bulk.

Do you fellow plastic recyclers have an easy implementation for recycling these two types of “menace”?


There are these compactors to help decrease the size of the residue for industrials, it makes this sort of “poop”-looking extruded doe. It doesn’t look like the molecules have been compacted.
So idk if heat collapses the molecules.
Chemicals do… like acetone and diluente… but those release vapours, and making them doesn’t look so pretty either.

So, back to the heat: what kind of objects can we make with extruded “poopy”-looking doe (that hardens).

I’d say: boards and tubes. And while hot, wire?

Hi – I tried making glue out of styrene and acetone. Youtube videos show the styrene melting invisibly into the acetone and creating a glue. My styrene becomes an elastic lump like playdough and never looks like dissolving. Anyone got any suggestions please?

Hi Dave, @enstyr
Am I correct to asume your machine is closer to a blenders than a shredder?
You are on an Open Source forum, so I hope you don’t mind me asking about your ‘trade secrets’ 😉

Most grinders will crush the eps in the process.  Enstyro equipment was designed to shred foam without crushing.  Typical packing foam has a lot of empty space and our equipment still only reduces the volume by half.  A bag of enstyro shred is around one pound per cubic foot.  That depends on the incoming EPS of course.  Check the density of your shredded foam if you want to know how much crushing is going on in your grinding method.

Contact dave@enstyro.com if you want to produce the best EPS aggregate on the planet.

Hello People,

My personal experience was, shredding the Styrofoam leads – surprisingly – to a reduction of the volume of the styrofoam.

From a 90 liters bag,  I got 5 liters of shredder styrofoam.
These volumes are only an estimation, but next time I try I’ll make some pictures.

Next step is to try in the Injection machine, I’ll try and tell you later.

EPS has extraordinary properties such as density, longevity, flex recovery, and water resistance.  I founded Enstyro Inc. which invents equipment and develops uses for this material.  In the decade we have been in business, we have found many great uses for EPS and shipped EPS recycling equipment around the world.  A customer in the Maldives that makes building blocks from EPS concrete introduced me to Precious Plastics.  There is great value in the low density, but these extreme properties mean that you need to get the particle size right for the job.  This video describes how Enstyro equipment creates the right EPS particle for each specific use.  https://www.youtube.com/watch?v=oDvQpqsVBno&t=56s

With the perfect EPS particle the possibilities are endless.  We recently sent our third shredder to a single company in Australia that makes a stucco or render as they call it down under.  A customer in Nigeria is making a sound proofing decorative veneer out of light concrete.  A Texas company is using our equipment to produce pump-able concrete firewalls.  Mixing EPS in concrete gets rid of the flammability issue.  A New York City organization is using Enstyro equipment to produce aggregate for green roofing soil which helps insulate the building while consuming CO2 and reducing run off during storms in the concrete jungle.  A university in Canada is mixing Enstyro Shred with natural materials like clay to design new building materials for the developing world.

There are so many uses and our favorite is concrete because we replace mined aggregates while adding insulation and crack resistance.  A little EPS in concrete maintains the high strength while preventing thermal cracking thus making concrete more durable.  Floating concrete is simple when you have the right mix of aggregate sizes like in normal concrete, but with a near weightless, moisture resistant aggregate.  Replacing about half the aggregate in concrete can produce a tough, structural concrete with much increased insulating value.  This added insulation can stop the condensation on concrete and prevent moldy basements in many parts of the world.

I do believe that the next material age is at hand and it will start despite the corporate oligarchs, not because of them.  There are many new materials and some new equipment yet to be introduced by Enstyro and our inventive and insightful customers.  We are here to help if your ready to recycle EPS into a better tomorrow.  http://www.enstyro.com

How about chipping the expanded polystyrene into small chunks, and then using it as insulation around biogas digester tanks?

In warm countries, biogas digesters can be built with little in the way of insulation. But in colder climates it is more difficult to keep the anaerobic fermentation active – as the bacteria cannot function below particular temperatures.  Hence the fermentation tanks need to be well insulated.  Even if buried, heat loss to the surrounding ground could be considerable – and so a thick layer of insulation would be an advantage.

There are probably plenty of non-plastic materials that can be used for insulation, such as glass fibre, wool, or straw.  But waste expanded polystyrene could have some advantages:
– it is cheap
– it still insulates if it gets wet
– it doesn’t rot

Also, the flamability of expanded polystyrene will be less of a problem if it is packed around a tank full of bubbling slurry, than if used for residential insulation.

(edit: Hmmm. That’s got me thinking about the possibility of moulding components for biogas digesters using HDPE or PP….)

Hi Guys I was sent a private message for a recipe of the aerated concrete so I thought it would be good for all to see and share so here is the link.


@btmetz Could we use a uv lamp to breakdown quicker? I think an experiment would be needed and I will start this week and give results.

Hi Guys Polystyrene can be turned into aerated concrete, beanbag filling, packaging filler etc
1 aerated concrete the polystyrene is broken down by a machine like a shredder but has comb like metal teeth which breaks the polystyrene into balls. Essentially it rips it apart into tiny ball like bits, the balls are then mixed with concrete and used mainly in the landscape industry for build ing non structural walls. In australia it is called a hebel block. (Private message me if you want the recipe). Also this can be used for other applications like tables or chairs or whatever you can thinkof quite a versatile material.
2 Beanbag filling – this is the same machine doing the work but the polystyrene balls is collected and bagged up and sold to be used as filling for beanbags.
3 Packaging filler – same as above but used for a different purpose.

I’ve use polystyrene with electronics. It’s pretty resistant to electricity so I’ve used it to repair laptop charger cords. They always seem to break at the place they go into the device for me. In order to fix this I cut them off and stick them into a jar with some acetone in it. The acetone is absorbed into the PVC insulation. After a while I take them out of the jar and peal of the PVC by hand. Next I fix the problems with a soldering iron, test the results and then encapsulate the whole thing in polystyrene. I put it some place cool to dry of and harden for a few weeks. It’s best to keep it out of the heat as that will cause the polystyrene to expand which is undesirable in this instance. The method has proven vary effective, but you need to be careful that there are no flaws when you do it because if it breaks again getting the polystyrene off is harder then with the PVC.

This is the best used I’ve found for it yet although I keep some liquefied polystyrene in a jar to use for various things from time to time (the jar keep the acetone from drying out). I’m guessing it could be used for other electric things like maybe you could use it to encase some simple circuits avoiding the need for a circuit board. Of course if it breaks fixing it would be a pain.

With regards to dissolving PS foam to make a moulding compound, or glue, you may be interested in this video.

Cuba’s DIY Inventions from 30 Years of Isolation

The typical solvent used was gasoline. Not nice to work with, but it got the job done.

Hey guys, so i’ve started sorting out my different plastics and in the PS zone I have quite a few expanded PS (mainly ice containers).
One of the guys i work w/ is a senegalese wood worker and already back then before coming to france, he would make glue that way.

Just in order to gather maximum different intell on the subject; what kind of dosage would you recommend for optimal glue (ratio kg os PSE/ liters of “diluant”)

Also, following someone here’s advice (so sorry can’t find the message again), i covered the pot where i mixed PSE & diluant with a plastic film, hopefully getting rid of air bubbles w/ this process.
Is there anything special to be aware of if willing to sell small quantités to craftsmen around my business?


good idea!, show us the results please

@btmetz, would a mixture of polystyrene and sand in the shape of a roof tile,a paving stone or a building block, be more UV-resistant ? If not, is it just the outer layer of the product or even the inner layer can be affected ?

Your answer might suggest to adopt or avoid the use of EPS for such applications.

Good day. We are currently studying about making a roof tile from waste expanded polystyrene by melting and mixing it with sand. If you guys know the ASTM standard for composite plastic pls let me know. Thank you.😊😊😊

By the way, this is a handmade domestic procedure…globes mask & safety glasses included of course 😉

Hi everyone, I’ve been recycling Styrofoam for about 5 years…I melt it with acetone and trepens, and shape it in to pots as you can see in the image.
You can check out my facebook page, there are few more pics of what I’ve done. among waste reduction and Conscious consumption tips. Tell me what you think. Regards!!


Hi everyone,
Has anyone tried feeding expanded polystyrene into one of Dave’s machines? Seems to me that as its 95% air it wouldn’t be a great idea… I wonder if the polystyrene he has tested is solid polystyrene (plastic cutlery etc.). I am testing the acetone-PS mix now – if just left to harden naturally it takes a few days and has bubbles still (I think formed by acetone evaporating). I will also be testing a few different ways of drying it to see if I can improve this. Has anyone then tried putting this dried/reduced polystyrene into Dave’s machines?